Head Float

[Prez]

Ok I just got doing doing a headgasket. Sent the head to a machine shop and had it pressure tested and valve seals, 3 angle valve job, the whole works. Anyway we reassemble it and I get it driving shortlly after a 40 mile drive it starts acting funny. Overheating starts so I shut it down right away.

I have disasemmbled the cooling system and all is in working order. Water pump is good, new t-stat, new cap, radiator flows. Everythign is fine. Start up and work the bubbles out after refilling the coolant. Car idles fine for 30 mins staright. Go and drive it and starts to over heat and I get air build up in the cooling system again. What can be causeing this. The car burns nothign and does not mix oil and coolant.

What exactlly is head float and can it cause my issue? Somone told me to warm the car up, tkae the valve cover off and then re tourqe the head studs while the engine is hot to 95FT LBS. Sound right?

 

[diambo4life]

I would increase the TQ on the headbolts another 10-15ft-lbs from where it is now. You did use ARP's right? A very good investment. I would check your compression as well.

Are you bubbling the coolant (in the catch can) when it overheats?

Head lift normally happens under high boost (normaly 20psi+) in my experience. If it's overheating even with regular driving (little to no boost) I doubt your head is lifting.

Hopefully the head is not warped or wasn't torqued down in the wrong sequence.

 

[Prez]

ARP headstuds and was tourqed down in correct sequence according to manual. Coolant is bubeling in overflow tank but the guage barley reads over half inside the car. I know id shouldn't go over half so I shut it down right away to try and prevent damage to the head.

The machine shop says the head is not warped and pressure tested fine. My exhaust is clean and nothing is burning. I think I will see what tourqeing them down another 10 does.

Now what is typiclly head float/lift, symptoms/causes?

 

[R3dR]

you can pressureize your cylinders and see if bubbles are present in the coolant with the cap off without running the car.

Just apply air into the cylinder threw the sparkplug hole using a compression tester nozzle.

If you have air bubbles then look at retoque on the head.