Hey guys. I was wondering if anyone could help with this on my rod. All temps are taken via Mech. gauge connected at the heater hose fitting right next to the T-stat.

I think I need more capacity but I really don't want to get a bigger radiator because my car has a custom build radiator 3 pass and it would be very expensive to get another radiator built. I think it holds about 2.5 gallons or so. I am quite sure if I got a 4 pass brass radiator it would do it.

Here is the issue. I can be driving around town w/ stop and go(30 mins or so) in 85 deg. F temps and it stays pretty normal but when I go up a steep hill for about 1 mile or so the temp rises like you would expect going up a hill. About to 207-218 at the intake near the t-stat housing.

After the hill I will be driving around normally and it can't seem to shake the 215 and it might even climb a little to 220 or so. It just won't return to 190 like it did before going up the hill. It just can't get rid of the heat after the hill. Remember these temps are at the intake right by the Tstat (heater hose fitting removed and mech gauge plumbed in) Not sure about the temps at the head. The other day is was 89 Deg F. sunny and after shutting off I did hear the radiator cap let out a little coolant in the overflow tank (non pressurized) and it sucked it back in this morning.

Car runs great. It is a 350 SBC, stock w/ 400 auto trans.. I sometimes run a tstat and sometimes don't. It doesn't matter either way. I have a fan off the water pump that runs all of the time. Have a very large and good fitting fan shroud. All fins are clean on radiator and condenser.
I do notice that my plugs look a little lean so I might richen the mixture. Would that help? I am running almost 100% water right now and corrosion inhibitor. A/C is not on during any of this. I never use it. I put an electric pusher on but it didn't help. I really feel it is a capacty issue. Never uses any coolant etc.


Is there anything I can add that would increase my coolant capacity or anything I can do so it will cool down after the hills? I know a larger radiator will fix it but it is too costly.

Any other ideas? , richening the mixture to a good toasty brown? Retard the timing? Any info would be appreciated.