help with vacuum line connections

[tkelley72]

I have been having problems with the Holley 600 carb. on my 72 vert. 302. I had someone that supposedly knew what they were doing work on it but now I have my doubts. The car is back to idling weird, running rich and surging at idle. One thing he changed was the vacuum line from the distributor connection at the carb. He capped the top port on the passenger side and hooked up the bottom port to the distributer. Is that right? From what I have been able to find on the net I should be using the top port for the distributer and cap the bottom one. Another thing that he found was some white trash in the carb. Any idea what that could be? I'm surprised to see that as I had checked the inlet screen on the carb and it was clean. Since I know my fuel sending unit has failed, is it possible that the float (if plastic) has deteriorated in the tank and sending junk into the carb? Can I get some direction from the experts please? This carb issue just keep going on and on and driving me crazy. Thanks guys!

 

[Hemikiller]

It's pretty common to find a white gel substance in carbs that sit for a time. It's a problem with ethanol fuel. I use Startron additive in my lawn and power equipment and it's reduced my problems to near zero.

The passenger side port on the Holley is "timed" or "ported" vacuum. It provides zero vacuum at idle, then full vacuum when the throttle is cracked. Your mechanic seems to have hooked up the distributor to a full time manifold vacuum port. Now, the ported vs manifold vacuum debate can get lengthy, but the simple answer is an engine combination has to be set up to run one or the other. You can't just swap the vacuum supply and expect good results. If you have a factory distributor, then I would hook it back up to ported vacuum as it was designed.

 

[tkelley72]

At the risk of looking like an idiot, which port is the ported vacuum? The one on the top? My distributor is a stock replacement with vacuum advance and Pertronix 1.

 

[BUCKWHEAT]

I was an idiot too. So I found the factory vacuum diagrams (two actually, one inside the firewall and one for the engine area). I took copies and drew on a copy my 'actual' vacuum hookups as they existed on my '73 302 with the Motorcraft 2100. Wow, the 'actual' didn't even resemble the Ford diagrams, so I tore out all the old, dry, crumbly vac lines and redid them with new. I did them Ford's way. Result: engine ran smoother, not so much gas smell, and HVAC doors were happier. Bought a new one-way valve and my vac storage canister actually worked. I also bought a hand-held vacuum pump to test the various items like the timing vac advance and HVAC door motors to make sure they all worked.

 

[Hemikiller]

At the risk of looking like an idiot, which port is the ported vacuum? The one on the top? My distributor is a stock replacement with vacuum advance and Pertronix 1.

I assumed you were referring to this port in your original post. That's the timed vacuum port on most Holleys. If you don't have that, we'll need to know the List # stamped on the airhorn.

 

[tkelley72]

I do have that port. So that is the one that connects to the distributor vacuum advance and the one below at an angle is to be capped , right? For reference, list number is 80457-1. Thanks for hanging in there with me.

 

[Hemikiller]

Yes, the 80457-1 is the same as the one I posted. Snip below from your manual. Cap the angled port, that's a full manifold source.

You'll have to reset your idle RPMs and double check the timing to make sure he didn't adjust it for the manifold vacuum swaperoo.


Link to the manual for your carb - https://documents.holley.com/199r11081.pdf

 

[tkelley72]

Great info Hemi! I really appreciate it. Maybe I can get this thing straightened out.

 

[mrgmhale]

I have not found any factory schematics (aka calibrations) for engine vacuum connections prior to 1973. But, the good folks at Mustang Barn took the time to put together some decent schematics for 1967 - 1972 Mustangs. With their knowledge and approval I assembled all of their schematics into a single PDF file, grouped by year and sorted by engine size. I also have an excerpt from the 1973 Mustang Shop Manual, Section VI, which includes the vacuum calibrations for all 1973 Ford/Lincoln/Mercury engines Volumn VI (Emission Controls). In the 1973 Volume VI you can find a lot of information on the various emission control systems for 1973 Fords, where a lot of the information is applicable to earlier years.

One area you may want to examine on your 72 Mustang is the Fuel Evaporative Control System. I have seen where a lot of times folks remove the carbon canister, and plug the "vacuum" line, or (worse yet) plug it into the intake manifold. The Fuel Evaporative Control System is similar to the Positive Crankcase Ventilation (PCV) system in that both are beneficial to the overall operation of an engine, and neither do anything to diminish the performance or stability of the engine. I suggest you take the time to look at the documentation re: how the Evep system iss supposed to be connected, and make certain yours is set up correctly. If the canister for the Evaap system has been disconencted or removed you will likely have fuel vapors inside your garage at best. If someone has conected the fuel vapor line from the fuel tank to the intake manifold you could end up with a strong vacuum being applied to the fuel tank, which will hinder how well liquid fuel is pulled out of the fuel tank by the fuel pump - and possibly causing fuel starvation of the engine.

An aside about the 1973 Volume VI content, the original manual omitted the calibrations for that year's 351C 4v engine. I found both of the missing calibrations and added it to the Volume VI excerpt provided. I also included the 351C 4v calibration file to this post for anyone who may need it.