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Return to Idle

1520 Views 9 Replies 3 Participants Last post by  Richard2
I'm still trying to get this car running right so I can take it to Berlinas to Bovine, But running out of time.

One problem is it takes 9 secs to return to idle from 3000rpm...very slow. The linkage is not sticking

I decided to start all over and check as much as possible. First thing to check was the valve timing. It's off slightly, but:
1. Is it off far enough to cause problems, or if it is dead on will performance increase without other notice able idle problems.
2. These are not stock cams. There are no marks on them. What are they? (11mmX252deg?) If they are, is this timing suitable for them?

Some pics showing the timing, followed by some of cam lobes.


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More cam shots

Sorry for bad pics, hope these are better.


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And more

Few more pics
Few more pics

And some more.

Any suggestions welcome


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Check your distributor advance mechanism. If the carb/injection isn't sticking open, that's the most common source of high idle/slow drop-back to idle. The springs may have stretched, come undone, or the advance shaft within the main shaft may be gunky and not moving smoothly.

Thanks, I checked the distributor earlier in the week. The car has Webers and a Bosch distributor. There was no rust or gunk. The weights were free and pretty clean. The little bit of dirt that was there I washed out. The distributor looked pretty good. This is the first time I've had a distributor apart, so I didn't check anything except the weights moving. I'll take it back out and look again, thanks.

I just finished taking the tops off the carbs and blowing them out even though they were recently cleaned. There was next to no dirt. I checked the plug gap (there're new) and the points. The points had closed up some. I reset them to .017.
After I put the valve cover back on, I'll recheck the compression, set the ignition timing to 3 deg while adjusting the carbs again.
Anything else I need to check?

The distributor look s good and moves freely, weights and outer shaft. There a 2 different springs, but I guess that's normal to get the curve.


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I give up!
It's all back together. I tried adjusting the carbs and it's still doing the same thing. It won't idle down at 3 deg or 7 deg advance. Blowing the carbs out didn't help. Regapped the plug and points no difference. Distributor seems fine. I moved the pickup for my timing light from one wire to another, all firing the same.

Compression is not great, but good enough to run right:
#1 130
#2 136
#3 138
#4 126

I used a propane bottle to look for vacuum leaks and couldn't find any.

I tried using my Unisyn to balance the carbs, but couldn't get it to work right.
I've always gone by the rule that timing is best checked at max advance, ie above 4500 or so. That said, this doesn't sound like a timing problem. After ignition timing, point gap and valves, etc., carb sync and then idle mixture -- and the idle setting itself, of course -- should be the last things to check. Are you sure your idle mixture is ok? Going off of memory, a baseline is 1.5 turns out from fully seated.
I started at 1.5 turns and adjusted from there. When I stopped adjusting, #1 was 3 turns out and still lean, 32 was 1.5 turns, #3 was 1.75 turns and #4 was at 2 turns and still lean.
I was making idle mixture adjustments .25-.5 turns at a time based on engine speeding up and checking by adding propane to each cylinder. If the engine speeds up with a shot of propane, it is lean, if it slows down it is rich.
I never come up with a good way to adjust the rear to front sync screw. My Unisyn just didn't work.
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