Need Help in Diagnosis!

[Anonymous]

This may end up a bit long, but please bear with me. As you may remember, I bought Lyle Bones' built up 200 with triple YF carbs. Am still working out the bugs, but my basic problem is that the engine really lugs down when I shift the C4 into gear. I'm talking about going from an idle of 1000 rpm to 550 rpm. The cam is a 264, so I should still be able to get a better idle.

The timing is set at about 8-10 degrees with the vacuum advance disconnected. At this, I'm showing 15 lbs of vacuum, the timing is steady and so is the vacuum guage. When I reconnect the vacuum advance, the idle jumps from 950-1000 to about 1300 rpm, and the timing pulsates back and forth off the scale. Is my vacuum advance screwed up? Something is causing a surging, and that seems to be the variable. I'm running a Duraspark II with new plugs, wires, rotor, and ignition module. BTW, this is single port vacuum advance.

The mixture seems right. I just checked it and reset it. I thought maybe my problem was my power brake booster, but I took it out of the vacuum circuit and capped of the port. (Booster is bad for sure, though)

At this point, I'm wondering about getting another Duraspark Distributor, but I hate to spend the money if I don't have to. Need Help!! Ideas?


Clint Lovell

 

[Anonymous]

If you remove your dizzy and check the bushings, you may find too much play.

 

[Anonymous]

OK. Changed out distributors and reduced standing idle to 800 rpm. When I engage transmission the idle drops to 550 rpm which is where the manual says it should be, but it sure sounds terrible. Getting a lot of vibration. Every plug is firing and the timimg is set at 10 degrees. I pulled off the power booster connection to check vacuum and I have 18 lbs at standing idle, but I did notice that when I pulled the connection loose, nothing happened with the rpm. Should have leaned way out with 3/8" hose opened. makes me think I running way rich. Any Suggestions?

 

[CobraSix]

I know from other people with the Offy that they had to can the vacuum advance system because it caused odd problems. Maybe want to go with just the mechanical and recurve the dizzy (or just advance more).

Slade

 

[Anonymous]

Check all your vacuum hose connections. Double check your timing...ZZ

 

[Anonymous]

Still having problems establishing a smooth idle on my I6 200 with triple Carter YF carbs. Drops from 900 rpm in Park to 500 in Reverse or Drive while holding brakes. Have one slight vacuum leak on the front carb at the throttle plate shaft -- otherwise, no leaks. With my diagnostic guage connected to the - side of the coil. I'm showing 7 volts in Park, dropping to 5 volts in reverse. Engine is rough at that idle of 500-550 rpm. Have new Duraspark distributor set at 10 BTDC. Idle mixture is set correctly. All floats levels are correct. Has a Crower 264 Duration solid lifter cam. Runs great except at stop.

Replaced the Wells ignition module this afternoon with a Borg Warner unit and added an Accel Performance Coil. Stays running at 500 rpm and does not die, but it just seems like too high a rpm drop off when in gear. I've tried different timing settings to no avail. Really need ideas.Help!

 

[Anonymous]

If the idle mixture is too rich, it will show symptoms of high unloaded idle speed and low, rough loaded idle.

It sounds like you have enough vacuum to close the power valve(s), but if one has a bad (cracked) diaphragm or blocked vacuum port (to the manifold side of the plate) then it will remain open, no matter what. Then it will run rich.

Holleys are famous for this: I can't speak to the YF, though, as I've never worked on one (that I can remember).

 

[80broncoman]

I belive the problem in the rich idle is in the fact that you have three times as many carbs as what it came with. it will flow the most air at a idle
with a stock type cam (one with a smooth idle). If your has a lope at a idle this will only make any problem with idling worse.
Jim