Camshaft Valve overlap / LSA with CIS

christian977 · 10-18-2021, 01:59 PM

Hi All,

Just had my cams reconditioned, they were rewelded, ground and re hardened.

Lift and duration is correct, but the lobe seperation angle is a little less than what i was expecting

..

I am sure i will find out for myself, but anyone think a 110 LSA will be OK with CIS? Anyone have any experience with CIS and 22degree of valve overlap...

Thanks
Christian

christian977 · 10-18-2021, 02:02 PM

Note that it will have 10.5:1 compression, nice rods, WUR and fuel distribution unit rebuilt, lots of new parts!!

racing97 · 10-18-2021, 04:58 PM

You will be just fine

christian977 · 10-19-2021, 02:42 AM

Thanks
I did quite a bit of research and have found that the lift and duration of my reground cams are very similar to webcam 20/21, (found the cam card on their website when looking for details of cams that work good with CIS) My cam moments on the intake lobe all a little earlier, the closing of the exhaust @ TDC is a little later though. (hence the larger valve overlap and the smaller LSA) Anyone with any theories as to how that will effect the engine behavior please chime in.

i would assume there is engine builders out there that check the valve moments once timing is set the Porsche way??
I would think checking the valve moments is more accurate than setting the timing the Porsche way to know exactly what you have? Any of you guys check the valve moments when you build engines??
I am planning on checking the valve moments once timed to see where it is really at.

racing97 · 10-19-2021, 02:19 PM

The SC cam and many later model cams are 112 L/C and your cams are 20/21 or Mod
S and usually they are ground on 110 to 106 L/C which would make the cam open a little earlier.
This format will scramble all my data but:
If you have an interest PM me your email and I will send you all the files you need off of my Cam Dr for SC 20/21 and 964
regards