On my 85 iroc the y-pipe is like 1.5 inches while after where the cat should be its about 3in how bad is that hurting performance.
The motor is the tpi 305.
Thank you

 

Well it's bottlenecking your exhaust.... But I can say this...it might actually be helping your low end a little bit. Why? Because your piping past the cat is 3". 3" is generally slightly too big until the car has a few more modifications under its belt. But I can say this..the Y pipe is dimishing the effectiveness of your exhaust past it.

 

People say a more flowing exhaust makes you loose low end. That may be true but I didn't feel any difference going from longtube headers, true duals, and 2 chamber flows to a edelbrock TES/hooker catback.

I didn't feel much, if any, low end gain.

 

Well it seems like that i dont have that much low end as it is. It dont seem to really pull till iam about 2500rpms. From a dead stop it hardly spins the tires.

 

Like I said...sounds like 3" is a bit too much for your current setup. But don't get rid of it. It'll work well once the car has some modifications under its belt...if you plan on it that is. My stang had true dual exhaust, with both pipes 2.5"....it was too big for my combo when I first got it but now that I have heads and a cam, it's the perfect size.
88350...what size were your duals and what size was the catback? I assume both 2.5"?

 

The dual exhaust was 2.5''. I was running hedman longtubes, 2.5''pipe, H pipe, then 2 chamber flows.

My current exhaust is edelbrock TES headers with 3'' y pipe, to a 3'' hooker catback exhaust.

Not nearly as loud as the duals but at least it doesn't scrape the ground

 

i have the same problem, i had a y-pipe made for my headers and the guy put tiny pipe after the Y or T in my case. when i had the stock manifolds any y pipe with 2.5" pipe it had a lot more on top. now with the headers and tiny y pipe it dosn't even push you back in the seat when you stomp on it at about 45mph. my engine has a bit more then your's even though its a 283. its got about 9.5:1 compression, 041 heads, a performer intake, 600cfm performer carb and a cam with 204int/214exh duration at .050. my enigne is a lot faster than a stock lg4 and it likes to be reved so i don't know if it will make as much of a difference on your's.

 

Its just weird i know i only have 275tq but i should beable to spin the tires more then i do. Also are the 85 305 just like this or is mine caused from the exhaust. Like i said before if i step on it from a stop it goes but it really dont throw you into the seat Intel iam about at 2500rpms, then she will really start to move. Or could it be sense my 275tq tops at 3200rpms, thats why it dont to really pull Intel iam about to that.

 

There are many possible explanations. Your torque isn't THAT high....but at the same time there should be enough bottom end to get tirespin considering it IS a V8 and they make low end torque. How wide are your tires? What's your rear end? My car will roast the tires off if I stomp the pedal, with 245 50 16 tires...(BUT, it's got 350+ ft lbs of torque and a 4.10 rear end)....but it doesn't start to pull really hard until 2500-3000, when it kicks you back in the seat. Lack of bottom end like that could be many things...crappy low end torque from the exhaust...a worn timing chain...running slightly rich so it bogs in lower rpms......the list goes on.

 

I have 16-8 rims with newer 245-50-16 tires. a 3:42 rear end. The timing is set to about 12. I am not to sure if iam running rich.

 

Man..12 degrees is quite a bit of advance. Those motors came with 6 degrees of advance I believe. You ARE running it on 93 octane right?

The rear end isnt bad..should definitely make your ride fairly snappy. Same with the timing...timing makes your low end better and your top end worse generally.

 

I think iam running 12, at least thats what the guy that worked on it said i was at. I run normal 87 unleaded.

 

And it doesnt ping?? Did he check it without the timing connector in, so it was at base timing? Like I said...I'm almost positive your car runs 6 degrees stock...so you've got your timing doubled if he's right. My general rule is..any increase of 2-3 degrees advance and run mid grade...4 degrees or more, and run premium. My F0rd 5.0 came stock with 10 degrees, it's advanced to 13 right now and I run 93 octane. I can run a max of maybe 16...but I wouldn't wanna try. Also...if you can't hear any pinging...does it run kinda hot? That's another thing too much timing causes.

 

If your exhaust is restrictive you'll feel it much more in the upper RPMs than you will down low. Torque curve will be down everywhere but much worse up on the top end.

 

Nope no ping. I am not to sure how he checked it. I will have to see what it is set at tomorrow.