LT4 Magnaflows Resonate Horribly on my LT4

[96CERon]

After reading and researching for many months here and elsewhere, I installed a set of the Magnaflow mufflers #15623. The sound at idle and "goosing" it is great. The notorious resonance on my first long trip between 1600 to 1800 rpm is horrible--I'm near deaf after two days of this. It is bad enough to rattle a lot of items in the car especially when pulling up grades on the highway. These are coming off and I guess back to the stock mufflers. This is on a basically stock LT4 engine and exhaust system. I have other Maganflow products on my son's Nissan Frontier and my brothers S10 pickup that are great. I called and talked to Magnaflow tech support--they are no help. Any other suggestings other than Corsas? Are the Dynomax replacments any better? I will make someone a great deal on these if they want them.

 

[wrenchmantee]

Been looking for some, How much do you want for them? And little more discription on how many pieces and what kind of tips...

 

[JamesRS2000]

I'll purchase them if you still have them for sale.

James

 

[KOPBET]

A couple of questions...

Just wondering if you had them installed or if you did it yourself. Were they welded or clamped?

Is the stock resonator still in place?

 

[LT4man]

You could try what I did do!

Get the Magnaflow X-pipe and have it installed in place of the resonator.

You need to find a sharp muffler tech who will know exactly where to place the X-pipe.

You should have no more resonance.

As a ps: Make sure your tailpipe tips extend just a little bit past your rubber bumper cover. This is also VERY important!

SAVE THE

 

[LT4man]

You can also check out this thread:

http://www.corvetteactioncenter.com/forums/showthread.php?t=82756

SAVE THE

 

[geekinavette]

As a ps: Make sure your tailpipe tips extend just a little bit past your rubber bumper cover. This is also VERY important!

THAT is the key to reducing in-cab resonance.

Bill

 

[svoch]

I have tri flow on my LT4 1st with cat back and now with long tubes. In 6th gear on the highway I experience the same deafening drone. It is worse when windows are up.

 

[geekinavette]

It is worse when windows are up.

Of course it is...that seals the resonant chamber!

The tailpipes need to extend beyond the rear bumper of the car...that will usually drastically improve in-cab resonance. Maybe try some sort of cheapo "clamp on" tip extensions (of course only as a test, and something that won't damage the existing tips).

 

[gmhowe]

I just had the Magnaflow back cats put on my 96 CE LT1, took it out on the highway and it wasn't that bad, actually kinda like it.
Gordon

 

[Silverrod]

Hi,

I run Magnaflows with no resenator, 3". The trick is get an x-pipe, they are available from a guy here in Florida, I don't remember exactly but they are 2 3/4 ". It welds in perfectly where the two pipes are close, near the crossmember. I run 3 " tubing from the x-pipe to the Magnaflows, sound is FANTASTIC!

Good Luck,

Roger

 

[svoch]

Roger, I have been looking for 3" x pipe. Do you have info where you purchased?

 

[svoch]

x pipe is the answer!

Roger, my ride enclosed

 

[Silverrod]

Hi,

It is 2 3/4 inch, not 3 inch. Stock LT4 pipes are 2 3/4. I had the x-pipe installed in the stock down pipe, then had the 3 inch welded to the x-pipe, it slips over perfectly.
They are Advanced Automotive 239-573-9933.
It was a whole lot cheaper than any other x-pipe, strong well made.

Roger

 

[Silverrod]

Hey Svoch

I replied, check and let me know.

 

[svoch]

Roger, I spoke with them. Unfortunately I need 3" X pipe. They can fabricate one but it will cost me big.
I have 3" triflow w/long tubes no cats.

Thanks anyway

svoch/Larry:eyerole

 

[LT4man]

You could use Magnaflow #10792.

Talk to your regular mechanic. He can order this from Magnaflow way below list price.

SAVE THE

 

[Silverrod]

Mine is cast iron manifolds, go figure, LT4,my '89 had steel tube maifold stock. Me too, no cats. The Mgnaflow x-pipe idea is good, I Love those guys

 

[LT4man]

GM did a lot of testing of different types of exhaust manifolds between 1989 and 1996. I heard they found out that the cast iron manifolds flowed just as well as the tubular header on your 89. Ease of production and consistency of production led GM to go back to the cast iron one for the LT4.

SAVE THE

 

[jonszr1]

not trying to disagree on the manifolds . long tube headers on my 90 made 20 rwhp over stk manifolds. they may have been comparing shorty headers Jmho. magna flow also has come out with a new cat back system that has an xpipe just before the resonator the whole system can be had for 724 . like said earlier tipps at least 2 in past the rear opening help a bunch .one other thing that helps tons on the resonance is a set of flow master heatshields that strap on over the mufflers i also put some sound deadening (spray on high temp) made a way big diff .i was told by some friends at spin tech to try this. hope this helps you stop having to take excederin everytime you driveotfl