ittybittyfds

well all i no longer have emmissions to worry about and i am thinking of running true duals now without a cat

if i am currently running long tubes and i have B&B mufflers
will running dual 2 1/2 pipes hurt my performance on the L98 stocks heads and cam
or should i run a x-pipe in the dual setup

dclafleur

I'm always curious about the various exhaust setups on the '85...

RRT vette

Sounds like a good setup. You might want to add the x-pipe for resonance issues.

Phatoscar

I had true duals with X pipe no cats and super 40 flow masters! The sound... amazing! The hp gain is also very good! I defenetly felt a huge gain! I would estimate anywere from 10 to 15 hp gain!

Steve85

On an otherwise stock 85, 2.5 will be plenty. I would recommend a compromise and go with two hi-flow cats (several reasonably priced options) they will not hurt performance 1 bit (you will see a gain from the existing system) and keep the smell down.

Do this on dual exhaust with x or H pipe and you will be good to go for now and have room to grow...a lot of room actually.

thirdtimevetteowner

So, that is to say that the Melrose 3" system is too big? For a stock L98, but what about w/a set of AFR 195's and a decent cam plus mini-ram and headers? I am stuck between choosing that system or a 2 &1/2" system. Also my 89 is a vert. Will the 3" even fit? Anyone know? Any help appreciated.

Rich K

emo-vet

hi guys,
sorry to but in guys,just wandering
is true dual 2.5 " diameter mandrel exhausts larger enough on a worked 350/383 at all ?
or would 2.75 " diameter or twin 3 " diameter be better may be?
thanks
shae

Corn Flakes

I have true duals, no cats, and no mufflers in 2.25 piping and its not what I thought it would be. I still want it to be louder. Throttle response did improve though. No resonance either. Everythings been welded to. Had clamps holding it together before and it rattled alot.

engle1147

to a degree. I have '89 with the same set up: 2.5 true duals, no cats/pre cats topped off with Borla ZR1 style mufflers. The system is fully welded together. There is no crossover/ balance tube on the car and thing sounds extra mean when the revs are up but it is still quiet as a church mounse at idle!

Corn Flakes

Very true when your hitting the rev limiter. I like mine loud at idle though to and it's not as quiet as stock and I can hear it standing behind the car but I want it booming. I figured if I get a new cam then it would sound louder.

GIJoe

I JUST put true duals on my 89.
lost a bit of torque, but seems peppier higher up in the RPMs now.
The sound is completely different as well

Since you got LT's I am assuming you don't have precats (not sure if they came in the 85 anyway)....

but for a cheap alternative, just swap the main cat out with a straight pipe... this will basically give you a near same effect as an x-pipe.


I asked a corvette tech/mechanic about my old setup once because i wanted to go with true duals.

I had gutted pre cats on the front Y, guttet main cat in the middle, and a rear Y with Borlas. He said this would pretty much give me the same gains as the stock size true duals (2.25"? I forgot the diameter)...

anyway, so I just kept that.


The only reason I put the true duals on is because it came on the parts car I bought, so I figured, what the heck

dclafleur

Yeah, the '85 doesn't have precats and the bolt pattern on the main cat is different then later years. I've been looking at various options including true duals because most catback setups won't bolt straight up anyways. I've also thought about just doing LT's into a high flow universal cat to a catback and just doing it all at the same time. So many options..

BADDUCK

True duals should work well and 2 1/2" pipes are fine unless you are making huge horsepower.

mseven

My set-up is like that 3" all the way to the x' and just past that is necks down to 2 1/2" to the muffler to keep the velocity up). Depending on gear and conv. it will drop a little low end, however it will still spin the tire pretty well even from a 20 roll. Clearances to the tunnel, trans. et.all on mine are very good. I would guess at most, a little work on your cross beam might be needed (mine is not a melrose system though).

teufelhund

I went true duals with magnaflows on the back and a home made H pipe that he did when he was bending the exhaust. It sounds GREAT and the SOP dyno says there was a BIG improvement especially up top. JMO.... Best mod I've done yet now I just need some long tubes to go infront of all that. All the exhaust work w/out the mufflers cost me $110 best money I've spent on the vette yet.

Muffin

This works for me. I do have an H pipe however.

CentralCoaster

It will sound good but be loud as hell all the time.

Cats really help quiet it down.


What would long tubes and no cats sound like with the stock mufflers? Surely it would be louder than stock and still bearable.

cv67

You want dual 3"s?..Hope you lilke resonance, cause thats what youll get, an no X, H or corssover or any of that bs is going to get rid of it, trust me. But youll look cool while youre going deaf.

Oh, and youll lose about 20 lbs of torque on avg...And gain what, 5 peak hp?10? Going backwards.

Cant wait to throw mine in the trash and get a good 2.5" mandrel bent system. 3" is overkill for a 350 unless you are making stupid huge power.

To anser your question, dual 3s will fit. Even with all those mods you dont need anything that big.

86GoldProject

I'm running hedman longtubes with a cut back stock exhaust system with the main cat gutted and the 2 precats cut out, I'm running a huge cam and a carb and I was shocked by how good it actually sounds.

davemack

I am running an LT4 exhaust on my 85 and really wanted to go with HF bullit cats, but after reading a post by tjwong(?), chose to forego them. Catalysis requires heat, and if you install cats where they weren't intended to be installed, you run the risk of buring your car. You might be able to install heat-shielding material, but I wasn't sure how well it would work, how well it would stick over time, etc. After hearing the story about the mis-placed cats (it was a car the author of the post worked on where he found the floor had a hole burned through and the carpet backing was badly charred..) I decided against cats. But, I would much prefer to have cats - it does smell w/o them.