SBC Cylinder Wall Thickness

[Indycars]

If you look at the Chevy block on page 2, this is remarkably close to my experience. I bored a
350 in² SBC .060", which is .030" on a side. My thinnest wall was .064" on cylinder #4.

If the Chevy block in the Hot Rod (Page 2) article was bored .060" over, it's thinnest cylinder
would be .062".

Wish I would have known these facts before I spent $200 on boring a block I'm not going to use
for a performance application.

 

[grumpyvette]

thanks thats a great post with very useful info, the one thing I will point out is that after talking with lots of machine shops and engine builders, the DART blocks tend to be rather consistent and well machined, thats not always true from what Ive heard about the world blocks, so don,t look at this one set of posted info and assume the world blocks are always thicker castings than the dart blocks.

Id bet 90% of the guys building a SBC based engine never give the basic block or foundation strength a second thought UNTIL they find out thru part failure that the basic OEM blocks are just not meant to be rigid and solid enough to allow you to build an engine that exceeds about 500hp without expecting it to eventually have major problems.
The reason so many people get away with using stock OEM blocks is BOTH that darn few SBC engines that people claim make 500 or more horse power actually do, and many that do are seldom run in the rpm range where they make that power level for more than a couple seconds, at a time. you really see the way the stock OEM block casting flexes in applications like stock car racing , where the stress is prolonged and the main caps tend to be subjected to more repeated and higher stress.
when you have a block magnetically or dye checked for cracks , and sonic tested for bore wall thickness, don,t forget to check lifter bores, and lifter gallery areas, and main cap webs etc. just because its not easy to access does not mean cracks can be ignored

watch this video, but remember , if you intend to partially fill a block to add cylinder wall rigidity, the block should be filled at least 48 hours prior to any machine work being done on the block, as the fill in the coolant passages will generally expands slightly as it sets and will change the bore dimensions slightly.
Id also point out that a DART after market blocks significantly thicker and stiffer and made from a stronger alloy than the OEM production block casting

TWO BOLT MAIN CAP BLOCK

4 bolt SBC block

Your Old 350 Block Sucks
Written by Mike Finnegan on August 19, 2012

VIEW ALL 29 PHOTOS

Vortec 880 stroker Block Breakage and Goals

Was about to order parts and found a couple of weird comments First this guy broke three 383 stroker blocks doing some dyno test Second on the summit site this comment about restricting the stroker 880 block to 500hp If this is all correct and the stroker 880 block is a weak setup as a 383...

garage.grumpysperformance.com

There’s a limit to what you can do with old-school GM passenger-car parts, and the breaking point is relatively low when it comes to the Gen I small-block Chevy cylinder block. Sure, you can bore the block to within an inch of its life and fill the water passages with concrete before stuffing a 4.00-inch stroker crank into it and make decent power for a while. The fun won’t last long, though, when the block cracks, leaks water, or flexes enough to pinch the main bearings or lose the head-gasket seal. To find the beef of the stock 350 and the aftermarket alternatives, we had Pfaff Engines sonic-test six different blocks with 350-style main journals (some are available with 400 main journals) and standard deck heights to see how far they could be bored and how thick the decks were. We also put them on the scale and called every manufacturer to find out how much work it is to drop a big arm into each one. The results were surprising, but we are savvy small-block Chevy shoppers now.

Dart Machinery SHP


Model PN 31161211
Block Composition SAE grade G3000 cast gray iron
Bore 4.120-inch (unfinished); 4.165-inch max
Maximum Stroke Clearance 3.750 out of the box using steel rods; 4.000 with some pan-rail clearancing and a small base-circle camshaft (0.900 diameter)
Deck Height 9.020 inch
Deck Thickness at Thinnest Point 0.430 inch
Maximum Recommended Horsepower 600
Weight 170 pounds
Price $1,578.57 from DartHeads.com

Chevrolet Performance

Model PN 101051237 late-model, one-piece rear main seal (adapter available for two-piece seal)
Block Composition Cast iron
Bore 4.040 inches (stock bore is 4.000 inch)
Maximum Stroke Clearance 3.750 inches with steel rods
Deck Height 9.020 inch
Deck Thickness at Thinnest Point 0.456 inch
Maximum Recommended Horsepower 360
Weight 157 pounds
Price $789.95 at SDPC.com

World Products Motown II

Model PN 084010 nodular iron main caps; PN 084110 billet steel main caps
Block Composition Cast iron
Bore 3.990-inch (unfinished); 4.200-inch max
Maximum Stroke Clearance 4.000 inches (pan rails are factory-notched for H-beam steel rods)
Deck Height 9.020 inch
Deck Thickness at Thinnest Point 0.338 inch
Maximum Recommended Horsepower World Products told us four-digit power, but not to quote them on it
Weight 225 pounds (deduct 9-10 pounds when boring to 4.125 inches)
Price $2,151.95 at SummitRacing.com (nodular iron main caps, splayed billet steel caps are optional)

Dart Machinery Iron Eagle

Model PN 31121212 (0.391-inch raised cam and 0.800-inch spread pan rail versus stock 350 Chevy
Block Composition Class 32B cast iron
Bore 4.120-inch (unfinished); 4.185-inch max
Maximum Stroke Clearance 3.875 inches out of the box using steel rods; 4.250 inches with pan rail and bottom of the cylinder clearancing
Deck Height 9.020 inch
Deck Thickness at Thinnest Point 0.488 inch
Maximum Recommended Horsepower Dart wouldn’t give us a number, but assume 1,000-plus
Weight 195 pounds
Price $3,026.46 at DartHeads.com (includes optional 2.125-inch BBC-size cam journal

OE ’69 Chevrolet

Model Casting number 3932388 standard two-bolt main
Block Composition Cast iron
Bore 4.000-inch (stock); 4.060-inch max
Maximum Stroke Clearance 3.800 inches with steel rods
Deck Height 9.020 inch
Deck Thickness at Thinnest Point 0.452 inch
Maximum Recommended Horsepower 360
Weight 171 pounds (includes cam bearings)
Price $200.00 (used standard-bore block)

Dart Machinery Little M Sportsman

Model PN 31131211 350 main journals; PN 31132211 400 main journals
Block Composition Class 32B cast iron
Bore 4.120-inch (unfinished); 4.165-inch max
Maximum Stroke Clearance 3.800 inches out of the box using steel rods; 4.000 inches with some pan-rail clearancing and a small base-circle camshaft (0.900-inch diameter
Deck Height 9.020 inch
Deck Thickness at Thinnest Point 0.488 inch
Maximum Recommended Horsepower Dart wouldn’t tell us, but we assume 1,000-plus
Weight 201 pounds
Price $2,314.45 at DartHeads.com (includes coated cam bearings, dowels, and freeze plugs)

The Science Behind the Sonic Checker

Sonic checkers, like NDT Systems’ CB110, determine the thickness of cylinder walls and decks by transmitting ultrasonic frequencies into metal, recording how long the signal takes to reflect back to the checker, and then converting that data into a measurement. It’s similar to the way a naval submarine’s sonar system operates to verify the range to a target, except that the frequency is much higher, 2-10 MHz, or two to ten million cycles per second in this instance.

The transmitter’s probe sends a short pulse into the metal using a coupling material such as water or oil, and then the checker records the total transit time through the test metal. This is called the sound velocity, which is what is converted into thickness readings used to determine if the cylinder walls or deck of our engine block are thick enough for the foundation of a reliable racing engine.

According to NDT Systems’ Greg Smith, designer of the CB110, the sound velocity is different for various types of metal. The pulse travels relatively slowly through cast iron, while it reflects more quickly through steel, and even faster in aluminum. Checking alloys complicates the readings to a degree because the metallurgy of a block fluctuates from one area to another enough to change the speed of the pulse by as much as 18 percent, ultimately affecting the thickness measurement by up to 0.055 inch. Using a test piece of material similar to the block you’re testing gives a reference for a “good” reading versus an incorrect one.

Did you know?
15 years ago, General Motors shipped the original tooling for the small-block Chevy from its Flint, Michigan, plant to the Toluca, Mexico, facility, where crate engine block production continues.

When to Buy a New Block?
At what point do you sell your stock block and invest in an aftermarket one? Engine design will dictate an upgrade if you plan to increase the stroke of the crankshaft beyond 3.800 inches or bore it more than 0.060 inch. Look closely at the sonic check results and you’ll see how thin the cylinder walls of a stock block are when you bore them to 4.125 inch. Cooling the engine also becomes an issue with an overly large bore. GM rates the original small-block cylinder case at no more than 360 hp, but we’ve seen them stay together at 600 hp or more by stabilizing the bores with a block fill (www.HardBlok.com is a well known supplier) up to the water jackets. Beyond that, we recommend stepping up to an aftermarket block. If you’re starting from scratch, consider the cost of sonic-checking, pressure-testing, and machining an old block before you ignore the option of spending more bucks on a new one. Here’s a rundown of what it costs to have Pfaff Engines chuck a block up in its five-axis machining center and boring machine:

• 
  
  
  • Bore and finish hone cylinders: $194.00
  • Machine deck surface: $169.00
  • Align hone main bearing journals: $206.00
  • Sonic check bores and deck surface: $40.00
  • Pressure test cooling system: $115.00

Say What?

Baffled by the terms in this article? Here’s the lowdown on the more confusing ones.

Blind Tapped: This refers to boltholes that are drilled and tapped into the block without protruding into an open space, like the water jacket. Non-blind tapped holes require thread sealent on the bolts or studs and are prone to leaking water.

Siamese Bores: Early GM blocks have water passages between each cylinder bore. Late-model and aftermarket blocks have what are called Siamese or conjoined bores, which means there is no coolant passage between them. The metal-to-metal contact of each cylinder wall makes them more stable and prone to staying round under intense cylinder pressure that forced induction provides.

Splayed Bolts: GM passenger car blocks have main caps with bolts threaded straight down into the main webs. GM Bowtie racing blocks and most aftermarket blocks have splayed outer bolts in Nos. 2, 3 and 4 main caps. These bolts thread into the side of the block at an angle, usually around 10 degrees or greater. The side of the block has more material thickness than the bottom of the web, making it a stronger foundation for the bolts to grip.

Priority-Main Oiling: A factory 350 block’s oiling system sends oil from the pump to the filter, then to the lifters and then to the cam bearings. The main and rod bearings are the last to receive oil, which isn’t a good thing at high rpm or when you first start the engine. Priority main oiling reverses the path the oil takes, giving the main bearings the liquid of life first.

READ THRU THESE LINKS



http://garage.grumpysperformance.co...bearing-studs-torque-stretch.9409/#post-34238

http://garage.grumpysperformance.co...4-bolts-or-stds-good-enough.10632/#post-45801

http://garage.grumpysperformance.com/index.php?threads/installing-splayed-caps.7267/#post-24723

http://garage.grumpysperformance.com/index.php?threads/splayed-main-caps.1014/#post-16462

http://garage.grumpysperformance.co...eventing-leaky-head-bolts-studs.50/#post-1253

http://garage.grumpysperformance.co...block-cylinder-wall-thickness.976/#post-22976

http://garage.grumpysperformance.co...gine-block-main-cap-movement.6162/#post-19172

http://garage.grumpysperformance.com/index.php?threads/main-cap-fit-in-block.5945/#post-18302

http://garage.grumpysperformance.co...-help-with-main-bolt-question.2851/#post-7377

 

[busterrm]

Okay, Tommy went and did what I told him not to, bought a block. Its a Chevy Bowtie, but I think we lucked out, from the casting number H-D 10051184, it looks like a Bowtie Sportsman with 350 mains. I found this online :


12480047 Block, Bow-Tie Sportsman "350 Main Size"
This iron block is fully CNC machined from the H-D 10051184 casting. It has siamesed cylinder walls, cast nodular caps, four bolts on all five main caps; the outer bolts on the three center main caps are splayed 20 degrees. Grade 8 bolts secure the caps. It features priority main oiling and 9.025" deck height. The blocks come finished bored at 3.980" and the maximum recommended bore is 4.150". This block features a two-piece rear main seal; "350" main size (2.45"). It features lifter bore heights (.842"), same as P/N 24502503

I did look and it does have the four bolts on all the main caps, but I do have one question. With the bores being siamesed I will need to have the 400 steam ports drilled in the heads won't I?
With this block being saimesed, what is a acceptable wall thickness Grumpy?

 

[grumpyvette]

when any blocks cast and then machined its almost unheard of for all the cylinder bore walls to be both equal or have the bore center line centered in each cylinder sleeve. the result is that its typical for the cylinder wall to vary in thickness from side to side and from top to bottom, having a cylinder wall in a stock production block casting thats .230 thick at one point but taper to .110 is hardly rare, so you need to have the blocks cylinder walls sonic tested. thin sections near the lower end of the cylinder are a bit less critical because theres a bit less heat generated there and a block can have the coolant passages filled with either epoxy and steel shot slurry or concrete to add support to the lower cylinder wall without compromising a great deal of the engines ability to transfer heat to the coolant as about 80% OF THE HEATS GENERATED IN THE CYLINDER HEADS AND UPPER 2" OF THE CYLINDER BORE.
the DART blocks are designed with much thicker castings and use a stronger alloy of cast iron, both add considerable strength
I was recently asked what block casting numbers a guy should look for,
to insure that the block he was going to base his engine on was more likely to have the thicker casting,
and cylinder wall depth that would safely allow a .030-or even a .060 over bore?
well youll ideally want a pre-1970 block for either the SBC or BBC engine.
keep in mind that block is now almost 50 years old you have no idea how in was stored or treated previously,
or how much internal coolant passage rust damage is hidden in the block's internal passages after all that time.
pre-1970 block casting technology tended to use MARGINALLY thicker casting's,
that the post 1970 blocks with their slightly improved casting tech.
but core shift was more likely so its a bit off in its bore wall consistency,
a no-win situation, you could have thicker castings, that were slightly off-set ,
making it just as weak as a later thinner casting.
the truth here is if your intention is to bore any stock block over .030,
you should first sonic test the bore wall thickness and consistency.
that being stated, a DART or similar aftermarket WORLD PRODUCTS block,
will have a significantly thicker casting with a stronger alloy.
if your going to throw $70-$1000 plus in precision machine work into a performance engine,
your much safer financially in the long term doing that on the much stronger aftermarket or bowtie block.

http://garage.grumpysperformance.com/index.php?threads/casting-numbers-vin.93/#post-29983

http://garage.grumpysperformance.com/index.php?threads/block-choice.10472/

http://garage.grumpysperformance.com/index.php?threads/blueprinting-a-block.49/

http://garage.grumpysperformance.com/index.php?threads/sbc-cylinder-wall-thickness.7646/

http://garage.grumpysperformance.com/index.php?threads/which-dart-shp-4-0-or-4-125.3219/

http://garage.grumpysperformance.com/index.php?threads/block-choice.10472/

http://garage.grumpysperformance.com/index.php?threads/darts-new-sbc-block.47/

http://garage.grumpysperformance.com/index.php?threads/why-build-a-bbc-vs-a-sbc.1009/

read these related threads

viewtopic.php?f=51&t=976

http://www.jegs.com/i/Dart/301/31132211/10002/-1

viewtopic.php?f=51&t=588&p=869&hilit=filled+epoxy#p869

viewtopic.php?f=51&t=11033&p=48899#p48899

Sonic Checking Your Block

Author Andy Finkbeiner Photos Ron Valera

Modern technology is great for us hot rodders. A few years ago, you practically needed a top security clearance before you could get your hands on technology like this. Now you can whip out the VISA card and order yourself a sonic checker like the one shown above.

Sonic checking is a fairly common term in the engine building business but many people might not fully understand just what it is all about. When the engine builder asks if you want to spend another $75 to have the block sonic checked, some people might think he is just trying to get more money from you. Actually, the engine builder is probably trying to save you from wasting a lot of money on a block that might not be any good. After all, most of the engine blocks in our musclecars are at least 30 years old now and have been through a lot.

Sonic checking is a method for measuring material thickness when you only have access to one side of the part. For instance, if you want to know how thick a cylinder wall in an engine will be, you would have to cut a hole in the wall in order to use a pair of calipers. The sonic checker is able to measure the thickness by sending out a sound wave and then measuring the time that it takes for the sound wave to get to the other side of the wall. Modern electronics allow this complicated task to be accomplished in a hand held device.

How thick the cylinder walls need to be is a fairly difficult question to answer but we do have some clues. Most production V8 blocks have cylinder wall thicknesses that range from 0.090 to .250 thick. Ford motors tend to be the thinnest while some Chevy blocks are the thickest. The thickness of the cylinder wall becomes more important as you start to make more horsepower, so a block that works in a passenger car application might not be suited for Winston Cup duty. If you can find a production block that is at least 0.200 thick on all cylinder wall thrust surfaces you’ve found a good one. Walls that thick should be good for at least 500 or 600 horsepower. If you’re going to be making more power than that then it is probably best to step up to a factory race block. Typically the race blocks are designed to maintain a 0.250 thick cylinder wall at the maximum overbore. They might start out with a wall thickness close to 0.400 as delivered.

Here is the sonic checker from Dakota Ultrasonics. This unit sells for $990 and is designed to be used for various automotive tasks. It can measure thicknesses from 0.025 to 20 inches in a variety of materials but is especially good at measuring cast materials.

Here is where you really need a sonic checker! Nine engine blocks to choose from but which one is the best? A sonic checker allows you to examine each block for core shift and casting flaws. Obviously, what you want to do is to pick the block with the least amount of core shift. Minimum core shift will be indicated by having fairly consistent thickness measurements for each cylinder.



Contact Information:

Dakota Ultrasonics

1650B Mansfield Street

Santa Cruz, CA 95062

(831) 465-8585

http://www.dakotainst.com/

 

[mathd]

people here try to avoid block filling(but well opinion are shared, some avoid it for street app and some fill every of they street block, talking about OE block obviously), if it has to be done they use a product called hard block, i think they are filling half the block or up to the freeze plugs on a chevy.
Some people report lower coolant temp with filled block but oil temp 20-40° higher then before. Its best to have a more oil capacity/deeper oil pan and usually an oil cooler.

now what are siamesed cylinder? is this the same as sleeved cylinder?(wich is best to avoid on a sbc because of some cracking around the head bolt hole problem)

 

[grumpyvette]

....
now what are Siamese cylinder? is this the same as sleeved cylinder?(wich is best to avoid on a sbc because of some cracking around the head bolt hole problem)

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Siamese cylinder block is simply a block cast so theres no coolant passage BETWEEN the cylinder bores, they effectively share a cylinder wall at the point the two cylinder walls are tangent or next to each other, on the standard block casting the TOP of the cylinder walls are attached into the upper deck and BOTTOM of each cylinder into the main cap webbing in the casting allowing coolant to flow around the outer bore walls , on a Siamese block the 4 cylinder bores are attached to the cylinders nearest them, end cylinders have about 330 decrees of free open surface the coolant reaches and about 30 degrees cast in common with the adjacent cylinder, the two center cylinders have two common cast points with adjacent cylinders at 180 degrees or on opposite sides so coolant cant pass between the cylinder walls

with the upper deck of the block the cylinder head bolts to machined off a siamese block would look similar to this

viewtopic.php?f=51&t=1516&p=3467#p3467

with the upper deck of the block the cylinder head bolts to machined off a STANDARD NON-siamese block would look similar to this

 

[busterrm]

people here try to avoid block filling(but well opinion are shared, some avoid it for street app and some fill every of they street block, talking about OE block obviously), if it has to be done they use a product called hard block, i think they are filling half the block or up to the freeze plugs on a chevy.
Some people report lower coolant temp with filled block but oil temp 20-40° higher then before. Its best to have a more oil capacity/deeper oil pan and usually an oil cooler.

now what are siamesed cylinder? is this the same as sleeved cylinder?(wich is best to avoid on a sbc because of some cracking around the head bolt hole problem)

Siamesed cylinders are when two cylinders next to each other share the casting material between them. This means there is no water passage between the cylinders, this was done on some of the SBC 400 due to the large bore. In a siamesed block 1 & 3, 3 & 5, 5 & 7, 2 & 4, 4 & 6, 6 & 8 all share at least one side with the adjacent cylinder; 3,4,5 and 6 are siamesed on both sides. My machinist told me those cylinders are the reason for the steam holes, otherwise you would have ten steam holes on each bank instead of 6.

 

[mathd]

ah, thanks for the explanation, its much more clear to me now.