I have a 390 that appears to be untouched internally. The factory compression is listed as 9.5:1. I want to raise compression to at least 10:1 and run my Performer rpm heads. The CC on the RPM's are larger then the stock heads by about 3 cc's from what I can find. I was looking at the TRW L2291. If I get these what would I have to do to get to 10:1? Stock heads would have me at about 9.95 and the RPM's would have me at about 9.5 according to the TRW info. I do not know if those numbers include gasket thickness. I was hoping to avoid machine shops due to the horror stories around here. One place lost my first set of stock FE heads which lead to the purchase of the RPM's. Is there a forged piston set that will get me at or above 10:1 with the RPM's without maching the heads or block? The car will be mainly track and sometimes weekend show/cruise so I don't care about gas milage or what octane it needs. I live across from an airport so I have easy access to 104 plus octane if needed. Basicly I'm looking for a piston for 390 that will yield at least 10:1 with the 72 cc RPM heads.

 

With the RPM heads, you cant run a steel shim head gasket. So you'll be stuck with a thicker Fel-Pro type head gasket.

The L2291's have 10cc's of valve reliefs. I used these in my motor, and measured piston to deck clearance at .012". Using these measurements, with a Fel-Pro head gasket, you'd have 9.55:1 compression.

Ross does make pistons for the 390. They only use two valve reliefs, and list the compression ratio at 10:1 with .050" distance between the piston and cylinder head at TDC. Part number is 99601, or Summit part number ROS-99601. Cost is $559.95. Compare this to the $295.60 you'd pay for the L2291's. I'd give up the half a point compression myself.

Wait a minute. They lost your FE heads??? Are you sure it's not stole? Trust me, if someone "lost" my cylinder heads, heads would roll!

At any rate, you'll need the services of a machine shop to balance the thing, as you're changing pistons. Even if you have to take a trip to find a good machine shop, it's worth the time.

If you want to spend money, there are other FE heads out there with much smaller combustion chambers. Might be worth a look. Also, FE heads should be readily available. You might grab some D2TE-AA's off a 360. Then you can run the thinner head gaskets, and maybe save money on pistons. Or just get more compression.

 

The "local" machine shop told me it would be about a week turn around to have the valves replaced and smooth the deck surface on my old D5's. After two weeks I called and he hadn't even got to them yet. I called a week later and he told me they were ready for pickup. I show up and he says "the 396 heads right?" Um no! 390 I tell him. He comes back and says the machinist is busy and he doesn't know where they are. I tell him I'll be back later that day. I get a call and he says they are having trouble finding my heads. I then tell him not to bother I'll go else where. I had $9K for the motor build so $1500 for a set of RPM's was no biggie. I now have a 67 390 with C6 heads and I really don't want to lose them so I may drive the 200 miles to the good machine shop. I already have a set of RPM's with less then 5K miles on them though.

 

I would have made him buy your replacement heads.

 

Looks like I'll go with the L2291's. I can't see spending almost twice the price for half a point.

 

I think if you CC the Ed Heads..you'll find out there closer to 74cc's than the advertised 72cc...JMO

RJ