Exhaust manifolds or Headers?
 

I have a 72 Lemans and I bought a set of OBX headers and the 4 speed linkage doesn't clear. My motor is a 462 with Eheads. What headers work on a 4 speed car or should I get some ramair restoration manifolds?

If you like to cuss and swear when working on your car, changing a starter, oil filter and/or starter, go with headers. If you like the easy life, want a nice sounding exhaust with no leaks, and dont mind giving up 5-10 hp, definitely go with the RA manifolds!

I had a similar motor in my 66 GTO 4spd and the RA manifolds were awesome compared to the headers it had.

My 68 bird has headers, which are way easier to deal with on this car vs the Abody. If you are a weekend warrior like me, I am a believer in the following formula...

Mostly Street Car = Cast Manifolds
Mostly Race Car = Tube Headers

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x2 on the RA exhaust manifolds. They offer 2 outlet sizes, so get the larger ones. Then use a 3" pipe and good low restriction muffler. The HP loss is not as much as you would think and most find them easier to install as well as a bit quieter.

You can also dimple headers for clearance. It was proven that putting dimples or banging in on the headers to get a little extra room for linkages did not effect the performance of the header.

On the headers, I purchased a set of Doug's for my '68 Lemans. Have not installed them as my project car is still quite away from re-assembly. However, we both have the same 2-piece cross-over shaft (bell crank) with the swivel link. The instructions on the Doug's headers recommends the earlier 1964-66 1-piece cross-over shaft. I suspect this eliminates the "bulkiness" of the '68 and up linkage and may eliminate some of the interference and fit issues.

I got a reproduction bell crank and I'll also beef it up a little with a the addition of some gussets that won't hit the headers.

The swivel link is indeed a better set-up and idea as it takes into account the engine torquing over as it provides a "joint" for flexure - especially if you break an engine mount. So I plan on using some form of limiting device to minimize engine rollover due to the rotational torque of the engine. Many different ways to do this, so you can pick one if you go that route.

So that is my plan as of right now which could change once I get to actually installing the headers/linkage and if it does not work, then I am lying, but just don't know it yet until I get there. :)

I think I am going to return the headers and buy the manifolds.

I took the cast log manifolds off my 455 GTO which has the 068 cam. It really woke the car up. The seat of the pants feel is I gained ALOT of power.
First time after they were installed I went to get gas they scraped on the pavement in the gas station on a dip in the concrete. I have stock ride height.
Keeping my fingers crossed they don't eventually get crushed like they were on my '72 TA long ago.

I assume those were standard manifolds and not the larger RA style?

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If not a dedicated race car no way I would run headers on the street if RA manifolds are avail!Everything clears and no leaks.JMHO,Tom

Headers are more for die hard performance freaks, (I'm one of those) I don't have an issue with headers on the street.

But nothing wrong with the RA manifolds either. Several engine builds that Paul has done with back to back testing has shown they are within a few HP and actually made more TQ on a couple of 455 builds he's done with his custom camshaft.

One thing Pontiac did well was designing some of their performance cast manifolds.

To Formula's point, it comes down to much you like jacking around to gain a few (and it might be very few) HP. About the time you spend 30 minutes to get the passenger side center bolt tightened down on D port heads, those RA manifolds might start looking "real nice " as cousin eddy would say.

On my first mild 455 build a few years back, we dynoed RA vs full length headers and was something like 8hp. 400 vs 408.

I later added KRE heads and stump puller cam to that motor. In a 4spd car, I had way more power than I could use on the street via the RA manifolds so never had a desire to go back to headers.

I assume my current 600hp street/strip in the 68 would see a bigger difference, but since I also fall into the performance freak category, I will keep the headers on this car. Automatic, no AC, remote oil filter, mini starter, and fbody- which equates to a relatively easy header install.

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I take it its not the car in your signature?

I put a set of RA exhaust manifolds on a '72 GTO years ago. They were no easier to install than most headers, for me. Seems like one bolts was REALLY close to the steering column, and it was not fun.

On my Tribal Tubes, I test-fit them on the engine while still on the stand. I tweaked them so that I can get a ratcheting box-end wrench on the rear-center bolts. I can now install/remove those bolts (either side) in < 1 minute.

I would like to see a back to back comparison on a 600 hp engine. I am thinking about the RA manifolds for my 65 gto but don't want to lose a lot of hp. Looking to build a 600 hp 428 engine with 4 speed trans.

Paul was doing comparisons on 520-530 HP 455's with good flowing heads and there just wasn't a lot of difference that I mentioned above. I doubt an engine making another 50-60 HP would see a big change.

I think you would have to get into big cubic inch engines making some steam to see some major changes.

I have had Dougs headers on my 69 Bird for the past 7 years. It has a 428 making around 475-500 hp. They fit great and never had a leak. My next project is a 421 in a 65 GTO. Not sure yet which way to go as headers are more problematic on the early A bodies. Looking to make 500-550 hp with this one. I hear tri-y headers fit very good, they may be worth a try if they would be available.

I may be thinking wrong, but I believe the cast RA manifolds have fitment issues in the '65 frame. So check if you go that route.

Jim, they fit nice on my wife’s 65. Had to do something different for the clutch return spring but no big deal.

Maybe


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I just decked my motor in my 65 a couple of months ago, dropped right in. No clearance issues at all. Getting them in with the engine in the car is probable a whole different story.

I put them on with the motor in place. I had Hooker Super Comps on it at first but changed my mind. The manifolds went on easily.

Murf


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Get the good head pipes if you go manifolds!!

Changed from Hooker headers( leaked terribly) last year for the RA cast and good head pipes for my 71 GTO with PB and A/C. The Hookers were banged up to fit the A/C suitcase (still heat damaged it) as well as clearance at drivers side. I cut the Hookers off in pieces just to get to some of the bolts. The RA manifolds went in super easy and seal great.