RB Cam Performing Right?

[lewtot184]

No.
The 231 degrees is the Mopar Performance BS of multiplying the advertised number by 0.85. The 221 degrees is the measured 0.050" duration of the 272 cam.

My 272 measured 223@.050", but seat timing was 277 at .006" in the 440 i ran in my r/ t. I think .85 number is ridiculous and is a marketing scam. I don't think a flat tappet cam can survive a real .85.

 

[gtxrt]

ok 272x.82=223. so his old 484 cam had about 233 duration at .050. 241x.82=233. about one size bigger than the 228 in there now. the big advantage of the 484 was the tight 108 LSA that even Chrysler knew back then to go for a tight LSA. what hurts is its low lift.

 

[dvw]

? I think the cam is:
112 LSA,
108 ICL

You are correct, I misread. I like the 112 much better for manifolds.
Doug

 

[lewtot184]

ok 272x.82=223. so his old 484 cam had about 233 duration at .050. 241x.82=233. about one size bigger than the 228 in there now. the big advantage of the 484 was the tight 108 LSA that even Chrysler knew back then to go for a tight LSA. what hurts is its low lift.

The 284/.484 i measured was 286@.006", 236@.050", 146@.200". I think they're racer brown ssh25 clones.

 

[gtxrt]

You are correct, I misread. I like the 112 much better for manifolds.
Doug

never seen a Dyno tests about LSA and exhaust manifolds.there are tests with a split duration with more exhaust duration but never LSA tests. or are just saying that you like it better.

 

[dvw]

never seen a Dyno tests about LSA and exhaust manifolds.there are tests with a split duration with more exhaust duration but never LSA tests. or are just saying that you like it better.

Andy F did a bunch of tests that liked the wider LCA with manifolds. I believe if you ask Dwayne about pure stocks he will agree.
Doug

 

[gtxrt]

470 HP and 520 TQ wouldn't be bad.

I have to re-think that. like pr heads said your in the ball park. his engine with header=482-528 then minus at least 25 HP and 30 TQ would be about 457 HP and 498 TQ without headers. yours is making 450 HP and 490 TQ very close. I know you have a bigger cam but with exhaust manifolds your not getting the full benefit of the bigger cam. the bigger the cam the more headers help. 460 HP and 500 TQ wouldn't be too bad. that 274 comp cam makes good power even if it is about one size smaller with more vacuum too. all dyno meters will give different numbers too.

 

[Road Grabber]

I have to re-think that. like pr heads said your in the ball park. his engine with header=482-528 then minus at least 25 HP and 30 TQ would be about 457 HP and 498 TQ without headers. yours is making 450 HP and 490 TQ very close. I know you have a bigger cam but with exhaust manifolds your not getting the full benefit of the bigger cam. the bigger the cam the more headers help. 460 HP and 500 TQ wouldn't be too bad. that 274 comp cam makes good power even if it is about one size smaller with more vacuum too. all dyno meters will give different numbers too.

Thanks for that info and calculated estimate. I did request future dyno testing with headers and manifolds.

If the numbers don’t impress me and I have to install headers to justify the build I would be interested in knowing about a higher lift cam to use with headers that maximizes the head flow and is streetable.

Also it will be interesting to see improvement if any with the right custom fit pushrods installed that aren’t flexing like the weaker 5/16 rods that bent. One set completely failed and at least half were bent.