Overheat at idle 67 300H.P Automatic and A/C

[Iron Duke NCRS #22045]

Re: What do you mean by "overheating"

A 50/50 mixture of ethylene glycol and water with a 15 psi cap won't boil until about 265 degrees F. 230 is fairly normal for modern cars in hot stop and go driving and they will boil over at 265 too. Add check the pressure cap to the above list, and I'd still suggest checking the timing with the vacuum advance connected. It should read the initial PLUS the max amount specified for the vacuum can. Specs are in your service manual and the total should be about 20 to 25 degrees at idle speed.

Duke

[G B.]

What radiator do you have?

And how old is it? An aluminum radiator can go terminally bad in two ways: external leaks and internal fouling. These problems don't necessarily happen at the same time.

[Iron Duke NCRS #22045]

'67 tune-up specs for 327/300

From Corvette News Vol.10 No.2 for the 300 HP engine

Initial timing - 6 deg. BTDC (with GM Air Injection Reactor 4 deg. ATDC intiial setting with automatic transmission)

Centrifugal advance - 0@900; 15@1500; 30@5100 (25@1500; 40@5100 with AIR and auto. trans.)

Vacuum advance - 15 deg.@12"Hg.

Idle speed - 600 RPM in neutral (with AIR and AT) Set higher as required to prevent engine from stalling in Drive.

If you have a California car with AIR it will run hot at idle even if everything is to spec. The retarded timing a idle increased exhaust gas temperature, which threw more heat into the jacket. Above 1500 RPM the total timing was the same as 49 state cars, which did not have any specific exhaust emission controls.

Duke

[Tom B.]

Re: Try a "flow restrictor kit"

Paul,

It's worth a shot, and inexpensive. Cheaper homemade versions are a thermostat with the center mechanism / spring removed. Kits are a mere $7-8 bucks. Summit Racing catalog is one source. They go in place of the thermostat. The purpose of their function has been debated. Some say it is less restrictive of flow, others say it reduces flow. Whatever, it's reduced my overheating. From a cold start I can idle a 68 427 in the garage on a hot day for 15-20 minutes before it begins to reach past 210. Before that, it wouldn't sit still for 10 minutes on any kind of day. TBarr #24014