1967 327/350 holley questions

[Brad H.]

Guys,
I just bought a 67 327/350 vert which is a mostly numbers matching car except for an added MSD ignition. It has the correct Holley carb on it. The engine was supposedly rebuilt in 2004 and in fact runs very well in all regards except that the engine runs rich pretty much all the time. Removed spark plugs are black with soot but mostly dry and they do not seem to be oily. The engine does not really smoke especially does not smoke blue as if it was oil fouling. The previous owner reported that the engine ran rich so he had a MSD ignition system installed which seemed to stop the spark plug fuel fouling. Obviously one of my first tasks is to get that MSD stuff out of there. The original dist came with the car so it's getting rebuilt to go back in. I have not done a compression test yet, but I suspect the Holley is at fault at this point. I have a good deal of experience with the Qjet, but not so much with the Holley. I suspect that possibly the power valve is blown and maybe the float levels are off some. I am hoping some of you may have some ideas and then a recommendation for the best place to send it for overhaul.
I really appreciate any ideas you may have.
Brad

[William F.]

Re: 1967 327/350 holley questions

Lots about this in previous threads. I agree I would suspect Holley. May be a bad power valve or some form of internal Holley gas leak or possibly high float level or pin hole in a float.. . If adjusting idle mixture screws have no effect on idle-it's a bad power valve or internal fuel leak. Unless you're restoring for judging, no need to remove MSD. I'll get some argument, but unless you like fooling with points, MSD distributor is solid and you can readily adjust advance curve. Assume it has vac advance as well as centrifugal. Have you checked initial and total timing with a dial back light?

'67 L79

'67 L36
'62 340 hp

[Larry M.]

Re: 1967 327/350 holley questions

Brad:

Agree that the Holley is probably at fault, and should be rebuilt. Float level and needle/seat shutoff are probably the issue, but the power valve could also be bad or incorrect. Why not buy a good rebuild kit and try the rebuild yourself?? Daytona Parts has some excellent rebuild kits. http://www.daytonaparts.com/kits.html

However,if you want the name of an excellent Holley rebuilder, I would contact Eric Jackson at Vintage Musclecar Parts. None better. http://www.vintagemusclecarparts.com/index.php

Larry

[Dick W.]

Re: 1967 327/350 holley questions

Guys,
I just bought a 67 327/350 vert which is a mostly numbers matching car except for an added MSD ignition. It has the correct Holley carb on it. The engine was supposedly rebuilt in 2004 and in fact runs very well in all regards except that the engine runs rich pretty much all the time. Removed spark plugs are black with soot but mostly dry and they do not seem to be oily. The engine does not really smoke especially does not smoke blue as if it was oil fouling. The previous owner reported that the engine ran rich so he had a MSD ignition system installed which seemed to stop the spark plug fuel fouling. Obviously one of my first tasks is to get that MSD stuff out of there. The original dist came with the car so it's getting rebuilt to go back in. I have not done a compression test yet, but I suspect the Holley is at fault at this point. I have a good deal of experience with the Qjet, but not so much with the Holley. I suspect that possibly the power valve is blown and maybe the float levels are off some. I am hoping some of you may have some ideas and then a recommendation for the best place to send it for overhaul.
I really appreciate any ideas you may have.
Brad

I know I will get flamed for this statement, but here goes. If you are going to drive the car, leave the MSD system on. You can forget about tune ups, plug replacements, etc. Kermit, the '72 LS-5 has had the MSD 6A box, and Blaster coil on it for over 25 years. Replaced one sparkplug in that time. A spark plug wire got against the exhaust manifold and allowed the plug to foul. Rather than clean it, I just replaced it. Starting is a lot quicker also.

[Larry B.]

Re: 1967 327/350 holley questions

Look on the front of the choke housing and get the list number.Then look at the jet for size.They are likely changed.Power valve can also be a problem leaking or cam in the motor may cause a low vaccum which causes the power valve to open. Look down the carb at idle you should not be able to see any gas,if the power valve is open or leaking you will see gas.Floats to high or needle leaking can see fuel to.With the list number I can tell you jets and power valve should be in it.

[Brad H.]

Re: 1967 327/350 holley questions

Thanks for arecommendations bradrecommendations brad

[Dick W.]

Re: 1967 327/350 holley questions

Look on the front of the choke housing and get the list number.Then look at the jet for size.They are likely changed.Power valve can also be a problem leaking or cam in the motor may cause a low vaccum which causes the power valve to open. Look down the carb at idle you should not be able to see any gas,if the power valve is open or leaking you will see gas.Floats to high or needle leaking can see fuel to.With the list number I can tell you jets and power valve should be in it.

One good backfire and the power valve is history

[Tom B.]

Re: 1967 327/350 holley questions

One good backfire while you are looking down the carb and your eyebrows are history.

[Jim T.]

Re: 1967 327/350 holley questions

Put a finger over the vertical vent tube with the engine running, if the engine dies right away, the power valve is not functioning and probably not holding closed with engine vacuum. The engine will die if the vertical vent is blocked after a longer time. Easy fix replacing the power valve, the individual part is available. The new Holley gaskets for the fuel bowl and metering block are available in blister packs and are reusable unlike the old style but are a different color.

[Duke W.]

Re: 1967 327/350 holley questions

Plug fouling can be caused by too cold a plug. What is the mfg/number of the installed plugs.

Measure head gasket thickness with feeler gages at the corners of the head/block interface. What's the number?

Also, measure idle vacuum at 750? What's the number?

The above will determine whether it's still a L-79 or something else.

Regarding the MSD, how is it set up - centrifugal and vacuum advance? If you want to know how to optimize it search for a December thread authored by me, subject: blueprint overhaul of a L-79 distributor. Typical aftermarket distributors are "one size fits all" and the spark advance map is likely not anywhere near optimized for your specific engine. It's and easy DIY job.

IMO you are better of with the Delco single point ignition, It's easy and inexpensive to optimize critical clearances and the OE spark advance map, and once you get it set up properly, it will last for many years at the rate we typically accumulate mileage on our cars, and there is no "black box" to suddenly fail. A dwell and timing check every couple of years is a good idea. That's part of the vintage car hobby - you get to work on your car once in a while doing simple maintenance jobs.

Duke

[William F.]

Re: 1967 327/350 holley questions

Unless the timing is way off,0r you're using plugs that are too cold( 45 heat range best all round)0r engine won't pull enough vac to keep power valve closed until needed, problem is the carb.

[Duke W.]

Re: 1967 327/350 holley questions

Unless... unless... unless... There is an old saying: 90 percent of fuel injection "problems" are in the ignition system, and that can also be applied to carburetors. The ignition system is easy to check out, correct a problem, or eliminate it as a cause if no issues are found.

Quoting from post #1: "The previous owner reported that the engine ran rich so he had a MSD ignition system installed which seemed to stop the spark plug fuel fouling."

That should tell you how bright the PO is - rather than finding and correcting the root cause, let's "re-engineer" it using the Jegs catalog. This happens WAAAAAAAY to often.

The OP just acquired the car. It has an aftermarket ignition system. Plug heat range is unknown... aw, never mind, it must be the carburetor.

Duke

[William F.]

Re: 1967 327/350 holley questions

Duke,
Got a lot of respect for you and agree lot of times carbs get blamed when problem is really ignition BUT if you'll reread my post, you'll see I suggested checking common ignition problems and carb in question is the infamous Holley. Probably more posts about Holley problems than anything else. Regarding MSD ignition, had one on a '66 L79 for years with good results-no points problems or plug fouling. I'll bet you an adult beverage or case of brew that this problem is carb related.
Best regards

'67 L79
'67 L36
'62 340hp

[Tom B.]

Re: 1967 327/350 holley questions

That is exactly what I was thinking. Instead of spending a lot of money on a custom ignition to mask the problem why not fix the carb for a few dollars?

[Joe C.]

Re: 1967 327/350 holley questions

I know I will get flamed for this statement, but here goes. If you are going to drive the car, leave the MSD system on. You can forget about tune ups, plug replacements, etc. Kermit, the '72 LS-5 has had the MSD 6A box, and Blaster coil on it for over 25 years. Replaced one sparkplug in that time. A spark plug wire got against the exhaust manifold and allowed the plug to foul. Rather than clean it, I just replaced it. Starting is a lot quicker also.

Sacrilege! Shameful! You should know yer audience before responding! I vote to suspend you from the TDB! String 'Im up! Get ready to meet yer maker! You feel lucky, punk! If it wasn't invented before 1970, then it ain't no good fer nothin'!

If the MSD system enabled the plugs to fire, even with a GROSSLY rich fuel mixture, then the MSD certainly damaged the engine somehow!

** NOTE: The above tongue-in-cheek commentary in no way approves of the OP not fixing the issue with his carburetor, which is likely a ruptured PV, high/stuck float(s), leaky needle and seat(s), excess fuel pump pressure, or improper jetting.