I just got done rebuilding my lt1. I bored it over .30 over made it 383. I had the heads reworked with pocket port, 3 angle valve job, new springs retainers and seals, and they were milled like .05 or something like that. I put everything brand new all new gaskets and all that good stuff. So my lt1 has been running hot it slowly creeps up to 210 and after that it will go close to the third mark and the fans kick on and it will go back close to 210. And after the fans go off it keeps flucatuating back and forth. So I put a brand new ac Delco waterpump, 160 thermostat, new radiator, slp manual fan switch. Is there any ideas on why it keeps flucatuating like that. Before the rebuild it stayed and 210 and lower all the time

 

Could be air pockets in the system. How much coolant did you add? Was the system completely dry? Are the fans tuned for the 160* thermostat? Not completely sure, but those temps are not far off for stock fan settings.

 

No they are not programmed for the 160 the stat. I'm pretty sure I have gotten all the.air out of the system. It has taken quite a bit off coolant but alot spews out when I keep the cap off. What I thought was weird was once it got up the 210 or a bit higher the coolant started rising and it was like boiling out Like lava I was wondering what the deal was with that. Possible bad head gasket.

 

And yes the system was completly dry at first once I got it back from the machine shop

 

Fans need to be tuned to take advantage of the lower temp thermostat. If it boils and spews that usually means air pockets. What you can do is fill the radiator, cap radiator, start engine, let it get to operating temp and then loosen the t-stat bleeder screw until either coolant starts coming out in a steady stream. If it is still bubbling when the pressure subsides, close bleeder screw and wait for pressure to build back up and repeat. Do the same for the heater core bleeder screw, but do the t-stat bleeder screw first. Also, pay close attention to temp gauge while doing this.
I was wanting a specific number of quarts or gallons you've used. The complete cooling system holds almost 16 quarts.

 

I'd vote improperly bled or you might have a coolant line mixed up

 

The rising coolant and lava action I think are normal. That's from the thermostat opening. Cold coolant hitting the hot block. Did you do like SS RRR stated with the bleeder screws? You can't get the air out through the radiator, you must use the bleeders. Also, was the car's tune adjusted for the new displacement? That is a parameter in the tune. The computer may be calculating how much fuel for a 350 vs 383.

 

I have bled it using the bleeder screws with the cap on. Steady streams come out of both bleeder screws. I guess I'll try it again is there any tips or tricks to try bleeding it again. I would say it took probably 16 quarts maybe a bit more. I have read that it helps to put it at an incline so I tried it on some ramps but no difference really.

 

And it has not been tuned for the new displacement. It running off the old tune from the 350 and procharger.

 

I was curious.....if you only bored it .030 over, how much stroke did u have to add to make it a 383?

 

Yes I had to stroke it out to 3.75 I think it was the stock stroke is just 3.48.

 

Well I put my air dam back on and it helped a bunch on faster speeds but when I was just cruising in town it got hot. When I got home I popped my hood and saw my head studs were seaping. I had already took some advice from the machine shop by pouring in a bottle of Barrs stop leak, it seemed to stop it and now there seaping again

 

Yeah, on the LT1 you need to use thread sealant on the head studs going into the block or they'll leak. It sucks cause you have to torque the heads down before the sealant dries, you have to have everything set up go go pretty quick on install. Looks like you'll need to pull your studs back out and re-install them wet with sealant.

Definitely need a tune too. Timing and AFR will impact how cool the motor runs.

 

Ok i will get it tuned for sure. So the best way to reseal them would be to take them out and pput a different thread sealant. I used that permatex thread sealant with ptfe when I first did them. Any other suggestions on what thread sealer works the best. Would I have to replace the head gasket when doing this or just pull them one at a time?