St4s based engines, seeking advice on pistons and heads

stiglarsenDK

I’m working on another 2 st4s based engines for the track.
Engine 1
Left side dual pick ups, RS flywheel and generator
Crank 996RS w rods and primary gear
Heads T1 w T1 cams (from 2000 SPS)
Throttles from 996 SPS
Question ; What pistons/CR should I look for

Engine 2 Less exotic
Left side dual pick ups, RS flywheel and generator
Crank : std, rods from SP5, std primary gear
Cams ; T1
Heads ?!
Throttles from 996 SPS

Question: I have only 1 set of T1 heads, but 2 sets of T1 cams .. does the drop head from ST4s vs a normal 996 make a Big difference ( valve size bring the same ) ?
Should I change the pistons or just give a squeze for higher CR?

Now ; Engine experts ; any advice to above ?

stafford

I did enquire about putting T1 cams into a Drop Head 99 unit but was advised that the intakes on the Drop Head just do not tune well, hence I shall not be bothering.
I continue to look for 996 Superbike heads.

nine16

Yes, just use regular 996 heads. I'm actually not aware of any differences between them and the SPS. Same valve size, just different cams.

Mine has a pretty similar spec except I kept the ST4S throttle bodies but upped the single injectors to 450 cc/min, but I do not know the CR--I'd guess 12.5 or 13:1. It's even tougher since different companies can measure differently. I just wanted it to be able to run on normal pump premium without detonation.

brad black

if you set the squish with std pistons you get 12:1 from memory. if you want more there's a pistal that gives 14 or so.

the drop cam heads have poorer exhaust ports, but they can be fixed. inlet is the same.

the 97-98 sps head is a different #, but all 996/996sps heads 99> are the same part #.

stiglarsenDK

Thabks for comments...

Have an eye on some 996 heads...