1967 corvette/fire from carburetor/need help figuring out why and how to resolve

[Greg S.]

I have a 1967 resto-mod corvette with a M35 2-speed Powerglide automatic transmission with side pipes, and power steering. As part of the resto-mod build, it now sports a 502ci 8.2L V8 producing 510hp/570tq with a forged steel crank, forged pistons and connecting rods, hydraulic roller cam, hardened seats, Edelbrock dual plane intake manifold, Headman headers, a MSD ignition, Be Cool radiator, and March billet pulleys. It is also equipped with a 3.90 rear end

My issue is this morning I went to turn the ignition to let the fuel injector turn on, which I do not think it came on since it makes a noise. I thought well no big deal so I went ahead and tried to crank the car. It somewhat cranked but make some terrible noises so I stopped and opened the hood. Good thing I did! I tried to crank it again and the black carburetor setting on top of the engine (see below picture--no damage thankfully) flamed up. I quickly blew it out. Anyone know if this is a simple fix. The car is in mint condition. Your professional assistance is appreciated! --Greg

[Ed S.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

Greg,
I assume the engine was running fine the last time you drove it or ran the engine. That said, generally - generally - when you get flames back out of a carburetor it is because there is either an ignition timing issue or a valve train issue. In either case ignited fuel is coming up through an intake valve, through the manifold and out the carb. Possible causes: a) Valve train is functioning properly but ignition timing is way off and firing plug when the intake is open. This would indicate that the distributor moved (because it wasn't tightened down properly) or one or more teeth on the drive gear broke. b) Timing gear jumped a link or more (if you have a chain) causing the cam to be off timing and opening intake (and exhaust) valves at the incorrect time - that is just one possible valve train issue - there are a number of possibilities, a bent valve that is stuck open, etc. I would not try to run the engine any more until you can determine the cause - you risk doing extensive damage to the engine if it is a valve train issue and you try to run it - not to mention the possibility of a fire. Diagnostic procedures are not terribly difficult but more than can easily be described here - perhaps others will provide additional advice.

[Stuart F.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

When you say it made noise when you first turned the ignition on to turn on the Fuel Injector, could you possibly mean the electric fuel pump? If so, for a not so serious problem guess; you may have had a stuck float in that big expensive Holley type carb which over fueled it not allowing it to start, but rather back fire through the carb and ignite the over rich mixture. just a guess. I never had such a beautiful non-stock engine.

Stu Fox

[Greg S.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

Wow, thanks for the responses! I think you may be correct--Stu. It appears fuel igniter is not working properly. I think the reason the carburetor caught on fire is for the reasons you explained and I opened the hood, which gave it the oxygen it needed. If the float sticks will it cause the igniter not to come on when I turn the key? Is this a simple fix? Thank you in advance for your professional opinion.

--Greg

When you say it made noise when you first turned the ignition on to turn on the Fuel Injector, could you possibly mean the electric fuel pump? If so, for a not so serious problem guess; you may have had a stuck float in that big expensive Holley type carb which over fueled it not allowing it to start, but rather back fire through the carb and ignite the over rich mixture. just a guess. I never had such a beautiful non-stock engine.

Stu Fox

[Gene M.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

You talk about fuel injector then mention a black carburetor. Do you know what is under the air cleaner?

[Leif A.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

Wow, thanks for the responses! I think you may be correct--Stu. It appears fuel igniter is not working properly. I think the reason the carburetor caught on fire is for the reasons you explained and I opened the hood, which gave it the oxygen it needed. If the float sticks will it cause the igniter not to come on when I turn the key? Is this a simple fix? Thank you in advance for your professional opinion.

--Greg

Greg,

You keep referring to a "fuel igniter"...there is not part on a Corvette that is called a "fuel igniter" with the possible exception of the spark plugs. Are you referring to your carburetor, your spark plugs, your distributor, your ignition coil??

[Bob H.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

Greg

I think you need to remove the black air filter so everyone can see what is underneath, carb or fuel injection. I can't read the numbers on the gauge which I believe would tell us by the pressure whether it is a carb or fuel injection. I would think it is a carb and as previously stated, an electric fuel pump feeding it. If the proper fuel pressure is reached then I believe the fuel pump will shutoff until it needs to provide the proper pressure. Does that gauge go to 7 pounds or is there a higher number on the gauge. The terms you are using are confusing us a bit. As lief said there really is no fuel igniter and what you are calling the carburetor may be the air filter on top of the carb. Ed is right that you could cause severe damage if this is not diagnosed correctly and you try to restart the car. I guess the most simple thing you could check is to see if you can turn the distributor by hand. You should not be able to. If it was my car I would hope it was loose so a simple re timing of the engine could correct it. More than likely it is going to be some simple fix to get you back on the road. Make sure you have and carry a fire extinguisher with you.

[Greg S.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

I have had some folks look at it and they think it is the electric fuel pump. I'm hoping I can simply replace it and all will be good. Any other thoughts?

[Stuart F.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

One other simple possibility for loss of timing set is the rare occurance of a rotor breaking. I don't know if it happens with MSD distributors, or actually with Corvettes, but back in the day with tri five Chevies it was possible if you had a broken motor mount or if the engine got a real hard shake/shock such as with wheel hop during braking or off line acceleration. Like I said, it is rare, but it does happen. The distributor cap being loose or during a shock, the rotor tip will catch a terminal, break, and throw the timing way off. You'd swear your engine blew up. I had that happen twice during my brief drag racing career back in 1961.

Stu Fox

[Bob H.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

I don't think a bad fuel pump would cause a backfire and what you have described as the problem

[Paul J.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

I don't think a bad fuel pump would cause a backfire and what you have described as the problem

Exactly, a bad fuel pump wouldn't be putting any fuel up there to burn. Greg, start with the timing.

[Michael W.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

I have had some folks look at it and they think it is the electric fuel pump. I'm hoping I can simply replace it and all will be good. Any other thoughts?

Without knowing how these folks came to this conclusion, it's hard to agree/disagree. Your initial post sounds like a minor carburetor fire. These can occur for a dozen different reasons, some of which can be without anything being broken or wrong.

I'd recommend doing some troubleshooting before random swapping of any one component or blaming a given system.

[Rick A.]

Re: 1967 corvette/fire from carburetor/need help figuring out why and how to resolve/

Uh, why are you NOT talking to whomever did the restomod? Or, did you buy it built that way from someone else? AGain, we need MORE information to give informed answers, as everyone is crapping in the wind right now!