How hot is too hot?
 

So, I've got less than 500 miles on my freshly rebuilt 59A-B flathead. .040 over, Merc 4" stroke crank, Isky Max-1, dual Stromberg 97s w/.041 jets, 180 thermostats, shrouded electric fan with 185 switch, 4# cap, dipped radiator. Before yesterday, it had been staying around that 185 mark, even in hot weather at highway speeds (65 MPH/1,580 RPM). Yesterday though, it was about 90 and I was cruising along at 70 or so and 1,680-1,700 RPM and it started to get hot . . . 206-207. I pulled off the highway, and it immediately dropped down. I got back on the highway, and cruised at about 65, and it went back to the 185 range. My question is, should I be concerned at 206-207? If not, what's the temp I should be concerned at?

Re: How hot is too hot?
 

I had a similar problem in an O/T engine I had rebuilt. The engine would overheat any time I let it sit and idle for any period of time. I was just getting ready to pull it and tear it down, but after about 800 miles, the problem went away. I can only figure the engine was built "tight", and with enough miles loosened up. Since your engine only overheats sporadically (and 206-207 ain't that hot), I'd give it a few more miles. The '51 Mercury in my '51 Ford runs consistently at about 180 (the thermostats) just about all the time. However, extended periods on the interstate at 70 and over pushes the temperature to 190.

Re: How hot is too hot?
 

As long as it's not boiling over you should be ok.

Re: How hot is too hot?
 

Heating problems aside and out of curiosity, just what transmission, differential and tire combination are you using to achieve (65 MPH/1,580 RPM)?

Re: How hot is too hot?
 

Trying to help. Water at sea level boils at 212, add 4 pounds of pressure, and at 3 degrees increase of boiling point for each pound of pressure, you get boil at 224. Eyhylene Glycol 50/50 changes these numbers up a little bit. Boiling makes pockets where there is no water contact with the metal among other issues.

I roll as JSeery suggests, if coolant is not coming out, it's not too hot. But I run much more stock stuff that the OP's rig.

Re: How hot is too hot?
 

Short answer= 230° is too hot.
If you are cruising at 65 mph and can't stay below 210° something is wrong with your heat exchange. Most old cars have the opposite problem. Good temps at speed and heat up when stopped.

Re: How hot is too hot?
 

Sounds off by 1000 rpm for normal gearing and tire diameter.
And .091 jets in a 97 carb is way rich. Something off there too.

Re: How hot is too hot?
 

What kind of capacity are you running as far as water volume?


My engine with Mitchell a 36z5 over od does at least 2 plus k at 70. cruising rpm.

Re: How hot is too hot?
 

T-5 trans., 2.73-geared Ford 8.8, 235/65R16 tires. Thinking I may need to change to a 3.08 to get it more in the engine's power band on the highway.

Re: How hot is too hot?
 

Typo on jet size. Should have said .041.

Re: How hot is too hot?
 

Thanks for all the replies. I'll just keep an eye on it. Trying to keep the RPMs varied as I break in the motor.

Re: How hot is too hot?
 

Sounds like a great and much coveted setup. The 3.08 should kick up the RPM by a few hundred.

Re: How hot is too hot?
 

Some .043's or .044's would absolutely cool it down.

Re: How hot is too hot?
 

I agree with Uncle Max - you are probably too lean on the jets - try .043 to .045s.

Also, you are correct on the rear-end ratio issue - you are nowhere near the RPM that you need to be - not enough torque to pull your final gear ratio.

Do your calculations (tire size, OD ratio, etc) - and get to at least 2200 RPM at 70 . . . I'd go a bit more 2300 - 2400. Right now, you're lugging the engine - which also isn't good for temperatures or anything else.

Re: How hot is too hot?
 

i'm running about 2300 rpm at 70 mph. Get around 20 mpg on the highway.

Re: How hot is too hot?
 

Assuming 27" rear tires, the RPM calculator says that Ritzy1 should be turning about 2378rpm at 70 in 4th gear (1:1 ratio). That would be an option to check the operation and temperature at normal RPMs.

Re: How hot is too hot?
 

70 at 1700 rpm. What rear end do you have? Overdrive?

Re: How hot is too hot?
 

See post #9 above--
"T-5 trans., 2.73-geared Ford 8.8, 235/65R16 tires."

Re: How hot is too hot?
 

So the motor is loaded up and lugging?

Re: How hot is too hot?
 

I have been fighting overheat at interstate speeds. Have 3 97's on progressive, all with .045 jets. Went to .048 on the center carb and that dropped cruise temp by about 10 degrees. At that speed, the secondaries are open, so they are getting .048 jets as well.