WHICH HEADER

[Silent]

I have a question regarding the Doug Thorley headers, or headers in general. I am needing to get a header as my stock one is cracked, and I want a better one. If I get the Doug Thorley, do I need to replace the downpipe? Also, what size pipe do I need. I put a new high flow cat and the Dynomax Super Turbo system on. Basically, everything in front of the cat is stock (down pipe and header). Well, all that typing for this. Do I need to do anything as far as changing size when I get new header? I am not sure what size the collector goes to, and downpipe as well to the cat. I like the dynomax sys. it really helped my jeep breathe more, but I do not know what kind of modding is needed for the replacement of the headers. Please any help would be great.

Sorry, I was long-winded.

Thanks,
Silent

 

[grimah1w]

Dang, this started as a question regard which header for a 1990 XJ...which is coincidentally my very question! So recommendations please, for a header and associated exhaust pieces parts for a 1990 XJ?

(The search brought me here )

 

[ehall]

I have a question regarding the Doug Thorley headers, or headers in general. I am needing to get a header as my stock one is cracked, and I want a better one. If I get the Doug Thorley, do I need to replace the downpipe?

You do not 'need' to replace the downpipe but you will probably need to modify the existing one.

The Doug Thorley headers have a three-bolt flange, while the stock uses a two-bolt flange. They also include a three-bolt flange for welding to the down-pipe, so you can cut off the stock flange and weld theirs on if the down-pipe is in good condition.

The collector output on the Thorley is 2.5". I believe that the factory down-pipe is 2.5" into the catalytic converter with 2.25" out of the converter--that's what Magnaflow shows for their "factory" converter, but on my beater it is 2" down-pipe and cat although I am pretty sure that was all replaced by the PO. Basically you need to get down there with some calipers and see what you've got if you don't know already.

What I am doing is a 2.25" down-pipe and keeping it that size all the way through the system (more low-end torque is what I want, I'm not running 10k RPM dragster), and using their weldable flange to mate the headers and down-pipe.

 

[scalper]

its a very good header my brother has one on his 5.0 stroker

 

[PurpleCherokee]

From the last couple posts, it sounds like the split exhaust manifold would be the way to go since they don't crack. So out of curiosity would a set of Clifford exhaust headers with a y-pipe be a better setup? Would I have to start worrying about cracked heads, especially if I decided to do a 99+ intake manifold swap at the same time?

Another vote for the Clifford headers. I noticed WAY more power than I ever expected from getting headers. As far as the y-pipe goes it'd simplify the installation greatly but at the expense of a little top end power. I ran duals all the way back w/an x-pipe and it pulls like it does at 3800 all the way up to the redline. I couldn't be happier. The problem is routing the pipes. It's not that hard, just a bit complicated. The exhaust shop I went to installed all the pipes a mufflers and everything for $150... oh, and it'll sound like this :firedevil