Hi everybody.

I'm a new user in this web. I'm from Spain and I have a 1985 Pontiac Trans Am LG4. I've read some information about performing this type of engines here. I decided to change the exhaust of my car and I want to do it the best I can. So, I started to contact with Summit support to choose the best parts according with this ideas I've read here:

"Exhaust - needs to be replaced, as an entire unit. Every piece from the heads to the back bumper. The replacement MUST NOT be designed to fit LG4; because if it is, it will PRESERVE the LG4 exhaust bottleneck, namely, the itty bitty Y-pipe. Get one of the quality brands of headers SPECIFICALLY for one of these cars, BUT NOT for the LG4; get the ones for a TPI 350. Get a high-flow cat such as a Catco from Summit, and your choice of cat-back. All of this for something like 89 TPI 350 without G92 (single-cat setup). This will retain emissions legality (except for the EFE valve)"

and...

"If you want to improve the performance of an LG4, you do the following: Replace all of the exhaust with headers, y-pipe with 2-1/2" downpipes to 3" at the cat, 3" cat, and 3" cat back to 3" inlet muffler (single 3" outlet or 2 x 2-1/2" outlets is your choice)"

Ok, I think I've got the idea but I've some doubts. I choose some parts from Summit but I need to be sure before I do the order. The parts are this:

- Headers: http://store.summitracing.com/partde...0&autoview=sku
- Y-pipe: http://store.summitracing.com/partde...0&autoview=sku
- Catalytic Converter: (Catco) http://store.summitracing.com/partde...0&autoview=sku
- Cat-back: (Flowmaster) http://store.summitracing.com/partde...0&autoview=sku -> 3" inlet muffler to 2 x 3" Outlet Size
or
http://store.summitracing.com/partde...0&autoview=sku -> 3" inlet muffler to 2 x 2-1/5" Outlet Size
Could you please tell me what cat-back is better to perform my car?

I proposed this choice to the Summit support and they said me that it's a poor choice for the 305 and it will kill torque. I think that the Catalytic Converter (Catco 3" inlet, 3" outlet diameter) and Cat-back (Flowmaster 3" inlet, 2 x 3" outlet) are a good choice, but I'm not sure with the Headers and Y-pipe. I try to choose the y-pipe with 2-1/2" downpipes to 3" at the cat, but I don't know..., and for the headers what are really good?

The Summit support proposed me this items before:

- Cat-back: http://store.summitracing.com/partde...0&autoview=sku (the same I had choosen)
- Catalytic Converter: http://store.summitracing.com/partde...0&autoview=sku (the same I had choosen)
- Headers: http://store.summitracing.com/partde...0&autoview=sku (up to 3" in collector diameter)
- Y-pipe: http://store.summitracing.com/partde...0&autoview=sku (this is 2.5". How can it fit with the 3" cat?)

I'm not sure.

Please could you hep me.
Thanks.

P.D. Sorry about my english.

 

Welcome to TGO. Your English is fine (at least as good as some of the native speakers on this site). The following direct-fit system is about as good as it gets:

Hooker 2055's (Jeg's 520-2055). Catco high-flow converter (Summit CTO-9118). Hooker catback (Summit HOK-16823HKR).

JamesC

 

The parts Summit suggested don't bolt up to each other. The catalytic converter is the only right part they gave you. Your list has the same problem.

JamesC's suggestions are completely correct. Much better stuff, too. And he is right about the English as well.

 

I second both these fine gentlemen; that hooker setup is IMHO the best header/y-pipe system you can get for these vehicles, then of course your choice of 3" cat-back.

 

Great!

I'm so thank with your help! Now, I see it clearly. I think that's the best choice for the car, without complications.

Only one thought; The Hooker cat-back is better or can I put the flowmaster I've listed? I've special fixation with Flowmaster...
But I think I'm going to order the Hooker... to have all by Hooker .

 

as long as its a 3" cat-back, purchase a cat-back (3"!!!) with the sound you like.

I've got a flowmaster, the hooker sounds really good too though.

 

The cat back you listed necks down to 2-1/2" at the cat connection.