'66 327/300 backfiring

[Jerry K.]

I have looked at old threads and haven't seen on to fit mine. Car does not backfire when the engine is cold or while driving. After driving at operating temp for a while, I shut the engine off. After maybe 5-10 minutes time, I re-start the car and it has backfired on several occasions. Is it the timing or fuel?

[Duke W.]

Re: '66 327/300 backfiring

Is it backfiring - through the carburetor; or afterfiring - pops in the exhaust system?

A lot of guys confuse the two.

Duke

[Jerry K.]

Re: '66 327/300 backfiring

You know Duke, I think it's thru the muffler. I am half deaf, but it does sound to me like the exhaust.

[Duke W.]

Re: '66 327/300 backfiring

Could be a burned valve or improper distributor installation. The first thing I would check is distributor installation and wire indexing. If correct I would do a compression/leak down test.

Duke

[Edward J.]

Re: '66 327/300 backfiring

Jerry, There maybe the possiabilty that when you shut down car the carb. maybe trickling some fuel into the intake,(generally it would backfire through the carb. with this problem) and checking the tune-up spec.s. (Timing and dwell couldn't hurt).checking the wires inside the distributor is a good idea, sometimes when cranking the advance mechanism will pull open and ground out the points feed wire.

[Robert G.]

Re: '66 327/300 backfiring

I had a condenser that was bad only when hot and would cause quite an afterfire. If you have a spare, it's an easy thing to try.

[Timothy B.]

Re: '66 327/300 backfiring

Jerry,

When is the last time the engine was tuned up?

[Jerry K.]

Re: '66 327/300 backfiring

I bought the car one year ago and I haven't had it tuned. I don't know when the prior owner had it tuned. I have put on about 500 miles in the past year and it has about 2k on it since the engine re-build in 2006.

[Joe L.]

Re: '66 327/300 backfiring

I bought the car one year ago and I haven't had it tuned. I don't know when the prior owner had it tuned. I have put on about 500 miles in the past year and it has about 2k on it since the engine re-build in 2006.

Jerry-----


Is this possibly a California-delivered car with it's original K-19 system intact?

[Jerry K.]

Re: '66 327/300 backfiring

Hey Joe, I have no idea about that, but I think it had been in New Jersey and Mass.

[Joel T.]

Re: '66 327/300 backfiring

Jerry;

Before you dig into serious things, I would check the simple stuff... as some have recommended. If you have an extra coil, I would add a swap out to my list of things to try up front.

Let us know how you are making out.

Joel

[Jerry K.]

Re: '66 327/300 backfiring

Hey Joel,

I'll try the coil, but the backfiring has only occurred three times in the past 6 months so it is hard to pin it down. The car has breakerless electronic ignition and has had N-11 exhaust installed in the past six months. I'll let you know when and if it happens again.
Jerry

[Jerry K.]

Re: '66 327/300 backfiring

Thanks for all of the ideas and advice, and I will eliminate them one by one over the next couple of months.
Jerry

[Terry W.]

Re: '66 327/300 backfiring

Hey Jerry
Does the car smell of fuel after you shut it down, If so check the power valve in the carb or replace it anyway if you think it is old or damaged. If that checks out , run the car to operating temp , turn it off , pull the air cleaner off look over the carb for fuel bubbleing into the front barrels, I have this problem with my 327-300 in my 67 ,I think it may be more so with the stock iron manifold, I am about to try a phenolic spacer and maybe a heat sheild ( available from holley or edelbrock) the fuel is in fact boiling and mildly flooding the front barrels so when you restart you get a backfire and then probably almost stall the car as it may have run the front bowl low on fuel.
good luck
Terry