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12A Exhaust size with stock manifold?

Old 06-13-04, 02:17 PM
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12A Exhaust size with stock manifold?

Hello all,

I am in a qaundry as to how to build an exhuast my race car. I have read through the archives but I didn't see anything that mentioned being stuck with the manifold.

Our rules dictate using a stock 81-85 manifold, maximum of 2.5 inch pipe; aft of the rear axle we can use 3 inch.

Sound maximum is 103 DB at most tracks.

I currently have 2.25 pipe over the axle with a dynomax super turbo (crap) and turn down. With this setup the car is very quiet on track, and I'm sure I am giving up available power.

thanks!
Marcus
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Old 06-14-04, 01:19 AM
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Quote:
"Our rules dictate using a stock 81-85 manifold, maximum of 2.5 inch pipe; aft of the rear axle we can use 3 inch."
_______________________________________

Well use a '84-85 exhaust manifold, its shorter that previous years. File the inside of the manifold to match the gasket (outlet side)
Use a short exhaust system on shorter tracks like Sears Point and Laguna Seca.
Run exhaust to the rear on longer tracks like Thunderhill and Buttonwillow. Run the pipe under the axle never over.

Do not like supertraps, I ran DynoMax Ultra Flo stainless. Making more noise does not mean you are making more power. Plus if you go over the sound barrier, you will be black flagged. And you day could be over.

John
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Old 06-16-04, 08:28 AM
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What horsepower difference is there between the 81-83 and the 84-85 exhaust manifolds? I picked up a 83 Pro 7 I want to do some track events, but I will at some point get to a few Cal-Club Pro7 races. Like everone else, I dont want to miss out on any available power.
Later
Steve Coe
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Old 06-16-04, 11:50 PM
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Alright, so I picked up a three inch inlet/ outlet ultra flo "welded", 6 inch round muffler. pictures: http://images.miller-motorsports.com/muffler/

I am set with the 2 1/2 pipe, my only question is running it under the axle; I'm worried about dragging and ripping it off loading the car on and off the trailer. Pics of the car on the trailer are here:
http://images.miller-motorsports.com...050104/friday/


The ramps are four foot long, with 6 foot 2 x10s, and we do pick up the front of the trailer as much as possible...
thoughts?

Marcus
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Old 06-17-04, 01:26 AM
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I like the paint job, sweet.

I had 6' ramps but did not run a drop axle trailer cause I wanted to be able to drive the car onto the trailer. Tie down and be on the road in 5 minutes.

Remember short exhaust at Sears Pt/ Laguna. Long exhaust at ThunderHill and Buttonwillow. Go under the axle is important, install a strap to keep the rear axle from coming down when jacking up the car.

I use to run Pro7 with NASA SF region when they were 50 car fields, and anything that you could do to the car to help power (with the rules) you did. Like plugs on the coolant passages that go to the intake manifold during the summer months.

I also chose to keep my heater core, you will know why when you are racing and its raining.

Concerns: It appears you have too much tongue weight on the hitch. Next you should buy some decent tie down straps, or switch to chain and chain binders.
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Old 06-17-04, 12:02 PM
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I ran in a spec class similar to pro 7 (but we allowed more mods). I ran the exhaust under the rear axle and trailer loading was a non-issue. If you are really worried, just use your trailer jack to lift the front of the trailer for loading/unloading. This will reduce the angle you have to climb over. Longer ramps help cut the angle as well.

-Trent
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Old 06-17-04, 10:02 PM
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Originally posted by rhinor61
I like the paint job, sweet.
Thanks! One of my friend's runs a bodyshop in San Jose. I turned him loose with the insturctions to make the interior white, and keep it simple. This is what I got, much better than I antipcipated.


I had 6' ramps but did not run a drop axle trailer cause I wanted to be able to drive the car onto the trailer. Tie down and be on the road in 5 minutes.

Remember short exhaust at Sears Pt/ Laguna. Long exhaust at ThunderHill and Buttonwillow. Go under the axle is important, install a strap to keep the rear axle from coming down when jacking up the car.

yep, will keep that in mind, but how do you run a shot exahuast at Laguna and stay withing the 90 db sound limit?

I use to run Pro7 with NASA SF region when they were 50 car fields, and anything that you could do to the car to help power (with the rules) you did. Like plugs on the coolant passages that go to the intake manifold during the summer months.

I also chose to keep my heater core, you will know why when you are racing and its raining.

I've already had half a mind to put it back in...

Concerns: It appears you have too much tongue weight on the hitch. Next you should buy some decent tie down straps, or switch to chain and chain binders.
I agree, the next items up for the trailer and real d rings, and some tie downs; the truck is getting air bags to hel pthe rear suspension.
It actually sits level with no crap in the bed. That was fully loaded for a weekend at Thunderhill.

thanks,
Marcus
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