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351W will not idle and backfires.

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Last of the Machicans:
     I bought the car from someone who had it stored for 4 years. It will start and run if I hold it at a high rpm but it will backfire intermittently. If I drop the rpm it will die. It is a 351W auto with a 4v Holley carb, which I removed and cleaned. The gas has been flushed, new fuel and air filter. I checked for vacuum leaks.

     As I understand it, the car was running when parked 4 years ago, so timing shouldn't be the culprit, right? I am going to do a compression test today. Any thoughts and ideas would be greatly appreciated.


If it is backfiring, it is either timing or some other electrical problem like the coil is shot and needs to be replaced.  Do you have an electronic system on it, or do you still have points? 

Last of the Machicans:
Thanks for the reply Soaring.

It does have electronic ignition: HyFire VI-A, Mallory system to eliminate the points and a coil upgrade. 

I just now got the car to idle and drive via tinkering with the carb. It still isn't anywhere near perfect and thinks about stalling if I try to change the RPM's quickly.

 Though I felt confident in my visual vacuum tube inspection I went and bought a vacuum gauge anyway (never had one for some reason), hooked it up, and the pointer doesn't even leave the zero mark...  Which, I suppose, can only mean a massive leak somewhere. 

Back to the drawing board. >.<

Yeah, if you have a massive vacuum leak it will also act like you described.  Start with under the carb and your intake manifold.  Spray some carb cleaner around the gasket, and if the RPM's pick up, then there is your problem.  I would also go ahead and replace all the vacuum hoses on that engine because pin holes and rips in them can be disguised.  They are obviously old after being stored for so long, and God knows how many mice and other rodents have chewed on them.   

Last of the Machicans:
Once again, thanks for the reply.

I am going to the garage right now to find that darned leak.

I'll post back if I come up with an answer so the next guy with a similar problem can have some hints.


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