Time to upgrade exhaust

mhjo

mhjo

Founding Member
Nov 9, 2000
490
0
17
Oslo, Norway
#1
After my AOD swap the H-pipe had to be removed because of placement issue, wich also led me into thinking exhaust again.

My current setup:

Hedman shorty headers
H-pipe (cut off)
2 x Dynomax super turbo
1 x Dynomax super turbo transverse in rear

This setup has worked fine, but it started ticking and popping a lot after the removal of the H-pipe. I also want most hp.

I have been adviced the following:

Get a HiPo manifold instead of the headers
Get rid of the rear muffler and replace with resonators



Any tips / ideas?

( I like it both ways, maximum hp and silent cruising!)
 
#2
Yeah, you kissed 5-15 hp goodbye when the crosstube was removed.

I got tired of headers years ago, when my 66 was a "driver", and put the 289HP manifolds back on it. Never missed the headers. I suppose a chassis dyno could have found a high-rpm power loss, but the trade off of better ground clearance, less radiating heat, easier to work on the engine, blah-blah-blah, it was a good choice for me.
 
#3
Just went w/ a 2 1/2 in exhaust w/ Thrush turbos and I love the growl. I had 2in and noticed i had to rejet the carb richer because of the increase in flow. I currently got Tri Ys. I'm not sure about the difference between those and Hi^po manifolds buy I'm sure its on here somewhere. The Tri-Ys seem to fit better than others as far as working on the engine.
 
#4
I'd add an H pipe back to the system just to equalize the cylinders, should stop the pop back and I'd try eliminating the 3rd muffler. With super turbos (quiet) already I would think limiting a dual exhaust down to single through 1 muffler would choke the system somewhat.
Jon
 
#5
I will keep it dual, but I will relocate and reinstall the H-pipe, maybe replace the headers with Hipo manifiold.

As for removing the rear transverse muffler, I was advised to install resonators instead. What is difference between mufflers and resonators? - and what are resonators for?
 
#6
I would definitely put the H pipe back in.

Resonators just smooth out the exhaust tone. I'd keep the dual Superturbos and dump the transverse rear one.

The HiPo manifolds are a great way to go on a stock or mild engine.
 
#7
The H-pipe crashed with a metal frame on the AOD, so it was removed. Now that I am getting exhaust replasced, a new H-pipe must be made. Should it be placed infront of or behind the frame on the AOD?
 
#9
The AOD 'crashed' with a edge on the AOD. I once read that finding the right position for the H-pipe is essensial. Makes me wonder: maybe use 2 H-pipes?

My setup will be as follows; HiPo manifolds, 2" pipes with H-pipe, 2 Dynomax super turbo and rear pipes with resonators.
 
#13
Hi
If you are looking for quality resonator muffs, Google "Stainless Works". Then check out P/N TDM25. Although this prticular P/N is for a 2.5" inlet with a 3.5" body, you can order them with a 2.5" inlet with a body of 3.0" body.
These are the "bomb" as far as I'm concerend when it comes to both quality and sound resonance.
Happy Trails!
 
#16
Not so happy after all..

We finally got:
- shorty headers off, and HipO manifold on.
- Rear transverse muffler off, and resonators on
- new prefab 2 "H-pipe and tailpipe from NPD

However, we didn't get the mid section pipe in 2" so we used 2.5 "
The H-pipe had to be cut and spiced in order to go clear AOD.
We saw after cutting the crossmember pipe in the H-pipe that the pre made holes in the main pipes where very small (finger wide).

So, the exhaust work ok but for a booming "hum" at 50 - 100 hz. It's a bit annoying.

Q1. Is this caused by the lack of flow in H-pipe crossmember pipe?
Q2. Or is it because we use wider pipes between H-pipe to rear mufflers?

I haven't noticed any performance gain after the exhaust swap. I find it strange since I reintroduced H-pipe and removed transverse muffler....
 
#17
I don't think its from the different diameter mid pipes or the H pipe. I can't believe that your having noise issue with Dynomax turbo mufflers and resonators. I know alot of people that have them with out resonators and they are pretty quiet. Are you sure they are turbo mufflers and not one of thier other lines?
 
#19
Update

We will replace the two Dynomax super turbos with the new 'drone free' VT's

Also we will cut off the H-pipe, enlarge the (small) holes in the main tubes, and make a H-pipe with an oval 2,5" pipe.

Our theory (partly made from advise from members of this forum) is that this will provide a optimum performance/low noise combination:

HiPo manifolds, wide H-pipe, Dynomax VT mufflers + straight through resonators.

I will post the results.
 
#20
I did the AOD swap in the 69 Ragtop a few years back.

Many have asked why the stock "H" won't fit, and the reason is the AOD is a much bigger case size, and the stock "H" hipe will not go around it. I had the same problem, I just ran true duals, no "H" connection between the sides, with quiet Turbos, it was fine.

When introducing a cross-over, it will change the tone of the exhaust. That is why you hear any modified 5.0 with an "X" cross-over, it has that distinctive rasp. But, having the cross-over does, or is supposed to aid performance by better scavenging and exhaust pulses. Most likely, the size and location are critical, but I do not know much more on that subject.

Like the others, I suggest a second "muffling" is redundant and not needed.
 
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