Hi,
I intend to build a custom 3" exhaust for my TA 85 305 lg4. Since im on alimited budget Im thinking of buildin everything except adding headers.
So Ill buy or let someone weld an Y-pipe that fits the manifolds and that is 3" outlet, a universal 3" cat and a good flowing/soundin muffler. The rest I will build from universal parts that are not( at least not in Sweden), very expensive. I do not want to use a cat-bak since these are somewhat expensive and only 2" 1/4 at the cat, so Id have to fabricate anyway...
Now is this totally pointless if I dont use headers, are the manifolds too restrictive? Maybe i will get to little backpressure if I "overdo" it for an lg4?
The only mod so far is a mild cam..

Hasse

 

you can get catbacks with a 3" connection to the cat.

there is no point building a good exhaust system and not install headers. the factory manifold are a huge bottleneck, especially on the lg4. your catback could be 4" and the manifolds will still kill any gain that could be had,

 

ageed. headers are a good investment for any car IMHO

forsale---> Hedman Street Headers with A.I.R. + Dual Cat Y-Pipe JET HOT coated

 

If you wanted to stay with manifolds, consider L98 manifolds. Not near as ggood as headers, but still better than LO3, LG4 manifolds. Just make sure, they are really from a 350, not a 305, to see any benefit.

 

Ok thanks, i might just do that..
Shouldnt be too hard to find at a junkyard. What about AIR -pipes and that pre-heater hose connection, do those manifolds have them? One of the reasons that im not getting headers is that im planning to become a deserter in 1 or 2 years....getting a bandit! And the lg4 is 155 hp stock, not too exciting! And from what ive read on this forom there seems to be alot of problems like heat and leakage with headers.....

 

get some hedman long tubes, there cheap and work, then just have someone fab up a y pipe with a bullet and a turn down or just go fromt he headers into 2 bullets to turndowns

 

Unless you're doing all the work yourself, you will spend more doing a "custom" job than just buying a boxed cat-back.

I think you have several misunderstandings about the packaged ones.

Here's a typical one. http://store.summitracing.com/partde...rt=FLO%2D17151

1. They're CHEEEEP....

2. They have a variety of inlet diameters; the one I posted is 3"

3. They FIT THE CAR, no questions asked, first time every time.

There are others, I just used that one as an example.

I would STRONGLY RECOMMEND a good-quality set of headers. Use chassis0specific ones, designed specifically for these cars; not "universal". Not, the cheeeepest thing you can find that says "headers" on the box; good ones. I've used SLP and Edelbrock and had good results with both. There are DEFINITELY others. Whatever you get, have them ceramic-coated.

those 2 things, plus a cat, and you'll have all you'll ever need.

 

long tubes on a LG4 305 ? get some shorties.

 

I think it's the shipping that kills. Going across the pond on something as bit as a cat back could easily cost $400. That makes it worth building yourself.

 

Any L98 manifold from...86?/87?, I think it started, will have the emissions tubes.

Pretty sure all verts got 305s...if it's a vert, it has a 305, keep walking. If the car has a T5, keep walking, it's a 305.

L98s got TPI, so they won't have the pre-heater connection. You should be able to transfer yours, to the new manifold. Pre-TPI 350s would, but then they wouldn't have the AIR pipes. The pre-heat connection is easier to make fit, than the AIR tubes.

 

Well, I would have to pay at least 600 dollars for a Hooker catback, about the same for coated shorties with AIR. Then there is the cat which i MUST have, a direct fit aint cheap over here and I wont use the lg4 one....
What we do have though, is different different bits of exhaust tubing, bends in different angles etc. And a universal cat isnt very expensive.
So i think ill start measuring, get the pieces i need, the L98 manifolds, and give it a try...Besides Ive got friends who can do the welding, but maybe only the y-pipe has to be welded since most parts are slip-fit. Or should I have all of it welded?
Thanks guys and wish me luck, at least i know it will be fun!

Hasse

 

Weld the slip fits. They work for fitting things together, but provide no real sealing.

I knew importing headers wouldn't be cheap to begin with, and you expressed manifolds over headers anyways, so I didn't bother suggesting ways around the AIR situation.

 

No need, Ill go with the manifolds. Cheaper and less problems. With less restricted manifolds and 3" exhaust I shoul get an increase over the excisting lg4 system...
Thanks everybody!

 

True, but the 5-speed could be behind an L69, which had the larger manifolds. I swapped in the L69 exhaust (JY manifolds, Y, and intermediate pipe) in my LG4. Along with the L69 dual snorkel (and some other tweeks), I was quite impressed. Check the following link for more info:

https://www.thirdgen.org/forums/exha...-question.html

JamesC

 

seems to be a good way to go! And Ive already got the full dual snorkle setup.

 

maybe the intermediate from L69 is good to use too? Dimensions?
Does anybody know?

 

My L98 y-pipe (T-pipe, if you ask me!) is no better than the others I've seen. It does seem to be a bit larger diameter, but still the stupid 'T' connection, and crinkle bends.

I doubt it is of any real benefit, worth switching to.

 

What if he were to bolt it all up under the car, then cut out the "T" intersection and use his bends and welder to fab up a more aerodynamic "Y" shaped merger?

But really, what is up with that factory y-pipe. When I first was looking under the car after I bought it, I was impressed with how the factory exhaust wasnt rusty yet. Then I noticed that "t" intersection and thought - this looks like an exhaust shop special. After looking online, I realized that GM really made this!

 

Considering size (check the comparison between the LG4 and L69 Y in the above link), I'd say the flow would certainly be less restrictive regardless of the "T". The L69 intermediate pipe is also bigger. Actually, the stock L69 intermediate pipe was larger than the after market catback that I purchased for the LG4, 2.5" vs 2.75, IIRC.

JamesC

 

A Y-pipe conversion from the T-pipe, certainly wouldn't hurt. I'm curious if it would make a noticeable feeling. A REAL difference, ya know? Not just a "I changed it...it has to work. Yeah...I feel it, don't you?"