First_Formula

Hey guys. I have a stock l03 at the moment, Plan on putting headers and a 4" or dual 4" CAI on it and headers with cat delete on it. I personally want 2.5 inch pipes from the Y back cuz I don't want it to be so open that I lose performance down low (she redlines at 5.5 so low is all i got lol)
What do you guys think is a good choice for headers that can be easily mated to a 2.5 inch dual setup? And or what is your general thoughts of the setup.

KrisW

iTrader: (5)

My general thoughts are... take it slow and easy with what you are about to do.

You have a ton of limiting factors on your setup that need to be corrected. As exhaust goes, I think you should go a bit differently...

Every part of your exhaust sucks, so you are doing good thinking to get rid of it. Your manifolds are the worst V8 pieces, chunk them for the headers.

An X-pipe is okay, but with the way the lower pan of the car is designed, they seem to put the pipes way too close to the ground. I would go with a custom built y-pipe. I like the two 2 1/2" pipes into one 3" with the flowmaster Y transition. Then your high flow cat, then a 3" cat-back of your choice.

You'll get seat of the pants power you can feel with that setup. With the "peanut" cam you have, you won't see gains (and may see a loss) with a bigger exhaust setup than that.

Next, you need a set of 87 305 4bbl carb heads, or 87-up TPI heads and a TPI or LT1 cam. THEN you'll start waking up.

Hit the Ultimate TBI threads and all the TBI section stickies. Do it all!!

Good luck!!

First_Formula

I'm not going to get TOO in depth with this car, Its my DD so i can't keep it off the road for too long, Also I don't need a 360 HP DD lol.

So as far as cams and heads go thats a far later project.

But for Headers and whatnot you agree with the current setup?
I kinda want to keep 2.5 inch instead of 3 inch also I don't plan on having cats (already got rid of the stocker) I don't live in an emissions testing state so i'm not worried about it. And 2.5 inches should be better for my lil peanut cam than a 3 inch. though i'm not against a 3 inch entirely.

Any thoughts on what kind of headers? I hear Flowmasters and hooker 2055s work good for these cars.

UnderCover89TBI

iTrader: (25)

flowmaster doesnt make headers. Your option are more open if you dont have emissions..you dont need teh AIR tubes in the headers so you dont have to have the 2055's. im not sure what other brands are out there w/o air tubes as I live in a smog state

First_Formula

Ok I'll look into headers w/o AIR tubes. Thanks alot!

KrisW

iTrader: (5)

A 2.5" cat back will be just fine with your setup, no doubt about that. I mistakenly thought you were talking about 2.5" DUALS, which I see now is not the case, sorry about that.

Your manifolds are so bad, ANY headers, even cheapies off of eBay, are better than what you have now. If you plan on doing other mods in the future, the Hookers are good for the long run with that.

Believe it or not, the absolute worst part of your setup is the Y-pipe. It is a horribly engineered piece of garbage. The ideal situation would be for you to get a headers/y-pipe combo first. Once you install that, you will feel the difference. Then do the rest as your budget allows.

Good luck!

First_Formula

So if i wanted duals (not true duals or anything but headers to Y pipe back) I would want like a 2" duals?
I believe your saying a 2.5 inch single pipe from the headers back is a good setup, correct?

85T/A350

I believe they are referring to a 2.5in into a single in/dual out muffler. youll have 2 pipes out of the muffler giving the appearance of duals.

First_Formula

I"d prefer to have an actual Y pipe dual setup, but I wouldn't be against the single in dual out...

85T/A350

A single in dual out is a y pipe setup. A ypipe merges the two pipes from the headers into one. With out a single in dual out muffler you cant have duals with a ypipe. I dont understand what you mean by an actual Y pipe dual set up.

KrisW

iTrader: (5)

If you are talking about the headers back, here is the deal; Mount your headers, have one 2.5" pipe coming off of each header, going into the Y-transition piece. I like mine to be 3" out and two 2.5" in, coming from the headers. Then, I run a 3" cat, and then a 3" cat-back all the way to the muffler.

I run the crossflow type muffler (like factory) and it is 3" in with two 2.5" tailpipes in the factory location.

First_Formula

I thought a Y pipe looked like this |---| <---engine
---------------------------------|__ |
--------------------------------|| ||
-------------------------------- || || <----Exhaust tubing
---------------------------- -----||||
----------------------------------||
----------------------------------here you have an upside down Y splitting the one into two,

I see now that its not that way lol. So for a dual setup i'd get an X pipe?

KrisW

iTrader: (5)

You don't have to have an X pipe to run duals, but lots of people like them.

Really, I think you should do the headers and y-pipe first, and then see what you think about how the car is running. Then do the cat and cat back system. You'll be happy, I promise you that.

Most people here can't believe the difference just getting rid of the restrictive TBI manifolds and crappy y-pipe. I just bought a beat to hell TPI Camaro from craigslist today for the transmission, AND the TPI manifolds and y-pipe to put on my TBI firebird. I have done this before and I know what a difference it is!

I'm giving the car to my mom for her birthday, otherwise I would put a set of eBay headers on it hahahaha, but she likes it quiet.

First_Formula

That'll be a nice present for her lol. So you think I should run headers into a Y pipe into a single pipe to the muffler which will have dual outlets?

Do you think 2.5 inches should do the lil 5.0 justice or will it require thicker piping, I've been reading up on it and 3 inch sounds too big for my lil v8

KrisW

iTrader: (5)

That's how GM ran the exhaust, so why not? The configuration is not the problem, its the parts themselves.

Your manifolds are substandard, so change them out with TPI pieces or use headers. The y-pipe is awful, so make a better one!

I have done that 3" swap many times, with only good results. But, you can use the 2.5" system too and it will drive just fine. I think people do too many upgrades at once, and then if they do lose performance, they are never really sure what happened.

My friend Pat's 90 firebird, 305 TBI and 5 speed, the first mod we did was a 3" cat-back and nothing else. We didn't see any performance loss from it.

kd5icr

iTrader: (2)

On a budget not a problem. I got a set of hedman shorties from a member of this board for 90.00, I took them and had them blasted for 30 dollars. I got a can of VHT header paint for 15.00 and did that. Then I got a hedmman y-pipe from summit for 115.00. So for 250.00 dollars I got rid of junk factory manifolds and y-pipe and picked up a few HP and get better milage. So yes it can be done on a tight budget for cheap. Yes some here will say get this or get that, Thats all well and good but in the long run what I did will last for years, at the worst I may need to pull them off in a couple of years and either get them coated or just rehit them with VHT. So what I still would have less in them than others pay for the same setup brand new.And for the record you will be happy with 2.5 inch pipe from the y-pipe all the way back into a good muffler because no matter what it will be better than the stock junk that came on our cars. This is just one of many ways to build ANYTHING on a budget. Yes getting new anything is always nice, but the money I saved I put in the engine itself, and darn it, it runs great. The point I am tring to make is, you dont have to get the very best as some like to call what they have, to get to the same point. I bet you can go to the classified area here and get a good deal on headers and a y-pipe. I would say try that first before you run out and order from summit or jegs and the like. Most all of the people here are trust worthy and you can find some darn good deals. And good luck on your build.

First_Formula

Wonderful informative and true lol. I'll look around for a cheap set of headers, Is there a good flowing muffler you can recommend with a dual outlet or do you think I should run no muffler, I don't know how loud it would be... maybe.

UnderCover89TBI

iTrader: (25)

just for the record. I understood what you wanted to do First.

KrisW

iTrader: (5)

Me personally, I love the flowmaster kit.

I know there are TONS of flowmaster haters on here, and they start talking about backpressure this, and flow numbers that. I even started a thread about the flowmaster flaming because it really bothers me that everyone who bashes them does NOT have a dyno sheet proving how bad it is.

I think you should listen to a few different ones, and then pick the sound you like. I like the flowmaster, but maybe you won't like the sound.

kd5icr

iTrader: (2)

Like Kris said flowmaster is a good one. But any new muffler will be better than the stock one. This is were summit comes into play. Call them they will point you in the direction.

the solitaire

Backpressure is a myth.
Red the stickies, they contain a lot of good information on why backpressure does not matter.

So much for the Flowmaster bashing. Even though not the best, they are a fairly good flowing design. Personally I do not care much for loud though.

First_Formula

I'm not worried about what kind of a sound it makes really but i DO care about how well my engine will like it. I read the stickies on backpressure and I understand them but they do say that a 4" exhaust on a 305 will only help at like 9000 rpms. Something my engine is incapable of doing lol. So i think that a 3.0 should only help at the REALLY higher rpms of my scale (like 4.5 and up) which my car rarely sees. I just want a general increase in acceleration and hopefully a few extra mpgs while i'm at it. a 5.0 with 2.5 inch exhaust should help even out my powerband down low if i'm not mistaken (around 2 or 3K rpms) which is where i see it most and being that my car rides 1.8K rpms highway I think that would be my most desirable rpm to increase for hopefully adding a few mpgs.

Correct me if i'm wrong please. That is my understanding. I just wanted some reaffirmation and or was kinda wondering if anybody here had put a 2.5 or 2 and 3 quarter exhaust on there 5.0 and what there results were.
Also thank you all for the posts and info!

KrisW

iTrader: (5)

My bone stock, 305 TPI 87 Formula, well it started life with advantages over what you have, so it may have responded a bit better to the modifications than a TBI would. I'll give you that.

With no other mods whatsover, I put a 3" flowmaster cat back system on it, and I had an increase of "seat of the pants" feel. I like the sound, too.

When i did the custom y-pipe, and the cat, it got even better. This was a dual 2 1/2" from the manifolds, to the flowmaster y transition pipe, with 3" out, and 3" high flow converter. It felt better, and sounded better, but the computer said I was starting to run a bit lean and would throw a code now and then.

To compensate, I put on a BBK aftermarket fuel pressure regulator, that was adjustable. I didn't even have a gauge on the engine except at the start. I started out by setting the fuel pressure at 45 at idle. It drove exactly the same. I bumped it up a 1/8th turn on the regulator, and never got a lean code again. I was in California, and it still passed the smog test.

Now, your engine is not so different in this respect. If you end up increasing your exhaust flow so much that you are leaning way out and losing power, you can buy an adjustable fuel pressure regulator off of eBay, and an adapter for your TBI to hook up a fuel pressure gauge. Start by adjusting fuel pressure to 13 at idle, and then slowly work up until you are back to the good feeling.

My 89 TBI firebird, also bone stock, LOVES the 3" cat back. I installed a GM vortec 350 fuel pump in it, and without adjusting fuel pressure (I have the stuff but have not installed any of it because the car is running perfect!) it perked up and runs great. I have not changed the cat (but it is burnt out) or the horrible y-pipe, but that is next on my list to do.

I just bought an 89 IROC for a project, and I am taking the TPI manifolds and y-pipe off of it to put on my TBI engine. I know that works, because I helped a friend do it to his 90 bird years back and it was a driveable difference. Back then all we had changed was the exhaust and it was much better to drive.

I think one reason that some people get a power loss is because their engine isn't as fresh as it once was. The compression is lower, and opening up the exhaust lowers the cylinder temperature, which lowers cylinder pressure more. THAT is the real truth. The car can run great, but 150k miles is not the same as 50k. Keep that in mind with what you're doing.

If you are really worried, then go with a 2.5" system. You'll still be way happier than the stock setup. Its more important to get rid of your manifolds and y-pipe than the cat back though, in my opinion.