Originally Posted by 77&79F250

Fenderwell versus block hugger IMO.

Fenderwell exit design get more of the heat producing pipe out the engine compartment faster. Way easier to finish the rest of the exhaust system, meaning header mufflers, turn down tips and done. Or at least you do not have to work around the trans/xfer case crossmember.

Block huggers produce heat also, but IMO the design puts it on the block/starter and that keeps it in the engine compartment. Also a caged starter meaning PITA to remove starter.

Full length are long tube/longer ended. Usually right in front of the crossmember. PITA again. Fenderwell exit are just that, exit outside the fenderwell.

I have Headman fenderwell on the F250 4wd red truck. Easy peasy, no steering shaft interference, little brake line reroute. Only had to trim like 2" tall X 6" long strip of innerfenderwell. Maybe bump grind a bit of the front cab mount cup?

Put the straights with tips at 1st (insert STUPID LOUD), then stacks STUPID LOUD X100....then the header mufflers. Way better now, I can hear myself scream in the cab. LOL

Here is a link to my 0.02 on it and what worked for me. https://www.ford-trucks.com/forums/1...l#post14696882

Originally Posted by SlikWillie

I'll be "That Guy". As I've said before in other threads, headers are a huge misunderstanding in the truck world. My biggest regret when it comes to my truck is installing headers. Look at the RPMs needed to see any power results from headers. We're talking above 3,500 RPMs before you gain anything noticeable. Not to mention the loss of low end torque at your normal operating range of 1,500-3,000 RPMs. But some people say headers gain MPGs. FALSE!! I got 12 MPGs with manifolds, swapped to headers and dual exhaust and it dropped to 10 MPGs. Once you understand that back pressure is a good thing for a stock to mildly built engine, you will see what I am talking about. Not every truck needs headers.
Once I find a good 460 worth buying, I will make damn sure it will have manifolds. I have spent way too much money on my 351M (close to $2k) just to see maybe 225-250hp. A stock 460 will give me much closer to the 300-325hp I'm looking for, with manifolds.
Now that I've stepped down off my soap box, let's talk "actual use of your 400ci truck"- DD, save your money and get manifolds. Play truck 250-300hp, shorties or mid-length headers. Mud truck over 300hp, then full-length headers. Quarter mile drag truck over 500hp, definitely FL headers. Just don't buy headers to gain anything. Headers are for the power that you already have, not to gain anything.
Okay guys. Somebody tell me I'm wrong!!

Originally Posted by SlikWillie

Same here. Used Summit brand (exact same as Hedman) and sprayed High Temp POR15 and baked them. Damn paint burned off anyway. But as for the headers themselves, no problem at all.

Originally Posted by Aaron-71

Sucks to hear that the POR-15 you used burned off.

I've got some high temp POR-15 waiting for my new headers. Hope to have better results than what you reported.

What was the process you used to strip the original paint off the headers (before coating with POR).

Originally Posted by SlikWillie

Sand blasted them, wiped them down with acetone, POR high temp primer, POR high temp silver paint, put them in a powder-coating over at 600* for one hour. Installed on truck. Less than two months looked like this.

Originally Posted by boingk

I'll tell you you're wrong... because you're wrong.

Full length, tuned headers will see improvements at the topend and significantly through the midrange. This is all proven.

Mid length headers will gain a bit through the range and topend, but not as significantly as the full length.

Cast manifolds don't kill as much power as you'd think, but the improvement by going to full length headers is very significant.

The biggest thing you'll find, though, is that having headers or not will dramatically effect the output of the engine with regard to other modifications - that aftermarket intake and camshaft, the higher ratio rockers, the four barrel carb... they won't perform to their full without a decent exhaust.

As for economy, that's tune related. Mess with anything in the intake or exhaust tract and you ideally need a retune.

Backpressure? That's for the wave/pulse modulation at play in two-stroke exhausts. There is generally no benefit for backpressure in four strokes. The exhaust is either adequate in that it can evacuate the gasses produced without restriction, or it is restrictive to some degree. That's all there is to it.

Originally Posted by Aaron-71

My first thought was sand-blasting was the issue - but that doesn't make sense if you wiped them down.

Man that's a huge bummer - I'm already praying to the Ford Gods that all my POR-15 efforts doesn't have the same result. You must have been pretty mad when that started given all the effort to sandblast those suckers down.

Originally Posted by SlikWillie

This is somewhat true, but I'm not fully wrong here. I watched the video too. It kind of proves my point. If your engine produces 475 horse power with manifolds, then yes LT headers will increase power as well. I don't know about you, but my 351M is getting maybe half that of the high performance race engine in the video. When Ford engineers designed the 351m/400, the drag strip was not in mind. Low end torque for pulling and a red line 4,000 RPM was more in the ball park, hence the reason they were in family cars and trucks and not in Mustangs. If you are planning 450+ hp engine then get headers, if you can find a tuned header for our trucks. If you are looking at a mild build for dependability and daily driving, at around 225-250 hp, keep your manifolds. Manifolds with 2.5 inch dual exhaust will work perfectly fine.

Originally Posted by boingk

The biggest thing you'll find, though, is that having headers or not will dramatically effect the output of the engine with regard to other modifications - that aftermarket intake and camshaft, the higher ratio rockers, the four barrel carb... they won't perform to their full without a decent exhaust.