[DeTomaso] 351 C Compression Question

[Thomas Borcich]

Jack, thanks for the help... take a look at the link below...this is supposedly a 351 OEM dished piston that came in 351C 4V motor...but your's didn't have that? Our motors were considered the Cobra Jet motors as far as my research leads me...those might have had the flat top vs. the dished piston.

http://www.fordmuscle.com/pictures/dsfordguy/351cpiston2.jpg

https://www.fordmuscle.com/forums/all-ford-techboard/461295-anyone-know-cc-s-dishes-stock-351c-pistons.html#post1306321

Your comments are interesting about the Quenched heads...I have read conflicting reports that the Open Chamber heads had better flame travel because the plugs were not shrouded the way the quenched chamber plug was, but I have also read that the open chamber head was more susceptible to detonation.



Best regards, 

Tom Borcich



From: JDeRyke at aol.com
Date: Mon, 8 Dec 2008 13:56:59 -0500
Subject: Re: [DeTomaso] 351 C Compression Question
To: tborcich at msn.com; detomaso at realbig.com

In a message dated 12/8/08 6:54:25 AM, tborcich at msn.com writes:



My 72 351C (low compression open chamber heads) was rebuilt with TRW Forged flat top pistons.



OEM cast pistons were also flat tops in my '72. The large open chambers dropped the compression from 10-1/2:1 to around 8-1/2:1, and additionally, the cam timing was backed off by retarding the crank chain sprocket. You really need to check the compression volume to see what you wound up with after block-decking (and maybe boring? You didn't say), but I doubt if its above 9:1. And thats about all those open combustion chambers will stand without pinging on todays gas. Closed-chamber heads had 2 large squish areas that vastly increased turbulence during the power stroke compared to open chambers, so even with domed pistons to fill up the space in your open heads, the useable power will be notably less. Expect a hp increase of 35-40 horses just from closed chamber heads, which also need less ignition advance. I'd continue looking for new heads- ideally, aluminum ones- which with your excellent pistons, will give around 10-1/2:1 as a bolt-on, and will work fine with todays fuel. I've been running SVO heads with flat-top TRWs since 1990 and thats what my measured C.R came out to be. Good luck, Tom- J Deryke


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