67 Running Poorly - Trouble Shooting

[Jace H.]

My 67 327/350 hp is starting to run poorly after performing flawlessly since complete restoration in 2003. The car has only been driven 6k miles in 11 years. I just completed a tune up with new plugs, points etc.. and adjusted timing as I thought I would start there. That didn't fix the issues. Symptoms are: Once warmed up the car lurches or cuts out if you will. It also wants to stall at a stop. I am running good gas without Ethanol and with a mix of high octane racing fuel. Running the original Holley and original rebuilt fuel pump. Is it obvious that it is time for another carburetor rebuild? Is there a good modern carburetor that fits a L79 setup without much modification? Any other thoughts on what to try next?

Thanks,
Jace

[Terry M.]

Re: 67 Running Poorly - Trouble Shooting

My 67 327/350 hp is starting to run poorly after performing flawlessly since complete restoration in 2003. The car has only been driven 6k miles in 11 years. I just completed a tune up with new plugs, points etc.. and adjusted timing as I thought I would start there. That didn't fix the issues. Symptoms are: Once warmed up the car lurches or cuts out if you will. It also wants to stall at a stop. I am running good gas without Ethanol and with a mix of high octane racing fuel. Running the original Holley and original rebuilt fuel pump. Is it obvious that it is time for another carburetor rebuild? Is there a good modern carburetor that fits a L79 setup without much modification? Any other thoughts on what to try next?

Thanks,
Jace

Jace,
Does the engine seem to be running rich? -- dark almost black smoke from the exhaust.

Could be a blown power valve. This especially can happen when the car back fires through the carburetor. If you can gt it to idle for a bit, put your finger over the bowl vent -- the tube that sticks up at the edge of the circle that the air cleaner assembly rests on. If engine dies when you block the vent, you need a new poser valve.

[Timothy B.]

Re: 67 Running Poorly - Trouble Shooting

In addition to Terry's question about running rich, have you properly adjusted the A/F emulsion screws after complete warm up.

[Ralph E.]

Re: 67 Running Poorly - Trouble Shooting

Could it be as simple as a vacuum leak?

[Jace H.]

Re: 67 Running Poorly - Trouble Shooting

I will try that Terry. It is not running rich.

Thanks!

[Jace H.]

Re: 67 Running Poorly - Trouble Shooting

Tim, hadn't thought of that. I will try that also.

Thanks,
Jace

[Jace H.]

Re: 67 Running Poorly - Trouble Shooting

Ralph,

I did find that the vacumm hose was cracked and I replaced with new. Not the problem. Thanks for the response.

Jace

[Frank T.]

Re: 67 Running Poorly - Trouble Shooting

I had similar. Problem I had a bad balest resistor

[Duke W.]

Re: 67 Running Poorly - Trouble Shooting

The most common cause of this type of behavior is electrical - coil, ignition switch, breaker plate ground wire, connectors including the bulkhead connector that carries the ignition feed from the ignition switch.

One simple test is to use some long test leads and connect a voltmeter or dwell meter to the coil and look for momentary drop outs in the readings as you drive. That can verify an electrical problem. Then it's a matter of finding the specific problem, but there are only a few possibilities.

Duke