Hey fellas! Somewhat close to finishing my build but I still have a few things that are up in the air. I put in the Comp 260 cam, a 4bbl intake, holley sniper 2 system and hedman headers. I was curious about exhaust size, the collectors on the headers is 2.5" and I want to do a single pipe. Should I mate the 2.5" together and run with that or mate them and run bigger the rest of the way? I don't need emissions on my 83 in my state so I'll probably end up running a magnaflow or cherry bomb etc so it'll essentially be straight piped
Thanks in advance.

 

Watching this thread with interest as I will have the same question in the foreseeable future.

 

You say "headers" and "mate them" are we talking about the 4.9 I6 or a V8?

If it's the 4.9, I don't think I would go bigger than 2.5". Did your header come with a collector? If so, you might want to go with the size Hedman provided (via the pipe stub on the collector).

As an aside, I had a Cherry Bomb on my '85 Ranger with the 2.8L V6. I used the factory y-pipe. That sounded much better than I expected but wasn't nasty. And, it was very affordable (~$60 IIRC?).

HTH.

 

Most headers for a straight six are 3 in to 1 x 2 so you have 2 outlets.
You would need to make a custom Y pipe to make it a single outlet.
I had a Toyota L/C with a straight six header and 2300 Holley carb with adapter and the Toy came with a v2 carb.
It had a custom Y pipe to a single run to a small turbo muffler and tail pipe. had a nice sound to it at idle but when you got into the upper RPM it barked pretty loud.
I am sure it had to do with the way the Y pipe was made.
Dont remember the size pipe as it was 30 years ago.

I dont know what year trucks you all have but may want to look into a 94 F150 factory system pipe size.
I cant remember if 2.25 or 2.50 with out looking it up but I know it is larger than 81 F100 system.
Because I run EFI manifolds I went with a full 94 F150 system, larger pipes, Y pipe on back to tail pipe (no cat) with a welded Thrush muffler.

What is nice is I can hit any parts store and get the system, maybe not muffler , but it was a bolt in in my 81.
Oh I am still running the factory Carter v1 carb and intake.

So check the pipe size of the 94 system.
Oh if not large enough for what you need may want to look into diesel systems but think you had to go up to think 2000 for the pipes to get larger, may it was 3"?
I say diesels and staying in the Fxxx trucks it should be a bolt in system as not much has changed where the EXH runs.
So why pay a shop crazy $$$$ when you can get a factory system than will bolt in in your drive way and save $$
Dave ----

 

For what its worth, a few years ago I built a 383 Cleveland for a customer with a Pantera. The headers used were a short style that had a 2.5 inch collector. The engine made right at 620 horsepower through these headers, short pieces of pipe and some glasspack mufflers. While this was a v8 using 2 pipes will your engine make more than 1/2 of 620 hp? If so, then it would probably be better with a larger pipe. Computer programs like Pipe Max cam be used to calculate header dimensions that are close to ideal if you have some idea about the volumetric efficiency of the engine.

 

Ah, thanks for the clarification Dave.

1980Great info Dave!

 

I would do a single 3" exhaust, they just sound right in any inline 6..

Hers a video of these guys installing a 3" exhaust on a 66 f350 with an in line 6 just to give you an idea of how it might sound

Skip to the 11minute mark to see the custom exhaust being measured and build and 20 minute mark for sound