tgilligan

Hi All,

My cooling setup is a 2 row radiator (aftermarket) with factory fan shroud and fan clutch. The radiator saddles and the top cover plate will only fit a 2 row setup. As I didn't have a gauge but wanted to keep the factory 'HOT' light in the gauge cluster, I added a set of mechanical AutoGage (temp/oil) to the bottom of the dash. I have the 190/195 (not sure which) thermostat in the factory water neck. As some additional info, engine is fairly fresh rebuild and includes all new belts, thermostat, hoses, water pump and all new gaskets and seals as I had it completely apart. Hopefully I can safely eliminate head gasket issues, water pump, etc. I did a cam swap (stayed with flat tappet), added an MSD ready-to-run, upgraded the heads to have some Comp Camps components, forged pistons and added a Holley 750 DP.

Took the car for a drive earlier on neighborhood roads this evening and temp was normal and sits around 210 on average. However, after a few minutes, temp climbed on the gauge all the way to 280 (max) and at the next stop light, it dropped back down to 230 until I started driving again. Stayed between 260-280 until I got back home when it dropped back down to 210-230 normal range in park. As it's a mechanical gauge, there isn't any grounds, it's just the capillary temp sensor going to the port on the manifold.

Has anyone else come across this? Thought it was really odd for it to drop in temp when it came to a stoplight rather than climb higher. Is it perhaps the gauge that crapped out on me? Engine didn't seem hotter than normal, no visible signs of any overheating and nothing overflowing out of the radiator.

oldcutlass

If it moved up rapidly, you probably have an air pocket. I leave the cap of and wait until the thermostat opens and put a water hose in the radiator neck on a slow flow and force the pocket out.

tgilligan

Thanks Eric. Any suggestions without the hose? Here in the northeast, it's still friggin cold so I haven't hooked up my hoses or gone into my crawlspace to turn on the valves to my outside spigots yet. I've seen some methods where people are sticking a funnel in the neck and filling as needed but I don't have an overflow bottle, just a small hose pointing down from the relief nipple. Don't want to screw it up by having is just **** out all over the place. Any other methods I could use? Sorry for being a noob, it's all things I'm learning to do as I go.

I think you may be right about the air pocket, I replaced the water neck as I had a chrome one when I put the engine back together but it leaked so I put my original tried and true cast one back on. I most likely let air into the system at that point.

oldcutlass

You can try leaving the cap off and running it until it warms and you see water flowing. Then add 50/50 coolant mix until the level is about 2 inches below the neck. Put the cap on and take it for a ride and hope it dissipates on its own over time.

joe_padavano

Since you said you have both the light and the gauge, where in the intake is each sensor?

tgilligan

As always, many thanks Eric. Seemed to work and a couple of road tests showed the temp stayed solid where it normally is. It likes to stay in the 220-230 range but based on some of the changes I made listed in my original post, would that be a normal range in your opinion for a 2 row radiator? In order to go to a 3 or 4 row I would need to get the bigger top plate and also have new saddles welded to the bottom of the core support correct?

tgilligan

Hi Joe,
The sending unit for the light is the first hole directly to the right of the water neck (looking at the front of the engine). Next to that in the far right corner of the Edelbrock intake, I used that port for the capillary sensor for the mechanical gauge. I attached a pic to hopefully help. Do I have it correct?

dragline

is it possible to test the gauge on the stove in a pot of water?

RandyS

Yes, that should work. Even better if you have a thermometer (meat, etc. that you could stick in there too for reference.

olds 307 and 403

What radiator did you put in it? Copper/brass replacement? That is plenty high, you have an air pocket or a faulty sticking closed thermostat. I just had this issue, got to happy with the RTV and was blocking flow, fine at idle, up and down all over the place on the hot side along with some 240 plus temps. Test the thermostat in a boiling pot of water. The Champion 2 core with 1" tubes a good choice and will your current saddles.

tgilligan

tgilligan

oldcutlass

Cutlass and Supreme are the same.

tgilligan

oldcutlass

No problem, the single row should have still worked at speed. Where you should have had issues is long term running at idle.

tgilligan

oldcutlass

I agree. What is your timing set to, initial, total without vacuum advance, and total with vacuum advance?

tgilligan

oldcutlass

Is your vacuum advance hooked to ported or manifold. Manifold is preferred. The only other thing is if your carb is running too lean. 220-230 is too high.

tgilligan

olds 307 and 403

Yes, check with the IR Thermometer, your gauge could be off. I am a proponent of 2 core rads with 1" tube or larger cores for cooling, like the Champion I mentioned, it will fit. If it is that hot, seriously test the Thermostat, it sounds like that or a partially plugged rad. How new is the water pump? But if the impeller was corroded, it would be just as bad at idle, you would think.

tgilligan