61 270hp cooling problem

[Joe S.]

I am new to NCRS. I just got my 61 270hp solid lifter car drivable. It is a fresh 283 bored 20 over with a Howard 097 equivalent cam and an original dual point full cent. distributor with and electronic ignition conversion and high output coil (Petronex). It has a new 180 thermostat, new hoses, and a fresh DeWitt Direct Fit radiator. The fan and shroud are original, but I have replaced the fan clutch with an after market version that kicks in at about 170, per the manufacturer, in an attempt to solve the problem. No help. The water pump was rebuilt a long time ago and stored until needed. The radiator cap is new. Timing is about 13 degrees BTDC at 800 RPM. I have driven it about 20 miles in short bursts in cool but not cold weather. As long as you are moving it runs at the center of the gauge (180). As soon as there are traffic lights or a series of stop signs the gauge starts to climb and will get to the 210-220 range. Yesterday, I pulled into the garage with the temp gauge reading near 220 and when I opened the hood I could hear boiling sounds. I assumed that it was the expansion tank, but found that it was the gas in the front WCFB and gas was busily percing into the front carb. Any suggestion would be appreciated.

[Joe L.]

Re: 61 270hp cooling problem

I am new to NCRS. I just got my 61 270hp solid lifter car drivable. It is a fresh 283 bored 20 over with a Howard 097 equivalent cam and an original dual point full cent. distributor with and electronic ignition conversion and high output coil (Petronex). It has a new 180 thermostat, new hoses, and a fresh DeWitt Direct Fit radiator. The fan and shroud are original, but I have replaced the fan clutch with an after market version that kicks in at about 170, per the manufacturer, in an attempt to solve the problem. No help. The water pump was rebuilt a long time ago and stored until needed. The radiator cap is new. Timing is about 13 degrees BTDC at 800 RPM. I have driven it about 20 miles in short bursts in cool but not cold weather. As long as you are moving it runs at the center of the gauge (180). As soon as there are traffic lights or a series of stop signs the gauge starts to climb and will get to the 210-220 range. Yesterday, I pulled into the garage with the temp gauge reading near 220 and when I opened the hood I could hear boiling sounds. I assumed that it was the expansion tank, but found that it was the gas in the front WCFB and gas was busily percing into the front carb. Any suggestion would be appreciated.

Joe-------


A problem such as you describe is almost always the result of a fan clutch not performing as it should. I realize that you have a new aftermarket clutch but I have found some aftermarket clutches to be "wanting". Another problem is that your original distributor does not have vacuum advance so running hotter might be normal. I hope that others that have personal experience with this particular engine can chime in on this..

[Mike M.]

Re: 61 270hp cooling problem

is the temp sending unit an AC or generic. generics typically give a higher reading than actual. Put an IR gun on upper radiator hose and compare its temp with what the gauge is indicating. mike mccagh

[Keith R.]

Re: 61 270hp cooling problem

I had a similar problem which was solved by going to a clutch fan vs. a fixed fan. Was the block flushed out during the rebuild? Had mine flushed out as part of the troubleshooting and a ton of orange crap came out of the block. Removed right freeze plug to do this. Maybe you have air in the radiator?

[Mark E.]

Re: 61 270hp cooling problem

Joe is onto something. If she only heats up at slow speeds, look into why airflow may be lacking in this mode. This would include a bad clutch, missing shroud, missing seals around the radiator or shroud, wrong fan. A radiator that's marginal or partially blocked is also a possibility but you say she has a new one.

[Terry D.]

Re: 61 270hp cooling problem

Too much timing can cause this problem also. Does the fan fit halfway into the shroud?

[Frank D.]

Re: 61 270hp cooling problem

I drove your same setup in my 61 in Orlando summer heat with no issues after some work..for 10 years.
You have two problems it seems: a) low speed overtemp, and, b) fuel perc...

I did add a vacuum advance to my car, an entire, Petronix II billet distributor with an Accel adjustable vacuum advance and ran the timing at an advance 12* BTDC at about 750 RPM curb idle. First thing you should do is deal with the fan clutch and
ensure its working. The #1 restorer of fan clutces states after shutting the engin off after a hot period of idling the fan should not move more than 1/2 turn when spun by hand if the clutch is good.

However, I eliminated my fan clutch completely with a spacer so I would get 100%, full-time air flow.

Next is to plug the sloppy fit of the 61 fan shroud...you should get some closed cell foam insulation and stuff it down both sides of the radiator and put a piece along the horizontal upper gap (see picture). The 61 should also have rubber seals at both front corners of the radiator and a
horizontal rubber seal along the lower front. These features will help greatly with low speed air flow.

Deal with these issues and if your cooling problem is mitigated then see if you still have fuel perc and we can deal with that..
I have several mods that attack that particular problem on these solid-lifter, dual quad motors.

One cheap & quick perc fix can be to add 1/4" phenolic spacers under both carbs - no larger or the hood won't close.
I fabricated my own from McMaster's stock but now a gent sells them in a kit (you'll need two) and life is easier:

https://www.dashman.net/product.html?id=349

[Joe S.]

Re: 61 270hp cooling problem

Its an AC and when moving it reads 180 which is the thermostat.

[Frank D.]

Re: 61 270hp cooling problem

Its an AC and when moving it reads 180 which is the thermostat.

Someone added AC ? Vintage Air ? With a condensor in front of the radiator ?

[Joe S.]

Re: 61 270hp cooling problem

Frank:
Thanks for the thoughts. I will check the new fan clutch next time I have it hot. I will say that it leaves the fan about 3/16 inch closer to the engine than the original. Not sure that is enough to make a difference. As luck would have it, I stumbled across Dashman yesterday and ordered two spacers. I also spoke to those folks and got some other ideas. He suggested that in the end, I may have to plug the exhaust passage in the manifold to control the carb heat problem, but the spacers may help enough. As for the temperature he suggested that the idle screws may be too lean. He has seen that before and said it is amazing what a quarter turn or so may do. He also said that fuel pressure needs to be checked. As for the foam trick, I had the same thought yesterday when I was staring into the engine compartment. It dawned on me that when I replaced the radiator in my 79, I bought a new seal kit at the same time. In those years they blocked up every gap. I have the corner and bottom seals on the core support, but I was thinking about exactly what your pictures show. There is plenty of places for air to be drawn by the fan other than through the radiator. Stay tuned.

[Joe S.]

Re: 61 270hp cooling problem

Thanks Keith:

The block was, per the machine shop, thoroughly flushed during the rebuild. It came back with all new freeze plugs so at least it was opened up. The block was one I acquired over the years and had only about 1500 miles on it. I have partially drained the system a couple of times and there was never anything untoward in the radiator. It has a clutch fan with a new 170 degree clutch. I did find some air in the system and I think I finally got it out. The top hose now has fluid in it when it is cold.

[Frank D.]

[Joe S.]

Re: 61 270hp cooling problem

Up date on the 61 270hp cooling issue. First, thanks to everyone who forwarded suggestions. I had it out for a run yesterday. It was about 60 degrees. I had blocked many of the gaps that might allow air to bypass the radiator including installing the side seals which, per the judging manual, were only used on the high HP 62's. Paragon lists them for 58-62 high perf. Since there were no mounting holes in the core support, I got creative with some double sided carpet tape. I also used some left over weather seal and pipe insulation in a few places. I had also richened the idle mixture just a little. After it warmed up, it took three or four miles to get to 180, it still crept up at an idle but for the most part stayed under 200. It was a little warmer than that after sitting turned off for several minutes and then restarted. Not s surprise. So it is better, but not great. At this point, I think the thing to do is richen the idle mixture a little more and not sure what to do about my new fan clutch. It doesn't seem much different warm or cold. Perhaps it is also time to get an IR gun and see where it really is. The sending unit is an AC but one I bought at Carlisle. At he lower running temp, I didn't have near the problem with the carbs boiling. That was a relief. I will still install the carb insulators that I got from Dash Manufacturing and see what that does. Any other thoughts would be appreciated.

[David M.]

Re: 61 270hp cooling problem

My expertise is 64-65 to 82. But general knowledge suggests 200*F is pretty good. But consider 60*F ambient. What will happen when ambient is 90*F with 75% RH?

First verify the temps you are seeing are valid.

Can you feel good flow when gripping the upper hose and throttling the engine? Do the hoses get hard once up to PSI/Temp? If no the caps not holding pressure.

Additional measures may be needed.
Counterintuitively try a 190/195*F HD Stant T-Stat.

Block off the integral exhaust heat crossover in the intake. I like to weld a plug into the intake vs the heads. Then remove the choke stove flap valve in the exhaust manifold. Leave the shaft and spring in if OEM look is important. If not weld up the holes. This will emanate 99% of any heat soak related problems. Choke tweaks/modifications will be required and it will be cold blooded. This is on my top 5 best modifications list...Runs much better without the additional exhaust heat.

Make sure the needle(s)/seat(s) are shutting off the gas when the float is at "level". There's a test for this. With todays gas it doesn't hurt to set the level a 32nd or two low.

[Keith R.]

Re: 61 270hp cooling problem

I hate to suggest this as it is a rather scary thought but you might check for bubbles in the coolant with the cap off as it might suggest a blown head gasket.

https://tinyurl.com/combustiongastester

I tested mine fearing a blown head gasket or cracked or warped heads and thank goodness, the fluid stayed blue! It is also a negative reading when you squeeze the bulb and you can't get it to expand.