Ignition Checkout - Part 2 - 01/17/2015
Working gas gauge? Check! Carb still popping and difficulty starting? Check! Need to investigate the base tuning before ripping the carb off, would hate for there to be more than one thing wrong...
Here we go, setting up the scopes and timing light again!
Wow. 19.5" of mercury at idle when cold. Not bad. It's solid as a rock too, which is a good sign to indicate no flat cam lobes or horribly missing cylinders.
770 RPM or so after first adjustment from 1050RPM with no choke. I eventually adjusted down to 690RPM when it was fully warmed up.
Now is when things started to get interesting... I put the timing gun on the engine just to check where it was. 8 degrees BTDC. Ok, vacuum advance must not be working which is pretty normal. Plug vacuum advance line just to check and verify. Engine RPM drops to 480RPM. Not exactly good... Check timing and it's now 30 degrees retarded at the crank. So what in the world?
Apparently the last person who tuned it set the timing arbitrarily to 8 degrees WITH the vacuum advance hooked up to full manifold vacuum. You're supposed to set it with the advance disabled and plugged. I reset the timing to the factory sticker setting of 12 degrees BTDC. The engine was over 30 degrees retarded, I was amazed it would even fire up but apparently it did. And amusingly once I did this the popping and backfiring through the carb went away (imagine that!). It's still lean and needs the carb kit, but that's small peanuts to do.
Final checkout settings:
Initial: 12 degrees at 690RPM
Mechanical advance: 24 degrees total all in at 2400RPM
Vacuum advance: 30 degrees at crank for 20inHg (15 degrees at the distributor)
It's a totally different engine now. It runs smoother and doesn't make funny noises or hesitations when mashing the gas. No more backfire or popping. Nice
21" of mercury at idle with these new settings. I'm kind of in awe that an engine can do so well.
Well that's another mystery solved. Balancer is wobbling ever so slightly so it will need to be replaced, ought to replace it and do a timing chain and water pump and thermostat at the same time! The only reason I can see for someone retarding the timing so badly is because of the disabled EGR? It had too much advance and pinged or backfired at cruise\part throttle? Honestly I don't know. Once I get the carb redone I will take it for a long drive under all different kinds of conditions to see if I can't find out. It may just be a case of whoever worked on it last was a moron, not like that's a stretch of the imagination. Car fires up considerably easier than it ever did before. I'll bet the power is up and it doesn't waste anywhere near as much gas as it did.
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Last updated January 17th, 2015