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.

 

[1KoolBee]

Overlap is your enemy on manifold motors. Some builders have found that anything hotter than the MP .528 solid cam is counterproductive on engines with factory exhaust manifolds. Interestingly, the factory big block solid lifter cams from Chevrolet had similar specs to the MP .528. So swap cams or get headers, headers obviously will make more power.

 

[lewtot184]

I think chevy used 114lsa on their 375hp and 425hp rat motors plus the solid tappet. My personal rule of thumb is 60 degrees of overlap as a limit and less might be better.

 

[Hemirunner]

Interesting situation. It seems to be a struggle between wanting more power and keeping street manners. It’s the age old question of what is streetable?
My perspective is way different than most on here for sure, but my curiosity has me inquiring as to how you came to arrive at this combination?
My other questions would be ….
Are we really set on running manifolds and that teeny tiny little hydraulic roller? Or actually taking advantage of those good heads?
What gear are you planning on paring with that engine?
What’s the rest of the combo and what kind of driving do you intend to do with the car?

I’m the last one to advise on how to make huge power through manifolds as I think they have 3 places they belong- Restorations, FAST and factory stock racing and bolted to a turbocharger in low buck builds, but I’d rethink the manifolds and the cam.

 

[dodgeboy440]

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

Makes perfect sense !

OEM manifolds have more restrictions, hence
Slower to exhale . Permitting the engine to balance it’s breathing with its heart , the camshaft!

Mopar2ya

John

 

[Road Grabber]

I get it. It’s typical to find things out when you venture into personal uncharted waters when you leave stock high performance using aftermarket components. Using the aluminum heads caused a chain reaction.

How did I come up with this cam?

During research I heard Howard’s cams are Mopar friendly with lifter bore diameters and other stuff. I called Howard’s and asked for a cam that would help maximize the potential of the Trickflow heads yet be able to function with power brakes on the street. It was their suggestion.

Looking at what others were doing

There’s a lot of YouTube videos on 600 horsepower with headers but none with manifolds. Only Nicks Garage with stock engines using manifolds on dynos.
I don’t recall any builders on other videos giving up the cam for their builds. Holding back maybe to make you want to hire them to build your engine. Whatever bottom line I took a suggestion from Howard’s hoping to make a sizable improvement and lower the risk of detonation with aluminum heads. High power/torque as a bonus. But not where I left off. That confirmation still to come.

The car has a 3.54 Dana four speed. It won’t race on the track. I had a friend who chased huge power and it led to a lot of suspension issues and frame strengthening. It’s a six pack RT and I don’t want to convert into a 1/4 mile monster with constant costly upgrades. So it will be a driver with some fooling around.

I would put headers on the engine to capture horsepower if that’s what needs to be done but I don’t see the point of buying TTI headers without changing the cam too. I know I won’t buy crap headers. Been there done that when I was 17 and didn’t care about noise, burn wires and heat under the hood.

Next question. If I do decide to grab the horsepower ring like I see RB engines are doing like with Top end kits from Trickflow is that an engine that can be driven on the street and one that doesn’t eat itself up in a few years because of more potential wear from heavy valve spring pressure, valve guides wearing out ( smoke out the tailpipe looks like crap) and another refresh just down the road?

That kind of first hand feedback would be useful because you don’t hear about how long the high horsepower engines are lasting. Are the 600 hp engines lasting long? I know my 440 six pack with the 284/484 cam was in the car over 30 years before I pulled it. Ran great except detonation with cast heads.

Choosing a cam is very difficult choice. The vendors want to sell their products making huge gains but you don’t hear much about applications and durability. I get how the cam needs the right combination.


I might hear back in a week or two about the new dyno tests. In the meantime any thoughts about a better option if you have one be my guest.

Thanks