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Joined: Jul 2021
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The Mallory distributor in my 1968 400ci automatic does not have vacuum advance. Google (or AI) tells me this type of distributor is typically used with high performance/race cars.

My car is a cruiser. Pls recommend the "best" distributor with vacuum advance for my 1968. Google also tells me that vacuum advance is better suited for routine use.

Thanks

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I can tell you that AI is way off from reality when it comes to most anything automotive.
Weather you have or don't have a distributor with vacuum advance has nothing to do with performance or racing.
As long as the distributor is in proper working condition and the advance mechanism is working properly and you are able to set the initial timing and the total timing where it needs to be and the engine is happy.
Vacuum advance just provides more timing advance when the engine is not under any load such as when you are accelerating or climbing up a hill. The engine can tolerate a bit more advance when just idling and cruising on the highway. Vacuum advance may help with gas mileage a bit but there are many other tuning factors.


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"there are many other tuning factors." Very true- timing is just one part of the total tuning package.

How does it run? Any pinging? It may be set up just fine for your engine. Good gas mileage? Maybe just leave it alone.

Is it a Mallory dual point distributor? Or a Unilite? I prefer a GM Pontiac HEI distributor w/vacuum advance but I always use low compression heads. It takes very little adjustment to get it dialed in. Low compression lets me use lots of timing advance.

Stock 1968 heads are usually high compression and that causes all sorts of issues with today's crummy gas. Often, hooking the vacuum advance up to full manifold vacuum helps a lot.

Last edited by Oldslowandugly; 10/13/25 02:12 PM.
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Big Chief,

Thanks for the advice.

The engine does run well. I have checked initial timing and its at 12, which I believe is acceptable. I don't currently have an adjustable timing light, so have not checked the total timing. I plan to get one so I can check it.

Gas mileage is around 11 mpg. I would like it to be better, but from what I have read, this seems typical. I had a 200r4 put in to improve the mileage, but really don't drive on the highway enough to see if its any better.

The car does overheat while idling, up to 225F on days when the ambient temp is 85F or hotter. When it gets that hot, I shut the car off, but pretty sure it would go higher. It stays at 190F or lower while driving at any ambient temp. I have tried just about everything to keep it cooler at idle, such as adjusting the water pump baffle plate, mixing coolant at about 25% antifreeze, adding water wetter, replace the 15lb radiator cap, radiator fan positioned 1/2 way into the shroud, flushing the cooling system. I think the radiator is pretty old. Its not aluminum and the tubes inside look like they have alot of deposits, so I am considering replacing it.

Thanks for your advice on the distributor. I'll keep the Mallory.

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Oldslowandugly,

Thanks for the information. The engine seems to run fine with no pinging. Gas mileage is around 11 mpg, which seems to be typical.

I have the Unilite distributor.

Based on your suggestion "maybe just leave it alone" and Big Chief's suggestion to also leave it alone, that's what I am going to do.

I am at least the 4th owner, so I am kind of questioning everything about the car's systems to see if anything needs changed/improved.

Thanks for your help.

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Things that cause an engine to run hotter than usual
1.Clogged or plugged radiator
2.Not enough air flow across radiator
3.water pump speed not fast enough at idle speeds (under 2000 RPM)
4.Not enough ignition advance


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Thanks bigchief


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