The Mechanics of Adv/Ret a Camshaft ?


Staff member
Without getting into the $150 and up range for timing gears and chain. There seems to be only two ways to adjust the timing for under $75, the crank gear can have several keyways or you can drill the cam gear and use bushings.

Pulling the crank gear would be alot more of a pain to change, than 3 bolts on the cam gear. The bushing in the cam gear would be alot easier!

Both ways only provide increments of 2 degrees, this seem kinda coarse for adjusting the cam timing. Does someone provide a system for adjusting timing every 1 degree without spending $150 ???


Staff member
they only provide 2 degree increments simply because anything smaller will seldom make a noticeable change in how the engine power curve is effected,
for every 2 degrees change advancing a cam you generally move the whole torque curve about 75-100rpm lower,
for every 2 degrees change retarding a cam you generally move the whole torque curve about 75-100rpm higher,
on average Ive found advancing or retarding a cam a full 4 degrees moves the whole torque curve about 150rpm on most of the engines I build.


now horsepower , is calculated as torque times rpm, divided by 5252
so lets say an engine makes 400 ft lbs of torque at 3800rpm and 370 ft lbs at 5500rpm
thats 387 hp
retard the cam 4 degrees
you potentially could get 398 hp or a gain of 11 hp but you also tend to loose about the same on the lower end of the power band, and because the lower end is almost always used far more than peak power its rarely a huge benefit, that's one reason why most cam manufacturers tend to have cams degree in 4 degrees advance on a dot-to-dot install.
keep in mind port cross sectional area restricts flow rats as rpms increase, so your frequently not going to get the full potential benefits

installing the cam strait up or even 2-3 degrees retarded ,
(what Id do, but of course you have a myriad of options)
might make more sense as it will move the whole power curve up about 150-200 rpm,
and significantly reduce any tendency toward detonation
why not try it both ways and see what you prefer:like:

as its only going to take you a hour or two to change, to either advance or retarded or strait up,index
related threads

degree it in correctly and get it to last,cam install info,

IM frequently asked (why bother degreeing in a cam, the timing set comes with index marks to install it?) it basically comes down to, a question of do you accept a random install where the timing can be almost any place randomly or do you insist on maximizing the engines potential and know...

degreeing cam and shifting the lca

I finally got to degree my cam tonight. First cam I've ever done on a build. How far off the cam card timing numbers before most builders would correct with adv/ret? My cam timing numbers were withing 1 to 1.5 degrees and my intake and exhaust C.L. were withing 1/2 a degree...

the IDEAL cam LCA ... teria.aspx ... index.html viewtopic.php?f=52&t=2782&p=7214#p7214 viewtopic.php?f=52&t=112&p=139#p139 viewtopic.php?f=52&t=324 in case you don,t understand the chart, you take the engine displacement PER...

degree in that cam correctly

now if your like most guys if youve never done it your thinking it a huge complicated deal, ITS NOT,just follow the instructions in the links, Id advise you read them all because some are more clear on some parts of the process than others and youll get a better over/all feel for the process...

gear drives for cams

IVE used both CLOYES roller chain drives and SEVERAL DIFFERENT GEAR DRIVES FOR CAMS IN MY CORVETTES 383,SBC ENGINE,s the CLOYES chain drive is probably the best value, Ive run both setups on lots of motors,I'm running a...

chain vs gear drive cam

Gear drive VS chain cam drives, ... es/117.pdf viewtopic.php?f=52&t=5734&p=17492#p17492 ... -20325.pdf ... 0-7892.pdf read... sells this KIT
Comp Cams #249-4796 Cams/249/4796/10002/-1

and you can buy these

MOR-62191 $44 (wheel)

MOR-61755 $47 (SBC)
MOR-61756 $47.(BBC)crank sockets

SUM-900188 $17 (piston stop, head off)
SUM-900189 $6.95(piston stop, head on)

TFS-90000 $94.95 (degree kit)

youll also want two flat tappet solid lifters and two weak check springs



you could buy these from summit racing or similar parts from jegs


BTW you CAN advance or retard the roller timing chain, as you mentioned, its done bye drilling out the cam index pin hole in the timing gear and installing an off set bushing ... toview=sku



don,t make your self crazy, install the cam at split overlap as best as you can determine, verify all clearances and valve train geometry and see how it runs before getting insane on 1-2 degree changes that will have little or no real effect on performance in most cases




related threads with valid info
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Staff member
I would have thought with all the talk about degreeing your cam, it would be important to get closer than 2 degrees. I guess in actuallity the worst you could be off is 1 degree. If you are 2 degrees off, then the bushing would put you right on. If it's 1 degree off, then that's when you have the hardest decision to make.

If using the bushing, do you drill all the way thru, or do you leave a shoulder to retain the busing in the cam gear ???

I assume they work just fine with the later cams that use a thrust plate....right ???


Staff member
Ive always drilled all the way thru, just remember the nylon cam button and bolt retaining plate on all the early engines that came with flat tappet cams,,if your using a more recent roller cam block engine with a cam retainer plate obviously the cam buttons not required, but the bolt retaining plate is still used to secure the bushing and screws.

some cam timing covers are much better quality

if your converting too a roller cam from a flat tappet design don,t forget the cam button, or cam retainer plate is mandatory on a roller cam

You Identify them by measuring the retainer plate hole spacing

(#10088128) GM roller cam thrust plate, used on all roller cam engines.
First design with 3.620" bolt pattern.
1991-2000 engines use # 10168501 with 3.294" bolt pattern.Please measure your center to center mounting bolt pattern if unsure.


this button is improperly installed as its missing the lock plate, that holds in both the cam button and bushing on the cam index pin



look closely theres three crank key slots and each is marked, with the crank key (R or rectangle) =(retarded 4 degrees) (0) strait up) and (A or triangle) =(advanced 4 degrees) located at approximately the 2 0,clock position the related mark(R or rectangle)= (retarded 4 degrees) (0) strait up) and (A or triangle) advanced 4 degrees) is at the 12 o,clock location that you use to line up with the cam gear while thats indexed at approximately the 6 o,clock location

BTW theres also 2 degree off-set crank keys


your degreeing in the cam to verify its within that 1-2 degrees of where its intended to be,as there are plenty of guys who make installation mistakes and a few manufactures that feel "CLOSE is GOOD ENOUGH!"
you might be amazed at how often the DOT-TO-DOT install location is NOT within a few degrees of where you would ASSUME it should be!
ASSUMING things are correct rarely gets the best results, its true it takes a good deal of extra effort to verify everything but at least you know its done correctly,thats a huge advantage over the thousands of guys who slap components together out of the box without verifying and then remain clueless when parts start self destructing because they never checked clearances or geometry etc

yes there is a good reason to avoid those cheap import timing chain sets that auto parts stores frequently sell for under $30.........heres one with less than an hours of run time

related threads
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Staff member
When you are using a thrust plate like below, will the bushings still work ???
Have you noticed any negatives when using the bushings ???


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Staff member
Indycars said:
When you are using a thrust plate like below, will the bushings still work ???
Have you noticed any negatives when using the bushings ???

yes they still work and no Ive never seen or even heard of a problem using them,
yes you may need to also drill the cam timing gear retaining bolt holes in the cam gear a bit larger in a few cases, but with a 2 degree change thats rare
(obviously I use loc-tite on the cam bolt threads and a cam bolt retainer plate)



this cam buttons correctly installed but the bolt retainer plate tabs have not been bent up to lock the bolt heads from rotating
why not call the tech dept at all five cam manufacturers linked below, and get their input,
(without discussing or letting anyone at those individual tech departments,know you talked to other sources

.what any other cam manufacturer might have said in any way)
write down the cam specs they suggest, lift duration and lsa,
If your ever in doubt, about the correct timing chain application,

cloyes tech dept 1-479-646-1662 EXT 228

then average the results and
select the cam thats the closest match, to that average , of the 5 cams that were suggested.

crane (386)310-4875

crower 619.661.6477

erson 800-641-7920


ISKY 323.770.0930

what your basically trying to do is to maximize operational compression,
over the useful rpm range
(this maximizes the torque curve efficiency,)
but, while keeping that cylinder pressure under the detonation threshold

related info

heres a bit of potentially useful info GOFAST POSTED

SBC Stepped Nose Cam in Early Block?
Just curious if anyone has devised a way to use the later SBC "stepped-nosed" cams in the early SBC's?

We are trying to eliminate the required use of any cam-buttons in the 100% stock-appearing builds on the roller platform?

Thanks, Gary in N.Y.

P.S. Open to any suggestions/recommendations. Have my own idea but like to hear some add'l possibilities/thoughts.
I brought this back because it turned out to be a fairly simple resolution. Wasn't sure it could be done without extensive machining, solved it easily.

I'll put a couple shots below showing the basic's of the "fix". Takes about 30/40 minutes or so for the entire machining and can be done on a simple (decent) drill press capable of holding the block on the table.

Originally Posted by novaderrik View Post
just use a roller cam block... the only real striking visual difference between them and an old small block once it's in the car is the size of the pad by the water pump where the id codes are stamped.
Hi nova, we do a bunch of 100% stock-appearing builds where ANY replacement block is NOT an option. Now we can set up the roller cams (mostly retro-hydraulics) with the late thrust plate. No more "playing-around" with cam buttons/end play. Much easier for us here.

Thanks, Gary in N.Y.

P.S. Anyone with any machining experience can accomplish this mod easily. With the way we designed the tool in the photo we can pick the 2 best spots on the original thrust surface to locate the 2 allen-head screws, an area that has some extra "meat" for the screw-threads.


don't need those ears on the sides anymore?

small taps in cast iron, any troubles there?
Hi Tom, correct on the "ears", they aren't needed with this method. Later today I'll put another shot here with the plate finished, "ears" removed!

No problem drilling/tapping for the fasteners, entire procedure went smoothly after devising the jig to set all the holes in place. The jig is used to locate/drill the new holes in the plate also, in the first photo you can see the "register" that holds the plate in place to back-drill these holes.

Like I stated above, was fairly easy when I finally got a handle on exactly how I was going to get it to come together.

The only potential issue on some blocks is the uniformity of the original cam-thrust surface face, many favor one side more that the other. In other words (looking at the block from the front) some castings are wider on one side making the other side narrower, we can position the 2 bolts anywhere on the surface. They don't need to be "clocked" so to speak!

(Add) This a huge breakthrough for us when doing the 100% stock-appearing builds on any roller platform. In the larger picture the cost is also less, no cam button/locking plate, just the cost of the OEM plate. Cost/labor of installing the plate is about a "wash" with the time spent on setting up the end-play with the button. We can layout the plate at the same time we drill/tap for the front (3) oil galley plugs, which are also done while on the drill press

(Add) Below is a shot of the finished plate installed.

Thanks, Gary in N.Y.

P.S. On a side note, we didn't find it necessary to drill (deep enough) into the oil groove behind the cam brg but it would not have made any difference when the bolts are installed. Also, I could put 2 more fasteners in the plate if I felt it necessary. Would take about an extra 10 minutes simply by "turning" the jig 90* and drilling the 2 add'l holes.


P.S. I've already "kicked" this around with a couple local builders just for opinion's sake, all are in agreement, looks like all will be fine! I most definitely would NOT attempt this procedure by "hand", you'll most likely ruin the casting. It takes a decent lathe, the Bridgeport, and a decent rotating table to make the tooling! Also necessary is a 10-24 "bottom" tap to get every last thread possible.
ast shot, "late" cam installed, .003" (nominal) end-play.

Worked like a charm, really.

Thanks, Gary in N.Y.

P.S. Mike (Wolfplace) thanks for the support. I'll say it once more, for us here we consider this a major accomplishment. I still need to dyno test a build or two but don't anticipate any adverse effects!


notice the early first gen block does not have the cam bearing boss cast and threaded screw holes for mounting the cam retention plate


old school
read THESE links
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Staff member
I came across these CROWER bushings this morning while looking for a cam timing set. Looks like what I was thinking I needed, every one degree is possible with these. Along with a crank gear that has extra keyways, I should be able to get damn close.


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Staff member
thanks for posting that I thought those were discontinued years ago.

valve springs must be installed at a specific semi compressed and listed installed height,
to provide the listed load rates and clearances,


the cam you select will generally come with a suggested listed valve spring load rate and installed height,
and the loads are listed)

you must maintain minimum coil bind and retainer to valve seal clearance and proper push-rod and rocker geometry
the distance between the lower edge of the valve spring retainer and the cylinder head is adjustable to achieve the desired valve spring height through the use of valve spring seat cups and shims placed under the valve spring which can be purchased to lock into a stock height, or plus or minus about .050, and valve locks that cam move the retainer (stock or aftermarket) an additional .050 either tighter or longer allowing the valve spring to expand taller, shims can be placed under the valve seat hardened cups that are almost always mandatory on aluminum head but may be optional on iron heads,(O.E.M. cast iron and lower valve spring load rates)













max lift is installed height minus .060 minus coil bind

related info you really need to read

do yourself a HUGE favor :like:
read ALL these links and sub links carefully
yeah it may take you a week, or more ,
but its sure to significantly reduce your chance of screwing something up,
or wasting a good deal of cash, or damaging your engine.
yes you can generally swap to the 1.6:1 ratio vs the factory 1.5:1 rockers,
if you just go with the roller tip versions like these do little and don't reduce friction/ losses much.


its probably not going to gain you much,
going to full roller rockers is generally a 15-20 hp gain


but be aware,
the resulting changes in rocker geometry and clearances may cause significant issues

I learned long ago to wait and buy what I really want rather that settle for what I can more easily afford.

yeah! Im aware your very likely to ignore the advice..
most readers will...
. but its a reference, I'm posting here, to help later
you , or anyone else doing similar
if YOU DO need to find out what went wrong ,
because there's frequently little things you fail to think through as a new engine builder.
and why its costing you considerable problems, if you don't read through the links
and yes I learned many the hard/expensive way, before I learned to do research
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The Grumpy Grease Monkey mechanical engineer.
Staff member

I’ve read something about camshafts that some cam companies grind advance into the camshaft. I thought that you could only advance the cam once it was installed in the engine? How does the cam company grind advance into the cam?


Jeff Smith: This is a great question. Everyone tends to look at the intake and exhaust lobes as separate movements within the engine’s operation, but what we really need to do is look at the entire function of the camshaft and how all the different events coincide. It is true that many camshafts are designed with advance built into them. The majority of these cams are intended for street use. Here’s how it all comes together.

The cam companies know that when it comes to choosing a camshaft, many enthusiasts tend to suffer from the “More is Better” theory of engine performance. The common approach is that if some additional lift and duration is good, then more is better. So instead of choosing a typical 220 degrees at 0.050-inch tappet lift cam for a mild street engine, many enthusiasts – especially first-time buyers – will upgrade their selection and go with maybe a 236 or 242 degrees at 0.050 cam instead because a buddy told them that’s what they needed.

The unfortunate result is that these longer duration camshafts tend to reduce low-speed torque in favor of top-end power. The camshaft companies know this. One way to improve the low-speed torque on a camshaft with too much duration is to advance the intake lobe in relation to the exhaust. Advancing just the intake lobe opens and closes the intake valve sooner which is one way to help improve the low-speed torque.

We’ve included a Comp Cams illustration of the intake and exhaust lobe lift and duration curves on a simple diagram that makes all this a little easier to understand. If all the cam company did was advance the intake lobe position on the cam, this would also decrease the lobe separation angle and increase the number of degrees of overlap.

You can learn quite a bit just by studying this Comp Cams illustration of cam timing. Advancing either lobe would move it to the left while retarding would move either lobe to the right on this diagram. So you can see how advancing just the intake lobe (the one on the right) would change the intake centerline but also increase overlap.
Overlap is the amount of time, in degrees, when both the exhaust and intake valves are open. You can see this represented by the small triangle shaped area in the center bottom of the two curves. Overlap was called the “Fifth Cycle” by Ed Iskenderian back in the 1960’s when engine builders were first discovering how much mid-range power can be improved by adding overlap. The downside to increasing overlap is that it tends to hurt idle vacuum. This is also what creates the classic lumpy, uneven idle that everybody wants so their engine sounds like a killer Pro Stock drag race powerplant.

Bu too much overlap can really hurt the off-idle performance so the cam companies typically advance the intake lobe and retard the exhaust lobe to maintain a decent lobe separation angle. For example, almost all Comp street cams use a 110-degree lobe separation angle.

There is a very easy way to tell if the camshaft has been advanced by the cam company when the cam was machined. Look at the cam timing card and compare the lobe separation angle (LSA) with the intake centerline number. If the numbers are the same, then the camshaft has not been advanced.

Let’s look at an example. This first example is a Comp cam we currently have in a 496 big block Chevy we built. It’s a mechanical roller with 261 degrees duration at 0.050-inch tappet lift on the intake and 270 degrees on the exhaust with 0.734-/0.737-inch valve lift (PN 11-851-9). The intake centerline is listed on the cam card at 108 degrees and the LSA is also 108 degrees. In this case, the cam has been ground with no advance as the numbers are the same.

Now let’s evaluate a much milder Comp hydraulic roller camshaftfor an LS engine. This is PN 54-456-11 with 219 and 227 degrees of duration at 0.050-inch tappet lift with 0.607-/0.614-inch lift. When we look at the cam card, the intake centerline is listed at 107 degrees while the LSA is listed at 112 degrees. The numbers tell us the intake centerline has been advanced five degrees from 112 to 107 degrees after top dead center (ATDC).

As a simple exercise to put all this in perspective, there is an easy way to mathematically determine the lobe separation angle. This does not necessarily require measuring the camshaft’s intake and exhaust centerlines. But for right now, let’s say we have the numbers with the exhaust centerline at 112 degrees BTDC and the intake at 112 degrees ATDC. Simply add the two numbers together and divide by 2. The equation would be:

112 + 112 = 224 /2 = 112 degrees LSA.

In the case of the LS cam, we know the intake centerline is 107 degrees ATDC and the LSA is 112, so if the exhaust was the same number of degrees from TDC, that would put it at 107, but adding 107 + 107 = 214/2 = 107 and the cam cards indicates that the LSA is 112 degrees. That means that the exhaust centerline has advanced 10 degrees because the difference between the LSA and the intake centerline is 5 degrees. Placing the exhaust lobe centerline at 117 degrees puts the numbers in place:

117 + 107= 224 /2 = 112-degree LSA.

Now because we have so many Dual Over Head Camshaft (DOHC) engines in production today, let’s just take a second and discuss what the OE’s are doing for 21st century engines. Since a DOHC engine uses a separate intake and exhaust camshaft, this allows engineers to move the intake and exhaust lobes separately. So now with hydraulic adjusters, the ECU can move either cam separately to advance or retard the intake or exhaust. So for low=-speed driving, they advance the intake and retard the exhaust to maintain a sewing machine idle.

Then, somewhere in the midrange when the engine would really respond to lots of overlap, they begin to retard the exhaust to create more overlap. In reality, most of the DOHC engines only move the exhaust lobe for emission reasons. As an example, Fords Variable Cam Timing (VCT) engines only change one lobe while the Ti-VCT (Twin Independent Variable Cam Timing) moves both cams.

This is probably more than you wanted to know about camshaft positioning, but this might come in useful at some point. If nothing else, you can use it to dazzle your friends with you incredibly acute knowledge of camshafts and how they work. Or maybe not…
use of a camshaft install handle generally reduces the chances of damaged cam bearings


Here’s a breakdown of the advantages of advancing or retarding your cam timing:
a standard chevy sbc cam will not rotate randomly and freely and clear the connecting rods,
in a 383 engine, if its not properly timed with a timing chain in place to force the cam being indexed correctly, so cam lobes, are indexed to avoid hitting the connecting rod bolt shoulder area,
,you need to correctly degree the cam in...BUT EVEN THEN,
.in some cases a small base circle cam must be used to clear some connecting rods in a 383.with its 3.75" stroke, remember the original 265/283 SBC has a 3" stroke






read ALL the linked info carefully and then ask questions

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Advance Cam Timing

  • Begins Intake Event Sooner
  • Opens Intake Valve Sooner
  • Builds More Low-End Torque
  • Decreases Piston-to-Valve Clearance
  • Increases Piston-Exhaust Valve Clearance
Retard Cam Timing

  • Delays Intake Closing Event
  • Keeps Intake Valve Open Later
  • Builds More High–RPM Power
  • Increases Piston-to-Valve Clearance
  • Decreases Piston-Exhaust Valve Clearance
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"One test is worth a thousand expert opinions."
I had to use a bushing on my 334 SBC. In addition to the retainer plate, I used a drop of
Loctite Sleeve Retainer on the bushing for extra insurance. Should I have to disassemble
the timing set for any reason, the bushing will not fall out. Also I would not have to figure
out which way it was installed if that were to happen.

Like you said Rick, the bushing are the easiest to use.