62 340hp Overheating

[Tom C.]

Guys, I know there have been many posts in the past on this issue but please bear with me. Just finished an under the hood redo of my 62 340hp. It had been running fine with no overtemp problems. I removed a replacement radiator and installed a brand new DeWitts repro. I am running a 50/50 Prestone mix. I also replaced the old (locked up) fan clutch with a new Eaton reproduction from thepartsladi. I also replaced the Edelbrock performer carb with a correct rebuilt AFB 3269S.
The car cranks and runs fine and will heat up to 180 deg when idling and stay at that temp indefinitely. When I drive the car around town for a few miles the temp (IR gun verified) goes to 210+. Increasing to 60mps backs the temp down maybe 10 degrees at the most and it continues to run between 210 and 220 until I take it back to the garage. I swapped the fan clutch out of my 66 427 (which has no overheating issues) with no change in the results. The carb may be a little rich because when I shut the hot engine down, it backfires one time (like a 410 shotgun) through the exhaust I assume caused by excess fuel in the cylinder.
My choices seem to be installing a FlowKooler water pump or eliminating the fan clutch with a Paragon solid hookup . Any ideas are welcome.

[Jack H.]

Re: 62 340hp Overheating

I don't hear anything in the symptoms discussion that indicates OVERHEATING... You don't say the rad cap 'pops' and you puke coolant at any time. Sounds to me like you're simply seeing coolant temps that are higher than what you expect them to be when running at slow to intermediate speeds since 210-220F isn't an indication of overheating (engine in danger of thermal runaway/melt down).

On the other hand, I'd expect the cooling system to remain relatively constant at/near 180F UNLESS it's VERY hot outside or you're working the car hard (climbing mountains, Etc.). So, since you see expected temps at idle + highway speeds of 60 MPH and above, that would tend to point to less than desirable air flow through the radiator at low speed which would suggest the fan and fan clutch aren't moving enough air in that particular portion of the fan clutch's temp/RPM vs. %-slip profile.

[Donald L.]

Re: 62 340hp Overheating

If you re using the correct distributor (1110985) it may be contributing to the extra heat as it does not utilize a vacuum advance control. You might consider using a 63-74 tach drive distributor with the proper VAC and a recurved ignition map.

[Clark K.]

Re: 62 340hp Overheating

Tom, what is the timing set at? -Clark

[Brooks G.]

Re: 62 340hp Overheating

Are you using a 160 or 170 degree thermostat? Years ago I found out the hard way that 180 degree is too hot to use in a 1962 and earlier Corvette.

Brooks Glover Jr. (2141)

[Tom C.]

Re: 62 340hp Overheating

I was accustomed to seeing 180 to 200 degree temps even on a hot day before I removed the locked up fan clutch and replaced it with one which (supposedly) works. Also, the reproduction Harrison seems to be thinner than the aftermarket radiator that I replaced. Yes, I am running the correct distributor (mechanical advance) with the breakerless se system (no points).

I am wondering how critical retarded timing might be to this situation?
Also, has anyone had any experience in the new higher flow rate water pumps? ie FlowKooler

[Tom C.]

Re: 62 340hp Overheating

The timing was initially set at 10 degrees at 1000rpm. In order to recheck it I'm going to have to pull off all that pretty new shielding..

[Timothy B.]

Re: 62 340hp Overheating

Tom,

Does the 1962 distributor have a vacuum advance?? If not, that 10* timing probably could be moved up a little but be carerful so total WOT timing does not exceed 38* (inital + centrifugal). I would try 14-15*BTDC

[Tom C.]

Re: 62 340hp Timing

Thanks for the tips on timing guys. I'll try to bump the timing up some,
14 or 15 at 1000rpm. 38 total....Does this sound reasonable?

[Michael H.]

Re: 62 340hp Timing

Thanks for the tips on timing guys. I'll try to bump the timing up some,
14 or 15 at 1000rpm. 38 total....Does this sound reasonable?

Tom, you might want to set the RPM down a bit before checking/adjusting the timing. It's possible that at 1000 RPM, the mechanical advance is already starting to come in??
I would set the idle speed at around 700, or less, and then check timing.

I don't have 62 340 HP distributor specs handy so I don't know when the advance starts.

[Donald L.]

Re: 62 340hp Timing

Tom, you might want to set the RPM down a bit before checking/adjusting the timing. It's possible that at 1000 RPM, the mechanical advance is already starting to come in??
I would set the idle speed at around 700, or less, and then check timing.

I don't have 62 340 HP distributor specs handy so I don't know when the advance starts.

111095 ignition curve

Start 0*@ 700 RPM
11*@ 1600 RPM
24*@ 4600 RPM

[Joe C.]

Re: 62 340hp Overheating

You changed the radiator.
Check for and seal any gaps between the new radiator and the shroud.
Make sure that the fan blades are 1/2 in and 1/2 out (front-to-rear) of the shroud.

If you never had this problem before, and you didn't disturb the timing in the renovation, then why Fv*K with it now????

Better still, throw away the fan and install a 2000cfm electric pusher fan.

[William C.]

Re: 62 340hp Overheating

Based on the '985 distributor specs, timing should be set at the slowest possible idle, and 12-14 degrees advanced, assuming the factory curve is in place and the centrifugal advance is functioning properly.

[Doug F.]

Re: 62 340hp Overheating

make sure you bled all of the air out of the cooling system, i usually take off the upper heater hose at the intake whole filling it till coolant comes out, when totally empty the system holds about 4 gallons.