The header question
 

So I was a Lucky one that got a set of those headers madgoat put forward in another thread. Price was to good to pass up. So my question is - should I put them on the car and if yes, what should I expect?

My setup is a 461 via a stroked 421. Tripower with gasket matched intake. Kre 290 cfm d ports. 230/241 470/470. 1.65 rocker. Ram air manifolds and 2.25 pipes with dynomax ultraflos. 3.36 gear. (Moving to 3.70 this winter).

I love the rare manifolds don’t leak, look good. But I always wonder if the motor would breath better and make more noticeable power with headers. It wasn’t worth $800 to find out. But $170is another story.

So what do you guys think? Worth swapping rare manifolds for hooker super comps?

Start with you induction!Tom

IMO, the performance gain offered by headers over the RARE manifolds is worth it only if the headers don't need to be hit with a hammer in order to fit, and don't hang down too low. If the Supercomps meet those criteria, then I say go for it. Otherwise, I'd think twice about it.

Thanks guys. Tom I should have added the tripower bling has been too good for me to pass up, so I want to stick with that. The carbs venturis are all opened up so perhaps the intake manifold is my anchor on that side.

Keep the manifolds, 2.25 exhaust is choking it. 3" should be a noticeable increase in power and noise

As OCMDGTO mentioned, the 2 1/4" pipes are a real choke point. Especially with crush bends right after the outlets of those RA manifolds. There has been a lot of dyno testing on that in the past.

Those RA manifolds really only perform decently if a mandrel bend right off the outlets are used, and at least 2 1/2". Then they start to show some improvements.

Personally I would improve the system after the manifolds first with a nice 2 1/2" mandrel bent exhaust. The Dynomax Ultraflows are an excellent choice for mufflers.

As far as headers go, they will certainly scavenge better and chances are that they will help mid range torque a bit, and maybe some HP. Only way to know for sure on your combo is a little track testing or a chassis dyno. The question is whether you care to go through all the effort.

Lee Atkinson here on a bone stock 455 in his TA clone picked up a bunch of HP on his chassis dyno going with cheapy headers over manifolds.

Agree with the exhaust size. On my 69 firebird/389 went from 2.25" exhaust with old turbo mufflers to 3" with Magnaflows and went from 12.35@106 to 12.00@111 with no other changes

Those 2.25 pipes are choking any motor that size. You`ll have to cut the pipes anyway to put long tubes. So, I would run 2.5 pipes with the headers.


But, you`ll have to change the whole exhaust system to do that. Unless, you change just the head pipes to 2.5 and bottleneck it down to the 2.25 mufflers. Then, I don`t know if the headers are worth it.

Full mandrel bent exhaust system.

The Dynomax Ultraflows are an excellent choice for mufflers.

X2


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Just to give you an idea what a simple exhaust system is worth.

I was (still do) routinely racing my 70 Formula. It's setup as a factory stocker. 400 RAIII and might make all of maybe 360-370hp at the crank. It did put down 301hp at the tire years ago.

I first started racing it with a factory 2 1/4" crush bent reproduction Gardner exhaust system. Did a ton of tuning and multiple trips to the track. Eventually the best the car did was 14.10 at 98 mph.

I decided to replace the exhaust. PS rules allow a 2 1/2" system. At that time I bought the Flowmaster Force II transverse chamber muffler system (no longer produced). All mandrel bent with an "H" pipe. I didn't touch anything else on the car. First pass at the track was 13.80's right off the bat and 102 mph. A little improvement in the 60 foot got me a solid 13.70 as a best pass. A solid 4 tenths and 4 mph improvement!! That's a substantial HP increase for just an exhaust system.

I fiddled more with the car making small improvements here and there, eventually changed the exhaust to another 2 1/2" system from Pypes, with their transverse muffler, and an "X" cross over. That system is still on the car today.

To date, I've been able to shave it down to a best of 13.10 at 106 mph without cracking open the engine. Corrected for our DA that was a 12.76 run.

If an exhaust can make that much of an improvement on a little engine that doesn't make a bunch of HP, think what it would do for a much more powerful 455.

My .02.... if you change to headers and want to keep them I'd suggest having them ceramic coated. The obvious, do it after you bang on them with a hammer during the installation !



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2 1/4" exhaust is too restrictive for that motor. I had years ago a similar setup to yours. At the track I lowered the 2 head pipes off the exhaust manifolds about 1/4 to 3/8 of an inch as they had long studs to relieve some backpressure and see if the car went faster. Trap speed went up to 109 from 104 and ET dropped .5 sec ,with the motor lean backfiring through the carb the last half of the 1/4 mile. I wished I had richer secondary rods for the Q-jet with me to try.

My motor is waiting in line to go on the Dyno as I type. We're gonna do pulls with a set of headers and my RA manifolds with 2.5" mandrel bent down pipes. Now, my RA manifolds are not the RARE 2.5". They are 2.3125" so we'll see what the difference is between that and headers.

Ram Air Exhaust Manifolds or Headers?

http://www.sdperformance.com/moreTech.php?newsID=39


Might be of interest. From Dave Bisschop.


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great discussions guys. Thanks for all the elements to consider. I was thinking about ceramic coating. Do those rattle can high temp paints work for this?

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.

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Paul C did a direct comparison a couple years ago and posted all the results on here with a nice 500 hp 455, running RA manifolds and then a set of headers.

You'd be surprised at the results.

IM just a old pontiac guy and for a true street driver with NO tack time,never 3in exhaust and never headers.JMHOAO!Tom

I had my fabrication shop do 2.5" stainless head pipes to my Tom Hand VOE Mufflers
and 2.25 stainless tail pipes. Very happy with all of the stainless parts.

Tom V.