HP differences?
 

Im getting a new engine built... a new 383 stroker...what do you think the hp difference is between the GM847 and this cam thats going in...

GM847 234/242 .575/.595 112lsa
My Cam 236/242 .555/.276 112lsa

Would that much lift even make a difference...thats with 1.6 rrs as well...

Thanks
James

Re: HP differences?
 

Is this with stock heads? Is the duration also listed using 1.6 ratio rockers? Your duration @ .050" will increase slightly if not. If your heads are unported then I don't think it would be that big of a difference. You will see some good torque #s though. Duration is what really makes the upper rpm power, but to me the strokers are better making power down low opposed to up top.

Re: HP differences?
 

I tried the 847 cam just a few months back. It only lost 5rwhp over my high lift Comp cam. It did however loose 200 rpm at the top end. I believe I lost too much curtain area with it's lower lifts over the I.608 E.613. Comp cam I had originally. I am not a fan of large extreme cams (assuming that's the Comp cam) they dump power just after peak power. You would do alot better talking with LLoyd or Bret Bauer about a custom cam...I mean a lot better.........!!!!!!! The 847 would be my choice for the off the shelf cam....Sorry to say, I don't see any horse power increase with that cam judging by my results with a higher lift cam than that Comp you want to use....


Jim

Re: HP differences?
 

Yah they are both with 1.6rr's and at .050". They heads are fully ported...to roughly i think 180cc (not sure) Heres what the build sheet says...

Type:
GM Aluminum LT1, three angle performance valve job, fully ported, valves back cut and new valve guides

Combustion Chamber:
54cc

Intake Runner:
180 cc

Intake Valves:
Manley Stainless Steel 2.00"

Exhaust Valves:
Manley Stainless steel 1.56"

They are stock heads, but modified. Being that the main difference in the cams is the lift and a bit on the duration...I didnt think there would be much difference...after all...Big lift doesnt always mean big numbers...
Any other comments would welcomed...thanks

Re: HP differences?
 

It's hard to tell without knowing what cam lobes and springs... your lower lift cam could have some lobes that are hard to control and really kill power over 5500rpm.

Bret

Re: HP differences?
 

Oops, my point got kind of screwed up....

I was trying to tell you that even though, I have a slighty more agressive cam than yours (above .200 lift anyways) I did not see any real difference in power between mine and the 847 cam. Real world testing....You'll also notice cams of same lift, valve events, but a faster (less base duration) ramp, will dyno close to that of another cam of same .050 duration numbers (but with a slower ramp used). The faster ramps are good for driveabilty but, have a tendancy to not rpm as well in the higher rpms. Average horse power is going to accellerate you, and that's why I like softer ramps (generally more rpm ability). The guy to really talk to is Bret...When I get around to changing out my cam again I'll be using Bret. He can get the correct intake and exhaust events alot better than I can, and that's way more important to making power than just comparing two similar cams. ;)

Re: HP differences?
 

OH SHET!! My bad...thats why none of this was making any senses...i typed the cam specs wrong...lol Sorry guys...thanks for your time and input on that though...lol

Lets try this again...
GM847 234/242 .575/.595 112lsa
My Cam 236/242 .555/.576 112lsa

Again...sorry about that...
-James

Re: HP differences?
 

No we understood that you did.... the point is the different cam lobes can drasictally change the output of the motor.

Bret

Re: HP differences?
 

Bret,
what else do you need to know to accurately make a judgement? OR is that just it...I just have to wait and see?

Re: HP differences?
 

very very close cams

Re: HP differences?
 

Thats what I thought...but we have some internet mechanics that like to act like they know what they are talking about so it made me think a bit more. I dont see a very big gain in giong with the 847 cam...considerign this one is close enough...Thanks Guys...

Re: HP differences?
 

I think in everyday drive around and occational track use you will not see MUCH difference.

I know the 847 works for an off the shelf cam My 3750# 97 T/A with a 10:1 383 in it runs 11.50s @ 119 at a 1500 ft elevation.

Re: HP differences?
 

What will I see in my difference in cams:

383 ci

old: cc306 230/244 .510/.540
new: cc486 242/248 .584/.579

I"m thinking more high end power than the cc306 which provides low end power and torque. I'm thinking the bigger cam here will increase my rpm range but build power at higher rpm's. Am i right?

Re: HP differences?
 

Yeah it will make it rev higher a bit. My car shifts at the track at 6800 to 7000 rpm. Its still feeling strong there, but I can also feel a taper start at about 6400 rpm.

Re: HP differences?
 

94evil,

I would run the 847 over that other cam if I had the choice

Mike,

I don't think your larger cam is the way to go, the lift helps but there is too much duration and LSA there to be effective. Basically it will have crap for low end.

Bret