Honing

[NE57]

Thought I'd seperate this from the piston knurling thread.

Well, I'm a little puzzled but a little hopeful too. As I mention in the other thread I'm trying to see if I can reuse my Jahns forgings by honing out the rust and scores. Today I honed one cylinder as a test. I still see some scoring and rust pitting but its much better than before. I can 'barely' feel the imperfections with either my finger or a razor blade tip. More honing might clean it up nicely.

I kept measuring often to see how much metal I'm removing. I dunno, it seemed to me I was doing a lot of honing but the measurements showed less than .0005" removed. I double checked with a feeler gauge. It showed i had .006" clearance with a smooth fit of the gauge between the piston/cylinder. .008 would fit but it was a very tight fit requiring a determined pull to remove the gauge. So I'm not sure how to interpret all that. It was suggested that I might be able to run a clearance up to .009". So this migth work afterall, at least on this test cylinder.

I'm puzzled...either my measurements are off or honing removes less metal than I would have thought. Am I right to assume that the more important thing is observed clearance(given successful pitting removal) rather than actual cylinder dimensions? If the feeler gauge says I'm good to go, should I be concerned that metal removal isn't what i expected? I don't know if I'm even phrasing the question correctly.

[flatheadpopup]

I'll be watching this thread as my 331 has some pitting in the cylinders and I have a set of new pistons that came with it...my motor was bored .030 and honed over 25 years ago and then left to rust I guess thats why I got it cheap but it doesn't make me feel good about the idea of not being able to use a set of brand new (25 year old) pistons. I have heard that cast rings are more forgiving of a slightly messed up cylinder wall. Guess we'll see what people have to say. Oh, what size is your hemi by the way?

[NE57]

Its a 392 with a previous .040 overbore.
I hope you're right about cast rings, as I have them in mind for another reason...less bore wear.

With your pistons being new, you have the option of selling them and putting the $ towards another new set of whatever size you'd need after boring. I see new and used pistons on ebay now and then, they seem to sell.

I was thinking the same thing for mine, sell 'em and buy replacements. I thought I'd give this a shot(honing without replacements) first.

To the board...at what point clearance-wise, does piston slap change from just an annoying sound to a mechanical problem? And what are the mechanical consequences,exactly? Maybe a better question would be...

What's the biggest piston clearance you or an acquaintance have successfully used? or... At what point did you start having problems?

Thanks again for letting me pick brains

[flatheadpopup]

I thought about selling my pistons (especially since they are cast) and getting some new ones but money is tight. If you were running a 354 I would have just tried to buy your used pistons and you could have went up a bore size...but being that you are running an overbored 392 that would not be very feasible. Do you know what the max bore size is for the 392? Hope you find a reasonably inexpensive solution to your problem. Maybe someone will still chime in and give a glimmer of hope to your using the existing pistons in a slightly looser bore. I'll look around and see if I can come up with anything regarding early forged piston clearances.

[NE57]

>Do you know what the max bore size is for the 392?

I was under the impression that .060 was it, but I saw for sale a set of pistons for a 1/8 inch overbore. I really wouldn't want to push things that far.

I'm currently at an .040 overbore, so boring more would work too, I just would like to save these pistons if I can.

[oldngood]

Thought I'd seperate this from the piston knurling thread.

Well, I'm a little puzzled but a little hopeful too. As I mention in the other thread I'm trying to see if I can reuse my Jahns forgings by honing out the rust and scores. Today I honed one cylinder as a test. I still see some scoring and rust pitting but its much better than before. I can 'barely' feel the imperfections with either my finger or a razor blade tip. More honing might clean it up nicely.

I kept measuring often to see how much metal I'm removing. I dunno, it seemed to me I was doing a lot of honing but the measurements showed less than .0005" removed. I double checked with a feeler gauge. It showed i had .006" clearance with a smooth fit of the gauge between the piston/cylinder. .008 would fit but it was a very tight fit requiring a determined pull to remove the gauge. So I'm not sure how to interpret all that. It was suggested that I might be able to run a clearance up to .009". So this migth work afterall, at least on this test cylinder.

I'm puzzled...either my measurements are off or honing removes less metal than I would have thought. Am I right to assume that the more important thing is observed clearance(given successful pitting removal) rather than actual cylinder dimensions? If the feeler gauge says I'm good to go, should I be concerned that metal removal isn't what i expected? I don't know if I'm even phrasing the question correctly.

with a 1950's Chrysler block, honing won't remove a lot of material- the block is high nickel content and very hard- the machinists despise those (along with most other early made in USA OHV V-8's) for that exact reason, they burn up their cutters on them. Chrysler and GM Pontiac-Olds-Buick-Caddy blocks from the 50's are so high nickel that sparks fly off the punch when I'm knocking rod bolts out of the rods and miss.

they made stuff to last a few lifetimes back then- thicker bores, better material

unlike the later Ford FE 390's, which were like putty dough, and would open right up with a hone

another option you have is, take it to a machine shop, have them finish hone it with a torque plate, you'll kill 2 birds with one stone, get them perfectly round and remove the rust- most times getting them round requires .5 to 1.5 thousandths be honed out of the bore, which won't hurt it

[David Hunt]

Clean with etching acid aka wheel etcher acid. Use 440 stock pistons that are aluminum. They work. My 2 cents. D Hunt

[oldngood]

Clean with etching acid aka wheel etcher acid. Use 440 stock pistons that are aluminum. They work. My 2 cents. D Hunt

that must be a typo, right ? because 440 pistons would not every fit or work in an early Hemi, the 440 pistons are way oversize something like a 4.32 bore.

you must mean 340 pistons, which are a 4" bore- how do they fit for piston pin size ?

good idea is they worked too

you could also use a Chevy 302-327-350 piston, which are also 4", but the pins would have to be adapted

there's many 4" bore size engines out there, another one is the 351M- 351C- 400M Ford

[NE57]

I've decided to go with new forged pistons in .060. Depending on how much block decking is needed might have to go custom. I'll find out when the machinist calls me. I dropped the block and crank off last week.

To tell you the truth, money was a part of the issue and I was getting antsy to get something accomplished. Things got tight after I bought the motor but they're loosening up. Money should be loose...not pistons.

[mart]

Money should be loose...not
pistons.

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You got that right!
Mart
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