[scott70]

Originally Posted by ponjohn

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.

[Region Warrior]

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. .

[Region Warrior]

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

[PAUL K]

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.



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[Stan Weiss]

From Pontiac.

Stan

[zippy]

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

[73ta]

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.

[SRGN]

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

[Formulajones]

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.

[PAUL K]

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.

[Jay S]

Originally Posted by PAUL K

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

[Jay S]

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.

[AG]

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.

[PAUL K]

Originally Posted by Jay S

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.

He had to stretch the video past twenty five minutes

[Formulajones]

Originally Posted by PAUL K

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.

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.

[HWYSTR455]

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.


.

[Jay S]

Originally Posted by AG

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.

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.

[Bruce Meyer]

Originally Posted by PAUL K

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 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.

[Formulajones]

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.

[73ta]

Originally Posted by AG

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.

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