C2 67 427 Overheating at idle

[Joe R.]

Re: C2 67 427 Overheating at idle

Hi Al:

I checked my records and the vacuum can that I now use is a NAPA VC1810. This was recommended to me by Duke Williams here on this board, when I was trying to overcome a loss of vacuum advance due to poor idle vacuum.

According to Duke, the VC1810 specs are 0 degrees at 4" vacuum, and 16 degrees at 8" vacuum.

In my case, I suspect that a previous owner put a more aggressive cam in my engine. In any event, the idle vacuum is not sufficient to provide full vacuum advance with the stock vacuum can. The VC1810 fixed that problem.

From your original posting I could not tell whether the 7" vacuum that you referenced was an actual measured value on your car or just a predicted value from the manufacturer of the camshaft. If 7" is what you presently measure, the VC1810 may still be adequate, since the idle vacuum will probably increase a bit once the vacuum advance starts to kick in.

However, if you really have only 7" vacuum with the advance working properly, even the VC1810 is probably not aggressive enough. I believe that the rule of thumb is that the vacuum advance should be all-in at a vacuum level that is at least 2" less than the nominal idle vacuum.

[Alex K.]

Re: C2 67 427 Overheating at idle

Joe,

I will give the vc-1810 a try.

Thanks again Al

[Michael H.]

Re: C2 67 427 Overheating at idle

Al,

There is a quick test that you can try. Instead of replacing the vacuum advance unit, try pulling the timing up several degrees when the engine is already running at 180 or so. This would duplicate the timing while running with full time vacuum and a different advance unit. If the over heating condition continues, I suspect there may be something else wrong. If it seems to be cured and no longer over heats, then the vacuum advance and it's system hook up is at fault.

Drove an L88 in a parade once at about 3 MPH with hot exhaust coming into the radiator from the car ahead on a 95* day and the temp never pegged the guage like yours is doing. Timing was at 10* and no vacuum advance at all.

Is this a fresh engine in your car?

[Alex K.]

Re: C2 67 427 Overheating at idle

Michael,
No not new it has about 10,000 miles in 6 yrs.Always had this overheating problem,thats why I re-did the complete cooling system.I thought that would do it.Now I thought the vacuum advance at idle was the only thing left to cause the overheating.
Al

[Michael H.]

Re: C2 67 427 Overheating at idle

Al,

I would probably try the easiest/cheapest items first. Try the vac adv unit and mod that Duke recommended or just temporarily setting the timing up another 10* at idle and see what happens.

Also, it wouldn't hurt to check the accuracy of the guage with an IR gun, unless you've already done that.

Lot of things can cause over heating. Vacuum leaks are typical but I would expect that to affect the normal running temp while driving as well as stopped and idling.

It sounds like you've covered all the bases on the cooling system.

[Clem Z.]

is the fan installed correctly,

with the fan blade tip half inside and half outside the fan shroud.

[Alex K.]

Re: is the fan installed correctly,

Clem;

Yes,the fan tips are half in and out.

Thanks for the info

[Alex K.]

Re: C2 67 427 Overheating at idle

Michael,
I will try the idle advance and see what happens.

Thanks Al

[Les Jacobs]

Re: C2 67 427 Overheating at idle

Al To determine what effect a working vacuum advance will have on your idle temp problem, hook up a vacuum tester (like Mity Vac) to your existing can, and with the engine running, apply vacuum directly to the can. The amount of advance should be measurable with a timing light, and the effect on the coolant temp could be checked. Les

[Alex K.]

Re: C2 67 427 Overheating at idle

Les,
I will check the advance befoe I put the new one on.

Thanks for the advice Al