Help Me Pass Some Gas

Help Me Pass Some Gas


Senior Jeeper
Calvert County, Southern Maryland
1986 Jeep CJ

Mostly stock, 258 c.i.d., T-176 tranny, Dana 30 front, AMC 20 rear, Dana 300 t-case, 31x10.50 tires, 2 inch body lift
So, I did a vacuum test on my Jeep project this morning...It's running about 21 inches of vacuum at idle, but drops to about 16 inches around 3500 RPM. This is a sure sign (I think) of a partially plugged exhaust system, and maybe why my Jeep loses power under load.

Seeing as how it's the 4th of July weekend and I won't have new exhaust parts until later next week...Does anybody have a temporary fix that will give a little backpressure relief while allowing the Jeep to still be driveable?? :wtf:

P.S. Should add that I don't know where the blockage might be right now, but both the converter and muffler are very old, and could even be original...
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The jeeps didn't have very good catalytic converters in the '80s. Air had to go through honeycomb shaped holes. These cats would clog up. I had that problem on my '82 CJ7. I removed my cat and fixed it with a pry bar and a large hammer. It's a very delicate procedure but for legal reasons I won't go into the details. It made a world of difference and ran much better.
The reason I found out that my cat was clogged was I had an exhaust leak at the manifold and when I fixed that my engine would not even start.
16 inches at 3500 is good. Keep looking:)
16 inches at 3500 is good. Keep looking:)

Hmm...I thought that if the vacuum dropped (and stays) below idle level as RPM increases then there is an exhaust restriction? Are you saying that a drop from 21 to 16 is not a big enough drop??

Also, the vacuum gage I'm using may not be exactly accurate (but close). Is there another test I could perform to confirm or rule out an exhaust restriction since the low number is close to 16?
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