My exhaust manifold on the passenger side has cracked.
I am thinking about replacing them with Headers.
The car is NOT going to be raced!!!!
Its just a pristine original 71 Cutlass supreme.
With working AC, Power steering, etc.

I want something that is Bolt-on, and will fit an AC car with power steering.
There does not seem to be many options for the Rocket 350.

 

If your motor is essentially stock you might want to think about Thornton short headers - they drop down to about the same stock location as the factory manifolds but look like headers from the top - they also arguably perform a bit better than stock manifolds (though the extent of any benefit is the subject of debate).

I have them on my 350 and think they're a great compromise - no fitment or ground clearance issues like full headers can create.

https://www.thorntonmusclecars.com/p...qbpTlC7jpSsez4

 

That's good information.
I have been looking at those as a possible option.
I think i may go with the black enamel.

Did you have any issues with Steering, or AC hardware issues?

 

Nope

Minor exhaust pipe mods needed for new bends to fit up against the manifold outlets but that's it.

I run a Vintage Air a/c system, so 2 things to consider if you still have the factory setup

- my compressor is a Sanden, roughly 1/2 the size of the OEM unit
- VA system eliminates the evap core unit from the passenger firewall, so mine is completely open (similar clearance to having a non-a/c car)

Even both these considered, since the Thorntons are essentially drop-in replacements for the stock manifolds, shouldn't be any problems.

 

My .02-

Hooker Competition 3901 series. Small tube, full length. Finish chosen to preference. Suggest painted version, installing to test fit & check for any necessary “adjustments” (dings) & make them, then get them coated. If lucky there may be an aerospace/ceramic coating biz in your area that can do them.

Any full length style should get test fitted, they’re “bolt on” but not always perfectly “drop in.” The shorties are reputed to be nice in that respect but don’t do much of anything power wise. That said, compared to SBO stock manifolds, plumbing pipe wouldn’t hurt you.

No OE starter (std or high torque) or linkage issues when I’ve used or seen them.
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On a pristine original '71 Cutlass consider replacing the cracked exhaust manifold with a nice used one. There is little to gain from headers in a stock engine driver car and plenty of maintenance and headaches headers might bring. Just my $0.02.

 

I still have my clean original exhaust manifolds in a box - would be happy to sell them to you cheaply if you ultimately decided to replace your bad one with another OEM part - shipping would likely cost you more than the manifolds themselves however.

But I will say the Thorntons have needed no adjustments since install well over a year ago, albeit I only put about 3-4k miles yearly on my ragtop. Doubtful to me that full length headers would provide any seriously measurable increase over the shorties on a stock motor, so consider your end goal before making any final choices.

 

The shorty headers fit full size starters which not all full length do. There is some gain over manifolds and usually no moving or denting tubes, only minor adjustments. None of the headers are cheap now. My last set of Sanderson shorties had shitty welds, was not impressed. I went with Chinese stainless full length due to their $200 shipped price. They needed one tube moved due to the early style motor mounts on the driver’s side and a very compact mini starter. The passenger side fit perfect, just needed a slight clamping to slide the 51258 oil filter past the tube.

 

The need for changing out to a mini-starter is practically a given for a headers install - even if you did manage to cram the driver side header in place with a stock size starter, the clearance would be too minimal to avoid heat-soak issues.

I run a 2.25" full dual exhaust coming off my SBO 350 roller-cam motor and even without clearance issues, I still run a Robb Mc mini starter - huge operating improvement over the OEM unit and much lighter in weight.

 

Thank you all for your input. I use my Cutlass in movies. So far the car has been in 5 films. Unfortunately, my car scene always gets cut. And I have to wait 2-3 years for the movie to come out. I hope to make a decision soon. I need a quick turn-around, because a current film production wants my year car [no commitment yet]. Thanks, see ya in the movies.

2021: Whitney Houston, I wanna dance with somebody: Cut, exhaust too loud!
2022: Madam Web: Cut
2022: The Instigators: Cut
2022: The Collaboration: Still waiting for a Release date!
2025: "In-Production": Parked out side of a restaurant, waiting for release.
"I was told the car was too pretty and did not fit the scene"

 

Why would this car need headers, unless their sound was desirable to the owner??

 

15, maybe 20 horsepower and the according torque increase, potentially better throttle response and gas mileage if carb & ignition optimized.

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it occurs to me.... Would full headers possibly make it too loud for close proximity filming?

 

You should barely hear headers themselves as long as they’re properly sealed. There might be a little “ping” sound from the tubes, maybe just a touch louder ambient wise, but exhaust pipes, config, mufflers, tail pipes will have far more influence over the sound.

Open the hood on a running car with headers, all you should here is fan & accessory noises. That said, manifolds do dampen sound more effectively

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Exactly. I run full length headers and 2.5" dual exhaust with Flowmaster FX straight through mufflers and full tail pipes. Not loud until I floor it and even then, mildly loud. I had shorty headers with a X pipe and 2.5" dual exhaust with Dynomax Superturbo's with the same rear exit tail pipes. It was way too quiet. I have really good hearing, I can hear every annoying sound under the hood that others might miss. The Thorton shorty headers should be the quickest turn around, no custom exhaust needed. Do you have dual exhaust?

 

My Thorntons didn't directly match up to the down pipes coming up to my OEM manifolds, my local muffler shop had to modify the pipes to fit. Was a simple fix for them but I suspect OP would face the same prospect if going that route

 

Headers are a little louder than manifolds, and the have a different sound. That’s one of the characteristics of thin tubes instead of heavy cast iron.

There are definitely some potential performance increases by going to headers, but only if you’re willing to make the potential tuning changes. Good headers can make a noticeable impact on the seat of the pants feel, since the improve airflow thru the engine they can also cause the engine to be slightly lean. Meaning to get the most out of them, you better plan on some tuning.

If that’s more of a hassle, I’d find a good replacement for your cracked manifold.

 

Very cool, please let us know when it finally makes the cut.

I think Matt's closing sentence here is key.

Headers are an added hassle no matter how you look at it. And the type of headers that are not a hassle serve no purpose. Outside of an added expenditure for not being able to locate original manifold's. And except for the ability to say one has headers.

Long tube headers sound great and serve a purpose, but cook starters, solenoids, lead to bottoming out, scrape, leak, etc. Often a car needs to be lifted to manage better in general driving activity. I would think all that works against you in her current existence. But if you want to hear the thunder and feel the thrust when properly tuned, go for it.

 

If I make any extra $$ from the films, I may Update the engine a little.
I believe my stock version of the 1971 CS, is only putting out about 160hp for the single exhaust version, from the factory.
I may add a few extras in the near future, Fuel injection, Electronic ignition, and other stuff that can be easily hidden.
This month, I am in 2 different productions at the same time [non speaking roles]. The second film, is also interested in renting my car, I hope.
This engine has under 50,000 miles. When I got the car it only had 18,500 miles on the car.