[thehornworks]

Just finished my car and found it was getting too hot. Who wants to play lets guess what the problem was? Car: 1970 454 ls6. Fresh engine, broke in on dyno. Gm 4core recored with stock core. Stock rebuilt water pump, 50-50% water /anti. stock pulleys . New gm clutch on a 064 (772) 7 blade fan. 180 mister gasket high flow thermo. After car warms up just idleing for 20 mins the temp is 220 deg. I drive it on highway 5 or 6 miles @50-60 mpg at it rises to 230 deg. lets play. gary

 

[pnugene]

You didn't mention the shroud. It certainly needs one.

 

[thehornworks]

Yes has factory schroud. Car is fixed, thought I would let you guys guess what the problem was. (Hint) not the temp guage . gary

 

[herb396SS]

Bad thermostat ?

 

[mrfuzzy]

bad fan clutch??

 

[bbmusclecars427]

Colasping lower radiator hose?

 

[Ark68SS]

If you're getting 50~60 mpg I'd say the carb's a little lean.
BillL

 

[71 chevlle]

I drive it on highway 5 or 6 miles @50-60 mpg at it rises to 230 deg. lets play. gary[/QUOTE]
@50- 60 mpg is the bigger issue let me know how you did it and I'll gladly invest in the technology.We'll make big $$$:yes:.
Timing is my guess.

 

[Dean]

Bad temp sending unit?

 

[INTMD8]

Well if temps increase at highway speed when there is more airflow it sounds like a water flow issue (unless the fan blade can be flipped and was pushing air instead of pulling it)

 

[mr]

stock GM 4-core radiator .....

 

[osdmike]

Temp should drop, when driving it on highway,even without schroud.
Blown head gasket?!


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[thehornworks]

I Always thought that if temp increases on the hwy that it was a water flow or capacity problem. I made one change at a time so that I can be sure of the solution. I first checked the thermo in a pan of water. It was perfect, wide open at 180. Next I drained the coolant and replaced it with distilled water and a water wetter. Same. Next I changed the engine oil to synthetic. It was time to get the break in oil out. The local race shop said I could get 5 degrees lower out of each. I got 5 deg total. Good water flow could be seen in the radiator when I revved the engine. I noticed earlier that the clutch fan did not get much tighter when hot but I discounted this as the problem because the temperature Increased on the highway. I got an 80's style truck fan clutch from my GM dealer. That was it. The solution was the fan clutch. The first one in question is a new GM replacement "JA" stamped. The truck replacement looks a little different but is much tighter. Part #88961767. I have never seen this before and neither had my friends, some 50 years combined around these cars. I decided that the looser clutch was allowing the fan to slow down and actually block the air flow through the radiator. 7 blade fans in a shroud can block things. Thanks for playing, your comments. gary

 

[forcd ind]

what did the temp drop to, 180-does it still climb on the hwy-i have seen the clutches to loose at idle cause a problem, but usually on the road it should cool down w/o a fan, but in some cases it could use the extra pull from the fan, esp a cast iron headed B/B
good job being meth. in solving the problem

 

[thehornworks]

Yes, It says at 180 no mater what. go figure.

 

[71 chevlle]

I decided that the looser clutch was allowing the fan to slow down and actually block the air flow through the radiator. 7 blade fans in a shroud can block things. Thanks for playing, your comments. gary[/QUOTE]
Just for curiosity do you have a five or six bladed fan handy? If so put the questionable fan clutch back on with the five or six blade fan.My thoughts would be with the fan was the issue not the clutch.Like you said seven blades can block things.

 

[mr]

....... stock GM 4-core radiator .....

When I finished my engine, I also found, it was running too hot .....

Car body: 1970 Chevelle SS454.
Fresh .030 454 low-compression engine.
Older replacement, brass 4-core radiator.
Rebuilt O'Reilly water pump.
50% Prestone antifreeze & distilled water.
Stock GM pulleys.
Rebuilt O'Reilly clutch on a GM#772 (7 blade fan).
180* Be Cool high flow thermostat.
Stock fan shroud.
Factory tempeture gauge and sending unit.
New Gates radiator hoses, upper & lower hose w/spring.


With the car just idling for 10-15 mins on a cool day, the temp would rise to 200*+, on the highway w/less than 10 miles of highway driving @ 35-55 mph, temp would keep rising to at least 230*+.

I tried several different timing combo's, thermostats, fan clutch's, and antifreeze/water combo's ....

Since my friends suspected the radiator was a problem from the start, (I tried the, cheap route first) I figured the only things left to replace were, the radiator and water pump ....

Even though I don't run a bypass hose, a couple of drilled holes in the thermostat, a HD transmission cooler, 70% Prestone antifreeze probably did'nt hurt, and I suspect the attention to timing helped some also, but when I noticed a big tempeture drop, was when I installed a brand new "Alumitech brand" aluminum radiator, (now the car normally/usually operates less than @180* on hot 90 degree+ July-August days) ....

If the radiator had'nt solved my problem, I was going to try a Stewart hi-flow water pump ...... my 2 cents.

 

[mr 4 speed]

My 454 runs at 185* with a 3 core replacement radiator and a 7 blade clutch fan.
A few weeks back,it started creeping up to 215* or so at low speeds (it was fine on the highway)
turns out the clutch went bad...replaced it and all was good again.

 

[03cts sport]

Pardon my ignorance, but what is the benefit of the clutch fan vs the standard fan. I assume that it helps the engine to heat up quicker, but doesn't the thermostat accomplish the same thing?...

 

[hobbiesracer]

Thehornworks, if I could reach through my computer, I'd kiss you man! I've had the exact same problem since I rebuilt my 396 in my 70 SS Chevelle 4spd, a/c car 2 summers ago. I would run at 215-220 on the highway. I rebuilt the original water pump, recored the original rad, new hoses, thermostats, fan shroud, new GM clutch fan etc... In fact, I have not driven the car in the last 7 weeks because I'm so turned off of it. With Swheaton I got the temp down to 212-215 because I had the timing too retarded. When you mentioned you had a new clutch fan with a "JA" code on it, I went out to check mine and sure enough, mine has the "JA" code on it also. Yesterday I went out and ordered the same GM clutch fan you decided to install, and holy crap, my temp is now down to 195, no matter where I drive. I drove it to work(45 miles away) and kept it at 65mph and it never moved from 195. And driving around town its runs a little cooler. It was finally a pleasure to drive my car. Thanks for eveyones help.

Richard