Manifolds / Headers

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Aug 16, 2025 | 07:46 PM

Rangerj245

Thread Starter

6th Gear

Joined: Jun 2025

Posts: 6

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Manifolds / Headers

Hey guys I'm having a bit of a dilemma and I may not be fully understanding the difference between the stock manifolds vs a set of headers but I'm doing a rebuild of me 302 with some gt40p heads and a mild cam will the stock exhaust manifolds be fine or do I need to start hunting some headers to work with the heads im also gonna be putting a computer in it and some 24pound injectors ik its a bit overkill but i have the funds to do so and I would like to do it so i can tune/see what all is going on rather than the nonexistent info you can pull from the original. I understand the headers will flow more exhaust but I'm not fully grasping all the benefits of that maybe. I understand it means more of the exhaust gasses can move out but what is the functional purpose of that? is it really that different ? I looked through and searched on a few of the forums and couldn't find anything related to exhaust outside of o2 sensor issues, smog deletes, etc. couldn't find much info on my specifics any help or clarification would be greatly appreciated

Aug 16, 2025 | 08:02 PM

85e150

Super Moderator

Joined: Apr 2004

Posts: 34,513

Likes: 2,824

Engines are basically pumps. Anything that makes it easier to get AF in and exhaust out can contribute to better performance.

Headers can be a nuisance in some cases. Cheap headers especially.

What are you looking to do? 9000 RPM mud racing or sub 6000 streetable reliable running?

Aug 16, 2025 | 08:06 PM

Rangerj245

Thread Starter

6th Gear

Joined: Jun 2025

Posts: 6

Likes: 0

more along the lines of sub 4000 driving/enjoying it having some power behind it im not doing any racing or off roading its a daily driver truck with a bit of cutting up here and there

Aug 16, 2025 | 09:24 PM

Duke5A

Tuned

Joined: May 2024

Posts: 307

Likes: 150

Long tube headers utilize something called scavenging. Exhaust pulses create a vacuum behind the pulse that helps evacuate the next exhaust pulse. I'm probably over simplifying it. Realistically you'd probably get 15 ft/lbs of torque out of it and 302s need all the help they can get. Cons are cheap headers use thin tubing that can rust through and thin flanges that result in exhaust leaks at the head. Additional cons can be having to remove the header to gain access to the starter and baking the starter to death. I don't know a typical set of V8 headers looks like on these trucks to comment on exact issues of tube routing. With this being a daily driver I would be looking at stainless headers if you want it to last. With popular applications like this means you can get a set for not a ton of money. Just make sure the flanges are 3//8" thick.

Aug 16, 2025 | 10:17 PM

My4Fordtrucks

Hotshot

Joined: Jun 2015

Posts: 12,878

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Quote:

Originally Posted by Rangerj245

… I'm doing a rebuild of me 302 with some gt40p heads and a mild cam will the stock exhaust manifolds be fine or do I need to start hunting some headers to work with the heads im also gonna be putting a computer in it and some 24pound injectors ik its a bit overkill but i have the funds to do so and I would like to do it so i can tune/see what all is going on rather than the nonexistent info you can pull from the original.

Which “mild” cam are you going to use? From what I have read you will have a very difficult time finding headers for the P heads and since the stock manifolds are for an Explorer, they do not dump out at the correct location for a full size truck. What computer are you going to use that is going to work with 24# injectors?

Aug 17, 2025 | 07:15 AM

GoinBoarding

Cargo Master

Joined: Mar 2010

Posts: 3,341

Likes: 293

From: Laramie, WY

I tried running stock truck manifolds on GT40p heads. Does not work. I ground down the manifold a bunch with a carbide burr and still had direct contact with plug boots. I could make it across town before it melted through and started misfiring.

Aug 17, 2025 | 11:14 AM

Junktownbill99

Fleet Mechanic

Joined: Nov 2022

Posts: 1,697

Likes: 416

Is your truck a 2wd? I have some mustang headers that would be a pain to fit to a 4x4, but may work on a 2wd.

Edit: might run into issues with gt40p heads.