340 problems

[matthew110366]

I have a 71 340 demon, 4spd, 3:91 ... it has a mild cam , X heads, I don't know what the cam size is , its not stock, on start up , it will idle with choke set , when the choke is off , it dies until warm after you feather the fuel, ... then when you get on the road and go from first to second it dies and then has a hard time starting again , but once it warms up your fine until you stop , sit for awhile then it s like it vapor locks and has a hard time starting up again ... is it a carb problem,it has a eldebrock 650 performer ( is it too small ) or a timing problem ... i'm at my wits end .... any suggestions
thanks
kevin

 

[Robbie2734]

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I have a 71 340 demon, 4spd, 3:91 ... it has a mild cam , X heads, I don't know what the cam size is , its not stock, on start up , it will idle with choke set , when the choke is off , it dies until warm after you feather the fuel

That sounds like it's too lean, try adjusting the idle screws out a half turn.

then when you get on the road and go from first to second it dies and then has a hard time starting again , but once it warms up your fine until you stop , sit for awhile then it s like it vapor locks and has a hard time starting up again ...

Try a carb insulater, and try to bump the idle a little, about 700-800rpm at idle. One more thing, look for a vacuum leak, I'd do that first. I run the eddy 1406 and had to use a insulater/spacer to help keep the thing cool.

 

[crackedback]

what is initial timing?

It will likely need to be in the 14-18 range is my guess. Tons of carb issues are rooted in initial timing settings.

 

[krazykuda]

I agree with crackedback. Check your timing first. 650 is plenty of carb for you.

I had a 340 that would start cold, but then hard to start warm. Finally traced the problem to the distributor. I never set the reluctor gap when I installed the MP electronic ignition package. My gap was .030 and should have been like .007" (brass feeler gauge). Once I set the reluctor to pickup gap correctly, it was fine.