Head and piston top CC numbers
02-02-2009, 07:28 PM
#17
Nordschleife Master
I compared the "compression height" ie the measure difference of wrist pin to top of piston with both 928S4/GT late model and 951 pistons. With my non-laboratory conditions I came up with a difference of 2,35 - 2,38mm. I am sure with better instruments one might get more specific measures. So in order to deploy 951 pistons in 928S4 block you should get yourself a GTS crank or specially made con rods (150mm + 2,35-2,38mm) in order to get the piston all the way up the cylinder. Regards Teemu S
02-02-2009, 08:24 PM
#18
Road Warrior
Rennlist Member
Rennlist Member
dont' forget that static compression isn't such a great tool compared to effective dynamic compression which considers cam settings which can impact compression considerably...
I've used this calculator before: http://www.kb-silvolite.com/calc.php?action=comp
I've used this calculator before: http://www.kb-silvolite.com/calc.php?action=comp
02-02-2009, 08:37 PM
#19
Nordschleife Master
From a senior member:
"Hi, I measured 3 pistons. They are from my GT. I don't have any S4 pistons. I measured 42.60 mm to 42.62 mm. Piston pin center to piston top."
This 928 community is pretty damn great!
"Hi, I measured 3 pistons. They are from my GT. I don't have any S4 pistons. I measured 42.60 mm to 42.62 mm. Piston pin center to piston top."
This 928 community is pretty damn great!
02-03-2009, 04:19 AM
#20
Addict
Rennlist Member
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Thread Starter
'78-91 pistons are all same 42.6mm AFAIK. Block height is same, crank lenght is same and rod lenght is same too. GTS is only odd one with different crank and piston compression height. Total height is 232.xx mm IIRR.
02-03-2009, 01:50 PM
#21
Road Warrior
Rennlist Member
Rennlist Member
85/86 had a totally different dish on top vs S4 and up, and heads/valve sizes were substantially smaller/cams were different too.
deck ht's vary as much as .010" due to block production/casting issues on 5L motors, as did wall thickness.
85 blocks had a much thicker cyl wall than later blocks (good for boring up to 104.5mm), later blocks had water jackets around exhaust ports, minor oil control mods depending on MY.
5.0 cranks and rods were the same, AFAIK.
12-10-2009, 02:35 PM
#24
12-10-2009, 02:38 PM
#25
Piston/Deck height is near zero right?
12-10-2009, 02:42 PM
#26
When I measured my pistons, I measured them after a quite thick thermal coating was applied - I remember specifically that it was a sizable difference relatively for the coating.
12-10-2009, 04:58 PM
#27
Man of many SIGs
Rennlist Member
Rennlist Member
04-15-2013, 12:51 AM
#28
Team Owner
for others that may have missed this thread,
a bump
a bump
