Steve Morris does header vs cast manifold Pontiac dyno test
 

Very interesting results. https://www.youtube.com/watch?v=eTOR9afWCRY

Those results blew me away.

I thought his camshaft design was the reason for the results.

Did he say what the cam specs are?

nope...i wish he had. All they said was it was a decent size.
,,,

Pontiac tested headers vs manifolds developing the SD455 engine

That is very interesting.
Which pontiac cam is the M7?

No general cam specs shared. At least on Engine Masters they’re pretty good at sharing cam specs, these guys not so much.

Calling Pontiac round port heads “oval port” and acting like D-port Edelbrock heads are somehow quite inferior to the “oval port” heads which they’re not. Resident Pontiac expert, sure.

Yes surprisingly they only were down about 15 horsepower with the exhaust manifolds but everything about that dyno session seemed lacking to me.

I’m thinking some 2” headers compared to the manifolds would have shown a much bigger spread, like 40 plus horsepower. No specs shared on the dyno headers either so…..

I think the performance viewed within enthusiastic Street RPM ranges shows the iron EXH manifold win.

Again though the EXH system after the manifolds matters so much for Reversion mitigation from idle through passing power RPMs.

The juice ain’t worth the squeeze for a street car (headers vs manifolds) IMO. I reckon if you took the time to properly install insulating header wrap it would help along with running a small high torque starter.

I'm sorry a set of ported heads, Northwind ported intake Holley and we barely drop HP and TQ with manifolds?? Heck Lee on his chassis dyno and a stock 455 lost more. Look at my recent dyno testing 2" vs Tri Ys and what we lost!

I don't know, I've heard it was a tight LSA version of the RAIV but never been able to verify that.

I think this is a "every combination" is different situation. It's definitely not the normal most folks see when comparing headers to manifolds.... Someday I'll watch the video. Cam, compression and head flow can skew the results in a big way.

I think the owner of the engine is a member here, hopefully he'll weigh in with more details.

for the Pontiac tested headers vs manifolds developing the SD455 engine post:

I didn't see any reference to M 7 on the pulls, but the only one that was really different is this one: (does have a 'M' in it, for mechanical/solid?)

it had 1 7/8" headers:

300/310 M w/High Lift
.345 Int .026" lash
.354 Exh .028" lash

uncorrected = 463 HP @ 5200 rpm 441 HP @ 6000 rpm

Most of the other pulls were 041 or 041 cheater cams with one a G/K 041,

:confused:

That cam your talking about (300/310) was 257/264 @ .050. I don't think that was the cam used in the test I posted. I'm thinking it was more of an 041 "cheater" cam..... But would like to know for sure.

Well mine only lost 4 hp and 4lbs of trq going from 1 3/4 headers to rare oversized manifolds and 3”head pipe so it can be real. Peak hp rpm was the same with both. Last time I did a comparison it was the same headers but used standard ram air manifolds and 2.5” pipes and there was a 15-17 hp difference. It looked like Steve morris video might have been 3” pipes welded onto the manifolds. They say if you double the head cfm you’ll get about its capability. My heads flow 254 cfm x 2 = 508 hp. It made 514 hp so I guess if I ever want more I’ll need more head?

Paul do you have the sheets of the pulls?
(got mine from SD Bob)


:confused:

I agree

The double the CFM is just a guide line. Big roller cam, single plane manifold with high compression would get you 600 horsepower using your dame heads..... and headers lol

No, I have the sheets Bob sent me

Running headers be like :D

Are these the 3" manifolds that have been out of production for ages?