Hot Rods Let's see your homemade speed equipment

I have admired those for some time now.....very nice!
I remember seeing the original GTO vacuum operated mufflers in a Pontiac parts manual. I became a real pest to the parts man at the GM dealership , trying to get him to find me some 40 years ago......he basically told me to "get lost"

 

Maybe I a little dense, but I don’t understand the flow through this muffler. It appears to me that at high vacuum( part throttle) the exhaust cuts across from the inlet to the out let! Then at low vacuum ( wide open throttle) the exhaust is forced through the small pipe and then has to make several turns, by going into the middle pipe, before exiting through the outlet!
Maybe I need some help understanding the flow of this obviously well made muffler!

It appears to me that the valve or plate needs to be on the other side of the partition, to function properly. But what do I know?


Bones

 

Vacuum applied in first pic...? I see a gauge.

 

That’s how I see it! To me the valve should be on the other side of the partition , that way when you lose vacuum, ( WOT) the spring pulls the valve open, the exhaust can go the normal route and also cut across from inlet to outlet. In my small mind I see no reason to block the flow of the quiet route. That way, you have normal flow and cut across flow!

Maybe I just don’t understand!








Bones

 

I'm seeing...if vacuum is applied in the pic, exhaust is passed through muffs. When vacuum drops off, valve opens and exhaust is passed through the whole system, but also able to take the easy route straight to the outlet.

 

Here’s a few things that I’ve made for my early hemi…
main caps, rocker arms, block adapter… I have a lot more to do.

 

That’s how I see it. But why make the exhaust turn three times at WOT? At WOT you should want a direct route, not one with three turns. To me you want the three turns at partial throttle, high vacuum!
The OP has obviously made these before, I am sure I am just not seeing or understanding how this muffler works!






Bones

 

Impressive work

 

On muffler drawing, above, inlet is at top left. The valve is closed so all flow is through three pass tubes and then out the bottom right. When the driver pulls the knob to open the exhaust, the valve pulls to the left closing off the center tube and the outlet tube and so the flow is through the big center port and into the four small 1" diameter ports in the outlet bushing. This is the OEM design; mine uses much better silencing material and much larger bypass ports, a valve that opens farther, and all stainless materials.

Even though it is tad newer than HAMB things, this is the real original ad car with my set on it. . .
Here is the original ad and the original car, same as one in first video.

 

Okay, where do you get the vacuum to operate the valves at WOT?




Bones

 

The GTO has a HiC fruit juice sized can with a check valve under the driver's side front fender that is evacuated while driving. So, at WOT, it is ready to suck the two 4" actuators open. They work really well.

 

Here are many of the parts on a display board.