Minimum Cylinder Wall Thickness?

Discussion of the 331-354-392 HEMIs.

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lucky13
Posts: 22
Joined: Sun Oct 13, 2002 4:43 pm
Location: Antioch, CA

Minimum Cylinder Wall Thickness?

Post by lucky13 »

I just recieved my standard bore 56 (poly) 331 back from being sonic checked. The lowest number that I have is .194" on a non thrust side down low. I was hoping to take this block out to standard 354 specs (.125 over). Most of my other numbers are in the .250 range. I am looking to make a solid 500-550hp with a blower, in my Model A coupe. I have 1 hole that needs to be sleeved, and I was hoping on gaining the extra cubes also. So what should I be looking for in minimum thickness? If I can ever figure out my scanner, I'll post the sheet on it. I figured that since I work in a machine shop, all it would cost me is time. Thanks in advance


Brian
Boost is like crack. The first hits free, after that it drains your wallet and bank account
DavidBraley
Posts: 163
Joined: Sat Jan 30, 2010 7:40 pm
Location: Fort Collins, Colorado

Re: Minimum Cylinder Wall Thickness?

Post by DavidBraley »

I'm by no means an engine expert, but if you are running boost, the difference in final HP numbers between boring it to a safe 0.060 over compared to a full 0.125 over will not make enough difference to be worth the risk.

If you've got your heart set on as many cubes as possible, I read somewhere that you could off-set grind the crankshaft rod pins to a BBC diameter, use a set of BBC rods, and you'll gain back most of what you where after with the 0.125" overbore. A 0.060 overbore and 0.050" offset stroke will net you 346 cubic inches. The extra stroke won't hurt your final torque numbers either. The procedure I'm told is very labor intensive, but it sounds like you have access to the equipment to do it.

Just my 2 cents.

David
Horsepower determines how fast you hit the wall. Torque determines the size of the hole you make. Holzwarth's Law
budmspeeco
Posts: 133
Joined: Tue Dec 21, 2004 5:35 pm
Location: South Houston, Texas

Re: Minimum Cylinder Wall Thickness?

Post by budmspeeco »

I hope the machine shop you work at is a productions shop & not one that does automotive work.If a machinist at an auto machine shop has to ask a question as critical as "How Thick?" , I don't think I would be dropping off much of work for them to be doing! With a .194 on the non thrust side, when you bore it .125 you still have .130 or so left. You can even off set the boring bar a little to the thick side & probably gain more than enough meat to still be safe with a blower. If you are still not sure , call the piston/ring manufacturer & get his input. Personally I would bore the minimum necessary to clean the cylinder walls for a good seal & off set grind the crank to 2.100 small block size. I think Ford rods are a bit thicker on the bottom so side clearances might not be a problem. Really get an arm in it. You will never miss the cubes in a blown street motor anyway. especially in such a light weight car. You will have more trouble sticking it to the ground before you EVER need more power!!! And forget a rebuild kit. Everything in the motor will have to be ordered to specs especially the pistons, rods, cam, bearings. Buddy M2CsW
Last edited by budmspeeco on Sat Dec 25, 2010 5:59 pm, edited 2 times in total.
'48 anglia
budmspeeco
Posts: 133
Joined: Tue Dec 21, 2004 5:35 pm
Location: South Houston, Texas

Re: Minimum Cylinder Wall Thickness?

Post by budmspeeco »

I was looking at some of your post Dec-2007 What happened to the injectors? Do you still have them? If so & you don't plan to use , are they for sale? I have a set but someone here may be interested!! Buddy




need some poly to hemi info

Postby lucky13 » Mon Dec 31, 2007 12:25 am
i'm gonna be picking up a 56 331 poly motor in a few weeks. I've got a set of 354 heads, and a hilborn injection for a 392. Will this stuff actually bolt up and work? What are the differences between a poly and hemi? I'm guessing i'll need 354 pushrods, head gasket, and head bolts. Will the injection work ok with the 354 heads? I am also gonna be putting a viper t56 behind this motor and slapping all of it into my 31 model A.
'48 anglia
dan miller
Posts: 86
Joined: Wed Dec 27, 2006 5:05 am

Re: Minimum Cylinder Wall Thickness?

Post by dan miller »

A couple things RE: 354/392.

Yes, short deck heads will fit on a 392. Hemi heads will fit on a poly block, and will work fine. Poly heads will fit on a hemi block, but the push rod holes are different. The '54 and '55 331 heads are far superior to the 392 heads. With fuel injection, the deck height is of no consequence, as the throttle bodies are not connected. You'll obviously need longer rods (or a very ugly set of pistons), and longer push rods. Connecting and push rods are going to be custom pieces anyway, so this isn't of any consequence.

Danny
lucky13
Posts: 22
Joined: Sun Oct 13, 2002 4:43 pm
Location: Antioch, CA

Re: Minimum Cylinder Wall Thickness?

Post by lucky13 »

I work part time at an automotive machine shop and I was asking people there opinions on minimum thickness. Honestly for me I think anything less than .200 is not enough for my own comfort levels. I wanted to know if anyone has gone lower and what issues if any that they have. I still have the injectors and will be keeping them for a FED project. Alot has changed since I first picked up this block. I will be running the "555" heads on the 331.
Boost is like crack. The first hits free, after that it drains your wallet and bank account
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