A question for the Thermo-quad gurus

[brandon64]

I'm working on a 1980 IH Scout, I know it's not a mopar but alot of it's parts are, including the carb. At first it bogged down for a few seconds at WOT and would slowly pick up speed. I took the carb apart, Thoroughly cleaned it, checked all of the adjustments and they were all in spec, I rebuilt it and stuck it back on and it ran the same. Then I adjusted the Idle mixture screws by the book. It idled a bit smoother but no other change. I then checked the timing and it was at 8 deg, I bumped it up to 12 deg and took it for another test drive and There was no more bog, but now it hesitates when you first get into it. It just falls on it's face for about a second and then picks up quick and goes. If I advance the timing any farther it doesn't start well. I'm fairly convinced that the issue is in the carb somewhere. Any suggestions would be greatly appreciated.

 

[YY1]

I've seen worn timing chains mis-diagnosed as carb problems a lot.
Especially if timing seems to change, but not fix the problem.

Good lookin' scout. One of my old buddies had one he painted in zebra stripes.

 

[ply64post]

timing

They don' have a timing chain they are gear drive.

 

[Meep-Meep]

Carbs are pretty dumb so if you have your adjustments correct, proper fuel pressure, no restrictions in the passages, the metering rod hanger has not been messed with, altitude compensator has no issues (assuming it has one), then you might look elsewhere as suggested. What's the manifold vacuum reading at idle? Are the advance weights in the distributor free? Vacuum advance hooked up to the correct port and operating properly? This is plenty new enough to have EGR and is it working properly? Ignition system good? Also the air cleaner is actually part of the carb calibration so if you have anything other than the factory one (I'm thinking OEM is a single snorkel) then that might throw things off a bit. Very late cars tend to be on the lean side.

 

[brandon64]

Thanks for the input guys. It turned out to be the PCV valve stuck open. I can't believe I didn't find it sooner.