Has anyone rebuilt their 394 engine and replaced the pistons. I have the ultra high compression engine, 10 to 1 compression ratio, and I am not able to find flat top pistons. The new replacements are dished with valve reliefs, and I am concerned if I use them, the compression ratio will drop down to 8.75 to 1. They also say they are no longer available, and that these are what everyone is using now. Any help would be appreciated, many thanks.

 

Have you tried Eggie or Ross Racing for your pistons they should be able to fix you up.They seem to be the go to guys on the first generation speed parts for Olds motors, give them a try.

PS. Kevin is the one to talk to from Ross Racing He is very knowledgeable... Tedd

 

I may be completely wrong here, but I was under the impression there were actually 3 different 394 pistons
1. a deep dish for low-compression versions
2. a shallow dish for hi-compression engines
3. a true flat top for Starfire engines only

I took this pic of the two 394 pistons I had on hand. The one on the left is a factory '62 Starfire piece. The one on the right is a NORS Ertl 741-P. Notice the shallow (approximately .040") dish. That's roughly 4cc's by my calculations.

 

Here's the Egge pistons:



They look like the same design as my old Ertl piston. The loss of compression from the little dish would be minimal. There are too many variables for me to calculate it exactly, but a rough guess using common Olds dimensions would be about 3-4 tenths of a point decrease. Maybe a good thing, considering today's gas. Just my opinion.

 

WOW, this is most interesting, I wonder, then, what I have in my 1961 super 88, as my pistons are true flat. And, the replacements I got look just like the ones from Egge. Say, do you think I would lose much hp and torque running the dished pistons? I did find a true flat top from Kanter that they dug around and found in a rebuild kit, that is the stock 10 to 1. What do you think. Should I send the dished ones back, and for 80 dollars more get the true flat tops 10:1, or just stay with the dished. Your advice is GREATLY appreciated. Oh, this is going to be a drivers car.

 

Knowing the way Olds built vs. rated these engines, I think it would be safe to say the actual compression ratio from the factory was lower than the advertised 10:1, probably closer to 9.5:1. So using the dished piston should leave it a bit over 9:1 after the rebuild. That's pretty safe territory for 91 octane gas.
What's your location and what's the best pump gas available there?
If you can get 93 octane or better, and it's important to you to keep the engine in it's original configuration, go ahead and get the flat tops. Since that's what you want and Egge has a set for you, the $80 extra shouldn't stand in your way.

 

check with these guys:

http://rossracingengines.com/c/2/old...early-catalog/

 

If I was to build a 394 I would shoot for something in the 9 to 9 1/2 range. My old 63 with 10 to 1 was a pain to keep the ping away, always a new experience with each new tank of gas. Just my thoughts...Tedd

 

Hey, thanks guys, I think I will just run the dished, its no hot rod anyway, just a drivers car for my "geriatric" years.

 

394's are torque monsters doubtful you would notice the small loss of HP anyway....Tedd