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Overheating 383

Tonyraca

Tonyraca

Registered Member
Joined
Sep 28, 2000
Posts
93
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Location
San Jose, CA
I just got my SB350 stroked to 383 with:
- Edelbrock Performer intake, heads, and Carb
- MSD 6AL ignition
- GMPP Serpentine Kit (new alternator, water pump, AC Comp)
- New Stock radiator (3 row I think)
- Flex a Lite Electric fan
- 180 Thermostat

Right now I am having an issue where when the engine warms up, I can feel the coolant go through the return hose when the temp hits 180 then I have the electric fan turn on. The temp goes up to about 190-200. When I rev the engine up to 1000rpm the temp goes down to 180 but when I let it go back down to idle (600 rpm) the temp goes back up. When I start driving the temp stays about 180 but when I stop at a light the temp goes up real quick to 220-250. If I put it in neutral and rev the engine the temp goes back down. I am thinking that I need a higher flow water pump, but is there anything else that could be wrong? I have my advance set at about 10.5 degrees. It is supposed to be at 8, but I don't have as much power there.

Any ideas?
 
I am using an electric fan so I don't have a fan clutch. Even if I have the fan on continuously I have the same issue.
 
Fan isn't correct size or operation, and/or your radiator is too small.

I'd lean towards the fan since the problem only happens at idle. What CFM is it rated at?
 
The electic fan is probably the culprit. They generally don't move near as much air as the mechanical one did.

Do you have a mechanical (clutch or straight drive) fan to try (make sure you have a shroud too). I would be that is your problem.

If you are really stuck on an electric fan, adding a pusher fan in front of the radiator will help.
 
Check your battery voltage with the engine idling and the fan is on, if it's below 13.0 volts then try a bigger alternator or turn the idle up to 750 or 800 and see what that does.

The water pump could be questionable. I've seen new water pumps with a lot of runout or excessive airgap between the body and the blade which will cause the pump to cavitate or let water bypass the blade especially at lower speeds.

Check or replace the radiator cap and make sure it's at least a 13 PSI or preferably a 16 PSI.
 
295fan.jpg

This is the fan that I am using it has an integrated shroud.
dual 13.5" fans, 2760-4600 CFM

But if the radiator was too small or the fan wasn't working why does reving the engine while standing still make the engine cooler?
 
Moving fluid faster through the radiator will cool better (with no load on the engine) and if it's a voltage issue, may bring the system voltage up more to increase fan effectiveness.

4600 seems to be on the low end of the spectrum for cooling, is that 2760 based on a variable speed switch I assume? And in yoru case, you are running it at max?
 
You sure you have the correct rotation water pump? Serpentine water pumps spin backwards from v-belt water pumps. You say you got a kit, but I'm not familiar if it comes with a water pump or not. Also, could be that there was a mix up and you got the wrong pump.

Seems like everything else is in order, that's why I ask.
 
I got the GM Performance Serpentine conversion kit which came with a new water pump. I believe that it is reverse rotation. If I was going to get a new water pump what kind would I have to get a reverse rotation pump?
 
which block are you using? if it is a vortec block, you need a bypass hose that goes from the water pump to the intake.
 
Tonyraca said:
I just got my SB350 stroked to 383 with:
- Edelbrock Performer intake, heads, and Carb
- MSD 6AL ignition
- GMPP Serpentine Kit (new alternator, water pump, AC Comp)
- New Stock radiator (3 row I think)
- Flex a Lite Electric fan
- 180 Thermostat

Right now I am having an issue where when the engine warms up, I can feel the coolant go through the return hose when the temp hits 180 then I have the electric fan turn on. The temp goes up to about 190-200. When I rev the engine up to 1000rpm the temp goes down to 180 but when I let it go back down to idle (600 rpm) the temp goes back up. When I start driving the temp stays about 180 but when I stop at a light the temp goes up real quick to 220-250. If I put it in neutral and rev the engine the temp goes back down. I am thinking that I need a higher flow water pump, but is there anything else that could be wrong? I have my advance set at about 10.5 degrees. It is supposed to be at 8, but I don't have as much power there.

Any ideas?
Click to expand...

if I may ask a dumb question..when you filled the radiator, did you leave the cap off and idle it until the t-stat opened, then refilled?

air bubbles don't help..
 
I left the cap off and saw the coolant level rise, but i don't remember seeing it go back down again. I will give it a try tonight.

Do air pockets in the engine/radiator cause overheating? If so, how do you prevent them from happening?
 
Tonyraca said:
I left the cap off and saw the coolant level rise, but i don't remember seeing it go back down again. I will give it a try tonight.

Do air pockets in the engine/radiator cause overheating? If so, how do you prevent them from happening?
Click to expand...

Air pockets will definitely cause overheating. In general, SBC's bleed themselves pretty well but 4by4bygod's method is generally accepted too.

I don't think I've ever bothered to try and bleed the cooling system. They have all bled themselves, IME :dunno:
 
Tonyraca said:
I left the cap off and saw the coolant level rise, but i don't remember seeing it go back down again. I will give it a try tonight.

Do air pockets in the engine/radiator cause overheating? If so, how do you prevent them from happening?
Click to expand...

when it gets to operating temp and the t-stat opens, just let the coolant rise, and if it splashes out a little, that's fine.. when it goes back down again, just watch it for a bit, and leave it run.. drink a beer while you watch..then top off, and put the cap on before you shut it down..

this is about the only method I know of to prevent air pockets from forming, and I did this for a friend who had overheating issues after putting together a built 440 mopar.. it solved his issue.

the biggest things i've seen cause erratic temp readings and overheating are: air pockets, or not running a fan shroud..of course, I've had bad gauges too..
 
issue only at idle? Sounds like airflow to me.. mine has a very similiar issue, (but no elec fan) I fixed it with a Duramax fan :)

does your voltage drop at idle? I suspect it does and therefore you fan is not pulling nearly as many CFMs. That's my bet as to why revving it would help.

Also, when you're moving you have the air being rammed thru the radiator, so the fan doesn't have to do as much. The fan may simply just not pull enough CFMs to cool it without air movement. but that wouldn't explain why revving would help at all...:confused:
 
If none of that works go get a high flow Stewart water pump put one in my Astro van that had a 350 in it and had no coolong problems at all, there thermostats suck if you need a heater in the winter they flow too well:D
 
So I tried just removing the thermostat and now it runs cool as a cucumber (170-190 after long warm up and driving around). So I think that the primary issue I was having was that my thermostat can't flow enough coolant.
 
If the problem is the t-stat, then go for the Be Cool themostats they are nice quality and flow about as much as possible.
 
Well now you need to fix that problem. Taking out the t-stat may temporarly fix your problem, but not forever. In all the motor I have setup(including high hp motors) I have had to run atleast a restricter if not a t-stat. If you have a good working system then it can actually flow too well and cause it to overheat because it doesnt stay it the radiator long enough to cool it. I would check your radiator as well as those fans. I have never had any luck with flex-a-lite fans. I use t-bird or winstar fans.

Dan
 
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