Hello,
I pulled the head off my 1995.5 FZJ-80 last week (blown headgasket, running hot and bubbles in coolant), and the cam bearings are out 1/32" on each end (guessing, it was too much for the thickest bar on the feeler guage).
Is this too much to be straightened without cracking? I've heard they can put aluminum heads on a big steel plate, bolt it down with counter shims on the high points, and stick it in a big oven that straightens them out (presumably with this much warping it would be done in a few steps to avoid cracking by just trying to bolt it down all at once).
vehicle background- mom bought it new back in the day, dealership car for first 10 years, shop down the street for the past 11 years (he's actually an 80 series guy who owns one himself and does good work).
Minimum of 340,000 miles (not km), probably around 360,000 - 370,000 (odometer broke at 290k).
still had original headgasket (surprising) but none of the fire rings were remotely round, and you could see where it blew through to the water passage behind #6 (typical EGR pipe cause).
I found a different head straightening method that I may practice on an old Chevy cast iron head from autoshop (I'm a highschooler doing this in class). not sure if it could be applied to aluminum heads with a reduced pressure of 1000-2000 lbs (maybe metallurgy people would know better).
Patent US5903975 - Cylinder head straightening method - Google Patents
Basically you expand the convex side with heat, while it has pressure on it from the press, and then the pressure causes it to contract to less than the original size (on the convex side only, which makes it straighten out).
With aluminum, it may conduct heat too well and result in the head shrinking in overall length (at least that's what I fear).
Thanks for any input!
Nick
I pulled the head off my 1995.5 FZJ-80 last week (blown headgasket, running hot and bubbles in coolant), and the cam bearings are out 1/32" on each end (guessing, it was too much for the thickest bar on the feeler guage).
Is this too much to be straightened without cracking? I've heard they can put aluminum heads on a big steel plate, bolt it down with counter shims on the high points, and stick it in a big oven that straightens them out (presumably with this much warping it would be done in a few steps to avoid cracking by just trying to bolt it down all at once).
vehicle background- mom bought it new back in the day, dealership car for first 10 years, shop down the street for the past 11 years (he's actually an 80 series guy who owns one himself and does good work).
Minimum of 340,000 miles (not km), probably around 360,000 - 370,000 (odometer broke at 290k).
still had original headgasket (surprising) but none of the fire rings were remotely round, and you could see where it blew through to the water passage behind #6 (typical EGR pipe cause).
I found a different head straightening method that I may practice on an old Chevy cast iron head from autoshop (I'm a highschooler doing this in class). not sure if it could be applied to aluminum heads with a reduced pressure of 1000-2000 lbs (maybe metallurgy people would know better).
Patent US5903975 - Cylinder head straightening method - Google Patents
Basically you expand the convex side with heat, while it has pressure on it from the press, and then the pressure causes it to contract to less than the original size (on the convex side only, which makes it straighten out).
With aluminum, it may conduct heat too well and result in the head shrinking in overall length (at least that's what I fear).
Thanks for any input!
Nick
