I have a 63 valiant with a 225 that I had rebuilt last year to pretty much stock specs. I left the stock 1920 carb on it, pertronix, and the stock belt drive fan. I put a rebuilt water pump in last year with the engine install.

My engine is running fine, but it seems to run too hot on long trips at freeway speed. The needle climbs to around 3 o clock and even got to the H one time so I had to pull over and nurse it home. It seems to do ok around town, though still runs hotter than I remember it running before the rebuild. I took out the thermostat the day it over heated to see if I could get it home easier, but it still ran hot.

Here's what I've learned from reading posts so far:

Could be clogged water jacket or radiator passages common after rebuilds

Improper thermostat heat range, or air locked around thermostat, unlikely because I removed it.

Engine could be running lean (or is it rich), running 55 main jet

There is a pressure leak in the system ( I suspect the manifold studs bolt holes because they were oozing a bit when it overheated)

Which of these would you start with, and can I rule any of them out based on my specific symptoms?

Thanks,
Dave

How old is the lower coolent hose? If its old, it can collapse at higher engine rpm's, causing the pump to cavatate and not move coolent through. Easy to check: Start engine, rev it up, watch the lower hose. If it gets deformed, there is your problem.

Bet it's the radiator getting little bits of crud from the engine after rebuild, look in the filler see if the cores have stuff in them

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Part of Tyrde-Browne Racing

I agree.. had this happen to me on 2 different radiators... same problems you have.

~THOR~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

Well let's see!
Yes, it could be the radiator.
Yes, it could be the lower hose
It could also be the Thermostat, it might be stuck open. It may also be too low in temperature. Some people put a 160 thermostate in their car thinking it will run cooler, if your radiator is pretty old and plugged up a biit, that is true. But if the radiator and hoses belong to a well maintained Slanty. Too cold, opens too much and the coolant does not stay in the radiator long enough to BE COOLED enough.

I had a custom radiator made for my wagon because it has A/C and an Automatic, this radiator had an extra row and an over-sized tranny cooler. It ran hot with a 160, it ran well with a 180, but a 190 made it run better, warm me better on the cold days and it gets better fuel mileage. Andf the temperature does not vary greatly. It climbs to a given level and stays there. I am talking about with a stock gage in a 1964.

If the springs are worn out in the distributor and you set the timing to stock it won't advance enough. Retarded timing ALWAYS makes for a hot engine on the freeway. Advance the timing until you get a little Pinging under acceleration. Then back-off until it doesn't ping anymore. THEN chack your timing with a timing light, if your BTDC shows beyond 12 degrees, your distributor is worn out.

BTW. I put the finishing touches on an HHO system three weeks ago. Two banks of thirty three plates. One bank comes on with the key, the other when you shift into gear. I read a post, some time back, that said, 'No matter what you do to a Slanty. You'll NEVER break 30 MPGs.' Well guess what. I drive using a cruise control and I set it on 70 MPH when commuting. Total Commute trip is 194 miles a day. I averaged 33.62 MPG on the first tank full. The sngine is quieter and smoother going down the freeway. I changed the oil after 1000 miles because I knew the HHO would steam clean the chambers. I switched to Royal Purple Synthetic Oil 10W-50. (I figured I could afford it after saving so much on fuel.) Well guess what. the next tank went to 34.28 MPGs. And the next one hit 35.22. At this rate, I can see myself getting a Gear Vendors Over-drive installed. My 64 Valiant now gets better fuel economy than my Chevy S10. Next I plan to tackle the S10s, 4.3 Bent Six. I'm thinking three stages. One turns on with the key, one with the tranny, and a third with the cruise-control. I thought these things did not work. For every site that says they do there's two that say they don't. But on the Slanty we have one huge benefit. The Slanty uses a CARBURATOR. In order to do the same thing on my S10, I had to purchase an sdjuster that lowers the voltage at the Oxygen Sensor, if you don't, the sensor 'reads' the 'O' part of the HHO and turns up the fuel and you, in fact, get WORSE MPGs. I think I'm really on to something here!

The 55 jet is leaner than most, but if you aren't getting a lean surge when cruising, then leave it alone. I'd place my money on the rad. Fortunately, there are enough salvage yards around with cars that have rads that will "fit" into an A-body, you could probably replace the one you have fairly cheaply... just for tests of course.

The nice thing about a Slant, is that they really don't take much to cool. What thermostat are you running? There is validity to SPHERT!'s hypothesis in that if you are running too cool a thermostat, that it may cause problems, however, again referring to SPHERT!'s reply, that vehicle had an oversized radiator, which I am assuming you don't have. A factory one is fine for pretty much all situations excluding the juiced up non street driven ones.

In my experience, the older radiators like what you've got tend to get plugged up a bit even if the car was kept in amazing shape. Fact of life there. A later style radiator will bolt in (it may not line up correctly on the bottom hose, so you will need to improvise there) and provide you with a longer period of usable time since they are made of a different material.

I also assume that since you had the motor rebuilt recently, you also had the dizzy done. In which case, unless you are achieving cruddy mileage, I doubt your dizzy has much to do with it.

Good luck!

~THOR~

_________________
1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

Take a look through this post for a description of things to check when you're experiencing high-speed/highway overheating.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

After I put the 2bbl on my car it "overheated" and stalled on a 98 degree day. I looked at the temp gauge I had and it was well over 215 degrees. I put a 180 degree thermostat in and it runs about 195 on a hot day, and about 185 on a cold morning like 35 degrees (yes we have temps that low here in korntucky)

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'74 Duster 225 Super Six w/904
14" Cragar SS wheels