SpeedTalk Store - Opinion Columns

Cylinder Wall Thickness vs HP Limits

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Cylinder Wall Thickness vs HP Limits

Postby 11secAvanti » Tue Mar 29, 2005 8:41 pm

Is there any guide for recommended cylinder wall thickness to HP? I was at the track recently and asked a few sbc racers what thickness their cylinders walls were and what the average 350 sbc had from the factory before overbore. To my amazement no one knew. Yet they knew if it had 2 or 4 bolt mains, etc. I would think this would be "need to know" information especially for cooling down the motor after each run. Is their a chart? If you plan for 400 flywheel horsepower do you say I want X amount of wall thickness and if so how much?
11secAvanti
Member
Member
 
Posts: 198
Joined: Tue Mar 22, 2005 8:51 pm
Location: Virginia

Postby CNC BLOCKS » Tue Mar 29, 2005 9:10 pm

On the Blocks sell and use we Shoot for 170 plus at .040 over on the skirt sides and on the wrist pin side we shoot for .080 at 040 over and so far no problems.

In one of Grumpy Jenkins books I believe he said as lomn as you had .160 on the thrust side you were safe.
Website is up and running
http://hinksonautomotive-cncblocks.com/
Machine shop tour
http://hinksonautomotive-cncblocks.com/shop-tour/
Monthly Specials
http://hinksonautomotive-cncblocks.com/specials/
Soon 55MM babbit cam bearings with 1 hole
CNC BLOCKS
Guru
Guru
 
Posts: 4555
Joined: Thu Jul 01, 2004 5:34 am
Location: NORTHEAST

Postby bill jones » Tue Mar 29, 2005 11:20 pm

-back in the old days when we all had to run the 327's it was very common to have the front and rear of the walls well under .100" and I've seen some as thin as the low .060"s and the thrust walls at about .100".
-These engines made some pretty serious power for their time.
-I would say that .200" is a luxury on a Studebaker.
-How are you measuring the wall thickness other than looking at the broken section of the frozen block?
-Do the head bolt holes go into the water jackets or are they sealed off?
-If they are open you can make a gauging system to reach down thru the bolt holes with something like a ball tipped pushrod and another ball tipped pushrod that the ball tips are used to gauge the distance apart and weld these to a pair of pliers with an adjustable stop, set the stop by feel then remove the pliers and measure the gap.
-or you can even usually get down thru water holes if need be.
bill jones
Guru
Guru
 
Posts: 2400
Joined: Sun Sep 05, 2004 5:38 pm
Location: salt lake city, ut

Postby bill jones » Wed Mar 30, 2005 11:47 am

-here's some examples of cylinder wall thicknesses.
---------------------------------------
1-brand new 454 marine block, one of two in a twin engine Reggie Fountain 33 foot toy:
-thinnest thrust wall .215", thickest thrust wall .286", thinnest front or rear wall .105" thickest front or rear wall .255".
2-the other 454 block in the same boat:
-thinnest thrust wall .217", thickest thrust wall .273", thinnest front or rear wall .152", thickest front or rear wall .241"
---------------------------------------
3-another 454 passenger car block:
-thinnest thrust wall .293", thickest thrust wall .357", thinnest front or rear wall .131" thickest front or rear wall .305"
---------------------------------------
4-283 chevy bored out from 3.875" to 3.990" with the bores moved offcenter to save some of the wall thicknesses:
-thinnest thrust wall .135", thickest thrustwall .204", thinnest front or rear wall .103" thickest front or rear wall .216"
---------------------------------------
5-a 307 bored out from 3.875" to 3.930" with intentions of going to 4" and the bores centerlines were also moved to save wall thickness:
-thinnest thrust wall .209", thickest thrust wall .245", thinnest front or rear wall .113", thickest front or rear wall .209"
------------------------------------------
6-one 350 block I used for several years as a fairly serious oval track engine in the 1980's, about 500 honest HP:
-thinnest thrust wall .196", thickest thrust wall .245", thinnest front or rear wall .085", thickest front or rear wall .210"
-----------------------------------------
7-this is a 400 SBC that I built into a 382ci engine in the late 1980's with intentions of about 575 honest HP used 4.132" bore size with NO corrections to help the wall thicknesses:
-thinnest thrust wall .154", thickest thrust wall .301".
-thinnest and thickest front or rear wall wasn't measured becasue of the siamesed bores.
-but there is five grooves down the bore walls inside the water jackets below the headbolt holes and the thinnest groove is .145" and the thickest groove is .238"
-(haven't ever used this engine yet)
-----------------------------------------------
8-a 390 Ford after bored .030":
-thinnest thrust wall .150", thickest thrust wall .174", thinnest front or rear wall .090" thickest front or rear wall .166"
---------------------------------------
9-a 4.3 V6 Chevy marine:
-thinnest thrust wall .174", thickest thrust wall .257", thinnest front or rear wall .129", thickest front or rear wall .194"
-----------------------------------------------------------
-typically the thickest front or rear walls is at one of the front or rear cylinders.
bill jones
Guru
Guru
 
Posts: 2400
Joined: Sun Sep 05, 2004 5:38 pm
Location: salt lake city, ut

Postby som32 » Wed Mar 30, 2005 3:07 pm

well It seems I have some freeplay still after .06 over. 400sbc .04 over and it still has .2 bore wall min at all places exept one cylinder below piston ring area at bdc is small spot at .118. And I tought that these blocks were thin;)
sonic checked.
som32
 

Postby Walline » Wed Mar 30, 2005 3:43 pm

Sometimes I think people assume because 400 have 4.125 bore, they are thin. I have seen my share that are as good if not better(wall thickness) then some 350's. I have ran a few at .060 over, with no problem, just have to find a block with minimal core shift. Just my two cents.
User avatar
Walline
Member
Member
 
Posts: 183
Joined: Thu Apr 29, 2004 4:19 pm
Location: Kansas

Postby phoenix » Wed Mar 30, 2005 3:50 pm

On my compacted graphite iron post, I think it was "Joe" that .064 on a CG block was compairable to .120 on grey iron. :shock:
phoenix
Pro
Pro
 
Posts: 264
Joined: Tue Feb 01, 2005 10:26 am
Location: Columbia Sc

Postby 11secAvanti » Wed Mar 30, 2005 9:05 pm

I like the concept of doing possible measurements via the water passage holes. Thanks for that idea. The head bolts on a stude do not pass through into the water passages. They enter into a cast boss that is part of the head deck. Head deck looks pretty thick (.400" plus). Got another segment out of number 8 cylinder today and this piece which starts at about 3/4 inch below TDC had .300" thickness and tapered down gradually to .250" at mid point for the bore. When combined with the first piece that I took out last week the size remained .250 until the lower part of the bore is reached where it became about .200. This gave a picture of a wall that was very thick at the top .300, still thick at the center .250 and thinnest only at the bottom end where it would tie into the casting that became the floor of the bore. Thanks for sharing the data on other blocks to get a perspective on this topic.
11secAvanti
Member
Member
 
Posts: 198
Joined: Tue Mar 22, 2005 8:51 pm
Location: Virginia

Postby b73 » Sun May 22, 2005 6:37 am

Which part of the cylinder wall is considered to be the 'thrust' area?
Do the inside (valley side) and outside walls bear the same loads, I guess not??
Thanks,
B.

btw, this forum is fantastic!!
b73
Member
Member
 
Posts: 58
Joined: Sun May 22, 2005 6:35 am

Postby bill jones » Sun May 22, 2005 11:13 am

-the major thrust happens on the passenger side of the walls and against the piston skirts on the passenger side of the piston (assuming the engine faces forward and the crank rotates clockwise looking at the front).
-------------------------------------
-The major cylinder pressure happens above the top of the pistons during the first 20 degrees or so, and as the pistons move down the bore the pressure drops away very quickly.
--------------------------------------
-Not considering detonation, the highest cylinder pressure happens on the power stroke when the piston is near the top-about 11 to 22 dregrees or so after TDC.
-By time the piston is down about 78 degrees the piston moves the easiest and the pressure has dropped bigtime so the wall thickness needs to be the thickest near the top of the bore.
bill jones
Guru
Guru
 
Posts: 2400
Joined: Sun Sep 05, 2004 5:38 pm
Location: salt lake city, ut

Postby joe » Sun May 22, 2005 3:15 pm

Since this has a bearing on the main topic I'd like to know what metal formulations (roughly) were in broad use by any of the big 3 back in the muscle car era .
Sometimes you'll hear people say "this block has high nickel content " or some such , but they do not know how much nickel in absolute terms.
I assume that the main line of muscle car engines had class 20 cast iron blocks with "nominal" amounts of nickel and chrome for that type of iron ? Is this so ?
I know that some of the special run 427's that ford made had high phosphorus which increased strength about 15% according too ford . These blocks had a unique , pale gold sheen when freshly machined.
All these things will have a bearing on block strength and nobody seems to know very much ,including me ! So ,somebody give me a clue !
joe
 

wall thickness

Postby PackardV8 » Sun Jul 30, 2006 1:24 pm

One factor which was not yet mentioned is length of cylinder wall section. The SBF has such short water jackets, it can live with thinner wall sections than the older, tall deck blocks. Some of the BBM, older Studebaker, Packard, late Cadillac, have decks above 10" and up to 10.625" These require thicker wall sections because of their length.

The good news is most of the above old school blocks do not bolt the heads to the cylinder walls. This makes them much more stable. Those engines with head bolts on the outer wall usually don't show much benefit from honing with a deck plate. Take a SBC, bore it to max, hone it without a deck plate, bolt one on and often the bore distorts so much the pistons won't even drop down the holes.

Also, on the older stuff, corrosion can be significant. Before putting big buck machining and parts in a wrecking yard block, spend the time/money to sonic check every square inch of bore. A bit of casting slag and 50 years of water need eat only one weak spot from the inside. Put some pressure on it and the whole engine can be toast in 1/4mile. Ask me how I know.

thnx, jv.
Jack Vines
Studebaker-Packard V8 Limited
PackardV8
Guru
Guru
 
Posts: 3596
Joined: Sun Jul 30, 2006 1:03 pm

Postby bullheaded » Sun Jul 30, 2006 1:42 pm

I don't claim to be an expert at sonic testing but have done a few.The old adage of looking for a block that the casting "looks" centered up may not always be true. I had one SBC that looked as good as your ever going to get. The sonic tester showed another story,way thin on major thrust. All I'm saying is,if going to make HP,get it checked.Cheap insurance.
The more I know,the harder it gets.
bullheaded
Member
Member
 
Posts: 59
Joined: Tue Jul 25, 2006 2:36 pm

Postby CNC BLOCKS » Sun Jul 30, 2006 9:42 pm

bullheaded wrote:I don't claim to be an expert at sonic testing but have done a few.The old adage of looking for a block that the casting "looks" centered up may not always be true. I had one SBC that looked as good as your ever going to get. The sonic tester showed another story,way thin on major thrust. All I'm saying is,if going to make HP,get it checked.Cheap insurance.


DITTO
Website is up and running
http://hinksonautomotive-cncblocks.com/
Machine shop tour
http://hinksonautomotive-cncblocks.com/shop-tour/
Monthly Specials
http://hinksonautomotive-cncblocks.com/specials/
Soon 55MM babbit cam bearings with 1 hole
CNC BLOCKS
Guru
Guru
 
Posts: 4555
Joined: Thu Jul 01, 2004 5:34 am
Location: NORTHEAST

Postby clueless » Mon Jul 31, 2006 6:17 am

FWIW a local engine builder has been building 4.165 bore engines using 4.000 inch blocks. These engines are used for bracket racing and are UNfilled !!! One was recently disassembled due to excessive blowby (made almost 700 dyno HP and ran over 100 8 sec 1/4s). A sonic test showed one non thrust wall was 0.033" thick !!!
clueless
Member
Member
 
Posts: 109
Joined: Sat Jan 21, 2006 7:15 am
Location: Australia


Return to Engine Tech

Who is online

Users browsing this forum: 70MC, Bing [Bot], ClassicComp, crdafoe, Don Whitmer, Fordracer347, frdboy, Old as Dirt, rfoll, Yahoo [Bot] and 19 guests