Technical Camshaft Gurus...2 minutes please

I have a 390 in my Cadillac, and plan to rebuild it in the future.

At some stage I will change the old Carter AFB for a Street Demon or go with a 2x2 or 3x2 setup. The exhaust manifolds are stock, and I will tidy up the heads up a little when the engine is apart. Nothing too wild, just a little more than stock.

I have found a camshaft, but don't understand camshafts enough to know how it will perform - the inlet and exhaust duration are quite different. The cam is a Sealed Power CS-256 (specs are here)

I would appreciate it if someone could tell me how his cam would perform in my engine....specifically idle quality, fuel economy and rpm range.

Thanks in anticipation

 

Generally speaking, with 203 degrees duration @.050 and .452" lift, that is a fairly mild cam. Should idle well & have good idle vacuum. Good low and mid range power band. I would guess it tops out around 4500 RPM. I am not a cam "guru", and don't know much about the flow charastics of that engine, but for a carbureted V-8 that should be in the ballpark.

 

that chart makes no sense to me , there must be a misprint. what i found on o'reilly's website is that both intake and exhaust have duration of 203 degrees at .050 lift

i'm guessing that is a stock camshaft or close to stock....or i may be wrong

http://www.oreillyauto.com/site/c/detail/SPO0/CS256.oap?ck=Search_cs256_-1_2126&keyword=cs256

 

Thanks for the replies Gents,

I was concerned about the big difference between the intake and exhaust duration. A typo would explain it.

 

Early intake closing to build compression for low static CR piston/ head combo. You have the chance to make the engine more efficient with a better camshaft/piston selection.

 

Hi Joel,

I sorta get what you are saying. There is a fairly limited number of cams available for this engine.

Any recommendations? Increased efficiency is exactly what I am looking to achieve.

 

The stock camshaft from my 59 390 is Intake 201 @.050 .268 lobe lift Exhaust 202 @ .050 .265 lift 113lsa.

I think the one you have linked is a stock replacement cam. Not sure where you guys are seeing it has different intake and exhaust duration?

I had Comp Cams re-grind my original cam to the following specs. Only other mods to the engine were a bit of bowl work, LS1 valves and LS7 valvesprings/retainers. It's not a race car but feels much stronger than I expected considering everything else is stock. I did have to raise the idle to a bit over 600 for it to idle smooth as it was a little choppy at the stock idle spec of I believe 450.

212/212 .280/.280 114lsa

 

Have you seen this blog? I know it's thrown around a lot for guys building early Cad motors. Maybe it'll help with the duration of cam.

http://hotrodcaddy.com/?p=17

Alex

 

Isky still offers several cams for the 390 Cadillac.

 

It's a 274 advertised with 203 int 203 exh duration at .050
Pretty close to stock duration but the ramps , CL s and overlap might be different than stock. I don't see any major differences though.

 

Thanks everyone. I am looking for a little bit more than a stock cam so I will let this one go, and will continue to scout around