P80 Valve cover bolt Helicoil , oil leak 985135

Post by **abscate** » 04 Mar 2024, 13:07

One of my cylinder head cover bolts is stripped and is leaking oil

1 I could pull the cover, retap, reseal

2 Im thinking I can do a Helicoil on car to fix

ANyone have experience here?

Flange screw
Part Number: 985135
Supersession(s): 975883

102338 Sjandix part
M7 x 35 mm flange bolt

WillieBeamen · Post by **WillieBeamen** » 04 Mar 2024, 15:49

I use timeserts. I feel like more of a professional repair, but helicoil is an FAA approved repair as well.

Post by **abscate** » 05 Mar 2024, 09:06

McMaster Carr has the correct M7 x 1.o mm pitch Helicoil

https://www.mcmaster.com/products/helic ... c+helicoil

But it is listed as a through hole tap, and the cam cover is blind...

Post by **erikv11** » 05 Mar 2024, 10:37

I had this issue on my 98, with one leaking cam cover bolt. It's just one of many and just the cam cover: I decided it is not worth the effort of a helicoil etc: I just tapped it larger on-car, carefully collecting the swarf as I did, and stepped up the bolt. Did not try to reseal or anything. No down time, no more leak.

Probably used a shorter bolt on the replacement so as to not tap too deeply, I could pull it and check length if you want.

Post by **BlackBart** » 05 Mar 2024, 11:47

I had to look them up to remember the difference. This is informative. The idea of a piece of Helicoil falling into a spark plug hole is a huge difference.

Post by **abscate** » 05 Mar 2024, 18:30

erikv11 wrote: ↑05 Mar 2024, 10:37 I had this issue on my 98, with one leaking cam cover bolt. It's just one of many and just the cam cover: I decided it is not worth the effort of a helicoil etc: I just tapped it larger on-car, carefully collecting the swarf as I did, and stepped up the bolt. Did not try to reseal or anything. No down time, no more leak.

Probably used a shorter bolt on the replacement so as to not tap too deeply, I could pull it and check length if you want.

Thanks Eric. I can pull it , measure it, and document it here

Post by **foggydogg** » 05 Mar 2024, 23:13

Another source that I mentioned earlier today:
https://www.mscdirect.com/browse/tn?sea ... words&rd=k
Getting any thread repair insert into a blind hole clean will be a challenge. There have been places I have done the one size bigger trick as well.
While this is the same, but different, we had a piston come apart in one cylinder on the stock car, with a big race the next day, so didn't have the time to do the right thing. An Ancient Machinist with an equally ancient portable boring machine came to the shop, bored that one hole 60 over in situ, we put it back together and went to the speedway. Engine didn't seem to care - aside from a bit more vibration over 8,000 .

Post by **abscate** » 06 Mar 2024, 05:54

Hey Foggy - a little bird told me you have a cylinder head currently off a car. Could you measure or SWAG the thickness of the head for me at tthe point where the M7 cover bolts go? I will post the exact one to measure here

Im leaning to drill and tap an M8

Three steps

Clearance for an M8 tap
Tap threads
Clearance cam cover for M8 through bolt

Post by **volvolugnut** » 06 Mar 2024, 07:26

Here is some general information on tap types and tapping threads. Go slow and easy. Key point on blind holes is to get the cuttings out the top by frequently backing out the tap and cleaning. Good luck.
https://www.cnccookbook.com/different-t ... -choosing/

volvolugnut

Post by **BlackBart** » 06 Mar 2024, 11:41

Can you put a tiny nozzle on a shop vac and suck any shavings out of there?