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Hey Eric, I hope you can help. My son bought a 1990 firebird T/Am it came with a chevy 5.7 liter engine.It was fuel injected but he changed the intake & put a 4 barrel carb on it. He went & rebuilt the motor. But with one exception he didn’t have the heads or the block checked for cracks. I know not smart. Anyway he got it all together & it seems to run good. Except the temp goes up to 250 degrees after idling for about 15 to 20 mins. He has 2 electric fans that kick on at about 190 so thats working, He put in a new water pump, a new thermastat,a new radiator & heater core for they were leaking, & after i had him watch your videos a new Radiator cap as well. We did a gas check & that seems to be ok. I thought that maybe he had the gaskets on wrong so i pulled the intake manifold & the heads to make sure. They were ok. While i had it apart I sent the heads out to be checked & they’re ok as well. I also checked for air blockage but being his a/c doesn’t work he had taken out the condenser so thats all cleared as well. Do you have any sugestions in what i can look for or try to do next. I would greatly appreciate your help. Thanks Ed
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as long as you have the engine all apart go through and flush the little individual coolant passageways with water and compressed air just to be sure that there aren’t any blockages.
and it might seem dumb, but make sure you’re installing the thermostat in the right direction. I’ve actually had 2 overheating issues so far come into the shop and the problem was people installing new thermostats in their cars in the wrong direction.
Couple of thoughts if you don’t find the answer in the cooling system..
– Advanced timing may cause overheating
– Lean conditions can cause overheating
Have all computer controls been shut down? Since this was built to run EFI instead of Carb controls.
How is the fuel being sent? What is the pressure?
Best of luck…
-Karl
Since a lot of conversion work has been done give a second look at your pulley diameter and which direction the pump is turning. Check the idle speed too. Just because the fans kick on, as they should, doesn’t guarantee the engine is getting sufficient water flow.
This car has been a real match for me & quite a few other mechanics. The pulleys are all ran by a surpentine belt. The water pump runs counter clock wise. When my son started this project i wasn’t around but i’m finding out more & more of what he did & didn’t do. He changed the timing chain cover which had the timing marks behind the water pump so now i’m trying to guess where the mark might be at. I made a mark to where top dead center is at & set the timing between 4 & 6degrees before top dead center. But not does it get to about 240-250 on the temp it pings like anything as well. I know hw put a cam in it but i have a feeling its in the heads. So i think i’m gonna end up pulling it all apart again & go with a different set of heads.He has a electric fuel pump on it which was putting out about 45 psi. I put on a regulator to lower it down to about 4 psi. I also noticed that when i turn in the mixture screws all the way in the engine still keeps on running. I have the idle set between 7 to 750 rpm.
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