Hello! I’ve got a 1988 Pontiac Firebird trans am GTA. The Kid before me blew up the original engine block so they replaced it with an L31 crate block. Me and my uncle pulled the engine and rebuilt it with new seals and bearings and put it back in the car. Now it’s overheating. It has an aluminum radiator, a new water pump, and new electric fans with a painless brand wiring kit. The only thing I can think that would be making it overheat is if there’s a mismatch in the heads that the head gasket is blocking. Do you guys know anything about the l31 with the original l98 heads? Thanks,
- Harrison

 

A mismatch notwithstanding, is there a chance you've got a water pump that's designed to rotate in the opposite direction? V-belt pumps spin one way, serpentine belt pumps spin the opposite way.

 

I don't have first hand experience with it but have done my reading. You may want to search and find more info on it to confirm or rule out this. searched "vortec block coolant bypass site:www.thirdgen.org"
Found this as related https://www.thirdgen.org/forums/tech...dnt-dream.html
Good luck

 

we pulled the water pump out because we suspected that may have been the problem because it looks like a previous over swapped it from a V-belt to a serpentine belt but it was spinning the right way. Regardless we bought a new high flow water pump but it still just loves to get hot.

 

Do you have a part number for the pump you bought?

 

I did suspect this may have been a problem but the block and water pump both have the bypass hole.

 

Are you running a heater core and if not do you have the bypass hose connected from the pump to the manifold?

 

I do, SUM-312675

 

yep, just bought a new spectra core and installed it last Sunday.

 

Long shot but are you sure it's getting hot? Or are you only reading the gauge on the dash?

 

Just to clarify:

 

I wish, the gauge is reading 260 and I’m using an ir thermometer that’s reading 270 at the coolant therm on the drivers side head.

 

that sounds way hot. What are the temps at the radiator?

 

My wagon was doing that at first, though with mine I bought a serp system with the water pump so it wasn't rotating the wrong way. The fan was.

But then again, that was a mechanical fan that was meant to rotate in the opposite direction. These F-Body cars take electric fans. Maybe they're installed wrong, or you have the wrong ones? They should be pulling air in, not trying to push it out the front.

 

How long have you had it running? Did you get the air fully burped out? A small hole in the t-stat helps with that if the bypass hole isn't in the block or waterpump.

 

If it's while the car is moving then the air dam could be missing too

 

That is my first question.

Does it over-heat when stationary and then cool down when moving?

If t stays cool when stationary, and only over-heats when moving its likely that you are missing the air dam. At idle, the fans move enough air to keep the engine at normal temps. But when moving the fans don't move enough air to cool the engine. So without the air dam it will heat-up only when moving.

If conversely, it stays cool when moving, but overheats when stationary you should check that the fans are working.

 

Any news?