70 GTO question

Tom Hand · #1 01-07-2006, 07:07 AM

BelAir, they use a former heater/ac vacuum actuator to pull a rod that opens a valve inside the muffler letting the exhaust bypass two of the pass tubes internally. Essentially, it is like running a straight pipe and a very very quiet perf. muffler and being able to switch between them using a vacuum switch.
Tom

Tom Hand · #2 03-12-2006, 06:06 PM

And here is a bit of data on how the 2" in, 2.25" out versions worked on my 69 340 Cuda and a shot of the car they are on, a true 70 VOE GTO four speed.

1969, 340 cu. in. 10.5:1 Chrysler engine in Plymouth Barracuda with 2.25” stock, 1969, 340 tailpipes with large rectangle chrome tips, measured at 10 feet from tailpipe outlet.

Closed Open
Idle (700 rpm) 68 dBA 78 dBA
2200 rpm 81.5 dBA 92.5 dBA
3500 rpm 88 dBA 99 dBA

They sound very good.

Tom Hand · #3 03-12-2006, 06:10 PM

Belair62, here is a closeup shot of the inlet so you can see the actuator and how it attaches.

Tom Hand · #4 03-12-2006, 06:14 PM

And here is the shot of the mufflers from the rear so you can see the spring portion; stand by for one more from the front.
Tom

Tom Hand · #5 03-12-2006, 06:17 PM

And here is the last shot showing the overall front configuration... We are currently finishing one more "stock set" and then will build one custom set for a local street rodder. Later this summer, we plan to build a handful more for our own cars and a couple of musclecar enthusiasts.
Tom

Belair62 · #6 03-12-2006, 08:14 PM

Nice work Tom....any idea of how many VOE cars were sold ???
How does the vacuum actuall hold the valve open on low vacuum situations ?

Tom Hand · #7 03-12-2006, 08:37 PM

Official documents show 233 and there were also dealer installed units. I bet the total is less than 270 but that is my guess only.
They have a vacuum can between the manifold's vacuum source and the switch and they have a check valve between the manifold vacuum source and the can. The can is evacuated and then the check valve keeps the engine's loss of vacuum (increase in pressure) from affecting the actuator and letting it go back to normal mode. As long as the can is evacuated and you have no leaks in the system, they stay open. I have pulled a vacuum on these and let them set overnight. The next day, they are still wide open so the system works pretty well.
Tom

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