Thread: Sbc vortec heads .480 lift single exhaust

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I have a very mild build and my issue is I think my exhaust is an extreme bottleneck. The shop did 2.5 to a Y pipe with 2.5 single out. Is this worth fixing and going to true duals or maybe 3 inch out of the Y or will I be just wasting money? Thanks

Welcome to CHR!

We're a pretty knowledgeable bunch of guys and gals that run the gambit from nearly stock to extreme competitive, professional builders. The exhaust question will certainly bring a few responses. The internal combustion engine is really just a big air pump and any time we can improve the flow it's typically a good thing. That said, your current exhaust is probably fine for a near-stock build. Tell us a bit more about the vehicle, the engine build and what your plans are for the car.

In my humble opinion, 2-1/2" pipe from each side (preferable via headers) to an "X" or "H" crossover and 2-1/2" through 40 series Flowmasters all the way to the rear bumper with chrome tips is a perfect setup for most applications. Looks cool and sounds great but before contemplating such, you need to make sure it will comply with the regulations in your particular area. Here in Oregon, 1974 is the magic year and anything made after that needs to pass our Department of Environmental Quality (DEQ) inspection and they can come down real hard on any exhaust modifications that do not include the original catalytic converter(s) and all related plumbing.

So tell us what you're working on and we'll chime in with probably more advise that you ever thought possible!

Regards,
Glenn

Cubic inches, rpm's and gear ratio in the differential. Those will be the things to determine the size and quantity of exhaust pipes.
One 2 1/2" pipe equals about the same area as two 1 7/8" pipes, which should be enough to support evacuating the cylinders of a typical mildly-built 350-ish street motor turning street revs with a street gear.

In the past several decades, pipe size has seemed to go the way of camshaft timing, bigger, bigger, bigger.

In my opinion, a good set of 1 5/8" headers with equal-length primaries, 2 1/2" collector, H pipe immediately after the collectors and a set of 2" to 2 1/4" pipes to the rear of the vehicle with mufflers of your choice somewhere in the mix would be about as good as it would get for a 350-ish street motor rev-limited to ~5500. All this crap about 3" pipes, to me, is just that.....crap, unless you're evacuating a 500 inch motor at 7500 rpm's.
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Thanks for the quick response guys! It's a 1975 280z with the short block from a 92 TBI and 906 vortec heads with a mild port and polish. The cam is roller with a .450 intake and .480 exhaust. It has a t56 6spd from an Lt1 camaro. Summit 4bb carb with vac secondary. The rear is 3.545. Car weigh about 2800lbs. The car is very fun to drive but I can't help to think that my exhaust is not efficient. Oh... it's a 5.7 and I shift around 5.5-6k

I'd mostly agree with the TechInspector. For a street / strip car, use an H pipe and I like the 2.25 to 2.5 inch pipes with mufflers of your choice. duals to the rear bumper.

What kine of vehicle? Just my opinion, I prefer my hot rods to have dual exhaust. I can't figure out why a shop would run a single even if it was adequate, besides just making their job easier

Originally Posted by Matthyj

What kine of vehicle? Just my opinion, I prefer my hot rods to have dual exhaust. I can't figure out why a shop would run a single even if it was adequate, besides just making their job easier

It's a 75 280z. I think he did it to make the job easier.