Headers for a stock 389??? - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 05-15-2017, 05:59 AM Thread Starter
 
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Headers for a stock 389???

I am thinking about picking up a set of headers for my 66 gto. The motor is stock and I've heard that headers may not actually be as beneficial as the stock manifolds. Is this the case? I was looking to pick up a bit of bottom end and, yes, a bit more grunt out of the exhaust. However if it is a big job (requires an engine pull right?) and I will lose power I probably shouldn't do it. Will I be losing power?
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post #2 of 6 (permalink) Old 05-16-2017, 11:14 AM
 
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My brother has done this on his Chevelles..the only change he had to make to accommodate the headers was to enrichen the carb a tad since the lowering of backpresure tends to make it run a tad lean. At the local 1/8 mile he picked up some speed but ET remained the same. That's his experience.
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post #3 of 6 (permalink) Old 05-16-2017, 03:31 PM
 
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Headers seem more trouble than they are worth, with fitment issues and exhaust leaks. They do sound awesome with headers though...
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post #4 of 6 (permalink) Old 05-17-2017, 09:30 AM
 
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Probably the easiest way to do headers is to do the repro factory headers; Ram Air Restoration does the most common and allegedly the best ones. Here is their link for ones for your year GTO:

RM-1 Ram Air factory headers
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post #5 of 6 (permalink) Old 05-21-2017, 01:20 PM
 
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Originally Posted by brixtonanimal View Post
I am thinking about picking up a set of headers for my 66 gto. The motor is stock and I've heard that headers may not actually be as beneficial as the stock manifolds. Is this the case? I was looking to pick up a bit of bottom end and, yes, a bit more grunt out of the exhaust. However if it is a big job (requires an engine pull right?) and I will lose power I probably shouldn't do it. Will I be losing power?
I put Doug's headers on my '65 389. Did not have to pull the engine, but did have to unbolt from the mounts and raise it some; the angle of the exhaust manifold bolts were such that they were almost unreachable with the engine fully installed. The headers do make a performance and sound improvement, but recommend you don't go with the 'standard' gaskets that come with the headers; pay a little more for a good set of gaskets that will likely prevent exhausts leaks down the road (so to speak).
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post #6 of 6 (permalink) Old 05-21-2017, 02:00 PM
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I have run Headman headers on my '65 GTO with a 389 since 1982. Car is modified with bigger cam, re-jetted carbs, etc. I have installed many sets of headers of all brands on Pontiacs. You need to remove the engine from the mounts, and get the car itself high up on jackstands so that you can thread the headers into place without the flanges bottoming out on the ground. The 'angle of the dangle' is critical for an install. That said: headers are good for top end power, not low end power. Higher RPM with a modified engine is where the benefits are. Tubing headers leak, they rattle, they bottom out, and nowadays, they are expensive. They will not make a noticeable gain in power on a stock 389 unless you change the cam and richen the carb. My suggestion would be to install the cast iron Ram Air manifolds: they flow very well, do not leak, and are an upgrade from the stock log manifolds. I have installed many sets of tubing headers over the years, and will not go that route in the future. Stick with the cast iron Ram Air/HO manifolds and you will be quite happy.
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