timing problem

[twotoedbandit]

Having an issue with my A14. Car is a 78 b210 auto. So, I set the timing to 10 degrees at idle per the service manual. Then I go to adjust the mixture screw. Problem is the timing changes when I mess with the mixture. I've tried plugging the vacuum advance and adjusting again in case that was leaking, but no luck. I'm kind of stumped here, not really sure what could cause the timing to wander like this. I though possibly the timing chain is stretched and could be causing different timing at different RPM's, but I'm not sure how logical that sounds. Any suggestions would be greatly appreciated! Thanks!! -Mike

[datsunaholic]

The distributor has more than just vacuum advance, it also has weighted "flywheel" advance built in. So, at higher RPM the timing self-advances. If it's doing it drastically, the springs are probably worn out. Or the dist has too much shaft wobble, which makes the timing erratic.. Both are indications of wear.

[datzenmike]

The idle may also be just so high that the mechanical advance kicks in. Some mechanical advance starts at as little as 900 RPM. Turn the idle speed screw down and re-adjust the mixture for the highest smooth idle and if it revs up just keep turning it down.

[twotoedbandit]

Alright, I'm gonna give it another go tomorrow and we will see how it goes.. Thanks!

[twotoedbandit]

Okay. So I decided that I should go ahead and do a tuneup while I was under the hood. Pulled the plugs and there was significant carbon build up, do I replaced them and decided to run some sea foam through the engine. Normally, I would expect the engine to stumble a bit when pouring the sea foam into the breather hose, instead the revs jumped up and it ran smoother, until the seafoam passed through and then started to sputter again. Any ideas what this could mean? Vaccuum leak somewhere in the carb or manifold?

[datzenmike]

Breather hose? don't you just spray into the open carburetor?

 

Seafoam is likely combustible so perhaps the carb is running lean and the extra (seafoam) helps it rev up.

 

Clean or replace the plugs. If the plugs are oil wet the rings may be bad.... does it blue smoke out the back???

 

If the plugs are dry and sooty it's running too rich or the choke is on and isn't coming off or not driven enough to clean the plugs off... in other words too many short trips.