HT4100 4.1, 4.5, 4.9 Discussion, Stripped Head Bolt Threads in Cadillac Engine Technical Discussion; What do I need to repair stripped head bolt threads on a 1992 DeVille 4.9L ? I contacted Timeserts.com but ...
The head bolts threads in the aluminum block are stripped out on bolts 1-2-3 which torque at 90lbs. Didn't blow the gaskets but combustion gasses were getting into the cooling system. When replacing the heads I got to 40ft lbs. and the threads came out. I need to install thread inserts but don't know what to use. Timeserts seem to be preffered but I emailed Timeserts.com and they only have kits for the N-Star engines. I was hoping the blocks were the same but it seems they're not.
I actually used helicoils in my '92 Deville. They held up great all the way till the end when the car was totalled by the guy who rearended me I've been through what you are experiencing right now man. It's frustrating to finally be on your way assembling the engine rather than disassembling and then strip out them threads. ? But anyway, you can get the correct size helicoils from probably anyone that sells helicoils. I'd also recommend getting new gaskets however...they have already been compressed from your installation and new ones will be needed. Good luck!
I would use the standard Timesert kit for an M12 x 1.75 bolt which is what the 4.9 head bolts were I think....
Those bolt holes were often repaired successfully with helicoils. Since they are larger bolts and are not as heavily stressed as the Northstar bolts the helicoils seem adequate and actually were an approved means of repair.
Personally, I would use the standard timesert kit, though.
Well I'm finally getting the 4.9 reassembled. For anyone with stripped head bolt threads on this engine, I would not suggest using Timeserts as there is not enough clearance in the bolt valley for the countersink tool or the lip on the insert itself. Had to grind the lip off to install them. Also had to drill the upper hole to allow the tap through. This has been a nightmare. About the time you think you've figured it out, something else rears it's ugly head. Kent-Moore has tools for this engine , part# J-29610 that may be the best way to go. I would have bought this if SPX.com would have been interested in selling me one. BTW bbob is correct on the bolt size - 12mmX1.75mm
Can you helicoil a 4.9 with the motor still in the car or must you drop the cradle to do so (like the Northstar).
I Timeserted the Northstar in my '97 Eldorado and I've recently been considering selling my '97 and picking up a '90 or '91 with a 4.9.