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Carrera3.5L Carrera3.5L is offline
Doesn't want/need a 3.6L
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Join Date: May 2004
Posts: 1,635
Originally posted by Roamer
In light of these well educated responses, it might make sense to look into new pistons with greater relief and higher static compression, say a 9.8:1 (to stay with a single plug) then combine that with a higher lift cam like the S or GE-60 (or some variant on either).

Ralph, how do the carb/MFI pistons you mentioned differ from a hemi style (which I believe may interefere with the flame propogation)?

Thanks guys!
The Carb/MFI piston is what is referred to as the hemi-style. This piston shouldn't be used with the stock Motronic system and single plug for some of the reasons you mention. It should only be considered as an alternative when changing to twin-plug ignition (like I am). In my opinion (and that of some other engine builders), the carb spec piston will work better with Motronic and twin-plugs than the stock shaped piston does. My buddy who was the head engine builder at Andial/Porsche Motorsport NA for over 15 years confirms this is the way to go, as the 962's all used a version of Motronic (albeit more advanced) and used this hemi-style piston shape with twin-ignition. Only the very early 962 engines with single ignition used a wedged dome piston similar in shape to the stock Motronic. I don't have a picture to reference that shows the contrast right now, but I think that Wayne's excellent book shows what I am referring to.

BTW, my buddie's 3.4L twin-plug with Motronic uses the hemi-style piston and with 964 cams, headers by George and Steve Wong's magic the car runs awesome.

1988 Carrera w/ 3.5L Twin-Plug

2008 Cayman S (coming soon)
Old 06-03-2004, 08:10 AM
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