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?

Actually I’ve never heard of 3” outlet iron manifolds. These are just the oversized rare 2.5” manifolds and the 3” head pipes rare offers. They neck down the end so it hooks to the manifolds.

Paul,, were you kidding or can you get 600 hp from a 254 cfm head? I built a 455 once with 325 cfm butler ported round e- heads, 260ish/270ish solid roller, port matched victor intake with a 1050 dominator and made 620 hp at 6100. Maybe I missed the mark on that one.

What you expect. Morris a top pro expert 1000 hp builds.
Same disappoint nicks garage same thing Mopar 30 yrs
Both where mild builds.
Least both spent whole day testing and tuning most othrr shops wouldn't. .

Ya its for show but ..
Id love see Butler or Kuffman do dyno tests m

No , not kidding Here's a pump gas build that made over 590 with 260 CFM heads . We were limited on intake manifold because it was a nostalgic build and had the be period correct

650 was common for our iron d-port, high compression 455's with a Warrior manifold.



https://www.facebook.com/share/p/18m7iC3HVv/

From Pontiac.

Stan

I have long tube Hookers on my 470 in my 2nd gen. They ARE a pain for sure. Down tubes are wrapped, Wrap never stays on collectors tho. Dual 3" all way to splitters. I wanted some RARE manifolds. But cost for me, being on Canada, couldn't justify it

I've run headers 3 times, manifolds twice. On my current engine done by SD Performance at approx 462" 570 HP, Dave said headers were worth 30-50 HP. Noticeable difference in the car, slower revs and different sound with 2.5" manifolds to a 2.5" stainless exhaust system. Back to Doug's headers again.

I'd like to see back to back timeslips, I've never pulled into the beams and seen a dyno in the other lane.

I had hooker 1 5/8 4 tubes on my stock 70 RAIII bird and raced it for a while that way. Went back to the RA exhaust manifolds years ago and have raced it extensively that way. Never changed the exhaust system just added the mandrel bent down pipes

The car never ran a tenth or two either way depending on the DA. So it was a wash for me but we're talking about a car that's completely stock, only 400 cubes, and only runs bottom 13's with a best corrected 12.76. maybe a bigger engine with more HP might see a different outcome but that's not what determines the choice for me. It all depends on what the goals are for the car.

Finally had a chance to watch the video. Attention needs to be paid to the exhaust ports if one wants to make big power with a d-port head. This isn't breaking news it's always been that way. Pontiac figured it out in the mid 60's.

Curious what folks opinions are with a trade trading power for conviencece when deciding between headers and manifolds?

With tuned collectors the headers would've been good for about twenty horsepower and two tenths at the track.

I agree, there was 20 HP improvement left on that engine with header tuning, on a really hot day I would expect the RA manifolds to loose even more power versus Morris’s climate controlled shop, and the octane required might start to climb on the manifold combo to. At 3700 RPM the RA manifold combo made 417 HP and 590 TQ, and the headers was 442HP and 628 TQ. That is a 25HP/38TQ difference, and probably gets worse when the pull starts earlier yet. It is also where a street engine spends most of its life. It must have had lot of a lot of intake reversion to create that much difference at 3700 RPM, probably needed a RPM intake for the RA manifolds?? If that engine was brought to our shop to install the engine you would have to tie me to a chair to let someone put exhaust manifolds on it. LOL

I was impressed when Morris took the time to cut apart the spark plug to read it and added the spacer for the next step to lean it up a little. Seems like he makes pretty logical steps in the video on the dyno pulls. I appreciate posting up the link to watch it, good stuff.

For me it's a decision between extracting every hp possible or sacrificing some hp for the stock look of RA manifolds. I have about a 415 hp 455 in my '72 LeMans right now with RA manifolds and will start on a 600 hp 494 ci motor soon to replace it. I'm struggling with should I use RP RA manifolds or headers? I have both, but I don't really want to move my brake lines and metering block that's on the frame in the way for headers. It's a 50/50 right now, but I'll probably end up with RA manifolds (2.5") since I'll never race the car.

He had to stretch the video past twenty five minutes :D

Like I mentioned, depends on the goals with the car. To me headers are not an inconvenience. I really don't have much if any issues using them. If I'm going for a max effort build with big cubes and I care about every HP I can squeeze out of it, it'll have a set of big tube headers on it without question.

If it's a cruiser, or more of a restoration, or some sort of sneaky build made to look stock, it'll have the manifolds on it. So it's really a pretty simple decision for me.

What I've seen time & time again is that aftermarket D port heads need like in the 38 degree range of timing, think that would have made a significant difference.

Since there was a dip/drop in TQ at a lower RPM with the manifolds, bet a Perf RPM intake would have taken care of that. Single planes would probable do better once you get over say 310cfm or so.

As for the SD testing, it was pretty common knowledge OE exhaust systems were restrictive, especially considering the constraints of regulations at the time. One of the top day-one mods were headers & true dual exhaust. Being an F body was considered the main recipient of the SD, it was well known the exhaust was even more restrictive than most, with the bends and crossover muffler.

At least that's some of my thoughts on the topic, in general.


.

Where that already has the RA manifolds with the down pipe and full exhaust, I can’t blame you for keeping with them. As long as it has the correct mix of parts, like a dual plane intake and the cam to match, there is no reason to use headers. But starting from scratch buying parts and a stock look is really not a goal with close to 600HP, my car would get headers.

That engine Morris had on the dyno loosing about 40 lbs of torque at 3700 was showing a bad mix of parts someplace with the RA manifolds, the headers solved it. Which would be easy to overcome, but running that engine as it is with the RA manifolds would not have been very ideal at all.

I have to agree with this and Steve Morris. The heads became a choke point. I would bet if the owner used ported Edelbrock round port heads the results would have been different. I dont understand why anyone would buy aluminum D port heads for a serious build. Back in the day everyone wanted round port heads. They were hard to find and expensive. Now we have several versions of aluminum round port heads and people go and buy aluminum d port heads. I dont get it.

The lower torque down low with manifolds doesn't surprise me. That's pretty typical of every engine going from short tube to long tube headers.

Short tube headers tend to do ok for higher rpm power and lack a bit in low rpm torque production. Long tubes favor low rpm torque production. Every engine Ive ever seen on the dyno shows a similar result. So what you saw on Steve's video with low rpm torque differences is pretty normal.

600hp 494" RA manifolds won't flow enough for that engine IMHO.

I agree, 600 hp with headers and I know I'll be killing hp with the RA manifolds. That's why I am struggling with the decision. I'll either use a TII or an RPM intake and dyno the motor with headers first and then with manifolds and then make my decision.

Back in the 80s I had a local exhaust shop make some exhaust for my 70 gto. I put on some ram air manifolds and I had a set of log manifolds. I think the outlet on the logs were smaller than the ram airs. He looked it up in his book for all the factory bend angles and stuff. I remember him telling me his book said to use 2" pipe and expand the end to fit the 2.25' outlets. He said it would be better just to use 2.25" pipe ..it would give me more power and I agreed.
Fast forward 40 years....The 3" pipes must be a improvement even though its necked down on the end. Im trying to keep a stockish look under the hood thats why I still have iron heads, intake and exhaust.

I didn’t spend the money to port my heads to 322cfm, and upgrade the intake valves to 2.19”, to wonder how many ft/lbs of TQ I’m losing by running manifolds. No one makes them to fit my ‘65 Lamnas anyway….so it’s a moot point for me.

The 1-7/8 Dougs fit great and tuck up nicely, so there’s really no downside.

When my engine was dynoed, I was more interested in how much I was leaving on the table due to intake choice….hood clearance, single vs dual plane, etc.

So we dynoed 4 intakes and found out. This summer, I hope to correlate the engine dyno results to the 1320 dyno….gonna have an intake shootout day.

So.................... what did the dyno say ?

30-50 hp drop was noticeable in my 462" 570 HP engine. Headers are a pain in the ass, but worth it IMHO. Spent money cnc porting heads & intake to gain HP, not going to leave that much on the table. Stocker or under 500 HP manifolds make sense.

455, 66 casting heads (stock, other than valvesprings), non-adjustable valvetrain, 7.8:1 compression ratio, Performer, Qjet, HEI, cam mentioned in signature below, 87 octane. Used a wideband, AFR corrected to ~12.8:1 for both run.

Stock log manifolds vs. Tribal Tubes Tri-Y headers.

Same exhaust/mufflers, other than what had to be cut out to fit the headers.

Had that same 455 in my G/A years age with a comp 280 cam not my favorite but was in it when I got it. HSD and a 800 Holley speadbore it went 12.88@107 I have no idea of HP but it ran ok and it would run on anything you put in the tank.

I can't argue with that.

Anyone seen a PUMP GAS naturally aspirated engine that was dynoed with EXHAUST manifold's that did better on peak power than this Pontiac engine MRE did in the video? Round port? Even from a different engine platform like a modern LS, BBC, Ford 385 series or a Hemi? Not counting header combos or race gas, just something using exhaust manifold’s on pump gas. I am not coming up with anything on pump gas beyond 600? This was 623HP@5700.

Friendly dyno?

Jay I have not but I have seen some "generous" dynos that the motor never "ran the number" by the wt/mph on the car. The "stingy' Stuska we used on my 455 pump gas in my TA was below what the calculators say. 525 on the dyno 124 MPH weighing 3750. 587 on Wallace calculator. Pump gas and a Torker II not a Northwind!