LT1 people

[BigWheelinBubba]

Just bought a cool sleeper. 1991 GMC Safari with a 1994 Z28 LT1/4L60E. It has a new aluminum radiator but the guy said he could never keep the temps steady. It's either freezing cold or he said it gets hot in summer traffic.

It has an aftermarket electric fan on it, but it only covers about 70% of the radiator and has no shroud.

I want to remedy this before it becomes a problem. Well, actually it is now not having much heat lol. But anyway..

I already bled the system out today and it had very little air in it. It helped the temps climb up a little but still not hot enough.

I'm going to swap out the thermostat.. he said it has a failsafe in it now that stays open just a tiny bit. I think with the temps being so cold it never gets a chance to warm up completely. It runs at between 120-160 right now.. i'd like to see it stay around 180 give or take.

Anything I might be missing?

[1BADAIR]

Since it's a lt1 make sure the radiator is plumbed right

[BLKHAWK]

what larry said

[1BADAIR]

If it has that small line on the top of the radiator make sure its not going back to the waterpump. Just went thru this on my truck. New rad was drilled wrong and was pushing hot water thru the vent to the back of the tstat

[beertestr]

If it has that small line on the top of the radiator make sure its not going back to the waterpump. Just went thru this on my truck. New rad was drilled wrong and was pushing hot water thru the vent to the back of the tstat

Ive had a dozen lt1 b cars and put an LT1 in a Porsche 944. That cooling mech is a little odd.

Rad hoses are right.

First let me know if you have a rad with a rad cap or not.
If no rad cap, plumb it like a Caprice.
Heater hoses come off the right side. Heater is on top, heater return is on bottom. Heater return is tee'd with the surge tank (pressurized coolant bottle) steam lines come off the back of the head and go to the vent port on top of the surge tank. You can decide if you want to send heat through the throttle body.

There is no overflow tank required in addition to the surge tank.

If there is a rad cap, there needs to be a vent port under the cap, that goes to an over flow bottle (not pressurized) and a vent port below it I the rad end tank. Hook this port to the steam lines from the back of the head. The heater lines are the same but do not have a tee to a surve tank. The reservoir is not pressurized.

Hth

Sent from my SCH-I545 using Tapatalk

[BigWheelinBubba]

Ive had a dozen lt1 b cars and put an LT1 in a Porsche 944. That cooling mech is a little odd.

Rad hoses are right.

First let me know if you have a rad with a rad cap or not.
If no rad cap, plumb it like a Caprice.
Heater hoses come off the right side. Heater is on top, heater return is on bottom. Heater return is tee'd with the surge tank (pressurized coolant bottle) steam lines come off the back of the head and go to the vent port on top of the surge tank. You can decide if you want to send heat through the throttle body.

There is no overflow tank required in addition to the surge tank.

If there is a rad cap, there needs to be a vent port under the cap, that goes to an over flow bottle (not pressurized) and a vent port below it I the rad end tank. Hook this port to the steam lines from the back of the head. The heater lines are the same but do not have a tee to a surve tank. The reservoir is not pressurized.

Hth

Sent from my SCH-I545 using Tapatalk

Thanks for the input gentlemen.

Mike it has a rad cap and an overflow bottle. It has the heater hoses on the passenger side of the radiator. I'm going to go out in the garage later and take a better look at it and see what's up.

[beertestr]

If everything checks out externally, the next place I'd look is the thermostat. Make sure it's an LT1 stat, not a conventional SBC stat. But, the erratic temperature swings sound more like an unpressurized system.

tstat.jpg

[BigWheelinBubba]

Everything checks out Mike.. only thing left is the thermostat which from what the guy told me is a "cold" stat, so i'm thinking it has a 160* in it. Might not have to mess with it though now that its' warming up outside

[beertestr]

Could be a funky or wrong stat. Keep me posted, I'm happy to help out. I'm trying to think what happens if the bypass circuit is not closed when the stat opens.

[OnyxSSS]

Sounds cool, is it AWD?? Pics?? I just changed t-stat that was newer b/c the fail safe worked and stuck open. Replaced it with a Normal one and heat is back.