Short of headers, what, if any, stock GM manifold will provide more flow than I currently have?

JamesC

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James, my friend, welcome to the dark side. In all likelyhood NO ONE else would EVER reply to a thread like this. But I will, my bother. Going fast on the cheap is a religion for me. I think you'll like it if you try it, too.

Long story short: Stock LG-4 manifolds have 2" outlets. Same-year L-69 305 HO maifolds have 2 1/4" outlets and slightly larger internal passages. They are accompanied by a larger diameter y-pipe and a bolt-on 2.75" in-out cat compared to the LG-4's 2.25" slip-fit cat. Yada, yada, right back through the muffler. Yes, you can bolt all the L-69 stuff under your LG-4 like it was made for it.

Good luck with it.

 

Thanks, Damon,

Though the LG4 y-pipe is smaller will it bolt directly to the L69 manifold or is the L69 y-pipe required (I know, I know--a little at a time)? By the way, according to "Camaro Performance Handbook" exhaust manifolds used on TPI engines--'89 and later--can be used with 305 HO or 305 engines with throttle body (2 1/4 diameter outlets). Any experience with the latter?

JamesC

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James,
The HO manifolds will only work with the HO y-pipe due to the different angle of the outlet on the passenger side manifold. Everyone will tell you to not waste your time and just do headers, but this can be done really cheap if you look around at swap meets and salvage yards. You have a couple options.

All 305 HO, and TPI motors(except the 90-92 305TPI/auto have the good manifolds and a 3" y-pipe or dual cat y-pipe.)

The cat back can either be made for you by a muffler shop using 3" pipes, or you can purchase one of the many aftermarket cat-back systems for whichever exhaust you find.

The bad part is that it all has to be done at once, but it can be done for a reasonable price and you will see a noticable improvement in power. Have fun.

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89 Transam GTA, 350TPI, auto, 3.27 rear, dual cats, gray.
Magnaflow cat-back,
K&N open element,
Best E.T. 14.63@95mph

 

Thanks, Guys,

I've found the HO manifolds and Y-pipe (at least the yardman said he had them) for about $50--I've turned to the darkside! By the way, are the 86 TPI manifolds ranked with the 'good ones?'

James

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