Jeep Strokers

I'm plannng to (at some point) build a 4.6L Modified Poor Man Stroker with stock cam and light weight Keith Black pistions as described in one of Dino Savva's recipes on his website.

That should put out around 245 HP and 310 Ft/Lbs.

Which header(s) would you recommend for that, and why?

How important is the size of the primariies' diameter to torque and HP? What would be best for stroker I describe? I'm after best performance possible (from that engine) from 1000 rpm to 4500 rpm. and I like good torque from 1000 to 2000 rpm for off roading (though I assume that's a given with a stroker).

Borla primaries diam is 2.25"

JBA and many others primaries diam is 2.5"

Thorley primaries diam is 2.625"

Your thinking collector size. Primaries are the primaries tube size. Secondaries would be on a "stepped" type header. Collector is where it all collects and connects to the exhaust/downpipe(s).

2.5" should be. Minimum with a nice 2.25-2.5 downpipe. I'm using a banks revolver & a ful 2.5" mandrel bent downpipe. Downpipe I made. I ordered a 2.5" section with a 90*, 45* 180* bends and cut it and welded it all up to make it work
2.5" no cat, 2.25 tailpipe after the muffler to help keep up the exhaust flow and help keep it a wee bit quieter. Full 2.5" was droning a bit on my stock 4.0, 2.25" tail pipe seemed to help out a lot.

Buy a header that has a 2.5" collector and make the rest of the system 2.5" as well. A 2.5" system might be slightly overkill on a 4.0 but it isn't on a 4.6 stroker.
Given that the engine has 1.50" exhaust valves, a header with 1.50" primaries is just about adequate but the Thorley with its 1.625" primaries is even better.

I just got a $120 Ebay exhaust header and its doing just fine. I got a walker downpipe which is supposed to be 2.5" not sure if thats outer diameter or inner diameter. And after that I put in a flex joint to help prevent future cracking of the header. Then i've got a Flowmaster Super 44 and 2.5" pipe running out in front of the rear tire on the passenger side. I think the setup sounds really good and I don't really notice any droning. Good luck with your future stroker build by the way. I did the same build and i'm just now wrapping things up. Definitely glad I went with the stroker instead of a regular rebuild.

I built that engine but with a Crower BajaBeast cam. I used the stock style header I found for $85 shipped because - I need to get CARB stickered, it was cheap, it was the lest likely to crack from what I have read, it flows good enough.

A stock header flows good enough for a stroker? I didn't know that.

No such thing as a stock header.

SilverXJ wrote:No such thing as a stock header.

The header that came on my 1999 4L from factory is stock. It's a primitive header, but still a header isn't it? It's made from welded together tubes. i.e. - it's not a cast manifold.

Isn't that the stock header RenoF250 said he used?

charley3 wrote: The header that came on my 1999 4L from factory is stock. It's a primitive header,

Tubular manifold /= header. As I said. Its not a header. Just because its made of tubes does not make it a header. It is not even a "primitive" header.

charley3 wrote:

SilverXJ wrote:No such thing as a stock header.

The header that came on my 1999 4L from factory is stock. It's a primitive header, but still a header isn't it? It's made from welded together tubes. i.e. - it's not a cast manifold.

Isn't that the stock header RenoF250 said he used?

Yes, I have the same definition as you - cast = manifold, tubes = header. I bough the newer version with the flex joints to reduce cracking and then put a flex in the exhaust pipe also.

For a somewhat lower cost alternative, I think the two piece Rugged Ridge header for 99-06 might be good.

Being two piece should mean no cracking. Have to get a Y pipe downpipe made and then it'd work for older model year 4L.

How do two piece headers with separate collectors compare for torque to one piece headers?