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  #1  
Old February 27th, 2008, 03:27 PM
JBOD77
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Question revisiting an old issue

First allow me to say YES I HAVE SEARCHED THIS TOPIC!!! I have spent much time reading and re-reading old posts. I need to find a definitive answer to the question of headers. I have a 95 3.9L V8. I have put NRP cats on tied to a Borla exhaust. I would love to put a set of headers on the truck. Is there anything out there that is truly bolt on with little to no adjustment necessary?
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  #2  
Old February 27th, 2008, 08:11 PM
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not really. Get some of those swank ceramic coated manifolds that someone on here is selling. Much better idea......it's not a fawkin race car.
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new expansion complete. Not only are we the only Rover shop in Eliot Maine...now we're also the biggest.

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Old February 27th, 2008, 09:54 PM
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I understand that it is not nor ever will be a "fawkin" race car. Just looking to get all the power I can out of the 3.9. It's my daily driver not a hard core trail truck so it would be nice if it was a little more peppy. I have already inquired to the person selling the ceramic coated manifolds and if true headers are really not an option, then that will be the way I will go. But, I know aside from heat reduction in the engine bay they are the same manifolds that are on the car and will not alter performance any, except of course in keeping the engine bay cooler.
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Old February 27th, 2008, 10:06 PM
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no bolt on option will give you very much! cam open & up the ports
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Old February 27th, 2008, 10:18 PM
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Not sure if COOKS custom headers is doing any custom work again yet, but might be a possibility. Just because there is no bolt-on option doesn't mean you don't have any options. Unfortunately, custom headers aren't cheap. And will probably also require modification to the Y-pipe as well.

However, there are other options that don't involve much modification for performance increases. One that comes to mind is swapping in the AM20 mass-air sensor. Does take a small wiring change and some tuning, but isn't a hard swap at all, and really opens up the intake path.

If I ever get around to it, I still have a THOR manifold sitting in the garage that I want to bolt on. But will take some computer changes to go along with it most likely.

-Hans
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  #6  
Old February 28th, 2008, 12:49 AM
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I know N/A motors don't gain much from bolt-ons but I'd be interested if headers give a little something to the 3.9 especially when combined w/ free flow cats. Another benefit would be the sound and throttle response - both of which, I would like to improve just as much as more power.

And I'm guessing there's also a decrease from base HP with the 96,000 miles on my motor as well.
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Old February 28th, 2008, 07:00 AM
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Quote:
Originally Posted by JBOD77
I understand that it is not nor ever will be a "fawkin" race car. Just looking to get all the power I can out of the 3.9. It's my daily driver not a hard core trail truck so it would be nice if it was a little more peppy. I have already inquired to the person selling the ceramic coated manifolds and if true headers are really not an option, then that will be the way I will go. But, I know aside from heat reduction in the engine bay they are the same manifolds that are on the car and will not alter performance any, except of course in keeping the engine bay cooler.
Not intending to be offensive, but ceramic manifolds are not designed to keep the engine bay cooler, this is just a nice side effect. They are designed to increase the exhaust temp allowing faster gas flow and with the motor you have will be just as effective as headers. Headers would be usefull in combination with other performance upgrades such as engine management, port matching, cam etc....which would require a little more than bolt on.

Headman makes headers that you can sort of bolt on, as does SS in England. They both require a little tweaking and a custom Y-pipe, you can buy the y-pipe etc from SS.
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new expansion complete. Not only are we the only Rover shop in Eliot Maine...now we're also the biggest.

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  #8  
Old February 28th, 2008, 07:37 AM
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No offense was ever taken. So what I am understanding is that if the exhaust temp is higher, thus creating faster gas flow, makes sense, the effect of increase speed of flow will be similar to that of free flowing header system?
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Old February 28th, 2008, 12:06 PM
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These effects sound like typical things for higher revving engines, would this benefit relatively low RPM applications like ours? Might the $$ and time be better spent elsewhere? (I couldn't tell you where!)
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Old February 28th, 2008, 07:58 PM
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Headers would benefit a higher revving engine, in combination with other modifications, by allowing an increased volumetric flow. Old school tuning trick was to wrap the headers to increase the temp and further increase the flow in a similar fashion as the ceramic coatings.

Ceramic coated manifolds increase efficiency which improves the performance of any engine, slower revving torque tuned engines in particular.
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new expansion complete. Not only are we the only Rover shop in Eliot Maine...now we're also the biggest.

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  #11  
Old February 28th, 2008, 08:01 PM
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Are the manifolds different between a 3.9 and a 4.6?
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  #12  
Old February 29th, 2008, 07:00 AM
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Quote:
Originally Posted by themaxx
Are the manifolds different between a 3.9 and a 4.6?
not if used in a Defender, which would re-use the 3.9 manifolds. In a Range Rover P38 theyare different , and more header like but I've never bothered to take the time to even look to seeing if they fit. Not worth it as far as I am concerned. If you're building a motor for torque the stock manifolds are fine.
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new expansion complete. Not only are we the only Rover shop in Eliot Maine...now we're also the biggest.

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  #13  
Old February 29th, 2008, 10:07 AM
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Suppose there would be any benefit to extrude-honing the stock manifolds before coating them? I'm not sure how clean they are from the factory.
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Old February 29th, 2008, 11:16 AM
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Quote:
Originally Posted by JimC
Suppose there would be any benefit to extrude-honing the stock manifolds before coating them? I'm not sure how clean they are from the factory.
There is a fare amount of casting slag in the mans I have seen. If you combine with port matching I am sure it would help. To what degree I am not sure...
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  #15  
Old February 29th, 2008, 02:10 PM
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Keith Kreutzer
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I put Headers (Hedman's) on my Disco, 4.6l, extra lumpy cam, ported heads, big free flow intake ...It made a huge difference. The car was noisier, smellier, the engine compartment was hot as hell, and I was always fixing exhaust leaks...
Oh?!?! Performance differences? Yup there where some good from it.. Was is worth the trouble? If it was the headers would still be on.
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