427 oversize pistons

[Greg L.]

What oversizes should be available for an L36/68 besides the common .030 and .060? I've heard of .010, .020 and even .001 and .002 and maybe .005? but I'm not sure if they are still made...

To be honest I haven't even checked the local parts guys because I just know they will say .030 or .060 and that's it! If there are other sizes available I know someone here will know about them.

Thanks guys.

Greg Linton
#45455

[Joe L.]

Re: 427 oversize pistons

Greg-----

If you're talking about EXACT reproduction pistons for an L-36/L-68, then there are NO sizes available. For one thing, original pistons for these applications were cylinder bank-specific.

If you're talking about suitable SERVICE pistons for the applications, you will find +0.020, +0.030, +0.040, and +0.060. Once-upon-a-time, GM offered +0.001, +0.030, and +0.060. I don't know of any manufacturer that ever offered +0.010 pistons and I don't know of any source other than GM that ever offered the +0.001 size.

[Bryan L.]

Re: 427 oversize pistons

My 427 is .040 over, the pistons are TRWs.

BL

[Greg L.]

Re: 427 oversize pistons

Thanks guys, maybe there are some aftermarket suppliers that sell this kind of stuff...maybe Summit?

[Duke W.]

Re: 427 oversize pistons

Look at manufacturers, not retailers! Google "Keith Black Pistons". Also look at Sealed Power and Speed Pro (Federal Mogul), and Mahle-Clevite (Dana Corp.).

For L-36 use a nominal 10:1 compression piston, and based on measured deck height, piston and head volume, select a head gasket thickness that provides a true measured CR of no more than 10:1, which will perform without significant detonation on premium unleaded fuel.

Be very careful with "specified CRs" as they are always based on nominal OE deck height and a particular gasket thickness, which may or may not be specified in the fine print.

Don't make the mistake that so many guys make - "low compression pistons" (often accompanied by a high overlap non-OE cam) that will result is mediocre torque bandwidth and power unless you want to run the engine on regular unleaded.

Duke

[Clem Z.]

for a price oversize pistons can be made in

any size you want. piston makers like JE will custom make pistons

[Greg L.]

Re: for a price oversize pistons can be made in

Thanks Clem, I just talked to JE and the conversation pretty much ended shortly after he said "we only have forged pistons"...so I guess that's one option out.

I have nothing against going forged other than I want it to be stock quiet during warm up and not rattle like forged pistons do.

I'll check around a bit and see what I come up with but all suggestions are appreciated!

[Joe L.]

Re: for a price oversize pistons can be made in

Greg-----

I would go with "off-the-shelf" +0.020" pistons. You might not even get all the cylinders to clean up at a +0.010 overbore if that's what you were thinking of trying to do. All it takes is ONE cylinder that won't clean up at +0.010" and you'd have to go to +0.020", anyway.

[Clem Z.]

JE forged pistons can be run at much tighter

clearance than some other forged pistons. GM bought them a special machine to do the 502 marine pistons that cuts a different shape than other companies use. i had some of their forged 4.00" piston that went in at .0020/.0025. the first set i bought for the cavalier race engines,3.500" bore went in at .0015. when i got them i called because i thought they had made a mistake on the spec sheet.

[Mark #28455]

Keith Black and Speed Pro

I got a set of 10:1 hypereutectic cast speed pro pistons with moly rings in 0.040 overbore for my 454 from summitt for about $210.

Hard to beat!

Mark

[Verle R.]

Re: 427 oversize pistons

The mass rebuilders can get pistons in many "non standard" sizes. I don't know who manufacturers them. They look cheap, but if you must have an unusual size piston you may be able to find them.

Verle