72Shark

Guys...just installed the Flowmasters and WOAH ....these things are loud! I hear that an "H-Pipe" or "balance tube" will soften the note up a bit. Where should it go? Near the point where the pipes come together near the rear diff??? Help..I'm going deaf (but loving it!).

Alwyn678

As close to the engine as you can get it...... :yesnod:

ericshaw

flynhi

Consider an X pipe from Dr. Gas.com

Jvette73

I had mine put in just aft of the trans crossmember. It does make driveshaft removal more difficult. Considerably.

Ryan77

I have an X-pipe form Hedman Headders, got it from Jeg's for $90, it is the "X junction only". They also have an H-pipe made by Flowmaster for $40.

goinbroke

I've heard "as close to the engine as possible" before, but am wondering if there's any way to locate the "H" forward of the cross member. It seems like the only way would be to loop under the tranny. This would create a ground clearance problem, and possibly subject the tranny to a lot of heat. I'm just days away from having a new system installed on a 74.

72Shark, hope you don't mind me intruding on your post. Just thought some ideas on this might help us both.


[Modified by rip74, 6:51 PM 10/31/2002]

Chris O'

Behind the xmember is fine - easiest place for a 'vette.

:cheers:

vettfixr

This is how my H pipe is set up. It's forward of the trans mount.

SLICKMAN

How much of a change did you feel when you added this "H" pipe?

vettfixr

That's a hard question to answer. I installed the headers and H pipe at the same time so it's tough to distinguish what performance gain came from which product. I can tell you that the combination added a seat of the pants difference around town and on the highway the difference is night and day. From around 2k to 2500 rpm and up it feels like an extra 50 horses. I think the H pipe made the biggest difference in keeping the sound acceptable. I have Dynomax Ultraflows on now (not installed yet in the pictures) and at idle the sound isn't much different from a set of stock mufflers. There is a slight resonance from 1300 to 1600 rpm but once past that the sound is again not much louder than a stock system. Once you put your foot in it or at engine speeds over 3500 rpm the sound is much like the old glasspacks with a nice rapping sound on acceleration but not annoying. On deceleration there is no popping or rapping at all. Now how much of this is due to the headers, or the H pipe, or the Ultraflows? I don't know. I can only tell you that the combination is sweet and makes for a very driveable ride. Hope this helps.

goinbroke

I'm wondering if the "H" pipe located forward of the crossmember is something that's easier with a manual tranny. Seems like the auto is a lot bulkier, and would be harder to fab pipes around it. Wondering if the guys saying "behind the Xmember is the only place" have autos.
Any help with this theory is appreciated.

Thanks

74 350 auto


[Modified by rip74, 2:48 PM 11/1/2002]

Aaron-74

Mines after the trans cross-member. I don't know of any power gains since I had the whole system welded up at the same time. It does make it a little more "mellow" sounding, and reduces exhaust "popping"...

fauxrs

My h-pie is in front of hte x-member - even closer to the headers than the one pictured above and I agree that it is much easier with a manual - you must leave room to remove the pan off the bottom of an auto so I dont think that in front of the x-member is even an option on the auto equipped cars.

Yes there is some very small amoutn of ground clearance lost but nto enough to matter

vettesite

Mine is after the cross member because of the auto trans. Get one, it will reduce internal resonance and some of the loud raspy sound.

mountainmotor

72Shark

I put mine right behind the cross member. The mandrel bent pipes from the headers are cut about 4 inches past where they run through the crossmember holes,the the two exhaust pipes are clamped as is the cross over pipe. I used a 2600 degree anti seize compiund so when the tailpipe clamps are lose,a couple good hits on the crossover clamps and the entire system is free to drop from the rear hangers to move completely out of the way for any work that needs performed and to put header mufflers on if needed.

Something that will also help reduce some noise is if you have 2.5 inch od tail pipe turn downs you can use 2 1/4 pipe expanded to fit over the muffler exits and will decrease some noise there without killing performance on a milder engine. The slash type cut you see on some OEM tailpipes are there for a reason also,try to have them cut this way if interested

goinbroke

Thanks to all who have helped clarify this matter.

I also want to thank 72Shark again for allowing me to intrude on his post.

Rip

Pat71vette

I have headers straight pipes just like the orginal set-up on a 71, What gains would I be getting back to add the H or x pipe besides just a sound change.
I have 1 5/8 headers 2.5 dual exahust thru dynomax mufflers, sounds great now. I there a power increase?

Ryan77

They claim about 10 horsepower form an X-pipe, which you should see since you have a good setup with headers already.
By the way, I forgot to mention that my X-pipe is after the crossmember, I have a manual trans.

Twin_Turbo

Are you guys placing the H pipe just where it fits? It would be most effective to place it there where you have a standing longitudinal wave (actually "knot") in the system. This is easiest found by putting some lacquer in a line from the trans back over the pipes, run the engine and where the lacquer burns off first you have a standing wave. That's where you place the H-pipe.

Marck