I'll try and summarize as best I can, hoping someone has an idea on this one!

Car runs at 200-205 at idle, 90* ambient air temp, w/ AC running. At freeway speed, that is where the water temp gauge creeps, all the way to about 250 if you don't turn off the A/C. Here is what has been done (in order):

* Reman Jasper Performance SBC 350 engine
* New AC/Delco water pump, hoses, belts, with 195* stock thermostat with brand new OE style Brass/Steel radiator
* Mr Gasket 4364 180* thermostat (with holes drilled)
* Radiator seals
* Timing and air/fuel mix verified to be correct
* Running 89 octange fuel
* Dewitt's SPAL fans on OE radiator
* Upgraded to Dewitts Aluminum radiator (kept SPAL's obviously)
* Added lower air dam (was missing from car)
* Upgraded to Edelbrock 8812 high flow water pump (to ensure it wasn't a flow issue at high RPM, saw lots of positive reviews paired with the high flow thermostat and high flow radiator)
* Plugged heater inlet on water pump, and outlet on intake (previously had a bypass hose, the heater core doesn't work so it has been bypassed)
* Added bottle of water watter (running 50/50 mix coolant)
* Temp in Phoenix today was 95*, 30 minute drive home

Temp sender and gauge in car have been verified to be accurate. I also tested myself with a heat gun at the thermostat cover and got about 10* less than the gauge was showing in the car (the temp sender is in the block which is supposedly about 10* hotter than where the thermostat is sitting).

My only thought is that maybe something is wrong with the A/C compressor? A/C is working, but the compressor does make a little noise sometimes (knocking and pinging). Belt is new and tight. It is an aftermarket compressor, and certainly not the one originally in the car, although it is still running R12.

Any help/ideas is appreciated!

 

If the temperature goes down when you turn off AC, then you might have excessive pressure in the AC system. This could be due to air in the system or a overcharge of refrigerant. If the pressure is too high the condenser will get extremely hot.

 

I am taking it to the shop that installed the A/C tomorrow (it's a different shop than the one that did the motor install, and I do have the original receipt with the refigerant levels/pressures etc.). I am hoping they can check the system, and maybe I am that lucky that the new shop overcharged the system At this point I am at a total loss as to whats happening, it's not like I'm towing a house behind this little car lol...

 

Is your vacuum advance working? If not, the timing being too retarded at RPM can cause the temperature to increase.

 

I asked about that multiple times. I was told by the shop "base" timing was like 13 or 14, and at RPM was like 33? Does that sound right? Im assuming the vacuum advance works at higher RPM... I know very little about timing.

 

All in, your total timing should be at 36 degrees. The easiest way to check this is by removing the vacuum line and the distributor springs. The best way to check the vacuum advance canister is to apply vacuum to it with a Mighty Vac and then check the vacuum gauge to make sure it holds vacuum.

 

I think Im going to go ahead and have an independent shop check the timing and test the advance as you outlined... If I chased cooling system issues for $1600 and it ends up being timing Im gonna blow my own head gasket lol...

I guess I figured if it were timing it wouldnt run well on the highway with the A/C off. Its at about 205 to 210 with no A/C. Really climbs when its on and driving 50+ mph.

 

Cooling issues can be so frustrating. When I finished building my small block a year ago, the only thing that wasn't perfect was the coolant temp that would creep up to 220 on the highway. After a few weeks, I finally tested the advance canister and discovered it wouldn't hold any vacuum. I replaced it and the problem was solved. Hang in there and be patient.

 

Does the temperature decrease when you turn off AC?

 

This can be a pain I know too well. I bought my 76 last year after Bubba decided to remove all the factory stuff installed a Be Cool radiator with dual fans. So I bought it from a Jeep dealer where he traded and they didn't know anything about it. I got it home and had all kinds of overheating issues. The system had no fan relays nor breakers,Well you get the picture. bought a complete wiring kit from Summit, relays,breakers sensor etc and now I know what I have, So hang with it the snake will show it head soon. Also Bubba removed thermostat..Good luck

 

30 mile drive to work today, no a/c on and the car didnt touch 200, stopped at like 195. 70* outside. Im betting it has to be an a/c issue, going to shop after lunch...

 

The condenser for the AC is usually in from of the radiator and when the AC is on, it gets quite hot, which in turn only allows hot air to pass across the fins of the radiator.

Do you have an aux electric fan in from of the radiator/condenser? This may what is needed in the AZ heat.

 

I'm not sure there is even room for an aux fan in front of the condenser... The hood would hit it There is a ton of flow through the radiator(s) from the upgraded fans.

 

How is the flow on the highway. Does the air have any way around the radiator instead of through it?

 

I'll throw a light in front of the radiator, turn the lights off in the garage and look in there and see if I can see any possible air leaks.


But with the electric fans, even at highway speed they kick on at like 195*. So with air kicking up and through from the air dam, and electric fans, I'm hesitant to think a small air leak would cause the car to run 50* hotter with the A/C on... But I'll doublecheck all the seals and make sure there isn't any other possible air leak tonight.

 

This seems high to me even without AC on. I've done almost the same mods as you to solve my temp problems. My car now sits around 175ish without AC on a +90 day. I do have a OD transmission and tranny cooler but other than that we are really close on our setup.

 

Sorry I missed the part about the upgraded fans ...

Good luck with this.

 

The A/C shop checked the compressor, temperatures, pressures, etc. and everything checked out to them.

Just so happened to be a corvette shop 2 bays down, they came over and looked at the car. They think my gauge is bogus, their heat gun was only reading 178* on the intake manifold by the thermostat, the gauge was saying about 205. They recommend that I throw an aftermarket gauge on my extra port on the intake (where I removed the heater bypass hose) and monitor the temp with a new sensor/gauge.

Also, they said if my car was getting as hot as that gauge is saying I'd be blowing coolant out the overflow, the cap, etc. and having coolant on my garage floor and smelling/hearing it bubble over.

I'm might throw a second gauge on there, at least temporarily, to see what happens on a hot day (today was only high of 75* so I could only get the gauge to about 220-I want to see what the aftermarket gauge says when it's getting close to the orange on a 95*+ day).

Also they said I am missing the top foam that goes on the hood, so I need to seal that better. At speed a lot of air will go over the top of the radiator instead of through it. I figure once it gets dark I'll throw a light in there and look and see if I see any possible spots where air could be leaking...

One other thing I did was spray the evap with some coil cleaner I had purchased for one of my other cars. I've never cleaned it, it looked find, but why not clean it just incase it was oily or something I couldn't see from the surface.

 

Definitely need the foam below the hood. Do you know whether the temp sender is original?

 

Temp sender was replaced, tested for calibration and resistance checked to match gauge... supposedly

However, I threw an after market temp gauge in tonight, and it matched exactly the 195/175 cycling on the dewitts fans. Where the gauge in the cab was reading basically 198 the whole time whether it was at 170 or 195.... A test drive I was able to get the oe gauge to 205, aftermarket gauge 178. So... OE Gauge is like 25 to 30* off for sure. Once it warms up again in PHX Ill see what happens when the OE gauge starts climing, and see what the real temp is...

I also spent a couple hours tonight double sealing all the possible air leaks with pipe foam. Including a makeshift seal for the top of the radiator where it meets the hood.

One thing Im curious on... on the bottom it looks like air was just coming up, under the condensor and through the radiator. So I sealed between the two on the bottom, so air will kick up and be forced to go through the condensor first, then get to the radiator. Makes sense to me, but not sure how the OEM seals were placed... Anyone have pics of all the seals, especially around the condensor?