hello, i bought used m52 head, dont know history of this head but i noticed cam tray studs were yielded, replaced all the studs with healthy ones, everything seemed ok, but when i was tightening cam caps i noticed one of studs was starting to pull out from head, loosened to inspect and tiny piece of thread was pulled from head, i've tightened stud about 3-4mm deeper and now i can torque cam cap without any problem, now it seems OK, how do you think will it work or not? i've built many m50 m52 engines and never had problem with these studs.
head has been overheated. It's garbage. Get a new one.
I wouldn't say it was overheated. I've seen this happen with dense mechanics reinstalling the caps too tight (stop using shit or too large of torque wrenches on critical components!).
You'll have to helicoil the threads. I got stuck doing this on a customer car after installing his head studs. The head had been rebuilt prior to me working on it and I knew there was going to be trouble based on how tight the nuts were removing the cams. It's a shitty job, but you can fix it with the head still installed. Just collect every bit of metal during the process.
thanks for answering
yeah i was thinking exactly same, someone before me tightened cam caps very badly
do i need to helicoil all the threads? or just stipped one? others seems ok, torqued to 15nm without a problem but is there a chance when engine reach operating temperature other threads also go bad?
I dunno ... I've seen it many times, and it's always from overheat. But sure ... give it a shot. Certainly the helicoil will work fine. For $300 for another head, I would just toss it though ... but that's just me. Especially if it's still off the car. If it was already installed, then maybe I'd try it first. Have you had it honed and tested for flatness?
yes i've rebuilt head, as i said studs were yielded from over torquing and i dont know why but bearing ledge aligment dowel pins were missing, i've pressure tested, installed dowel pins, replaced studs everything seemed OK, then ported and polished, did valve job and resurfaced, now it's mounted on block already. it was really hard work done on this head also dont want to waste already compressed head gasket. i'll try heli coil on stripped one, then when engine gets warmed i'll remove valve cover and inspect if all the studs sit fine.
There's two ways to fix these, one without removing the cam and tray. Obviously, a helicoil or timesert is best.
The other way is to isolate the area around the offensive stud and hole, measure then drill ONLY the cap and tray to allow a 5/16" tap to fit, then tap the thread area in the head to 5/16-24. Cut a piece of 5/16-24 B7, slot one end and screw it in.
You can tap a lot deeper than the original threading, you don't need to drill the threaded area because the old pulled out threaded hole is exactly what's needed for the 5/16" tap and you need a pulley tap to reach all the way in. A standard length tap won't work. Done many and not only does it work, it turns out stronger than stock. AND, a helicoil or timesert will still work normally for the next time the head comes apart.
Last edited by tjm3; 05-26-2020 at 12:52 PM. Reason: spelling...again!
See ya later,
tony
'98 M3, '92 Dinan3, '05 R1100S BCR, '07 R1200S, Aprilia T
Ick. Yes, clearly that'll work, but ick.
In a few years we'd be reading a "You won't believe the Frankenstein fix I found in the freakin' head of the M3 I just bought" thread.
@OP: Just do whatever it takes to install a thread repair insert, with the knowledge that you'll have fixed it properly and won't have to think about it again.
Neil
PS: Damn you Braymond141 for flaunting that luscious Snap-on electronic torque wrench! Does it do angles also?
Agreed, 100%.
But, how many times have you been in discussions about why that $1.50 Heli-coil costs $800 to install? It's only an option. It works. And it really is stronger that stock. And I back that up as a certified engine machinist.
Anyway, you gotta admit, compared to some of the other choices made here this is a minor issue.
See ya later,
tony
'98 M3, '92 Dinan3, '05 R1100S BCR, '07 R1200S, Aprilia T
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