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SicBastard · 09-13-2008, 02:15 PM

I've been reading up on piston design. I've read a few debates on reverse dome vs. traditional circumferential dish. I was leaning towards a reverse dome when I cam across some writings by Larry Widmer of Endyn.

He has some interesting theories about basically building a reverse dome on the exhaust side of the piston with a regular dome on the intake side of the piston in order to mechanically induce swirl and a better/faster/more localized burn. Even more interesting than his theories are his results! His personal street car is running 13.4:1 compression on 92 octane with VERY little ignition advance (down to 10 degrees), and 300 hp out of 2L with incredibly low BSFC. He originally developed his ideas in the 70s while working on 2 valve nascar heads, though Endyn now seems to specialize parts for N/A hondas.

I've really enjoyed his articles:

The Old One - Energy Dynamics

and here are some pics of his ideas on piston design I pilfered from his web site (I hope he doesn't mind)

I have a set of stock CNC LS7 heads that have been milled to a 63cc cumbustion chamber

What's up with the funny button of material in the chamber just above the spark plug between the intake and exhaust halves of the chamber? I hope some of the head porters stop by.

With the cam that I am considering now with a IVC of 43.5/68.5 @ .050"/.006" lift I am going to need a dish of about 16cc to keep my DCR below 9. I think that might be a difficult piston to design. Especially for these LS7 heads which seem to have the majority of their chamber volume below the intake (which Mr. Widmer suggests I eliminate with a partial traditional dome; even at the expense of intake valve lift!).

Has anyone tried "soft head" style design on an LS or any other engine?

09-13-2008, 02:15 PM	#104
SicBastard Zilvia Addict Join Date: Mar 2006 Location: New York, NY Posts: 803 Trader Rating: (0)	I've been reading up on piston design. I've read a few debates on reverse dome vs. traditional circumferential dish. I was leaning towards a reverse dome when I cam across some writings by Larry Widmer of Endyn. He has some interesting theories about basically building a reverse dome on the exhaust side of the piston with a regular dome on the intake side of the piston in order to mechanically induce swirl and a better/faster/more localized burn. Even more interesting than his theories are his results! His personal street car is running 13.4:1 compression on 92 octane with VERY little ignition advance (down to 10 degrees), and 300 hp out of 2L with incredibly low BSFC. He originally developed his ideas in the 70s while working on 2 valve nascar heads, though Endyn now seems to specialize parts for N/A hondas. I've really enjoyed his articles: The Old One - Energy Dynamics and here are some pics of his ideas on piston design I pilfered from his web site (I hope he doesn't mind) I have a set of stock CNC LS7 heads that have been milled to a 63cc cumbustion chamber What's up with the funny button of material in the chamber just above the spark plug between the intake and exhaust halves of the chamber? I hope some of the head porters stop by. With the cam that I am considering now with a IVC of 43.5/68.5 @ .050"/.006" lift I am going to need a dish of about 16cc to keep my DCR below 9. I think that might be a difficult piston to design. Especially for these LS7 heads which seem to have the majority of their chamber volume below the intake (which Mr. Widmer suggests I eliminate with a partial traditional dome; even at the expense of intake valve lift!). Has anyone tried "soft head" style design on an LS or any other engine? __________________ BURN OUT IN YOUR FACE! 1998 S14 LS7/T56 swap in progress, build thread: http://zilvia.net/f/tech-talk/147301...d-gto-pan.html Last edited by SicBastard; 09-13-2008 at 04:17 PM..