You've got to route the exhaust pipes out the sides behind the rear wheels.

Carl Lee
67 Jeepster Commando
"Old Reliable"

 

Are you SURE there's no leak from your exhaust manifold or a small crack in a coupling or a small hole. Sometimes it's very hard to tell. The only time I have had fumes in my vehicle is when I have had leaks before the muffler and unplugged holes in the firewall. My pipes exit in front of the rear tires and I get unbearable fumes when I'm in need of a tune-up. Other than that I'll never smell them even when sitting idle.

Walt

 

The best place to exit the exhaust on flat back or squared back vehicles is on the sides, just ahead of the rear wheels.
The flat back creates turbulence right behind the vehicle, the rear exit pipes feed exhaust into the vacuum created. In other words, the exhaust tends to follow you in a cloud and come in the interior any way it can.
Exiting out the sides breaks it up enough to minimize the problem.
Also check where the pipe joints the manifold, it leaks there sometimes, then comes in your shifter boots and any holes in the firewall.
A good way to find the leaks in the tailgate, on a dark night have someone get inside with a strong flashilight shining on the possible cracks. Stand outside and look.
Rich

 

I , also am having a fumes problem . I just had a new total system installed, out the back. It was really bad at first, so I added a chrome down-turned extension. This helped quite a bit, but still getting some fumes if I open a window. I think I will take a trip back to the muffler shop and ask them to route out the side ,,I can't go forward of the rear wheels, unless they move the muffler forward. I was looking in a parts book that I have for the Jeepster, and it shows the tail pipe out the back!
Any words of advice would be greatly appreciated.
Linda

1970 Jeepster

 

Just a thought that might be totally out in left field (thats why they call me the Dolt)but I have had two Commando's that had rear exhaust pipe exits and have never had a problem with either. Both Commandos were 1968 and both had the tire carrier mounted on the back. I wonder if the turbulence created by the carrier somehow broke the vacuum created by that flat rear window. Just a thought. Also, on the back pressure versus free flow controversey: The point is often made that if back pressure is so bad for performance, why don't race car drivers run without pipes at all? The answer I got from a race car mechanic is that the exhaust valves would warp from being exposed to the cool air. He said that the only reason to use pipes is to keep the valves in good shape and keep the exhaust fumes out of the cockpit. He said the more free flow the better. I just had the original crossover type exhaust on my Commando (225) replaced with dual exhaust and have noticed no performance difference, but a more annoying resonance problem.

 

My book shows the exhaust exiting out the back on the right side - it was a small pipe with one muffler.

Back pressure: Your friend is right about cool air hitting exhaust valves - makes them look like pretzels! Notice the tennis balls they use in Zoomies - straight individual pipes on dragsters. It's not in case it rains.

Putting freer exhaust systems on will be noticed the most at very high RPM, if the old system was restrictive.
Headers work on a pulsation principle, pressure waves actually suck or "scavenge" the exhaust out - it works only at critical RPM's, usually high speeds.

The controversy - I talked to an old muffler guy yesterday about backpressure etc. He said he has experienced it a few, but very few, times.
When he put low restriction pipes on, it ran worse - mainly small engines. I asked about timing, he said he made it "less worse" by advancing the timing radically. He said it usually helps but not always.

The mystery in the 225's and 231's, both even and odd fire, timing problems:
Why does the problem exist on only some engines and not others?
Why doesn't it "kick" or "buck" during cranking when we set the timing to 30-35 initial? (During cranking there isn't any backpressure even with straws as exhaust pipes, so that eliminates exhaust as the culprit.)
Why doesn't it "ping" when total advance gets to 60-70 degrees?
Yes, damper hasn't slipped, chain/gears new/good and not off, etc. All the "normal" things have been investigated.
Several people here have the problem, but most not - strange.
One fellow has the problem in a boat - had a 225 odd fire with the timing problem, then swapped in a 231 even fire - STILL HAS IT! Go figure.

Rich

 

Is the back-pressure created by a smaller diameter pipe fundimentally different than just restricting at the end? For example, using no muffler and 2 1/2 inch pipe, but partially closing off the end by pinching it down, as opposed to the backpressure created by smaller pipe all the way along a stock muffler?
The reason I ask is that if they were the same, AND our timing was a result of incorrect exhaust pressures, I could fix it by pinching the end instead of replacing the flowmaster with a muffler. (=>cheaper)
My exhaust is stock until the muffler, but the pipe between the manifolds and the flowmaster have multiple, tiny holes (they look rusted out). I'll do a whole new system once I KNOW it will help.
Michael

1967 Commando SW
A labor of love, (mostly labor)

 

Michael,

Your problem is not exhaust backpressure. I have run my jeep and all my other vehicles without an exhaust at on time, sometimes due to road hazards and have found no difference in the way they drive. I just couldn't hear very well. Have you tried finding top dead center and re-seating your distributor yet? I still think your about 1 or 2 teeth off from TDC.

WalterX

 

Nope, just mental calculations at this point. Kid got pretty sick this weekend, so I had little interest in working on the truck (104 fever, scary). Mon. I drove it to work and it started stumbling and hesitating REAL bad, just like right before I changed the points the last time.
So,
1) switch out for the regulator I got from you
2) pull the points out and verify that they're toasted (most likely)
3) Double-check for TDC
4) Double-check timing
Hopefully this weekend, will post result
Michael

1967 Commando SW
A labor of love, (mostly labor)

 

I seem to have completely eliminated the fumes on my Jeepster. I went back to the muffler shop, told them my problem. They bent the tail pipe at an angle from the last hanger and took it out the corner( drivers side) with a turn down. It is perfect now..Wow, am I glad! Had my lungs out a few times from breathing all that junk!
Thanks for the advice.
Linda , without black lungs!

1970 Jeepster