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#21
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that actually gives me an idea. i always open the shop doors, then start the car, so it starts on high idle and i have to rev it briefly to step it dow. i bet if i start the car first and drop it off fast idle before i open the doors that will help a bunch, especially if i switch from manifold to ported advance and cut the idle rpm down some.
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#22
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Jim Hand runs 2-1/2” mufflers with a 3” X-crossover reduced right before the mufflers and 2-1/2” tailpipes on his 11-second Le Mans wagon if I’m not mistaken.
I know one of his favorites was the 2-1/2” Dynomax Super Turbo 17749 20” case muffler, quiet and free flowing. I use those mufflers on both of my Pontiacs and they’re great mufflers for quiet street performance.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
#23
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#24
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466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2 373 gears 3200 Continental Convertor best et 10.679/127.5/1.533 60ft 308 gears best et 10.76/125.64/1.5471 |
#25
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Did you say if you have a “X” pipe or a “H” crossover pipe on it now?
I’ve read here about going from a X pipe. To a H crossover making a difference.l
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1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... |
#26
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x pipe on mine. i miss straight duals, easier to work on!
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#27
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Farther to the rear, the cooler the exhaust and the less impact a muffler or resonator has on power output. A resonator should have much less impact than more restrictive mufflers. I was considering something like this for the Bonneville 505 build since I thought it would be cool to have a much quieter exhaust and still blow the doors off the competition on the street. It would be very interesting to know the db drop with resonators and also how much they actually restrict horsepower.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon in progress. |
#28
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#29
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What I've done in the past is run the system I want on the car, what ever that might be, and if it's a touch too loud, I reduce the tailpipe size after the muffler or mufflers. It's surprising how much difference a little change like this makes in sound. It's also shown to have very little if any impact on performance in a mild application. |
#30
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I used to work with a friend of my dads who used to race his 1961 Ventura back in the 60's. He always stepped down in pipe size the farther back he went. His theory was , as the exhaust cooled, he could reduce pipe size to maintain gas velocity. He was not making as much power as many here are talking but the theory is interesting.
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#31
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It's a real theory, hence the reason you see stepped headers.
The exhaust gasses cool as they move through the system, and they lose velocity, which is why a smaller pipe towards the end of the exhaust system doesn't have as much affect. |
#32
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"Generally, the X-pipe will deliver a more high-pitched exhaust note, making a car sound more exotic, whereas an H-pipe gives a deeper tone with more of a traditional hot rod sound"
Like different muffler sounds and levels of sound some will dislike one mid-pipe type over the other. X-pipe here: https://www.youtube.com/watch?v=c90Jnw8hqbk “As for the difference in power gain between the two, it is very minimal" http://www.superchevy.com/how-to/exh...-for-your-ride Just Google "X-crossover vs H-pipe" and you will get a dozen or more comparisons. Some with actual dyno testing. .
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'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
#33
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2 cars have the more expensive Dr. Gas "X" in the system custom made, and one necks down from 3 1/2" to 3" at the "X" and continues 3" for the rest of the system. Still a couple cars here with an "H" and they'll likely stay that way since I can't find any measurable difference between the two, I'm going to spend money in other places. |
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