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Vacuum Advance / Retard?

vlvman

vlvman

New member
Joined
Mar 31, 2009
Location
Jefferson City, MO
I have a dizzy with advance and retard on it. Does the vacuum retard need to be at intake pressure for it to function correctly?
The engine pings with very little throttle during acceleration and deceleration.
 
This dizzy came from an N/A car and I put it on a N/A car.

I am having bigger problems with the car thou. I installed a wideband on it and adjusted the A/F ratio. Drove it a bit then installed an adjustable cam gear and started playing with cam timing. During one of the test drives it suddenly started missing during acceleration. I have not had time to diagnose the missing problem yet, but I was curious about the pinging. It seems to do it with any and all base timing settings.
 
I believe that stock it is vacuum retard to the manifold, and vac advance to the ported advance nipple on the other side of the throttle plate. So the main function was to retard timing at idle for emissions reasons. I experimented a bit, and haven't seen a car yet that ran better while using the vac retard. Same on a B20, most people plug the retard.

I really don't think that would be the cause of pinging though. With missing/pinging, weak ignition?
 
82 240 K-jet B21F mpg. Had chrysler ignition system, still has the "L" cam. Now has bosch system from either a 77 or 80 240 N/A car. I may go back to the chrysler system as the swap has not yielded better results.
 
Timing is adjusted via RPM with weights in the dizzy guts, and/or by vacuum. Both need to be functioning correctly to get the proper ignition curve.
 
Find a vacuum advance only canister from something like a VW. Or you can do what I did with my old VW Dasher. Converted it over to mechanical advance by locking the advance plate with a screw and working with different sizes of advance springs. But you will have a learning curve if you try this.
 
When I drove an 82 VW Quantum with K-Jet I thought I had pinging and it turned out to be noise related to the fuel injectors and lines. I think it was caused by the lambda (oxygen sensor) system. This system used a frequency valve to adjust fuel pressure. When I replaced the frequency valve with a home-brewed adjustable valve (with a relief valve) that allowed adjusting the fuel pressure the pinging went away.
 
professor245 said:
How can timing be adjusted under load without vacuum?
Click to expand...

Canuckvolvo said:
Timing is adjusted via RPM with weights in the dizzy guts, and/or by vacuum. Both need to be functioning correctly to get the proper ignition curve.
Click to expand...

I was meaning only use the advance part of the dizzy timing adjustment. Some of the older dizzies have both vac advance and retard functions, through 2 different vac lines on the canister. I wasn't saying get rid of vac advance.
 
And to OP, are you sure its pinging under light throttle? Pin hole exhaust leaks can sound like pinging under varying situations, it took me a while to work out that my motor wasn't actually pinging while engine braking.
 
Yes it is pinging.
I know many people disconnect the retard function, my question is will the dizzy still function as normal with it unhooked? My concern was it might need the retard hooked up to return the advance to zero.
 
The most sure fire way to tell what is happening is to use a hand pump on the 2 lines and watch the timing with a light. On my old setup the advance would vary from 0 to ~20 deg compared with base timing as you applied vacuum to the advance line, regardless of whether the retard part was plugged or just disconnected. I ran with it plugged just to stop dirt getting in more than anything else. I never tested how the retard portion worked as you applied vacuum to it.

But as emissions requirements were tweaked by year, YMMV with exactly what amounts of advance/retard you will get.
 
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