bore size Hypereutectic pistons

Yikes. No. Those pistons are set for .0025" piston to bore clearance.

A forged piston like the old TRW's need MINIMUM .0055".

You want rounded edge skirts on these things to reduce the cold start up slapping. .0055" is a lot.

You had better talk to Keith Black tech about this. Don't go by what I say or anyone else tells you for that matter. Do what the piston manufacturer advises.

Before you do any boring though you need to test that block for existing wall thickness.

Just because the pistons are made in a +40 does not mean it is a good idea to go that big.


I believe it is Race Tech that will make a piston in absolutely any bore size including the rings. So theoretically you could go to something like .031" presuming you can clean up the bores at that size. Good luck to that though. You might all clean up at .035 BUT you can actually use all different size pistons matched to each bore. They will make them that way for you.

The 427 Ford blocks are so scarce, that's really what is getting used for pistons in many of them.

Frank, these are the pistons that i warned about in your other thread, your friends pistons probably broke due to spark timing / engine tune. when hypereutectic pistons experience knock, ping or detonation they break into pieces

insufficient cylinder wall clearance is very unlikely because hyper pistons are suppose to run very little (tight), they don't expand like a piston made of 2618 alloy, or even 4032 alloy

do you want your engine to end the same way as his, then use the same pistons i guess?

standard cast pistons are more durable than hypereutectic

forged 4032 pistons are more durable than standard cast

forged 2618 pistons are very durable

You must do a sonic cylinder wall thickness test before you do anything else.

While your block is at the machine shop you should also perform a magna flux test for any unseen cracks.

I am just going through this myself and have been told the minimum, at finished bore size, should be 85,000's thickness on the thrust side of the pistons.

Thrust sides are on the right-hand side of each cylinder bore when viewed from the rear. Outer walls on cylinders one through four, and inner walls on cylinders five through eight

Larry

i have already sonic the block. And no crack or thin walls are found.

But at my first question....what must i bore the block for the hyper BK??

Did you read Doug's wise advice?

You had better talk to Keith Black tech about this. Don't go by what I say or anyone else tells you for that matter. Do what the piston manufacturer advises.

Larry

Frank, normally the piston "size" stamped into the dome of the piston is actually the bore size, and whatever clearance the piston's manufacturer wishes to have is built into the piston by reducing the OD of the piston. As an example, if the piston manufacturer wanted 0.001 clearance, the piston would be 4.039 diameter, giving it a 0.001 clearance in an 4.040 bore.

Larry ... 0.085" on the major thrust walls?!

Are you sure you're not quoting the "non-thrust" figure?

To both of you gentlemen, I'd take the block back to 4.000 with dry sleeves before I settled for 0.085" thrust walls. In fact I'd install dry sleeves before opting for 4.040 pistons. Or I'd purchase a set of forged 4.030 pistons and live with a little bit of taper. Done that many of times.

Complete used 351c engines can be had all day long for a $300.00- 400.00 range.

NO need to incur the cost of dry sleeving or +.040 oversized pistons.

quote:

Larry ... 0.085" on the major thrust walls?!

Just checked my Dave McClain notes. We were talking "90-100" as being reasonable, with "85" as a minimum. I'm sure he didn't mean 85/100.

As you are far more learned on the Cleveland than me, please share your thoughts.

Larry

quote:

Complete used 351c engines can be had all day long for a $300.00- 400.00 range.

Alex,

6-8 years ago I scoured Craigslist here in Fresno, and in about 6 months had four standard-bore Clevelands - some complete short blocks, some just blocks, in my shed for less than $400.

At that time, folks had started noticing readily available offerings were getting pretty hard to find.

Last USA Cleveland was made in 1974, now forty years old.

Not many 40 year-old cars showing up in the self-pick wrecking yards, and nowadays I seldom see them in Craigslist, either.

Your $300-$400 pricing for a block seems reasonable, but I don't think they are so common as to be readily available "all day long".

Do you have a secret wrecking yard somewhere?

Larry

Curious folks want to know....

This is the testing result of a 2-bolt block I recently had tested.

Cylinder #5 has me a bit concerned. Seems to have a LOT of core shift to the outer wall.

I'm thinking two more blocks are destined for the machine shop next week for clean and test.

George?

Dear Larry,


Since you didn't find optimal results with the sonic test on the first block, I would recommend that you go ahead and test the remaining blocks in the inventory, so you and your engine builder can pick the best one....or if that is disappointing, then send you off to buy more gently used Cleveland blocks for sonic testing.


Chuck Engles

Chuck,

As soon as the rain stops, I'll yank two more blocks from the shed.

While the 0.107 figure is low, the bore is still 4.00. A 0.010 overbore would still give a thickness of 0.102.

While I await George's feedback on his thickness views, what are your thoughts on minimal thickness?

You've built enough engines to have a valid input, IMHO.

Larry

Try here,
Next I do will be here. http://www.ausfordparts.com/block.html


Mark

Opinion differs, but minimum 0.12" on the thrust side is a good recommendation IMO.

The question is what HP engine are you building with the block? Are you prpeard to partially hardblock it?

Julian

quote:

Originally posted by LF - TP 2511:

quote:

Complete used 351c engines can be had all day long for a $300.00- 400.00 range.

Alex,

6-8 years ago I scoured Craigslist here in Fresno, and in about 6 months had four standard-bore Clevelands - some complete short blocks, some just blocks, in my shed for less than $400.

At that time, folks had started noticing readily available offerings were getting pretty hard to find.

Last USA Cleveland was made in 1974, now forty years old.

Not many 40 year-old cars showing up in the self-pick wrecking yards, and nowadays I seldom see them in Craigslist, either.

Your $300-$400 pricing for a block seems reasonable, but I don't think they are so common as to be readily available "all day long".

Do you have a secret wrecking yard somewhere?

Larry

Curious folks want to know....

Hello Larry; No "Secret Wrecking Yard", just due diligence & perseverance.

Here's a current perfect example...

4 bolt main engine standard bore AND HEADS ( the heads might be closed chambered ) for $600.00 asking price, might be had for $500.00 cash & a 12 pack.

http://sacramento.craigslist.org/pts/5885191958.html

Dear Larry,


My thoughts on minimal cylinder wall thickness:

1) I don't know that much and I do rely on people that build engines for a living for good advice on these issues

2) Personally and simplistically, I prefer all of my cylinder walls to be .125" or greater. Not easy to do, so...

3) My method is to have all of my blocks ( I think I have about ten in total ) sonic tested and then I pick the one with the thickest walls. Out of the bunch about three or four are good. About three are OK for street builds, but not big HP builds. About three are not usable without sleeving.

4) Whenever you really need a good block, then you can't find one. When you don't really need another block is the time that you'll find a good one. The metaphysics of machine shop metallurgy!


Warmest regards, Chuck Engles

quote:

Originally posted by LF - TP 2511:

... George ...

On cylinder number 1 you have 0.060 on a non-thrust wall, on cylinder number 3 you have 0.048 on a non-thrust wall , on cylinder number 4 you have 0.070 on a non-thrust wall, on cylinder number 5 you have 0.107 on a thrust wall, and on cylinder number 6 you have 0.067 and 0.080 on the non-thrust walls. My limits are 0.120 on the major AND minor thrust walls, plus 0.080 on the non-thrust walls ... AFTER they have been bored.

You realize that 0.048 isn't much thicker than the cellophane wrapper on a package of cigarettes?

The nominal cylinder wall thickness of a 4.000 351C bore is quoted to be 0.160. Ford limited boring to 0.030, that would reduce "nominal" wall thickness to 0.145. I forget where the 0.120 number comes from, Ford or elsewhere. However I think this number came up after electronic cylinder wall thickness measurement became available ... we take the ability to "sonic check" cylinder walls for granted these days, it wasn't always an option.

I would like to explain something however. I've already given you and Frank my best advice. Here's the best way I can explain my reasoning to you. When the valve guides in a cylinder head are worn we don't replace the cylinder head ... we install bronze valve guide liners, or we press-in bronze valve guides. The result is a better valve guide, more compatible with stainless steel valve stems, and far more wear resistant (durable) than the valve guide based upon the original iron casting. The same principles and results hold true with cylinder liners. The good quality "spun" liners are made of a better alloy, with better metallurgy and better grain control, than the original iron block casting. They are a better match for piston rings, they are more wear resistant, and they are stiffer, i.e. less prone to flex. The good quality "spun" liners are an improvement to the block, as are bronze valve guides to a cylinder head. Yes they are more expensive than a simple over-bore ... but if you discount the price of purchasing another block, well the price of the liners starts looking like a good deal considering the benefits. At least in my book.

If the block in question has no other issues other than the cylinder walls having been previously over-bored to their limits, I would install liners rather than throwing money away on other used blocks of unknown quality ... which is simply gambling, and since the blocks you're buying are 40 years old, the odds aren't all that good.

Obviously I don't perceive the installation of dry liners the same way others do.