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This car was not started for four months due to an accident. Started two days ago idled ok but had irregular backfire with flame through tailpipe.

Added more gas, HEET (enough for full tank which is what guage is showing) and Lucas gas treatment. Now on starting the engine backfires through the 'carb' with flames. Tried opening the butterfly thinking it was choke related but no difference.

Removed 2 spark plugs. One was clean a good, one was 'oily' (from the Lucas?).

Any suggestions would be appreciated. This vehicle ran like a scalded dog before the wreck (which damaged the left rear). Also, there is no gas cap but the vehicle has been under cover and not in the open weather.
 

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Which plugs did you pull and which were oily?

Any reason to think the base timing changed? (dist position)

What year car? Which motor?
 

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This car was not started for four months due to an accident. Started two days ago idled ok but had irregular backfire with flame through tailpipe.

Added more gas, HEET (enough for full tank which is what guage is showing) and Lucas gas treatment. Now on starting the engine backfires through the 'carb' with flames. Tried opening the butterfly thinking it was choke related but no difference.

Removed 2 spark plugs. One was clean a good, one was 'oily' (from the Lucas?).

Any suggestions would be appreciated. This vehicle ran like a scalded dog before the wreck (which damaged the left rear). Also, there is no gas cap but the vehicle has been under cover and not in the open weather.

If your engine is back firing through the carb, then you have a problem with your ignition timing, you have an intake valve that has been adjusted way too tight, or you have carbon tracking on your distributor cap and a cylinder is getting fired ahead of time. If your distributor cap has a lot of miles on it or if it has ever been wet, I'd suggest you replace it before you do anything else.
 

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Any suggestions would be appreciated. This vehicle ran like a scalded dog before the wreck (which damaged the left rear). Also, there is no gas cap but the vehicle has been under cover and not in the open weather.
Question: Did you have a gas cap on it before the wreck? :food-smiley-021:
 

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:iagree: I would start there. Have you added or removed, changed anything while it was sitting?

If this car has been sitting with the hood off, then the distributor has likely gotten good and wet. There could be a lot of moisture inside the cap and it's that moisture causing the backfiring as cylinders are being lit off ahead of time. I'd start off by removing the cap and checking it out real close. There could be carbon tracking from terminal to terminal on the inside AND the outside. Caps are relatively cheap so I would just replace it.
 

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If this car has been sitting with the hood off, then the distributor has likely gotten good and wet. There could be a lot of moisture inside the cap and it's that moisture causing the backfiring as cylinders are being lit off ahead of time. I'd start off by removing the cap and checking it out real close. There could be carbon tracking from terminal to terminal on the inside AND the outside. Caps are relatively cheap so I would just replace it.
OP states car has been under cover. No telling though. Flames can be caused by few things. I'm wondering if he 'tinkered' with anything while it was sitting. Sounds odd to me that this is the result from an accident alone or that a certain part suddenly went bad or came to a head from a wreck.

I fixed a friends old Pontiac that did the same all because he reversed the firing order after he replaced the distributor. He though all GM firing orders went clockwise.
 
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