340 running hot (long)

ok finally got the demon back together and running broke in cam and noticed it was getting a bit warmer tha i liked but between the big fan and playing with the timing we got through it. took it to get aligned (rebuilt front end and detailed while out)and then tried to get it dialed in .re-worked distributor am running 20 degree initial and about 35 total stock 70 intake and stock cast iron manifolds built back to stock specs with comp 274h cam as only major up grade over stock now it runs hot before i rebuilt it it barley would hit 160 (when i took it apart it had no thermostat in it)now sitting and idleing runs about 190 running down road it gets up to 210 or so and when idling up the gravel stretch to house it keeps climbing has a freshly recored stock 3 row radiator (has factory air but not working yet) it was full of rust so was block when i took it apart didnt think i would have a problem after every thing was cleaned up the only things that are diffrent than before is intake had spread bore and fan had a 7 blade direct drive put a 7 blade clutch type on instead any help will be greatly appreciated this car is about to get me down thanks in advance ozz

I have a very similar setup with my 340 Demon and it is so hot I can hardly work on it after a cruise. I removed the headers, still hot. Ironically, it doesn't overheat. I took the thermostat out, nothing changed. If someone told me a pure stock 340 wouldn't be so hot, I would trade engines.

mine was great before now not so...ozz

Shot in the dark here, but what pound is the radiator cap?

do you have a new fan clutch? a shroud? what t-stat?

15lb cap. stock shroud and a tight feeling stock fan clutch 180 degree stat if i have time today im going to swap out fan setup for the direct drive to see if that helps ozz

General rule of thumb:

If it runs too hot <40 MPH, look at the fan/shroud.

>40 MPH, look elsewhere. Frequently missed: hood-to-yoke seals, lower air panels, etc.

Actual temp isn't really critical as long as it doesn't boil. Once that happens, you're dead meat - zero cooling.

Rick

im having the same problem with my stroked 340. granted its warm out but it runs at 190 while cruzing, and easily goes up to 210 when stopped at a light. i didnt put a thermostat in it tho. thats the first thing im gonna try. im a little worried that the thermostat might restrict too much tho. so if it still runs hot with it, i think i will leave it in there but take the middle out of it. please keep us posted if u fix the problem and what u did. i will do the same!

p.s. i am running an electric fan with no thermostat on it (direct to the key) and a 3 pass rad

I will agree but restate
Idle/low speed heating is typically fan related. Be aware that Electric fans are ususally overated cfm wise and the performance of the fan is usually directly porportional to the price of it.
If it's getting warm above 30 to 40 MPH you have other issues as the fan should be out of the picture unless it is postioned as such that it is blocking the air flow.
I usually start with a digital thermocouple guage and probe inserted into the coolant as close to the thermostat as possible. This allows me to see exactly what is going on. I do not rely on infared meters as they can be inaccurate.
I have seen brand new gauges etc be off by as much as 50 degrees for various reasons
As previously mentioned if it's getting warm at low speed/idle and OK going down the road look at the fan
If it's getting warm going down the road
Make sure the lower hose is not collapsing,
Make sure your pulley ratios are correct,
Make sure the belt isn't slipping

Check for restrictions to the air flow

Check for air flow escaping by going around rather than through the radiator

Long shot but I have seen loose impellers on the water pump

make sure there are no vacuum leaks and that the motor is not running lean,
Timing being to far advanced at low speed or at higher speeds

block check the motor to make sure there is no internal issues

If all of the above checks out then it may be time to start looking at the radiator itself

Did you mean to say the radiator was cleaned up as well as the engine?

That was my problem. The new high flow water pump shoved all the good out of the engine and the radiator filtered the coolant for me. I took the radiator to get cleaned and it was more than 75% blocked.

Quote:

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make sure there are no vacuum leaks and that the motor is not running lean,
issues

If all of the above checks out then it may be time to start looking at the radiator itself

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Richen it up, I'm sure it will help. Clutches on the fan go bad all the time. It will run hot when that happens, been there, done it more than once.