Open

According to a 1987 General Motors Performance Parts catalog I have: ID # 3947886 is part # 3959105 Piston assembly STD, 427 CID, Chevrolet 68-69 W/H.D. & Aluminum Block (RPO L-88 & ZL-1) 12.5:1 Open Chamber, Forged Aluminum, Floating Pin Design, Use retainer P/N 3942423 (I.D.3947886 or 3959108) I hope this helps.

Bill

Thank you BB Bill....
RA

Your welcome, glad to help.

Bill

Open chamber.

1967 1st design L88 was closed chamber.

Thanks, Im looking for 1st design pistons that work with the 3919842 aluminum heads. It has around 106.8cc closed chamber head. I thought the combination could work one way, but not the other. I don’t think open chamber pistons will work with a close chamber head.

No they will not

Bill