kevdog442

Looking for some advice on pistons for my 69 400 rebuild. I’m ok with cast as I’m not a racer, just looking for oem quality. Not finding a whole lot. Falcon global performance on feebay. I think Kanter, Supercars unlimited etc. have them. Please no comments about the 400 being not a great engine, it’s original to my car.

Fun71

Egge Machine is another source for cast pistons. Be aware that almost all of the aftermarket cast pistons will be shorter than the factory pistons, which will lower the compression ratio. Prolly not a bad thing on what was originally a 10 or 10.5:1 engine, but some really short pistons coupled wiht thicker aftermarket head gaskets could lower it into the 8.xx:1 range, so be aware of what you're buying.

edzolz

Have you tried EngineTech. The owner is on here costpenn is his user name. They have complete kits for rebuilds.

kevdog442

Couldnt find any at Egge for the late 400. Also what do you mean by shorter? The dish?

kevdog442

No, I have not.

Fun71

Here's a link to the Egge pistons:
https://egge.com/part/egg-1000-l2346-8/

No, the distance from the pin centerline to the top of the piston. It's referred to as Compression Height. The aftermarket cast pistons are typically .015" to .025" shorter than the factory spec.

kevdog442

well they don’t have to be cast, just trying to stay within my budget. Would like to keep the compression ratio up.

Oldsmaniac

Kanter gets their pistons from Egge, Egge has them you must not have looked correctly.

kevdog442

curious as to why they are shorter?
And thanks for the link, don’t know why I didn’t see them before.

BillK

They used to but lately they have been sending some "offshore" brand I have never heard of. I sent two sets back in the last 6 months and ordered direct from Egge. A lot of guys do no like Egge's pistons but they have a lot of oddball old stuff and I have never had a problem with them. You might want to find some old part numbers and check Ebay too. I found a set of old TRW pontiac pistons a few months ago and paid less than Egge's price and they were probably better pistons.

edzolz

They are shorter because when rebuilders machine a block they usuially cut the head surface to clean it up for gasket sealing. Sometimes it takes off as much as .015 to clean up the surface. So the piston won't be above the block surface when assembled.

Fun71

I’m not gonna disagree with the above, but if you consider that most factory pistons are .020” or so below the deck to begin with, and aftermarket head gaskets are .020” or more thicker than the factory gaskets, that means a lot of material would have to be removed from the block to bring an aftermarket piston that is .020” short up to even with the deck surface.

kevdog442

I guess I realized that after I asked, and of course mine is uncut. Do you know of any pistons that are not short?

joe_padavano

Supercars Unlimited has G-block 400 pistons is a variety of bore sizes. Mark Remmel can get you aftermarket forged pistons for a little more than the cost of those cast ones. I know what I'd do.

tru-blue 442

Here's a link to Joe's website.

https://enginetechcatalog.com/

Koda

It's worth pointing out here that rotating assembly engine parts, which are hard to get to later, are the things to spend extra money on now when you are already in there.

fleming442

I have some 030 over TRWs if you're interested. They're just taking up space. On stock rods....

Fun71

Almost all of the forged pistons are the correct compression height. For whatever reason, the cast pistons are short.

matt69olds

I seem to remember reading somewhere you can use oversized pistons from a 350 Olds engine in a early 400 block. The 350 Olds has a 4.057 bore, the early 400 is 4.00.

Instead of boring the 400 engine to 4.030, you bore it to give the correct piston to wall clearance with the .030 oversized 350 piston. Assuming the other dimensions are the same, is this a option?

joe_padavano

Actually, you just use a standard bore 350 piston, which gives you a 0.057" overbore on the early 400. The resulting combo is 412 cu in. The compression height on the early 400 is the same as on all the SBOs.
The problem is that the OP is asking about a G-block 400, which does not have the same compression height.

kevdog442

I do need.030 but those would be cast right? And if what Kenneth is saying about them being short, I guess I’m looking at forged. Can’t sacrifice compression ratio for a few bucks.

kevdog442

Who is this Mark Remmel you speak of?

kevdog442

I do agree with that.

Fun71

I thought the TRW pistons were forged, and the cast pistons from the same manufacturer were under a different moniker (such as Sealed Power or Federal Mogul).

OLDSter Ralph

The G block also doesn't have a 4.000" bore. 3.870" ?

joe_padavano

cutlassefi on this site

joe_padavano

Which is why I said that the 350 pistons only work in the early 400 motors.

OLDSter Ralph

Joe, you are correct, I must have had something on my reading glasses and missed it.

kevdog442

Ok thanks I sent him a pm

kevdog442

they don’t appear to have anything for Oldsmobile

fleming442

They're forged. Mondildo claimed 9.7:1 compression, but I never ran the math. My 400G ran pretty good with Edelbrock heads, but the XE274 cam was too much. That's why I question the compression claim.

fleming442

Hey, Kevdog, make sure you run them at 004-005 piston to bore, regardless of what TRW says or any "OEM spec".

Andy

that xe274 cam with aluminum heads should run very strong. Its an excellent cam for the combo you listed. Maybe the tune needed looked at or timing?

skyhigh

Haha, like what you did with the name there lol

fleming442

it ran pretty well for a bunch of mix match parts. It needed a ton of timing; that's why I thought the compression was low. I think it would have been better if I had decked the heads down to 70cc or so.