my exhaust shop offered to put true duals on my 86 transam. i have a 350 with melling cam in and its also chipped with a custom one from TPIS.

He said he will put 2.5" pipes running back, two 1 chamber flowmasters where the car used to be and then go straight back and dump it before the rear axle. How will this affect my gas mileage?

Thanks

Gary

 

Always a tricky question to answer without knowing the specifics of your combination(are they designed to move the torque peak, what are the spec's of your cam, converter, etc.,...). If the duals replace the stock exhaust, you might see a small gain in mpg(5 - 10%), or little to no gain if replacing an aftermarket performance exhaust. However, if the duals do not contain a crossover, you can expect to lose some low-end torque, which will probably hurt your bsfc numbers.

Since you are concerned about mpg's, is it safe to assume this isn't a race-only vehicle? If so, it brings up other questions: if the muffler shop plans on putting Flowmaster race muffler in place of the cat, are you planning on trying to pass emissions without cats? Will the muffler shop pay for any fines resulting from what could prove to be an illegally loud exhaust.

I have been following the debate regarding California's noise abatement laws. The laws, as written, tend to be very vague and leave it up to the individual enforcement agencies or officers to correctly interpret the statues. Some agencies(notably CHP) refuse to enforce the statues until the definitions are clarified. However, in some jurisdictions there appears to very vigourous enforcement.

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He who hesitates,... is lost!

 

There is no problem passing emissions and my exhaust guy is willing to do it. He offered too. The Flowmasters would go side by side where the cat used to be. And then I would take 2.5 pipes back and dump it before the rear axle.

Should I put on the bolognas or just put 2.5 inch turn downs. Is there really a sound difference.

Also, anyone out there wil true duals. Are you happy with it? And what is your setup?


Gary

 

Great, but as suggested, get a crossover (or "X") pipe installed at the same time. minimal extra cost/time and the guy will probably do it anyway.