FE Power Forums

FE Power Forums => FE Technical Forum => Topic started by: 66gtafairlane on October 15, 2026, 09:39:43 PM

Title: 0.030 piston availability for 390 - around 10,5 compression target
Post by: 66gtafairlane on October 15, 2026, 09:39:43 PM

Hi,

Street 390.Stock 3.78 stroke and connecting rods. Currently bored 0.020 and has around 9.2 with L2291 pistons.
These pistons have 1.776" compression height and 10 cc dish/ recess.
Edelbrock RPM heads with 72 cc chambers.
Targeting for 10,2-10,8 ratio.
Have not been able to find any off-the-shelf pistons yet - is a custom piston needed ?

Thanks !

Title: Re: 0.030 piston availability for 390 - around 10,5 compression target
Post by: chilly460 on October 16, 2026, 04:22:06 AM

Autotec 1000778

Title: Re: 0.030 piston availability for 390 - around 10,5 compression target
Post by: blykins on October 16, 2026, 07:37:22 AM

The Edelbrocks will probably run a little fat on the chamber size, probably closer to 74.

Another option is a DSS Piston, 5cc flat top.  Would put you at around 10.0-10.1:1 set up at zero deck at TDC with a .040" gasket.

Title: Re: 0.030 piston availability for 390 - around 10,5 compression target
Post by: 66gtafairlane on October 16, 2026, 08:09:19 PM

Ok, guess there is no easy way around this.The block needs to be decked. Now L2291A pistons sit 0.024" below deck and with -10 cc recess volume compression is 9.2.
Decking the block to 0 clearance and adding set of -5 cc pistons would bring the compression up to 10.0 - 10.2 with 0.040 gasket- perfect for this pump gas Galaxie.

Thanks for your input.

Title: Re: 0.030 piston availability for 390 - around 10,5 compression target
Post by: frnkeore on October 17, 2026, 11:15:47 AM

You can pick up a extra 1.1cc using a .038 x 4.33 Clevite/Mahle 3389 gasket, over the Felpro 1020 .041 x 4.40 gasket.

.038 isn't to close.