331 Cylinder thickness

Discussion of the 331-354-392 HEMIs.

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Matthyj
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331 Cylinder thickness

Post by Matthyj » Fri Sep 09, 2011 9:29 pm

I am new to this board but I saw Scotts posting on 331 cylinder wall thickness, I took a 56 Industrial 331 to a machine shop yesterday to have the cylinder thickness checked in order to bore it out to a std bore 354, instead of an actual sonic check the machinist used a special long reach micrometer that drops in through the water jacket hole and into the cylinder hole and measures the wall thickness, though it can't go 360 degrees around the cylinder as a sonic check it does give a very accurate measurement for the wall thickness on two opposite sides of the cylinder.
The rumor is that the 331's where actually underbored 354's, I can't say whether thats true or not but pretty consistantly the walls where .270 thick, the thinnnest being .250 so if a .125 bigger bore is achieved .062 will be taken off the cylinders thickness leaving the walls plenty thick, he only builds pro race motors and was recommended by my machinist so I trust his judgement as he said the minimum wall thickness is .150 on a motor which my machinist said holds true as when they thinwall sleeve a motor its only .125 thick.
This blocks number is IND56 and it is the exact same as a passenger car block, no lower water outlets and such, its not a truck block either, the IND56A is a 354 also, the strange thing is the crankshafts casting number is a 354 number, I know they are the same as a 331 dimension wise but it does appear its possible they are underbored 354's at this point.
One point he did say worth notoing that appears consistant is that the strongest cylinder is the thickest and transfers less heat to the water, so if I left it a 331 it would tend to run cooler, however he said the walls are plenty thick to overbore to a 354. I bought this block from a guy who has been buying up many Industrial blocks, he says they generally have fewer hours on them and are better serviced as a rule, some have the lower water outlets like a 51-54 and truck blocks but some do not and are indentical to the passenger blocks, I do know the crank in this motor did not require a thing as it looked brand new. Hope somewhere this helps somebody! Thanks for the forum its usefull. Matthyj

George
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Re: 331 Cylinder thickness

Post by George » Sat Sep 10, 2011 9:00 am

331s aren't underbored 354s. 331 started in 51, 354 didn't come along untill '56, though there are underbored 354s(331s) made after '55. Generally speaking you can bore a 331 out to 354 std bore.

George
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Re: 331 Cylinder thickness

Post by George » Sat Sep 10, 2011 9:02 am

Short tail 301/331/354 cranks are the same.

budmspeeco
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Re: 331 Cylinder thickness

Post by budmspeeco » Mon Feb 20, 2012 9:10 pm

To George; again! The cranks share the same stroke, journal dimensions, maybe even the same casting numbers, and MOST physical characteristics. Except the counterweights and balance specs. Smaller bore engines have smaller pistons, which translates to less rotating/reciprocating weight. Modern stock type aftermarket pistons are normally manufactured to be roughly the same weights as original ones, even different oversizes. Theoretically an engine could have std., .020 ,.030, and/or .060 pistons in different holes without problems. But switch the cranks without rebalancing the assembly will make the entire engine vibrate like sex toys with new batteries !! More of my pennies !!!!!!! Buddy
'48 anglia

Rob
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Re: 331 Cylinder thickness

Post by Rob » Sun Feb 26, 2012 6:36 pm

I am waiting on a correct size transducer for our sonic tester to test cylinder bores. We have the smaller transducer now, but it is for cylinder head ports and does not give a correct reading for bores. If there is any interest, I will post some numbers for my 56 331. I plan on boring to 354 STD bore size, but only if it sonic tests thick enough for the STD size not to be it's last bore. Opinions welcome as to what minimum major thrust thickness should be for a naturally aspirated street engine.

George
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Re: 331 Cylinder thickness

Post by George » Tue Feb 28, 2012 10:56 am

Rob wrote:I am waiting on a correct size transducer for our sonic tester to test cylinder bores. We have the smaller transducer now, but it is for cylinder head ports and does not give a correct reading for bores. If there is any interest, I will post some numbers for my 56 331. I plan on boring to 354 STD bore size, but only if it sonic tests thick enough for the STD size not to be it's last bore. Opinions welcome as to what minimum major thrust thickness should be for a naturally aspirated street engine.
Any info is of interest. especially the '56 engines.

wayfarer
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Re: 331 Cylinder thickness

Post by wayfarer » Tue Feb 28, 2012 6:39 pm

Maybe I'm just old and thick headed, but why does anyone want to make giant bore cuts on these engines? You can easily exceed the perceived gains in power simply by using forged pistons at 10:1 compression. The standard bore 354 castings that are on the market may or may not actually make the 9:1 as advertised so then what do you do?

Someone please enlighten me....
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Rob
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Re: 331 Cylinder thickness

Post by Rob » Tue Feb 28, 2012 8:00 pm

wayfarer wrote:Maybe I'm just old and thick headed, but why does anyone want to make giant bore cuts on these engines? You can easily exceed the perceived gains in power simply by using forged pistons at 10:1 compression. The standard bore 354 castings that are on the market may or may not actually make the 9:1 as advertised so then what do you do?

Someone please enlighten me....
The large bore is not my goal. I don't give a rat's butt about bore. .125 ain't gonna add 5 HP. My engine was a 56 331 engine. Which, if you know, means it was a truck engine. That also means, if you know, it had only 7.5:1 compression rating from the factory. Probably less knowing Chrysler's dismally inacurate deck heights. I found a set of Chrysler STD 354 pistons for less than 120 bucks on ebag. These were CHRYSLER NOS pistons that were on the shelf since the 1950s. They were not "on the market". They came in the original Chrysler box with all Chrysler part numbers and casting numbers on them. Granted, they may not spec out perfect, but I will be ALOT closer than the original flat tops. I have access to a machine shop and can do all the machine work myself for free, so boring is not a problem. Since I am on social security, I am watching every penny. I have no doubt that as long as the cylinders sonic good, I can acheive 9.5:1 MUCH easier with the 354 pistons than I could with the truck flat tops. Wouldn't you agree? If you feel generous enough to purchase some custom pistons for me and send them along, by all means, I will be more than glad to follow your recipe. Maybe you can "easily exceed the perceived gains", but I cannot as easily do that. At least not by your method. My method may not even work, I will have to wait to sonic test before that determination. I do appreciate your input as you've helped me before, but not everyone can do it the same way. I have pinched and saved and waited for deals so this could happen. That's the only way I can do it as I don't have a blank check. I'm sorry it does not meet with your approval. This is after all my project, like it or not.

wayfarer
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Re: 331 Cylinder thickness

Post by wayfarer » Tue Feb 28, 2012 8:06 pm

I just don't remember pissing in your Cheerios.....I only asked a question.
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Rob
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Re: 331 Cylinder thickness

Post by Rob » Tue Feb 28, 2012 8:38 pm

You didn't. While you cannot understand why someone wants to bore the hell out of an engine, likewise I cannot understand why some people think there's only one way to skin a cat. No piss or cheerios involved. You just assumed that part.

George
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Re: 331 Cylinder thickness

Post by George » Wed Feb 29, 2012 12:17 pm

He's just saying too many want to do a max bore where in most cases they can't tell the difrence between that & a .030 job. Was your block one with 331 casting # or 354 casting #? can't recall.

Rob
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Re: 331 Cylinder thickness

Post by Rob » Wed Feb 29, 2012 5:01 pm

I understand. It has the 331 casting number. However, I found out today that the cylinder head probe was actually correct all along. Some cylinders read as little as .077" in places. Why? Simple. Somehow at sometime, the block has had 8 sleeves installed. The tester was reading the sleeve thickness. I suppose now I will look for some .030" 331 pistons, because the bores are actually in good shape and even retain some cross hatch. How bout them apples?

George
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Re: 331 Cylinder thickness

Post by George » Wed Feb 29, 2012 7:42 pm

Amazing! Most people would have got a diffrent block than sleeve 8! :o

George
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Re: 331 Cylinder thickness

Post by George » Wed Feb 29, 2012 7:44 pm

Rob wrote: I suppose now I will look for some .030" 331 pistons, because the bores are actually in good shape and even retain some cross hatch. How bout them apples?
What luck! way to go on that! :D

Rob
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Re: 331 Cylinder thickness

Post by Rob » Wed Feb 29, 2012 7:46 pm

Yeah. I caint figure it out. There are a couple large chips taken outta the bottom of two cylinders. I was thinkin maybe it busted a cylinder and they sleeved it......but then, why the hell bore it to .030"? ....unless maybe the sleeve job was done WAY back when and done to STD and then it was built again. Now I have a set of NICE 354 STD Chrysler pistons for sale.

George
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Re: 331 Cylinder thickness

Post by George » Wed Feb 29, 2012 7:50 pm

Put em on the HAMB & HH classifieds

Rob
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Re: 331 Cylinder thickness

Post by Rob » Wed Feb 29, 2012 8:45 pm

Yeah uh huh. This is me we're talkin about. They'll never sell.

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