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Discussion Starter · #1 ·
Guys, I have a 70 SS with a 396 375 in it. recently I ordered and put in a new fuel tank. the old one was rusty and full of 30 years of stuff. Now I know I should have blown the fuel line out before I hooked it up but I didn't, had a new filter on it. After a long winter I wanted to get it on the street.

well the problem I have now is it has a rough idle, it seems to go away somewhat when I am up to speed but I can still feel it. The timing hasn't been checked, not sure what cam is in it? The valves have not been adjusted either. It never had the problem before.
I checked the plugs and they are gray in color so I know that I am not loading the thing up real bad.

I hope this is enough info to get an opinion from someone.

thanks. gordie
 

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Normally, my pat answer for rough idle is "start with timing". Given your recent fuel tank change and winter storage, I have two other thoughts:
The easy one -- is the choke opening all the way once it's warmed up?
The hard one -- rebuild the carb, you may have trash in a needle/seat (rich condition) or emuslion tube (lean condition).
 

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Discussion Starter · #3 ·
Zeke, the choke comes off when warm and the carb is a new carb (Holley Avenger 630 cfm), that doesn't mean there can't be junk in there.. I guess the only thing to do is pull the carb and take a look inside. thank you Gordie
 

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What rpm is it idling at, and if running vacuum advance, is it hooked to ported or manifold vacuum?

I'd also pull your fuel filter and replace it - there is a possibility it is now choked full of stuff due to the tank swap.
 

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Discussion Starter · #5 ·
What rpm is it idling at, and if running vacuum advance, is it hooked to ported or manifold vacuum?

I'd also pull your fuel filter and replace it - there is a possibility it is now choked full of stuff due to the tank swap.
Mark it is running at 1,000 off choke, the advance is hooked up to the carb port.

the first thing that I did was pull the filter and replace it.

I just got done pulling the carb and had a look at it. no signs of crud inside. I got it running and what ever I did seemed to have helped but it still wants to run rough. I also put a can of fuel cleaner in the tank.

thank you for the info and I guess I will start going through other things to see if there is anything I missed. I think I have forgot to many things about tuning.

Oh by the way Mark nice car. I like the way it sits. what do you have as far as wheels and tires?

thanks again. Gordie
 

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Note before messing with the carb, you really should get your timing set. It will change everything you do. So this advice is for after your timing is set. 18° initial IMO.

I think 1,000 rpm is too high unless you've got a wild cam that needs it. It's possible you're getting into mechanical advance at that rpm, and when you put it into drive you lose the mechanical, and it will try to die. It will exacerbate the problem keeping it that high unless you really need it. I run off manifold instead of port vacuum for the advance, the car responds better at idle and cruise that way.

If it is still just crud in the carb, try some carb cleaner right down the vent tubes before you start it and then when running, it might help. I do this every spring before I start the car after sitting all winter, it's never failed and I don't use Stabil. Had back luck whenever I use that stuff.

Thanks for the compliments - they are Billet Specialties Cruise Classic wheels, with 295/50x15 rear tires and 235/60/15 front, with Hotchkis 1" lowering springs.
 
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