[chlebowskicj]

I just finished putting on a pr of Hedman elite-coated full-sized headers on my 70 GTO to replace the old dual exhaust w/ stock manifolds and Walker mufflers. It's a 400, .30 over, all else is pretty much stock--cam & valvetrain, carb, etc. I'm looking at either a Flowmaster or Pypes dual crossover kit. I want something that sounds good on idle and acceleration but not the metallic/ tinny loud that you get with some mufflers when you get on it. Am looking at 2 1/2" pipes from header back. Car is for street driving and cruising, not racing/strip.

From the mufflers I've heard before, either on the websites or in person, I'm leaning towards the Delta Flow 40's or 50's. Also want to have a cross-over system too--are both Pypes or Flowmaster both OK?. And any comment on the muffler type and pipe size?

Thanks

[chlebowskicj]

I just finished putting on a pr of Hedman elite-coated full-sized headers on my 70 GTO to replace the old dual exhaust w/ stock manifolds and Walker mufflers. It's a 400, .30 over, all else is pretty much stock--cam & valvetrain, carb, etc. I'm looking at either a Flowmaster or Pypes dual crossover kit. I want something that sounds good on idle and acceleration but not the metallic/ tinny loud that you get with some mufflers when you get on it. Am looking at 2 1/2" pipes from header back. Car is for street driving and cruising, not racing/strip.

From the mufflers I've heard before, either on the websites or in person, I'm leaning towards the Delta Flow 40's or 50's. Also want to have a cross-over system too--are both Pypes or Flowmaster both OK?. And any comment on the muffler type and pipe size?

Thanks

[bonneville Joe]

Highly recommend the DF 50. Have them on our '66 Starcheif Executive. Nice combo of awesome sound but not overpoweringly loud.

[cujo]

From what I've read I hear that the x-pipe crossover is better than the H-pipe design. For your setup the 2-1/2" system should work fine. I'm curious as to how the Headman headers you installed fit your 70 GTO. Were they difficult to install and how is the clearence for Oil filter removal, starter, brake proportioning valve, and ground clearance.

[chlebowskicj]

The header install was a "challenge" for sure. It helped that I took the heads off and had work done on them. So I just laid the headers in to the side before putting the heads back on. With the heads on I think raising the motor off the mounts would be a requirement. No problem with the starter or oil filter housing but I did remove both for the install. And I did get the 3-tube not the 4-tube headers which the tech rep said would clear the oil filter. So the middle 2 exhaust ports have a wider diameter pipe and the collector is less crowded. Brake proportioning valve--if you mean the junction box for the brake lines, yes, that I had to move that from the inner side of the frame to the top of the frame. It wasn't a pretty job, just bent it up and over carefully--will need to go back and do it right at some point. As for ground clearance, it's definitely lower to the ground than I would've wanted, about 4-5 in. I'd say, maybe a little more, but I have scraped the collars once or twice already. Have to ake dips or speed bump carefully. But I probably need new front springs also...separate project. 2 other slights problems were the automatic shifter bracket that's in 2 pices attached to the driver side frame, near the emergnect brake cable routing. Had to unbolt and take off the outer part--made no functional difference on the bracket. Also had to rebend one linkage bar from the steering column collar by the firewall that runs to the transmission linkage. Problem I had with it was that it wouldn't let me shift past Reverse on the shifter. Not sure what kinds of problems a manual linkage set up would have, if any.

[chopper john]

Clubber70,

I also have a 70 GTO and am very happy with the PYPES system w/Dougs headers. The X-pipe seems to smooth out the roar. I like it loud so I run the 14" Goerlichs, but the 18" ones are available if you prefer a mellower sound. I have flowmaster 40 series in my pickup and it sounds ok but tinny to me. The goerlichs use more of a straight thru design with fiberglass packing vs. the chamber design the flowmaster has. If you want a deep, throaty rumble at idle and loud as hell when you get on it, go with the Goerlichs.

[GoatDr]

I installed the American Thunder Flowmaster kit on my 70 GTO. I did the 2 1/2 inch. Just about as easy as can be to install on headers. I had my brother-in-law weld it up, but could be done with clamps. Sounds great not too loud, but loud when you romp on it. I put 2 1/2 to 2 1/4 reducer on tailpipes and installed the original chrome splitters. I have the Hooker Super Comps, coated.

[chlebowskicj]

GoatDr,
Does that kit come with a cross-over pipe, x-type pipe or neither? And are the mufflers offset inlet/outlets?
Was the install pretty easy or any mods that I need to do? Thanks

[David Jones]

H pipe comes with it and they recommend offset inlet and offset outlet mufflers. It is available without mufflers for those that don't like the Flowmasters. I paid a muffler shop to install mine since I don't have a lift or a welder. I started out with the 50 series Deltaflows and after realizing I liked to speak and hear my passengers, swapped out for some 20" Dynomax's and have been very happy.