Difference between 1 1/2 and 1 5/8 headers - Ford Mustang Forums : Corral.net Mustang Forum
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post #1 of 3 Old 04-16-2002, 11:07 PM Thread Starter
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Difference between 1 1/2 and 1 5/8 headers

Im looking to get some headers and I've been seeing the JBA 1 1/2 headers and the 1 5/8. The 1 5/8 are considerably more expensive than the 1 1/2 headers. Is there a considerable performance difference between the two? I know that the 1 5/8 comes in ceramic black where the 1 1/2 does not. What kind of difference does this make? Any suggestions/feedback would be appreciated.

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post #2 of 3 Old 04-17-2002, 07:45 AM
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I see no one has responded to this. I know as a blower car, I use the 1 5/8". I know Bob Cosby choose the 1 5/8" for his NA car. He drag races with low gears and spends a lot of time near max RPM. I also have read where JBA recommends 1 1/2" for more normal NA applications for more HP and TQ over the whole (or lower) RPM range. That makes sense to me as a lot of NA cars report little gain with 1 5/8" headers (except maybe at high RPM).

If I were you, I would contact JBA and get whatever data they have RE dyno data from both sizes as pertains to your car. See if one is better at somewhat lower RPM, and the other at higher RPM. One may make more low RPM TQ, and the other may make more high RPM hp. I don't know. Consider your intended use and gearing.

Also consider what future mods you plan for your car with regard to how much air you will be moving thru it. The HP levels you plan for the future. MHO

Ralph Greene
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post #3 of 3 Old 04-17-2002, 10:32 AM
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I would recommend getting ceramic coated with either size. It will prolong the life of the headers and reduce under hood engine temps significantly.

I opted for the 1-5/8" for a couple of reasons. One was the possibility of going with a blower later on down the line. The second was I looked at people running the best times N/A and of those using shorty's the JBA 1-5/8" were it.

They may cost you a little torque in the lower and mid rpms but topend pull seems to be great with them. If you primarly drag race and come out of the hole at 5k+ I really don't see a reason to go with anything smaller. However if you spend most of your time on the street you might have a more enjoyable car with the 1-1/2".

As one last addition I've seen very good results from the 1-1/2" headers on nitrous applications.

Here's my dyno sheet if you want to get an idea of the powerband with the 1-5/8's. http://tampabay.dsm.org/images/chiptest-AF.gif This was testing a JMS Chip that sent to me, a little of fat side so there's still more left to get out of it with the headers.
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