[ZeGermanHam]

Originally Posted by Steve C.

Proper coating helps to lower the header's external surface, compared to uncoated headers. This means lower underhood temperatures.

See the comments on that subject here:

https://www.motortrend.com/how-to/headers-dyno-test/

Are you going to test on a engine dyno ? In the old days we used to do so before ceramic coating the headers. Ceramic coated headers coming off a dyno session were dulled a bit.
Maybe these days its no big deal and therefore take this comment with a grain of salt.

Pretty dramatic reduction in surface temp in this article! I knew ceramic coating made a difference, but wasn't aware that it was so extreme. I believe there was a somewhat recent Engine Masters episode that tested various header wraps & coatings, and they arrived at the same outcome: No changes in power on the dyno stand, but big changes to surface temp. Makes me feel a little better about springing the my ceramic coated Doug's headers.

[Tim Corcoran]

Performance gains with headers will depend on many factors. One thing to consider is a wide LSA cam will work better with the RA manifolds, but a short LSA will benefit more from headers and a free flowing exhaust system.

[Sirrotica]

In the past I've run dirt track classes that required cast iron manifolds. At first I used logs, then I came across a set of RA III manifolds, there was a seat of the pants difference that you could feel. Later on I replaced the stock head pipes with pipes I made from driveshaft tubes (roughly 3 inch) another seat of the pants improvement.

The following year I moved up a class that allowed headers, and again a marked improvement. I've almost always run headers on all my street cars too, you leave HP, and efficiency on the table using cast iron. Whatever you gain from log manifolds to RA manifolds I feel you'll gain as much switching to headers, if not more. BTW, this was with with an 068 cam, nothing at all radical, cast iron intake, Q Jet carb.

I'm not someone that wants iron manifolds because headers are tougher to put on, and require a bit more maintenance, it's worth the effort for me. It took me a little while to get the procedure down to a science, but when I started using RTV on the sealing surfaces, everything worked much better. I installed Hookers on a 1976 D Port second gen, in 1988, never been off the engine, original gaskets.

[Formulajones]

Here is a back to back comparison that Paul C did using 4 tube headers and then a set of RA manifolds. All the engine details for the build are in there. Very nice pump gas 500hp 455 build.

As Paul stated, it only lost a few HP and actually made more peak torque.

Post 49

https://forums.maxperformanceinc.com...=808474&page=3

[Sirrotica]

I'm assuming since you posted after I did, the reference is to contradict my post, seems logical.

Are the manifolds in his test RARE oversized? Yes. Were mine? No, stock Pontiac RA III castings from a 1970 Judge. The crossmember had to be cut in order for the later casting to fit the 67 chassis.

Can anyone buy RARE oversized castings, as of right now, no. They've been on back order for probably 2 years.

I wasn't talking about RARE oversized manifolds, I used these Pontiac manifolds in 1976, so it's not apples to apples, is it? I've never owned a RARE manifold.

In 1976, RARE wasn't even a thought, so my experience I was talking about was a Pontiac casting, untouched.

I did explain that this was a stock class, and you had to run stock untouched parts. That's the reason for a 068 camshaft, rules said it had to be a production camshaft for the year and make of the car. The car, 1967 GTO, which had the available cast iron HO manifolds, introduced in 1967 and a 068 camshaft, 400 engine.

No dynos were involved, it was my observation on how my car behaved while I drove it. Headers picked the engine up over the RA manifolds I used in 1976. In 1977 I switched classes, and headers were allowed, I picked up more power over Pontiac castings. That's my actual experience, if it doesn't agree with the test you cited, I can't change what I experienced.

Citing a test that has different combination other than what I posted isn't apples to apples, but apples to oranges is close enough, right?

Racing stock cars you don't get time slips, you get checkered flags, I got plenty of checkered flags, so I must have been doing something right.

I have never dynoed anything I owned. I always knew if an improvement worked by passing competitors, or if it didn't work, getting passed. Not one iota of printed data, because in a few laps, I knew if it worked, or not.

FWIW, just attended Norwalk a few weeks ago, and I bet I could count the number of cars in the pits with cast manifolds on one hand. Maybe no one saw the test results.

Gotta go, sprint cars are racing tonight, I'm going to watch in person.

[Formulajones]

Um no Sirrotica, not everyone is out to get you.

That post is in reference to myself, where I mentioned it in post 18. It just took me a while to find the thread I was referring to

As far as the RARE oversized manifolds go, that's what everyone uses today so it's actually a better comparison to real world in the present time. No one (other than a restoration purist) is searching out correct dated original castings for their performance street builds, and they certainly don't want to pay the prices they command either. So it's really a non issue.

[Sirrotica]

Maybe I get that impression from this post from you, do you remember this post commenting on? Not all chevy guys like the new LS engine, some prefer the old SBC design? Your response was

Does that sound familiar?

Since it was a contradiction to my post, and it was the next post after mine, how would it look to anyone reading the thread?

I relayed my direct actual experience for the OP, if it doesn't match the test Paul C did, it insinuates my post, and experience, must be incorrect. That is the reason for the second post, further clarifying my direct experience switching from cast iron, to headers, and all the nuances between my experience with Pontiac cast manifolds, not RARE oversized manifolds. That makes my experience, and his test, not under the same parameters.

If it wasn't meant as a contradiction, then I apologize for the misunderstanding. I'm not the least bit upset, I just felt his test was on a different level, and that's the reason for me explaining the differences, so it wasn't an apples to apples comparison.

If there was a misunderstanding, I apologize to FJ, and anyone reading the thread.

BTW, the sprint car racing tonight was as good as it gets......
Good hard racing, very close racing in all 3 divisions.....

[Formulajones]

Originally Posted by Sirrotica

Maybe I get that impression from this post from you, do you remember this post commenting on? Not all chevy guys like the new LS engine, some prefer the old SBC design? Your response was

Does that sound familiar?

Since it was a contradiction to my post, and it was the next post after mine, how would it look to anyone reading the thread?

I relayed my direct actual experience for the OP, if it doesn't match the test Paul C did, it insinuates my post, and experience, must be incorrect. That is the reason for the second post, further clarifying my direct experience switching from cast iron, to headers, and all the nuances between my experience with Pontiac cast manifolds, not RARE oversized manifolds. That makes my experience, and his test, not under the same parameters.

If it wasn't meant as a contradiction, then I apologize for the misunderstanding. I'm not the least bit upset, I just felt his test was on a different level, and that's the reason for me explaining the differences, so it wasn't an apples to apples comparison.

If there was a misunderstanding, I apologize to FJ, and anyone reading the thread.

BTW, the sprint car racing tonight was as good as it gets......
Good hard racing, very close racing in all 3 divisions.....

I don't remember any of that from me but I don't recall what I had for breakfast anymore. It's all good on my end I'm only relaying good data points and information related to the subject on a very streetable pump gas engine build that mimics what most here are doing. Anyone is allowed to do what ever they want

That build was basically the recipe most here use. A 455 with Dave B ported D port heads that flow 260 cfm, a hydraulic roller that mimics the road paver camshaft, a ported factory iron intake, and 9.5:1 compression.

I did a nearly identical build on a 455 with ported iron round port heads that flow 280 cfm, 10:1 compression, same cam used in the example I posted above, a stock aluminum 455HO intake, and made 507hp/571tq through the RA exhaust manifolds on the same dyno with Paul C.

It's a drop in the bucket to make over 500hp with a Pontiac using the manifolds these days with a simple selection of parts.

You Pontiac guys have it pretty good with these RA manifolds. I play with all types of engines and very few if any have the luxury of a really nice exhaust manifold, let alone the aftermarket support that even cares to reproduce such nice pieces.

[pippintook]

I think this debate and power differences between headers and ram air manifolds will go on forever - its good debate to have
.
When I was kid I called the HO Racing Tech Line about using D port ram air manifolds versus headers on my 455. My combo then was a 455 with 96 heads (very light port job, cut .050, performer intake, qjet, stock bottom end, THM350, 3.08s, 81 TA). I think it was Ken Crocie who told me that if I ran the HC-01 (highlift version of 068) cam with ram air manifolds I would lose approx 15hp versus headers. If I ran the HC-02 cam (highlift version of 744) with ram air manifolds I would lose approx. 25hp versus headers. I am not 100% sure what size header I asked about. I am thinking I may have asked Ken to compare with the Tri-Ys. But, I am pretty sure I have the numbers right...though it is possible I may have not copied the correct info in my notes.

In this thread ( https://forums.maxperformanceinc.com...+air+manifolds ),
Ccass said when he swapped out ram air manifolds for Doug's Headers - they picked up 25hp at the wheels !

Paul C's tests where he lost only a few HP with ram air manifolds versus headers are interesting too. I like Sirrotica's approach - results and winning races. Who (maybe Smokey Yunick?) said "you dont race dynos".
For sure , the ram air maniolds are very good. I think in my next build , I am leaning towards ram air manifolds.
.
Seems a nice 2.5" mandrel bent downpipe helps a lot. When you see pic of the factory downpipe on the SD455 it almost looks like a 2.5" mandrel bent downpipe. Guess the Pontiac engineers know a good downpipe could help a lot
.
Some related questions

If you run the same 2.5" mandrel bent downpipe /mufflers etc - is there a performance different between the RARE 2.5" oversized ram air manifolds versus regular 2.25" ram air manifolds ? I asked this same question about 12 years ago ( https://forums.maxperformanceinc.com...+air+manifolds ) I am still not sure on the answer - I thought I read where someone said they found no performance difference between RARE 2.5" oversized ram air manifolds and regular ram air manifolds.

Seems we are all waiting for the RARE 2.5" to get cast in the foundry. What is going on with the regular 2.25" ram air manifolds that Ames (and other vendors) sell ? Are we also waiting for these regular 2.25" ram air manifolds to also get cast or are they available ?

[Formulajones]

I honestly don't think you're going to see a big change in power output using a 2 1/4" vs 2 1/2" RA manifolds.

Like I've said before, as have others, these manifolds work the best with a nice mandrel bend coming off the outlets. How many people actually pay attention to that detail is probably a small percentage.

The tests I've done always used a mandrel bend, and what you see on Paul C's dyno testing, is with mandrel bent head pipes. You compare that to headers as in that example I linked to, and you don't see as much difference.

Compare the 2 with some crush bent down pipes and you're going to see a significantly wider spread in power between the two because headers completely eliminate that first sharp 90 degree crush bend.

There are other variables like head flow and camshaft profile that will dictate whether an engine will like one or the other, but for the majority of guys here they like their engines with wide LSA camshafts and smooth idle where the chances are less that the scavenging affect of headers makes a big change.

The RA manifolds are a decent design for a compact oem manifold.

[mgarblik]

Last week on a 468 Cu In engine, bathtub intake, on the engine dyno. Removed long branch HO iron manifolds from Ram Air restorations with 3' extensions and replaced with lousy 1 3/4" primary tube headers from Hooker. 18" extensions. Torque with the headers increased 22-28Ft. Lbs. everywhere from 3000-6000 RPM. Average HP up 10 HP. No other changes. This was after optimizing tune with the manifolds. No tuning with the headers. So if racing, the difference is substantial. The left long branch manifold is particularly constricted around the starter. I am going to run the manifolds anyway because I like the sound and the ground clearance. Depends on the end goal. Headers make more power. Even the wrong ones. My engine needs 2" primary tubes to be the best it can be.

[Formulajones]

Originally Posted by mgarblik

Last week on a 468 Cu In engine, bathtub intake, on the engine dyno. Removed long branch HO iron manifolds from Ram Air restorations with 3' extensions and replaced with lousy 1 3/4" primary tube headers from Hooker. 18" extensions. Torque with the headers increased 22-28Ft. Lbs. everywhere from 3000-6000 RPM. Average HP up 10 HP. No other changes. This was after optimizing tune with the manifolds. No tuning with the headers. So if racing, the difference is substantial. The left long branch manifold is particularly constricted around the starter. I am going to run the manifolds anyway because I like the sound and the ground clearance. Depends on the end goal. Headers make more power. Even the wrong ones. My engine needs 2" primary tubes to be the best it can be.

That is more in line with what I would generally expect, more torque with long tube headers and marginal gains on HP. The longer individual header tubes do a better job at torque production.

Very similar to the comparison you see all the time on the dyno, shorty headers vs long tube headers. The shorty headers usually get close on HP but they fall a bit short on torque production, where the long tubes help torque production, especially through the mid range.

Which brings up the question.....how long are the runners on those long branch manifolds? Rough guess??

[larrygroskopf]

These Super duty fActory headers or 4 tube headers? I have a 462” 455 6x “4”s . Intake port matched to heads. Intake EDL 5056 intake using a800 CFM Holley dOuble pumper mechanical secondaries . ARP Main , head and rod bolt’s. Spc CS5779-0.040 head gaskets. Comp cam P8 296AH-8 .562 lift int. .577exh, 246 int,253 exh.
It’s in a 1962 Grand Prix, 3660 lbs,me in it. 390 posi 3500 stall with turbo 400. I’m 77 yrs. Old had this car decided to go racing on lsomle weekend s. Hopefully running mid 12’s.

[MidnightAuto]

Well now I am slightly confused. I thought the change from ra manifolds to 4 tube long headers might cause loss of torque at lower rpm but then higher hp at higher rpm? Last couple posts suggest otherwise. Doesn’t some back pressure help torque?

Forgive the ignorance. I suspect it’s all in the details enigine, but I was mentally resolved that I might lose a little at low end, which is where the move to 3.70 from 3.36 comes in….

[scott70]

I think it varies engine to engine on gains or loses between ram air manifolds and headers. Ive read from anywhere from only a 10 hp gain to 30 and up. I did back to back on the dyno from 1 3/4 hooker headers with no extensions to standard ram air manifolds with mandrel bent 2.5" headpipes. There was about a 18hp and 18 ft lbs difference. Im going to oversized manifolds and going up to 3" headpipes and calling it good.

[highway star]

From that Motortrend link above about coating, OMG! Their temp testing: "The coated headers measured 258 degrees F dropping to 195 degrees F a minute after shutdown. In contrast, the uncoated header measured a scalding 870 degrees, retaining 520 degrees a minute after shutdown".

[pippintook]

Midnightauto - Engine masters discusses if an engine likes back pressure in this video , https://www.youtube.com/watch?v=_PVX...orTrendChannel
.
I attached a pic of the SD455 downpipe, this is from Rocky Rotella's book , The Definitive Firebird & Trans Am Guide: 1970 1/2 - 1981
https://secure.amesperf.com/qilan/Se...M+Guide&sort=0
The SD455 downpipe looks pretty nice - not as much crimping in the bend. Maybe one of reasons why ram air manifolds and headers can be closer in torque/HP is when the ram air manifolds are using a good mandrel bent downpipe.
.
Does any one know - are the regular 2.25" ram air manifolds and the 2.5" ram air manifolds the same casting ? And the 2.5" castings are just opened up at outlet via some grinding (and cleaning up of ports) ?
I know RARE is getting their 2.5" manifolds cast in a foundry (soon - possibly this month?) . What about other Vendors , like Ames, that sell ram air manifolds ? Does RARE also cast manifolds for other vendors ?
Maybe someone from Ames can help shed some light.

[Formulajones]

It's been talked about a bunch, and numerous dyno tests done.

In a nut shell, the ram air manifolds work the best with a nice mandrel bend. If you put a crush bend right at the outlet to make the 90 degree turn, it really hurts HP.

The factory manifolds, although touted as 2.25" opening, I think are closer to 2" if you stick a micrometer in there. Been a while since I've looked at mine but I think that's what I remember.

As far as whether they are the same casting as the 2.5" outlets, I'm not sure. I've had both on my engine and as far as outside appearances or clearance, nothing really changed. Still the same clearance at my factory starter. Only big difference I noticed is that a 2 1/2" exhaust pipe is a really tight fit between the studs on the manifold. Tells me they didn't make the outside of the manifold any bigger. Least not there anyway.

[Skip Fix]

"Does any one know - are the regular 2.25" ram air manifolds and the 2.5" ram air manifolds the same casting ? And the 2.5" castings are just opened up at outlet via some grinding (and cleaning up of ports) ?"

Thought this posted earlier-yes at least the RARE are the same ones just opened up. And less surface area for sealing the head pipe. Also makes it tougher to get a wrench on all the studs/nuts.

[Formulajones]

Originally Posted by Skip Fix

Does any one know - are the regular 2.25" ram air manifolds and the 2.5" ram air manifolds the same casting ? And the 2.5" castings are just opened up at outlet via some grinding (and cleaning up of ports) ?

Thought this posted earlier-yes same ones just opened up. And less surface area for sealing the head pipe. Also makes it tougher to get a wrench on all the studs/nuts.

Yep that's what I was eluding to, so I figured they were the same size externally .