I'm ready to install the 396 small block that Pete K built for me .
I want to avoid the strange cooling problem I had with the last engine.
I asked before in the past about this ... but I try again.
383 engine.
180 thermostat
stock new water pump (3000 miles)
stock radiator.
reprogrammed fans .
situation: Highway 70 mph or less:
The temp is in the thermostat range (around 180)
even at 30 or less speed I have the temp around 180 -190
Idleing at the traffic light on in heavy traffic.(the wrost situation):
The temp start to rise, but the fans starts too , so I can maintain
the tenp between 190- 200(max). The fans never stops, but it will never goes over 200-205
even if I stay 1 hour idleing in the heavy traffic. the temp flctuate from 190 to 205.
Sprinted drivig in Hot climate:
example a 1/4 miles simulation..:
After a pair of runs I see the temp riseing up to 220-225.
Obiouvsly the fans come on. I wait with the engine at idle expecting to see the
temp going down. I can stay even 20 min without noticing a temp decrease in the 190-200 range...
Alway 220-225....(in this situation I can't do another run..)
From this situation, the ONLY way to decrease the temp is to take a ride for 2-3 miles at 50 -
60mph, staying under 2000 rpm (so, without loading the engine).
I thank you in advance for your help and your suggestions.
-Beppe-

 

That a weird cooling problem. I would suggest getting a bigger rad. In cooling I always believed bigger is better.

 

Probably a bigger radiator can help, but it can't explaine (and cure) the weird cooling problem....having the FACT that the stock one can cool down the temp with speed and at idle when the water is not too hot..

 

could be that the chip was re-programmed with too lean a fuel mixture (the upper table is hot from the factory), and/or too much timing. this is just a guess though.

 

mmm, I managed in the chip the timing in the safe side and the fuel on upper rpm and high load in the safe side also. The 383 was new so I used this safe strategy. But even if i'm wrong... (too little fuel and too advance..-but I'm pretty sure I'm right..- ) I can't explaine why once the water temp is over 225 there is no way to cool down (the only way is to do a ride at sufficient speed...the fans are not enought).
The same fan speed is enough to cool down a 205 deg situation to 190 quite fast ...
-Beppe-

 

I have a 396 also and my temp stays at 180 in bumper to bumper ac on,my motor has heads, cam, intake full exhaust plus some others with a edelbrock waterpump, I had a new stock pump that was changed out cause I was having similar prob as you are with fluctuating temps.
In other words try changing to a hi flow waterpump and make sure your rad is clean

Alan

 

Thanks, I'm waiting an Hiflow Flowkooler water pump, and I'm removing the radiator to check it better.
the upper and the lower radiator hoses can have a role in the simphtoms described?

 

Good points. I had purchased a Flowkooler (hi-flow -- 30%) water pump as one of the many "while you're at it" items when the engine was built. Rad was clean. Just .02 if this helps.

 

I have also to add that the fans are turning in the right direction.. and the thermostat is not the culprit... I tried at least 4 differents brands/design...

 

Similar temperature situation / symptoms here (new 383 motor)......burped the cooling system a couple of times and it seems to have settled down. Last run around town saw the temps ~190 (highway and city traffic). When I came to a stop (outside my garage) and waited for the temp spike (previously it jumped to ~225-230), it didn't occur. Gotta believe that I had an air bubble trapped and it eventually worked its way to top and was relieved when I last opened the bleed **** on the thermostat housing. I'm much happier with the way the temp is cycling now. Good luck.

 

You are concerned with heat gain following 1/4 mi simulations. I do not
think what you are experiencing is unusual.

You posted before that your car has an external trans cooler, plumbed in
line after the fluid passes through the OEM in-rad cooler. In the past
you used a stock stall converter and foot-braked to preload it prior to
launch by holding RPM at 1500-1800.

You have also posted before that your '90 has the OEM engine oil-to-water
heat exchanger mounted at the oil filter pad. Coolant passes through this
and returns to the radiator. (IIUC, your car had a second, additional
aftermarket cooler adapter stacked in place that didn't appear to be hooked
up and which you were going to remove.)

You have an under-drive pulley on the crank only, slowing water circulation
at all engine speeds.

My vote is that the radiator, fan and water pump combination has sufficient
cooling capacity to cope with the BTU's generated in low load situations but
strains to cope with high load situations.

Stalling the converter prior to launches and the 4700-5100 RPM shifts heat the
trans fluid. The engine oil temp goes up. The runs heat-soak the drivetrain
and engine compartment. The underdrive pulley slows coolant flow. The external
cooler trans cooler impedes air to the radiator and increases the temperature
of the air passing to the rad.

If you increased the stall speed of the converter significantly the heat issue
may be greater now.

For corrective action, I would start by switching back to the OEM pulley and
ensure that light shines through the OEM radiator all across the fins. Then
if heat is still an issue, I recommend running the in-car heater, cool down
runs after passes, raising the hood while stopped. If you want to spend money,
my vote is to spend it on a DeWitt radiator.

I had trouble with temperatures climbing at idle and remaining higher than desired
after runs of 100-110 seconds. Each run was followed by short periods at 20-40 MPH
but then I had to pull into line behind rear-engined cars. Essentially stock 5.7L,
195º t-stat, lower engagement fan switch, 50:50 distilled/glycol, Water Wetter,
March Power & Amp pulleys and the OEM '89 water pump. A DeWitt radiator ended
the temperature issues.

.

 

i agree, i had the exact same symptoms with the 406 in my vet. i by passed all the non sense and got a de witts radiator. problem is gone.
it sounds like you are ready for a radiator upgrade.

 

Thank you,Slalom4me. You are always so good to focus the problems.. Thank you.
It seems you have the story of my car better than me ...ALL True.
You let me think to a thing I never take i account... the underdrive pulley.
With a stock WP i have at least 10% less flow....
I have in order a FlowKooler WP that is advertised to double the flow at idle and about 30% over stock above 3500 rpm.
About the external trans cooler... I don't think it can remove so much area from the radiator. I see fellow members with very bigger Trans radiator without problems. I was thinking to buy one bigger to be more with peace of mind with my new Pete K trans with a 9.5" 3000 stall converter...
Do you think there is a significant heat exchange from the hot trans fluid to the water thru the OEM in-rad cooler?
So, It is better to bypass the OEM in-rad cooler before to go in the external one?
I'm thinking also to remove the A/C radiator (just in front of the water radiator..) Do you think it is good? This should expose more area to the airflow...

Thanks again to all who responded to these questions.

I'll check also the the conditions of the stock radiator... i can afford a new dewitts radiator now.
If i see that i continue to have cooling problems ...the new radiator will be my next step.
-Beppe-