1990 Ford Mustang GT catalytic convertor

[ar_legend]

Hi,



I’ve owned my 1990 Ford mustang GT for over 7 years. Had future goals of adding performance parts for power and sound. Ultimate goal is to add a pro charger, swap a manual transmission, and convert the 4 lug to a 5 lug.

***with that said, so I believe my catalytic converter needs to be replaced and I rather just go with kooks long tube headers, x pipe, and exhaust. My question is what the biggest size headers I can get? I’ve seen 1-7/8” but not sure if that’s the biggest size I can get and what will ultimately make sense once I’m ready for the pro charger.

Thank you in advance.

 

[AeroCoupe]

1-5/8" long tubes are more than enough on a 302. You get them any larger and they are harder and harder to install unless you have individual primaries that go into a slip type collector. If you are emissions tested then you better make sure long tubes will pass.

 

[Mustang5L5]

I agree, especially if you still plan to keep the stock E7 heads with the supercharger.

 

[ar_legend]

I agree, especially if you still plan to keep the stock E7 heads with the supercharger.

No im planning on swapping the heads too.

Ive been thinking of going with a pro charger, cold air intake, air intake manifold, Cam, heads, long tube headers, x pipe, and exhaust

 

[Mustang5L5]

Really the question is what is your intended use with the car? Is this something you are looking to actively race at the track and trying to chase peak HP and best timeslips? Or is this a street car that you'll drive mostly around to shows with some spirited WOT pulls on the backroads.

You can get 1 5/8", 1 3/4", 1 7/8" and 2" long tubes. Might even be bigger.

At your probably power level of 400-600HP, i would think 1 3/4" or 1 7/8" would be more than enough but even that not really necessary over the 1 5/8".

Here's a decent read. Really what I'm getting at is if that 5-10HP is really that important to you to go with increased costs and fit issues with larger headers. For some it is.

https://www.corral.net/threads/1-3-4-vs-1-7-8-long-tube-headers.1414653/

 

[AeroCoupe]

Unless you are going with some really high flowing heads the 1-5/8" primary long tube headers will work great.

With a 302 inch motor and if you have 2-1/2" exhaust from the collectors back then I would say anything past 1-5/8" is not going to gain you much. Lower end torque will drop off with bigger primaries and you will need to spin the motor well past 6000 rpm to see any gains.

Here is a calculator to play with if you want to do the math being I have no idea what your cam specs are or your cylinder head of choice will be:

Primary Header Tube Length and Diameter Calculator

Calculate Header Tube Length and Diameter - by Wallace Racing Home of Pontiac Powered Firebirds,Trans Ams,Pontiac Powered Dragsters,Pontiac Power Rules!

www.wallaceracing.com