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backfire off load, timing?

1K views 20 replies 9 participants last post by  Sandals 
#1 ·
OK all seems to be happy, but i dont think the timing is correct.

AMC 360, HEI dist, 4bbl carb

Where i have the motor timed right now it seems to be happy, starts easily, accelerates etc. with a vacuum gauge attached it seems to be reading a little low indicating bad timing.
When coming off the throttle from like 3K rpm's i'll get a nice backfire and pop, making me think it's too far retarded.

If i advance with the dist any at idle it starts to run really rough.

any ideas, i still suck at tuning motors
 
#5 ·
Have you run it on the road?
Mine runs rough when I'm cruising at 3k with very little load on the engine. Mine is a result of the vacuum advance pulling the timing ahead just a little too far when there is no load on the engine. The timing when it's loaded is great. Plug your vacuum advance and start there. It'll make tuning easier anyway. After you get that all sorted out, then re-attach your vacuum advance and see what the thing runs like. Vacuum advance is only supposed to work when the engine is at part throttle and slightly loaded. It pulls the timing ahead for better economy, etc. when at part throttle.
 
#6 ·
i've been timing it with the advance unplugged/plugged.

this was with it plugged in though after i think its timed :d:

although it may all be for naught as i need to replace the accelerator pump so i can get gas in it to start it, as spraying starting fluid in it when it's a cold motor will get old really fast lol
 
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