Precision measuring tools


I’m looking for the best quality precision tools on a limited budget (i.e. I don't want to pay $300 for one mic). I plan on building the occasional small- & big-block Chevy (more than one, less than 1000). Names that come up on the limited results I’ve found on the web include Starrett, Browne & Sharpe, Fowler, Mitutoyo. I was hoping for some feedback on both tools to consider as well as what brand you’d buy or what you’d stay away from.

I was thinking about a good set of snap gauges in lieu of an expensive dial bore gauge?

An assortment of micrometers 0-6”, I’ve heard that carbide tips are a necessity. I’ve also read, & seen the higher prices for, mic’s that are coolant resistant?

A 0-6” dial caliper? Thinking about a digital?

A good magnetic base w/a 1” dial indicator for degreeing cams. Curious if anyone can explain why a 16” “Professional degree wheel” is so darn expensive at $180+?

Has anyone bought any of the stuff from Powerhouse?


Staff member
great question,

first ID suggest that while its always nice to have super accurate precision tools its generally NOT critical in a basic engine rebuild to have the best or even close too the best measuring tools available.
now Im not suggesting accuracy is not important , but you seldom need accuracy to be less than than .0001 and some of the more expensive tools are designed to provide that level of accuracy, what you need is repeat-ability and consistency and the ability to get accuracy down to about .0002.

For measuring equipment Mitutoyo is tough to beat. The better stuff from Starrett is good as ,is the better quality tools from a few other sources.
I think youlll want to think thru how often youll use the tools and really how accurate you need to be ,take a step back and honestly ask your self, are you doing this often enough to invest a good amount of cash in tools you may not use more than once or twice a year or less, you have to ask yourself how much use the tools will get and how much having them will mean to you, I have several quality tools that I don't use enough on a consistent basis to really warrant their price they cost,but too me it was worth it to have them, and in most cases i got them at a discount (STILL DARN EXPENSIVE) so I could do the precision measurement work myself and do it right, and be sure of the results, but I,d be the first guy to admit I double check most bearing clearances with plasti-gauge strips
from a practical stand point, getting clearances in an engine down into less that a 1/4 of 1 thousandth (.00025 ) or less on the most critical components) and most down to (.0005 ) is usually sufficient, and on many even a full thousandth variation is not critical., example, a difference in rod side clearance, ring end gap or quench distance is far less critical than a thousandth difference in main bearing clearance, or piston to bore clearance.
now IM not suggesting the more expensive tools are not slightly better, but IM surprised at the level of accuracy the cheaper tools exhibit.
even a basic calculator like this is very useful, so I carry one much of the time







they measure the piston deck height after the machined block has the rotating assembly test fitted

piston down in hole at TDC.jpg ... 47261.html
IVE got a wide selection of MICS and Calipers and IVE checked the cheap Chinese crap measurements and consistency against the much more expensive Japanese and American tools and surprisingly most are consistent , and reasonably accurate and decent quality if you get the stainless steel tools
Mitutoyo, makes a good set that Ive had for years ( I bought a used set similar to the picture below, cheap at a yard sale, for $150 )



heres a cheap chinese import set, Ive used, a a friends house that work ok


Ive found that a decent set of snap gauges and mics and a decent digital caliper will allow you to get bye quite nicely when used with some other checking tools, like plasti-gauge. repeatability and consistency are important.
plasti-gauge is an excellent cross check tool, easy to use and accurate, if used correctly, and I would not be a bit concerned if thats all you had to check bearing clearances, I use a fairly expensive set of mics, and snap gauges but I always cross check with plasti-gauge, and you ll be surprised at how accurate its really is ... C1530.aspx


even the cheapest Chinese tools are usually adequate if you know what your doing, and are only using them occasionally and take care in carefully measuring components, and you verify with plasti Gage ,feeler gauges, and your consistent and take care during assembly
(SURELY NOT IDEAL BUT FULLY USABLE, frankly IM amazed at the cheap tool accuracy levels) I think a good deal of the reason is that once your down to clearances of a 1/2 thousand or less a few ten thousands difference are less a concern to durability than consistency and care taken in assembly and clearencing, and polishing, or smoothing parts

you'll need check standards to verify accuracy before each use, and you must keep the standards remain rust free in zip loc bags with a fine coat of wd40

it certainly helps to have a few tools that measure accurately

checking standards
or youll miss a great deal of related useful info


viewtopic.php?f=50&t=3157&p=8449#p8449 ... clearances ... 32a8c0____

most micrometer sets come with check standards,but youll generally want a few extra sized ones, its important that you verify accuracy with them, remember heat expands metal, don,t expect parts that are warm to measure the same when its cool ... Micrometer ... p-971.html







viewtopic.php?f=53&t=88 ... Q&start=20


viewtopic.php?f=44&t=374&p=457#p457 ... mber=97389 ... mber=66512 ... umber=5649 ... mber=32214 ... 9/10002/-1



viewtopic.php?f=50&t=723 ... nkCode=asn
Last edited by a moderator:


Thanks for the quick reply.

I've got an itch for a 572 w/afrs w/a mech roller on a dart block for my chevelle. hoping for around 700hp. Mike Lewis on team chevelle has inspired me. I know this sounds insane but I want to take a crack at it.

I was amazed at what Amazon had available to be honest. I'd found some stuff on their earlier as well. Guess it's not just a book store anymore.


Staff member
buying higher quality matched and ballanced rotating assembly components,from a single source goes a long way too reducing problems, durring engine assembly. and dealing with a quality machineshop on the block and head machine work removes several other potential problem areas.
youll also need a rust preventative oil


the new wd40 rust preventative spray works far better than the older version READ THRU THIS LINK

the secret of diagnosing most auto related problems lies in careful observation,
and applying logic, knowing HOW the part or component or system is SUPPOSED to function,
and then carefully observing HOW it is or is not currently functioning.
and logically deducing, the reason for any differences,
and potential reasons for that observed difference.
this can and frequently will require tools like meters,
timing lights, vacuum gauges, pressure gauges
and measuring tools like ,dial calipers, but careful observation is critical.
tools like drill presses, clamps, gear pullers,welders, floor jacks, mechanics hand tools,
feeler gauges, multi-meters, etc. will all be helpful at times

Back to Basics: How to Read a Micrometer

Most people think of an outside micrometer when they hear the term "micrometer." An "outside micrometer" is one that measures the outside of something such as diameter, length, thickness.

By Jim Tapp

There are other types of micrometers, including depth micrometers and inside micrometers. As the names imply, they measure depth and the inside diameters, respectively. Often other tools (such as bore gauges) are used with micrometers to determine sizes so knowing how to read the micrometer is absolutely necessary.

A micrometer is a measuring gauge operated by a screw with 40 threads per inch. This means that one complete revolution of the screw advances one thread or one-fortieth of an inch. 1/40˝ equals 25 thousandths of an inch or 0.025˝ (40 x .025˝ = 1˝). The beveled edge of the thimble is divided into 25 equal parts. Each line of the micrometer's thimbles equals 1/25 of .025” or .001˝ (one thousandth of an inch). One complete revolution of the thimble therefore equals .025˝ or one line on the barrel scale. With that in mind, here's a quick quiz: What is the reading shown in Figure 1?

How do you think you did? Did you come up with .385˝? If not, look at the drawing again. Each of the lines on the barrel represents .025 of an inch. Each of the longer lines (the ones with the numbers above them) equals .1˝ (4 x .025”). So, we’re showing 3 full lines (.300) and 3 of the small lines (.075). We’re up to .375˝. The last .010 is indicated by the reading on the thimble. Add that to the .375˝ and you have a reading of .385˝. Sounds a little confusing I know, but trust me, you’ll get the hang of it the more you do it. Heck, even my wife can read a micrometer now and I still can't boil water.

If you need more precise measurements, which is quite common in machining, you can achieve readings in ten-thousandths of an inch by using a Vernier scale (optional on some micrometers). The vernier scale, marked on the barrel, has ten divisions, each equaling 1/10 of 1/10,000”. The difference between a thimble division and a vernier division is 1/10,000 of an inch. Therefore, when the zero lines of the vernier exactly coincide with thimble lines (Figure 2), the number on the vernier lines is the difference between the vernier line and the next thimble line in ten-thousandths of an inch. Thus when the fifth line on the vernier coincides with a thimble line, the thimble has moved 5/10,000 of an inch.


First determine the number of thousandths, as with an ordinary micrometer. Then find a line on the vernier that exactly coincides with a thimble line. By adding the vernier reading to the thousandths reading the actual reading in ten-thousandths of an inch is obtained. The reading shown in Figure 2 is .260˝ plus .0005˝ or .2605˝.

Hopefully, you haven’t run screaming after all of that. It sounds confusing, but take your time and keep at it. It will make sense.

Jim Tapp is Tech Services Manager for Goodson Tools and an ASE-Certified Master Machinist.
shop carefully the exact same set of mics from the same company can cost $270-$900 depending on where you buy the set

Last edited by a moderator:


Let me preface by saying this... I was a Tool & Diemaker for 20 years and have worked in gage calibration for the past 16 years. I have been part owner of an A2LA accredited gage lab for the past 9 years.

With any gaging... mics, calipers etc... You get what you pay for. IMHO, the Chinese Harbor Fright stuff is pretty much crap for any serious work. Believe me.. I've had literally thousands of different micrometers in my hands and there is a difference.

That said, there are a lot of people using them and saying they work well.

An alternative I always suggest is to look on Craigslist or Ebay for used Starrett, Brown and Sharpe, or Mitutoyo tools (to name a few) rather then buy the cheap stuff.


Staff member
Ive got a full set of Mitutoyo mics 1" 2" 3" 4" 5" I paid several hundred dollars for,
and a cheap duplicate set from northern tool mics along with half a dozen different digital calipers and so far they all are consistent enough that theres not been any effective difference.
now I fully agree theres a very noticeable difference in quality , that's not debatable,if you need to know that last couple ten thousands of an inch your wasting any money spent at HF like stated above.
but if your just measuring something like a piston ring thickness, or crank journal diam. and getting within 2 ten thousands plus or minus is ok, they all work well enough, and for most hobby level builders I think thats true!
and yes I constantly cross check them against each other, in fact I generally use several mics and a digital caliper during engine assembly, and constantly recheck against the precision gauge blocks and feeler gauges


viewtopic.php?f=53&t=2726&hilit=plastigauge ... f3f1075a76

notice how one side of the bearing holding section has a radias (left)(GOES TOWARD CRANK COUNTER WEIGHT) but the opposite sides flush (right) (FACES MATCHED ROD)the larger bevel faces the crank counter weight, the smaller the adjacent rod its paired with, don,t forget the piston, has an exhaust and intake clearance notch on most designs that needs to match the valve lay out also

read these threads above

if youve used a quality assembly lube it should require NO MORE than 40 ft lbs of force to start an engine to turn and under 20 ft lbs to keep it spinning, and thats with new rings in a newly honed bore, that effort required should drop rapidly to the point that less than 20 ft lbs are required to spin a short block after its been well oiled and rotated dozens of times.
one factor some new guys over look is that rods and bearings are designed with one side having a bevel that faces the counter weights and a non-bevel edge facing the matched rod

heres some calculators you might use

viewtopic.php?f=52&t=4299 ... patibility ... index.html

gear spread sheet that comes in handy THANKS TO 1FATGMC ... index.html ... index.html


a few resources to allow you to calculate the ideal results

heres some different calculators
average the results
Last edited by a moderator:


Staff member
READ THIS LINK ITS IMPORTANT ... e753501149 ... e753501149




SUM-900041.jpg ... MTY511-753 ... M=612-5910 ... A=325-1304







Tapered Ring Compressor


read the factory shop manual or connecting rod manufacturers info VERY carefully...FT LBS AND NM ARE NOT THE SAME

HUSKY $88 (worked rather well, over all I was pleased)
youll need a good quality torque wrench

Piston Ring Squaring Tool[/B]

damper tool

Degree Wheel
checking lifter

degree wheel



Dial Bore Gauge

Pushrod Length Checker
Proform Pushrod Length Checkers 66789 SBC 3/8" rocker studs

Proform Pushrod Length Checkers 66790 SBC 7/16" rocker studs

Proform Pushrod Length Checkers 66806 BBC 7/16" rocker studs
Oil Pump Primer

23301a.jpg ... 60669.html

harbor freight has cheap and perfectly acceptable calipers
spring micrometers,

a crank snout, turning socket,

a dead blow mallet ,

a can of moly spray lube,
ring install pliers

piston ring filer,



Im 68 years old and Ive been building and racing cars and engines since I was in my teens,Ive probably built an average of 3-4 BBC, and or SBC engines a year
(with more than a few mopar, caddy, Buick, Pontiac engines along the way)
mostly for the local muscle car guys and myself over the last 45 plus years and I can assure you both research and experience maters, I look back at what I built during my 20s and remember the frustration I felt not knowing what was required and thinking about all the mistakes I made back then I have constantly tried hard to help the newer guys avoid many of the pit-falls I learned from.

yeah reading links sucks but it takes far less time and wastes FAR less money than blindly and randomly jumping into an engine build ignoring the potential problems and knowing what your doing and why and how its done never hurts
Last edited by a moderator:


Staff member
I was over at Franks house today and he was in the process of tying to find the correct pilot bushing or bearing to instal in a crank he purchased and I was amazed that his first thought was to try to look up the correct part on the internet?
to me that was absurd without knowing the inside diameter of the recess in the rear of the crank, its depth and the diameter of the tip of the transmission shaft it was to support that was to slide inside it.
ram-bu656_w_ml.jpg ... /overview/
Pilot Bearing, Steel, Roller Type, Chevy, 0.600 in. I.D., 1.096 in. O.D., 0.720 in. Each


in case your unfamiliar. pilot bearings support the front of the splined shaft that slides thru the clutch disk




Last edited by a moderator:


Something I learned from experienced machinists Grumpy is the fact you don't want to hold a Micrometer in your hand longer than 30-seconds at a time.
Your body heat transferred is enough to cause the Mictometer frame to grow & expand.
It matters if your trying to measure down to .0001"-.0002" / 1-2 Ten Thousanths accuracy.


Staff member
floridas hardly the ideal climate for keeping tools rust free so i generally take my set of micrometers out of the storage case and open and close them and spray them down with a light oil like WD 40 and place them back in the box then place the whole box in a 2 gallon zip lock bag in a shallow tupper ware type air tight storage box that is just the size to fit inside one of your tool chest drawers too protect the precision measuring tools , feeler gauges and plasti-gauge youll need to measure clearances correctly.when not in use along with the dial calipers.


How to Use a Cylinder Bore Gauge To Measure Cylinder Block

How to Use a Cylinder Bore Gauge To Measure Cylinder Block

Why engine can perform a rotation outpu ? it because the engine generating power from a combustion. The power of combustion pushing down the piston. But the movement of piston must produce a friction between the cylinder and the piston ring. In a long time, this friction will cause wear between the two components. That's why older engine have less power complaints with low compression pressure.
If the cylinder is worn out, it means the power is also hampered. So it needs to be over size or replacing this one. But to know whether the engine cylinder is still feasible or not, we need to make measurements. It will calculating the size of the cylinders and engine block wear out. So how to step, consider how measure cylinder block using cylinder bore gauge below.
Differences Tautness And Wear out
Before we go any further, let's understand the meaning of these two words. Tranquility and innovation have different meanings.

  • Tautness, is a cylindrical wear when viewed from the side of the cylinder. This form of is tapered because there is a different size of the lower and upper cylinders. This difference will show a great tune.
  • Wear out, is a form of engine cylinder wear when viewed from the top. The normal cylinder, will definitely be a perfect circle when viewed from above. But when it form more oval, then it might be a signal that showing the cylinder wear out.
How To Measure Cylinder Block Diameter ?
To measure the diameter of engine block, we need a special tool called Cylinder Bore Gauge. This tool can measure the diameter of the cylinder with precision reaching 0.01 mm. But before making a measurement, we need to make some setting on this tool.
cylinder bore gauge component and function

  • Dial gauge. This component will show the size scale with units of milli meters.
  • Lock position. This component serves to hold the dial gauge remain silent when bore gauge is used.
  • Grip. This component serves as a handle when applying a bore gauge.
  • Replacement rod. Component of a rod of varying length to measure many cylinders having different diameters.
  • Replacement washer. Similar to replacement rod, but replacement washer has a small thickness. Ranges 0.5 mm.
  • Measuring point. In the form of a bulge, when pressed it will move the needle of dial gauge.
1. Steps to adjust the bore gauge cylinder.
To make the adjustment, we need to know normal specification of cylinder diameter, you can find this specification on the service literarure each car or you need to measure directly using vernier caliper. But you need to know that this measurement is not a real measurement, because we just need a scale to set the right replacement rod.
If you already know the diameter of cylinder then, continue to assemble the cylinder bore gauge. Start with installing the right replacement rod on the bore gauge. Suppose the diameter of the cylinder is 62.05 mm. Then we choose a replacement rod with a length of 60 mm plus replacement washer with a thickness of 3 mm. So a total length is 63.00 mm.
Why is it higher?


Because we will measure a wear. Components that experience wear and tear must have an enlarged diameter. If we choose the replacement rod of the same or smaller than the diameter of the cylinder, then the measuring point can not be depressed when taking the measurement.

Once installed, set the dial gauge to zero using the micrometer. Position outer micrometer at size 62,05 mm, put the cylinder bore gauge (replacement rod parts) on timble micrometer. Then the measuring point will move and the dial gauge needle moves. Set the dial gauge scale to zero position on the dial gauge needle.
2. Step to Measure Cylinder block diameter.
Perform measurements inside the cylinder. There are three measurement positions of each cylinder that is on the X and Y axes of each upper, middle and lower positions. The X axis is the line that intersects the engine horizontally. While the Y axis is the line that cuts the machine vertically or elongated. So total, there are six measurement each cylinder.

How to measure it ? input the cylinder bore gauge into the cylinder. Then, shake this tool left and right while watching the dial dial indicator. We need to pay attention to the farthest point of moving needles. Because this point will show the difference in diameter of the cylinder with a standard diameter. Perform this measurement at each position of each cylinder.
To calculate wear out, we need to find the difference between the measurement of X axist and Y axis at each position. While the tautness, we can know by finding the difference in measurement of the top and bottom diameters on one axis.

Another way of measuring the diameter of the cylinder.
The step above is the correct procedure to measuring size of cylinder block. However, in its application sometimes encountered several constraints such as measurement results that are smaller than the standard. It could happen because each engine has a different diameter even made in the same factory. For that there is simple way that many technicians use to measure engine block diameter.
The first step, we need to see the standar diameter on technical specification. Remember, we need to know the right specification and dont measure with vernier caliper. Why, bceause this data will be our benchmark to get the wear out. Once you see the right standar diameter then assembly the bore gauge and, make direct adjustments inside the cylinder.
Like the above procedure, there is six position each cylinder but for first enter the cylinder bore gauge to the bottom position of cylinder to set the bore gauge. In this case, we are based that the bottom position is an area that does not experience friction with piston rings. So the diameter is still standard.
Continue to move the bore gauge right and left. Notice the farthest point of the dial gauge needle. Position the dial gauge scale to zero position exactly on the needle moving to the furthest point.
Furthermore, we directly conduct the measurement of the diameter of the cylinder in the six positions as described above. In this case, to know the cylinder diameter you should looking for the difference between standar diameter as benchmark and the result of measurement.
Once you find the correct diameter, you can calculate the wear out and tautness of cylinder. From this data, you can conclude the condition of engine block.

Similarly, guidance on how to use cylinder bore gauge to measure the diameter cylinder. Aside from the cylinder's sharpness and wear out, diseases of the engine can also be caused by non-standard pistons. Check how the piston check to be more clear. Hope can be useful.

the reason I bring this up is I recently was over at a friends house where I needed to accurately measure a u-joint bearing cap and asked if he had a micrometer or dial caliper, he responded he had a very expensive looking imported micrometer, he had acquired recently at an estate yard sale for $30,

when he opened the very impressive looking brass and mahogany box the micrometer, inside was a solid rusted mass, I soaked it in marvel mystery oil and acetone mix for 30 minutes then gradually worked it loose and polished it up with 1500 grit wet/dry sand paper figuring no loss at this point and was amazed that after about 30 minutes of constant cleaning it not only looked fairly decent it seemed to read accurately on a test gauge so I think it was mostly ugly surface rust, but it sure looked horrible, and to someone who appreciates good tools,that was depressing.
always accurately measure the crank main journals, and remember the crank and block bearing sizes on a 400 sbc and 350 smc are different as are the early 283-327 sbc


btw look around at yard sales and estate sales every so often youll find amazing bargains in used precision tools
yes it sure helps to have the correct tools and know where to measure parts
(take advantage of millions of hours of previous engine builds, by skilled and experienced people, and the knowledge gained)

A couple days of
reading the linked and sub-linked info
could save you a great deal of wasted time and money
and money spent on wrong or un-necessary parts
read the links and sub links below
a day or so spent doing reading and research,
(reading links and threads)
will frequently save you thousands of dollars and weeks of wasted work.
if you want a fast dependable car you will need to either do the research required to know exactly how and why things should work, or pay someone else to do the work that has taken that time and effort.


your going to need decent feeler gauges


if the ring gaps, or piston to bore clearances are not carefully checked, or not correct your engine could easily get screwed up
Due to machining tolerances on both pistons and bore sizes theres always some minor differences between components,
when your assembling any engine, youll file fit the ring gaps to individual cylinders,and youll,
generally you'll want to carefully measure each individual piston diameter and each individual bore diameter very carefully,
and match the larger pistons to the larger bore sizes to keep the average side clearance as consistent as possible


most applications would have a ring gap of about .004-.005 per inch of bore diam.
but tests have shown even a .050 end gap has only a marginal effect on engine power or blow by, simply because at even 1000rpm theres slightly more than 8 power strokes per second, and the pressure is near max mostly in the 10 degrees before and 30 degrees after TDC, theres very little time to force much thru a .005 or less piston to bore clearance and two .050 end gaps even if that was the case








this cam buttons correctly installed but the retainer plate tabs have not been bent up to lock the bolt heads from rotating







yes I use both micrometers and snap gauges and cross check with plasti-gauge
and yes when you compare the crushed width of the plasti-gauge youll find it rarely falls as an exact match to the bar chart tape that is packaged with it so you can judge clearance based on crush width









almost every mechanics tool box needs a few basic measuring tools and supplies, dealing in proven facts as to correct clearance sure beats guessing

Last edited by a moderator:


The Grumpy Grease Monkey mechanical engineer.
Staff member
allen said:
Grumpy ? why should I spend a dam dime on all those precission measuring tools, especially, if I will more than likely simply pay a local machine shop to buy and assemble the parts I want in my engine?

DEAL WITH A QUALITY MACHINE SHOP with a GREAT REPUTATION that depends on maintaining good customer feed back for repeat work.
a competent and experienced machine shop, machinist, you can trust to point out whats REQUIRED and what is SUGGESTED is a very valuable asset , you really should look for and researching what you think needs to be done, how that is accomplished and why its likely necessary in any particular application, goes a long way toward preventing both disagreements and wasted money on an engine build AS does having access too or better yet owning some precision measuring tools that allow you to check and verify that any machine work you pay for was in fact correctly done!

ITS mandatory that YOU as an engine builder be aware that theres a few machine shops that are run by scam artists willing , even happy to cheat the less informed customers, and the decepion and cost cutting saves them considerable money while basically providing you with a very inferior product at an inflated price.
IMPORTED parts from over seas being substituted for much more expensive, well known brand name components, DOES HAPPEN!
It helps your engine's potential durability tremendously, if you take the time and effort to verify that you have, and that if you have a machine shop do all or part of your engine assembly that they, actually had the quality components, you paid for installed in your engine, Ive had several machine shops try to pass off and install really crappy quality components in engines while charging top dollar for brand name parts.
now I'm sure that easily 70% -90% of the guys never bother to check what they got back from the machine shop for accurate machine work or that simple things like the bolts, studs and bearings , rings and gaskets the machine shop used during the engine assembly were actually the parts you paid for, but I know for a fact that less than honest shops don,t bat an eye over making a few bucks extra with this bait and switch B,S.
Ive seen connecting rods, main caps, studs rockers push rods pistons, piston rings, cranks and several other components being billed as name brand components and lesser quality parts actually installed!
there was a machine shop in Hollywood florida , that for decades was well known for this deceptive practice



Obviously if you want to totally trust a local machine shop to build your engine, and your simply going to install it after you take delivery and pay the bill, theres little need for any precision meassuring tools.
but most of the machine shops, Ive ever dealt with charge a good deal of cash per hour to assemble an engine! now your not just paying for physical labor, your supposed to be paying for the guys experience and the use of his tools and expertise , so in theory your saving money going that route vs buying all the required tools and needing to learn all the required skills and having to look up the parts, clearances and assembly specs like bolt torque and bearing clearances ring gaps, thrust bearing clearances rocker geometry, etc.
but going that route too a real gear head is a bit like being a total virgin, being told, a 1 minute description , by a buddy about an explicite 2 hour long PORN movie,
vs having a very friendly and horny wife back at home to play with,in the bedroom.
the depth of your own experience, and hands on skills and satisfaction you get from the process is a whole lot different,
between what you learn doing the job personally vs hearing a second hand version about what went on during the process.
expecially if youve never personally been envolved!
Id also point out that most machine shops Ive ever dealt with can,t be 100% trusted to verify every clearance and meassurement,
in fact Ive seen dozens of cases where guys that paid for expensive components while the assembled engine, was being built,
either had less expensive parts installed or the clearances were not accurately verified.
Its a sad fact that many machinists and engine builders would rather rush through a job to maximize the potential profit,
("time is money" by minimizing the time spent on any one project. and I get a strong feeling that many of them assume,
many of the guys paying for expensive parts are rather clueless, and lack the knowledge to tell the difference between what they paid for,
and what was used and installed in the engine.
now Im certainly not suggesting most shops are scams or dishonest but Ive sure run into a healthy percentage of badly machined parts, obviously never verified clearances and
" mistakenly used sub standard components,that got installed in the confusion" ( or machine work that was) "billed but never done" because of a "NEW GUYS OVER SIGHT" ....yeah! RIGHT!
so I eventually learned that EVERYTHING YOU PAY FOR MUST BE CHECKED,
all machine work must be verified on delivery, and ALL parts MUST BE clearly and PERMINANTLY marked,as to your ownership
before and after photos taken,
receipts signed and firm prices, dates, and detailed and accurate prices,
details on listed work to be done and times for delivery MUST be listed,
the "we will get to it in a couple days crap"
won,t cut it!
"should cost only a $100 or so",
is a sure lead up to over billing!
If you can,t afford to pay for top quality work by a reputable machine shop,
in checking all the work PERSONALLY
and knowing everythings been done correctly,
that requires YOU verify every step of the engines assembly process

always ALWAYS get everything in detailed writing before you start,
specifying all machine work, to be done in detail,list parts and labor costs, due dates and have every single part you supply ID stamped, and photographed, listed and a value assigned, with both YOU and the machine shop having identical signed copys
listing the cost and dates and work details


Last edited:


I read your post here today Grumpy.

I can't get enough Precision Measuring Tools also.
Yoy can not trust any.
Just too many politics going on.
All want to be #1.
There can be Only ONE.



The Grumpy Grease Monkey mechanical engineer.
Staff member
if your serious about building engines as a hobby or even as a part time side business,
you'll be forced to either buy or borrow some decent quality precision measuring micrometers,
simply due to the need to check clearances accurately
the first few rule's of GRUMPY'S engine assembly





(2) if in doubt, about how to do anything, on an engine, do some detailed research,
find and compare at least 3-5 valid trust worthy sources info,
read the instructions over again, several time's very carefully
and if available watch several related videos.

(3) if any component will not easily function as designed or requires a good bit of physical force to install ,
or your not 100% sure your doing something CORRECTLY

theres a reason, and you better verify your clearances are correct , and your following the instructions before you proceed.

(4) never assume the parts you purchased can be used without carefully , cleaning them prior too,
checking the physical condition, verifying clearances and using the correct sealant, lubricants etc.

(5) the quality of a component is generally at least loosely related to the cost to produce it,
and the amount of detailed research and quality machine work that went into its production.
if you got a significant reduced price, theres typically a reason.
it might simply be because a new improved part superseded the one you purchased,
but it might be a far lower quality imported clone with lower quality materials and machine work.
its the purchasers responsibility to research quality.

(6) if you did not do the work personally or at least take the effort to verify it was done correctly and personally verify clearances

ITS almost a sure thing that it was NOT done , correctly, and yes that mandates you fully understand what your looking at,
and how the components are supposed to function and have high quality precision measuring tools.

(ABOUT $415 a set)
(ABOUT $877 a set)

dial bore gauges are about useless without a set of accurate mics, in the sizes of the bore diameter your checking as you use a dial bore gauge to measure consistency in a given bore size and basically how consistent or "ROUND" a bearing is but you use the mics to verify dimensions.
in my opinion you,ll also be smart to cross check ,bearing clearances with plasti-

if you want to get accurate measurements you,ll need precision measuring tools designed specifically to measure , inside diameters like the main cap bores and cylinder bores, and matching micrometer sizes





yes I use both micrometers and snap gauges and cross check with plasti-gauge
and yes when you compare the crushed width of the plasti-gauge youll find it rarely falls as an exact match to the bar chart tape that is packaged with it so you can judge clearance based on crush width





Last edited:


The Grumpy Grease Monkey mechanical engineer.
Staff member
many valve train issues can be avoided with careful measurements and some basic calculations,
but I find it amazing how often I find I go to help people who, want to do precise automotive engine work, that,
don,t have even a dial caliper or machinists dial indicator and stand, or simply calipers and modeling clay available

are there any other people out there with this mental issue... yes his is meant to be a bit of a grin..
I,ve come to the inexplicable conclusion , that I,m a irredeemable
" tool junkie"
I find if I start a repair and don,t know exactly how to do it to better than what most dealerships could accomplish,
my first step is to grab a shop manual, or look for related videos on YouTube ,or I grab a chiltons manual,.. which inevitably ,
seems to lead to either instructions or a video showing how some tool I,ve yet to acquire or some accessory to a tool I do own is,
needed to either complete the job or to make it easier.... now that would not be all that bad in many cases ,

because many people at that point will either farm out the job to a professional who owns the tools required,
or find a place they can rent or borrow the tools they need!
but for some reason my mind absolutely does not work that way......
I feel an absolutely almost totally irresistible , almost overwhelming NEED to both purchase the tooling, or accessories,
and to learn the skills required to use that new tooling.
it does not mater a bit if I,m unlikely too need to use that tooling or accessory ,
again for a similar repair project for years, in fact it may be a tool I need to fix a friends car that (you,ll be unlikely to believe this)
and it shows, the depth of mental depravity, it may be a tool thats only required for some car like a ford or Toyota,
that I've never owned or will ever likely own, still I feel the desire to purchase the tool and learn the skills.
yes we all have our metal failings but , this one has been my cross too bare for decades,
I have been forced to mentally step back and ask myself on countless occasions...
whats the likely-hood of you ever really needing that tool again in the next 2-5 years, and if I can honestly,
and objectively appraise , the situation, as "very unlikely" I force myself to ignore that mental " tool junkie" screaming like an insane banshee, in my mental ear,
BUY THE TOOL YOU KNOW YOU WANT IT! and save your limited cash flow for parts and tools you know you'll need on your own cars !
and, yes crap quality tools are usually not worth buying, that's an issue,I've learned long ago, that you tend to get what you pay for, and comparatively cheap prices frequently are a good indication of lower quality in tools of a similar design















GrumpyThe Grumpy Grease MonkeyStaff Member
23301a.jpg ... 60669.html

harbor freight has cheap and perfectly acceptable calipers




one factor I find rather annoying is that every time I price out tools, I purchased years ago , or need to replace worn out tools,
, the price has increased a great deal, Ive purchased dozens of tools over the decades,
and yeah, occasionally lent those out and its seems like a great many never get returned or get returned with broken or missing parts.
yeah I'm well aware of inflation, but its still a bit of a shock when a tool you purchased a decade ago now lists for 2-3 times what you originally paid.

Measuring Main Bearing Clearance

Pat Mancuso - -

Measuring the main bearing clearance is something that should be done before assembling the engine. This is commonly done with plastigage, but that method is not very accurate. Here's how to measure the clearance with an outside micrometer and a dial bore gauge

The obvious answer is to measure the main journal on the crank, and measure the diameter of the main bearing, and subtract. Not so fast. The problem with that method is that you're using two tools to do the different measurements, and there is no way to know what the error was in measuring each.

The textbook measurement for the main journals on a SBC 400 is 2.6500". Let's say you measure 2.6500 on the journal with the outside micrometer, and 2.6525 with a dial bore gauge on the bearing. That sounds like you've got 0.0025 clearance, right? Wrong. Let's say the error rating on the micrometer and on the bore gauge was +/- 0.0005. That means the journal could have really been 2.6505 to 2.6495, and the bearing could have been 2.6530 to 2.6520. Taking the worst pairs, 2.6505 - 2.6520 = .0015 and 2.6495 - 2.6530 = .0035, so your clearance is really somewhere between 0.0015 and 0.0035 once you figure in the potential error. That's a pretty wide range for the tolerances you need to check.

How do you get around that without spending a fortune on more accurate measuring tools? Easy, always use the same tool to measure with and you eliminate half of the error uncertainty. The basic idea is to measure the journal with the outside micrometer, then zero the bore gauge inside the micrometer, then use the bore gauge to measure the bearing. The actual measurement doesn't matter, you end up seeing only the difference in the measurements, which is the clearance measurement you wanted to check in the first place.

Going through the steps, measure the crankshaft journal with the micrometer, zero the bore gauge against the micrometer, and then measure and get .0025 (+/- .0005 error) which means your actual measurement is between .0020 and .0030. Much better than the previous method.

When using this method, you must be sure to measure each journal and re-zero the bore gauge before measuring the corresponding bearing. Measure the #1 journal, zero the bore gauge, use the bore gauge to measure the #1 bearing, measure the #2 journal, zero the bore gauge, use the bore gauge to measure the #2 bearing, etc.

To get an accurate measurement of the bearing diameter, make sure the bearings are installed properly in their correct location, and the bolts are tightened to the final assembly torque specifications.

Using the outside micrometer on the main bearing journal:


Zeroing the dial gauge against the micrometer measurement:



Reading the clearance at the bearing:


Showing .0030 difference:





replacing worn valve guides
valveguidemes.jpg ... ditioning/ ... seals.html ... -sleeving/ ... inding.htm


Take the effort to read through ALL the related threads, with info you might need, as it will without any doubt be time very well spent and save you hours of wasted effort and a couple wheel-barrows full of cash over time!

FAILURE TO verify all clearances


a bit of research, and taking the effort of reading related threads will help, but you need a few precision measurment tools and a good understanding of what to look for and how to meassure accurately
if you just assume that the machine shop must have cleaned the parts they worked on carefully...


can get very expensive and time consuming, and aggravating


any time you have precision machine work done youll want to very carefully verify that what you paid to have done to the engines components was in fact done correctly, I'd bet 90% plus of the people who have a machine shop do work like that
would have naturally assumed that the precision machine work was done correctly,
and simply assembled the engine without thinking a second about that work being done correctly.
this is one reason I strongly suggest most serious engine builders may want to have some precision,measuring tools,
and spend the time and effort to check that machine shop work you paid good money for, was in fact, done correctly ,
taking the time too verify the precision machine work was done correctly,
takes a good deal of the time required, in any engine build
(vs slapping parts together out of the box and wondering why it never quite runs up to your expectations)
and yes you probably could use the block in its current condition and find the engine runs,
and most people would never know the engines measurements were not correct or why the engine did not produce power to its full potential,
and the results might be so close that it would hardly matter ,too most car/engine owners.
but that engine block machine work ,being off specs, does not mean its been built correctly either

related threads
Last edited:


solid fixture here in the forum
many valve train issues can be avoided with careful measurements and some basic calculations,
but I find it amazing how often I find I go to help people who, want to do precise automotive engine work, that,
don,t have even a dial caliper or machinists dial indicator and stand, or simply calipers and modeling clay available

shop carefully cam bearing tools sell for $40-$300 plus and almost identical tools car vary in price by over $120, and be awre all cam bearings in a single block may be different sizes based on the location, so pay attention as you remove them as to the oil feed hole location(S), how they are indexed or clocked and the outside diameter and be aware in many cases the bearing is beveled on one side to aid installation








FAILURE TO verify all clearances


a bit of research, and taking the effort of reading related threads will help, but you need a few precision measurment tools and a good understanding of what to look for and how to meassure accurately
if your looking for a local machine shop,
in the west palm beach fla area
be damn sure you get all the details in writing
dates prices, details on what needs to be done
delivery dates and take pictures
these guys generally do decent work

first choice (use them fairly often to rebuild heads)

Engine Rebuilders-Palm Beach,
1722 Donna Rd, West Palm Beach, FL 33409

second choice (mostly for block line hone & decking)

Keener's Engine Machine Inc
2517 N Military Trl, West Palm Beach, FL 33409

third choice
these guys get decent reviews but Ive only been there once)

170 Commerce Rd, Suite 1A
Boynton Beach Florida 33426


can get very expensive and time consuming, and aggravating


Some or most of those people don't have the smarts to do things properly or the money and time to invest in learning how. They just depend on others to straighten out what they had read would work. If you charged them for your knowledge and the time spent to correct their mistakes, most would just pay you to do the whole job and never complain or have trouble with their engines.
Last edited by a moderator:

Strictly Attitude

solid fixture here in the forum
Some or most of those people don't have the smarts to do things properly or the money and time to invest in learning how. They just depend on others to straighten out what they had read would work. If you charged them for your knowledge and the time spent to correct their mistakes, most would just pay you to do the whole job and never complain or have trouble with their engines.
My favorite are the ones that build a high maintenance engine and think they can just run it like a daily drive never check lash or develop a proper plan to keep up with maintenance or inspection of a vehicle. Usually the ones with the stories of crying when there budget roller cams fail in only a few thousand miles. Mismatching parts and such.


solid fixture here in the forum
I have always said knowledge is power. I save any and all things that give dimensions and specs for it, from cars to guns or what ever in files on my computer.
Last examples was to make receivers from sheet metal for an AK 47 and an AR15. Works great and looks pretty good with coating of Pour 15.
Also bought from Speedway a front brake kit for '40 Ford spindles [20 years ago] that had inner bearing adapters and it gave all the dimensions for them. Have never bought a complete kit again as I make most of it my self. All adapters are s/s and the first ones made to those specs and when I pressed it on, it split. Too hard to stretch as easy as carbon steel so I loosened the tolerances to the inside a bit and have worked flawlessly since.
Inventions are the mother of necessity and if more people would use their brains a little more, we would have a lot of problems in the world solved, especially with cars and guns.


The Grumpy Grease Monkey mechanical engineer.
Staff member
yes theres zero doubt having a MILL or or at least quality drill press, and ideally a lathe, and a decent quality MIG or TIG welder in the shop, is a great asset!

heres some info from napa


When rebuilding an engine, there is nothing more critical than getting the bearing clearance correct. Every engine has its own bearing clearance specs, but the measuring procedure does not change. There are two main methods used for checking bearing clearance – Plastigage® or gauges.

Plastigage® has its place, as it serves a purpose for backing up and verifying your bearing clearances. Plastigage® is a special plastic that expands a specific amount when squeezed. Sold in sleeves of threads for specific thickness ranges, Plastigage® works really well in situations where the components are not being completely removed, such as in-engine bearing replacement, and other non-automotive uses. Originally put on sale in 1948, Plastigage® is fairly accurate and the method of choice for many DIY enthusiasts.


Plastigage® is quite useful, so don’t automatically throw it out. It is a good way of verifying your measurements.

In reality, the right way to check bearing clearances is with the proper tools. In order to check the clearances for rod and main bearings, you need a set of micrometers and a dial-bore gauge. These are readily available at budget prices, but if you are going to use them a lot, better quality tools are advised.

This looks like a horseshoe with a round handle attached to one leg. Micrometers typically only adjust 1”, so you need multiple sizes to get the job done. A 1-6” set usually has the sizes you need for most jobs.


This a complete micrometer set that will cover just about anything you could need for automotive work.

Dial-Bore Gauge
This tool uses a dial indicator on a post with a small wheeled measuring apparatus. These are adjustable through graduated post extenders that increase the diameter of the measurement circle.


The dial bore gauge measures the inside of round holes, such as the bearing journals.


This one tool can measure 2″ up to 6″ diameter holes.

Both tools are needed in order to check the interior and exterior dimensions of the crankshaft, rods and engine block journals, as well as the thickness of the bearings themselves. Making all of this happen can be tricky, so here are a few tips to help you work through the process.

Using a micrometer means following a couple of rules. The key to a micrometer is not to tighten it too much. There are two knobs – a large knob and then a smaller one. The smaller knob clicks when the micrometer is in contract with the part. DO NOT use the larger knob to tighten the mic onto the part as this can damage the tool.

Reading a micrometer can be confusing, they are graduated differently than rulers. The inside barrel is marked in .100” (large) and .025” (small) notations. Once you reach those marks, the scale on the thimble (large rotating knob) comes into play to get the finite measurements. The thimble is scaled in .001 divisions from .000 up to .025”.


The hash marks are how you read micrometers. It takes some practice, and unless you use them daily, you will forget over time. Just be patient.

Outer Diameter Measurements
These are fairly simple, just choose the micrometer that covers the range needed and measure. It is a good idea to check the part in three different locations, staying away from the oiling holes as they can throw off the measurements due to the chamfers.

Measuring Bearings
Even though bearings are flat enough, they cannot be accurately measured with calipers, instead you need a micrometer. There are special micrometers available for measuring round inside surfaces, but you don’t have to have one of those. Instead, you can use the shaft of a drill bit (good quality, and use the smooth part, not the fluted section). Place the drill bit on the inside curve, and then measure the bearing. Subtract the thickness of the drill bit (measure, don’t assume), and you will have the thickness of the bearing.


An tube mic is useful for measuring bearings and over inside-curved pieces. In a pinch, you can use a drill bit or pushrod and an outside mic.


This is how bearings are measured. DO NOT use calipers, you can easily scratch the babbit material and ruin the bearing, plus they are just not accurate enough.

Using A Dial-Bore Gauge
Setting up a dial-bore gauge requires using a micrometer. You need the base measurement of the bore, rough is enough. Set the gauge to just over the diameter, using the correct extensions. Set the micrometer to the bore size you need, then place the gauge between inside the mic and rock the gauge back and forth, and side to side. Note the minimum reading, and zero the gauge to that reading.


Setting the dial bore gauge uses both the bore gauge and a micrometer. Make sure the measuring ends are square inside the micrometer’s anvils (not as shown)

Inside Diameter Measurements
With the dial-bore gauge set to the correct size, place the gauge inside the journal or rod end and rock the gauge back and forth and side to side, just like the setup process. Note the smallest diameter, that is the size of the journal. Just like the outside measurements, take the reading in three different places. One note – the bore must be as it would be in use, so torque the caps to their correct specs and they need to be clean, no oil at all.


Place the gauge inside the journal and move it slowly till you find the largest measurement. Take readings in three places.

they measure the piston deck height after the machined block has the rotating assembly test fitted

piston down in hole at TDC.jpg

no, if you have any engine and want too find the rure compression you need to deal in verified fact, not assume what the manufacturers suggest is always correct.
you just cc the heads, combustion chamber volume, place the piston 1" down the bore and seal the rings gap around the pistons,
above the rings with moly grease or Vaseline and measure that volume and calculate what a bore diameter cylinder 1" tall would
contain, minus the volume you,ve measured, the piston dome took up.then calculate the true compression.




read related linked info
Last edited: