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13K views 23 replies 13 participants last post by  beveluv 
#1 ·
What do I need to repair stripped head bolt threads on a 1992 DeVille 4.9L ? I contacted Timeserts.com but they do not have a kit for this engine.
 
#3 ·
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.
 
#4 ·
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!
 
#6 ·
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.
 
#7 ·
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 ********* is correct on the bolt size - 12mmX1.75mm
 
#17 ·
Thank you.

There is plenty of room to get tools in there to install inserts and so on? What about studs? Enough room, perhaps, for studs? I ask because I'm seriously considering dumping my '97 Eldo for a '89 to '91 Eldo because my Northstar has been such a pain in the a**. As nice a motor as it is I'm sick of the bull s**t I've put up with from it.
 
#23 ·
Gents,
I've had the pleasure of having to throw heli coils into a 4.9 while still in the car. All the threads i had to fix were thankfully on the side closer to the radiator. I dont think you'd be able to repair any on the opposite side with the limited room back there. Getting the propper tools to get the job done, was the hardest part of the install. If i can remember correctly you have to drill out the threads with a 31/64 drill bit, then tap the threads with the appropriate tap, then use the insert tool to insert the heli coils. it honestly took me about 2 weeks to find all these tools. drill bits had to be bought online, a 9in 31/64th is non existent in any local hardware store. the tap and the insert tool were bought online as well. the insert tool i bought was a 4 inch long platic t-handle looking thing. so i had to cut off the handle, and ghetto fabricate a way to make it longer so that it could reach the threads deep in the block. finding half inch long helicoils took an entire week of calling every fastener shop in the state, and i had to buy a bag of fifty. its been about a year and a half since ive done this but i would be more than willing to give any advice to anyone who has to knock this out. in my personal opinion; id do it to every head bolt, because they are all extremely weak. im pretty sure i still have the tap tool, and plenty of heli coils for anyone who is interested. if you guys have any questions about the process, email me at gmp428@yahoo.com. ill post on here later the exact tools and sizes needed once i check my FSM. GOOD LUCK!!!!!
 
#24 ·
I helicoiled 2 head bolt holes on the back side of my 4.9 while the engine was still in the car with no problem. Yes getting the drill bit and tap extension were a pain to find. Note the the bolt holes that had the problem were on the rear head, but it was two of the upper holes (two of the 3 that call for the highest torque. I dont think the lower holes can be done inside the car.
 
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