The exhaust manifolds on my 02 are cracked and after reading several threads here I've decided to have Thorley headers put on.

I originally was going to replace the whole exhaust except the cat, even though the stock muffler and tailpipe are still good, but I'm having second thoughts about that part of the job.

If I did have the whole system replaced,
I'm leaning towards a Flowmaster 817345 Force II or just a Dynomax superturbo muffler.


Any opinions pro or con on my selections would be most welcome.
Thank you

 

Get the Force II stainless system it is better than the aluminized kit with better hardware.(aluminized hardware is not even useable IMO) I had the aluminized kit but now have the stainless kit on my truck. The aluminized likes to rust through at the muffler outlet.(mine did and my dads is doing the same)

I have the Thorleys on my truck and it sounds good with the Force II system. I had a Dynomax ultra flo (packed muffler) on it when I got the Throrleys put on. The Flowmaster system was on within a week, the Dynomax sounded horrible.(like a crappy V6) The headers WILL completely change the sound vs the stock logs and a lot of exhaust systems will sound like crap with them.

I see you are PA, me too.

 

Thanks for the reply dkf.
The Thorleys is a definite.
The rest (Flowmaster Force II) might wait until we get a better look at the OE stuff; a cursory examination indicates that it is all still good.
No reason the job can't be done in two stages, if appropriate, I don't suppose.
Wonder how the truck would sound with the headers and the rest stock?

 

With the stock exhaust and the Thorleys it should sound ok. Should be nice and quiet. The Thorleys are engineered to bolt up to the triangular flange which is forward of the stock cat converter. So you should not have to mod your existing system for it to fit.

 

Well, we can't have it too quiet, gotta cover up the wild turkey chirpin in the brakes

 

The headers are on, with the rest of the stock exhaust.
It's not loud but sounds good.
Will check mileage and report results; might take a while.

 

REALLY curious as to what - if any - Sincere Performance Improvement (not "Sound") came of Your installation of "Headers"... : ?

 

I've got a '99 and I'm in the throes of replacing Mine "Header-Back" for not liking that U-Turn made - and subsequent HEAT EXCHANGED no-doubt - there at the "Y" just-below the Engine Oil Pan...I'm in a non-controlled region where "Cat-Delete" isnt' a problem (though I'm considering it's restoration as the right-thing-to-do ; ) and have-choice of either "Y" in/out of a 3" Flow-master Series 40 OR "Y" into this HUGE "Stock" S.S. Muffler salvaged from a "TUNDRA" that offers TWO OUTLETS in simulation of "Dual Exhaust" ~ That said:

The LAST THING I want it to sound-like is a V-6... : ?

 

After a few weeks of running the stock exhaust with the headers, I went ahead and replaced the cat (flowmaster) and the whole rest of the exhaust with the FM set up DKF recommended.

( I did not check mileage before doing so. Performance gain with just the headers? Maybe slight. Or it might have just sounded stronger. )

IMO, FWIW, the quality of both the Thorley headers and the FM stuff is good.

With all the new stuff, the truck is definitely louder than it was when stock, but it's not really loud; not even as loud as some stock Chevys or Dodges I've heard.
Whether it sounds " good" is subjective.
I'm not crazy about it but it doesn't bother me and I'm sure not going to take the stuff off.
As for performance, maybe the truck is a bit quicker. Maybe.
As for mileage, I was getting in the 10's and 11's before this job, but remember I had exhaust manifold leak(s), which is the only reason I got involved in this project to begin with.
The first tank after the new system was on I got up to 13.3 per my machine in the ceiling. This was highway, 65 mph avg.
A few tanks later it seems I've settled in at 12.8' highway and around town mixed.

 

Well the 99 Y flows better than the necked down versions. If you live in the continental USA then you are in a controlled region. It is a Federal Crime to remove the cat. The V10 has 2 more cylinders and an oddball firing order. It will never sound like a V8. The few times I had my cat off it got unbearably loud and I didn't notice any gains. I have been happy with Borla, Dynomax and now Jones mufflers.