stripped valve cover bolt

[Paladin]

Hi, I have a 454/330 Mercruiser. I was going to look at the oil leaking (not bad) from the valve covers, maybe tighten them down a little or change the gaskets. I found they were really tight in some places, too tight, and pretty unsnug (almost loose) in others, like someone (the PO) had been fooling around with it.
Ok so far, but one of the bolts, at the rear of the engine on the starboard side, is stripped. It won't tighten, but it seems like it will loosen out, if I'm careful. So, I'm wondering (it's hard to get to, with the exhaust right there) what I can expect to see. What are the chances of it being just the bolt, and not the block that's stripped? If maybe the bolt was softer than the block? Has this happened to you before? How did you fix it? Thanks, Paladin

 

[l-skynyrd]

The valve cover is bolted to the head not the block. Does not make much difference because both are made of
cast iron. The bolts are made of steel and are much stronger than cast iron. My guess the threads in the head are stripped. To fix, you need to buy a heli-coil kit for that size hole. (or know a machinist or machanic that has one)
You drill the hole out and re-tap with the heli-coil tap
and install the heli-coil. Now you have new threads just as
strong or stronger than original.

 

[l-skynyrd]

By the way...If you have never done a heli-coil before I
would not suggest learning on the head of your boat
motor. I would find someone that has done before.


Len

 

[JUST PULLIN MY DINGHY]

Here's a quick easy way to fix the thread take a small soft cotter pin long enough to hit bottom and hang out of stripped hole now with a new bolt start to thread it in until it's about half way then rock pin back and forth until cotter pin breaks then tighten until snug . Now you have a "cheater coil" .

 

[Paladin]

Hmm I got it, head not block. well that makes sense.
Both cast iron, steel bolt. Shucks.
I will have to do the heli-coil or cheat method I guess. Kind of leaning towards doing it "right" but it is after all only the valve cover bolt. Hmm Think Think.
Thanks for the great ideas, Paladin

PS: any luck ever with trying to rethread the head with a tap and die set?

 

[JUST PULLIN MY DINGHY]

yes if its a american thread just go to metric and you can get a good tap out of it.For instance if you have a 5/16 x20 also none as coarse thread you can go with a 8mm x1.50 tap and make a good thread and just use a metric bolt here.

 

[Paladin]

when you say "also none as coarse thread"

you mean they are not as coarse?

But I think I got the idea.. you can't rethread it to the same size because the hole is now too big, eh? So you get a slightly different (metric) thread pattern and use the metric bolt that fits it.

 

[fc3]

Use a Time Sert. They are far, far better than helicoils. Helicoils are the Model T of thread repair. Time Serts are the 911 GT2 RS. Once inserted, they don't come out or work loose and since they're steel, they're stronger then the base metal.
http://www.timesert.com/

 

[Happy Hour IV]

Have you completely removed one of them or taken a close look at them ? You may find that they are actually studs and it is just the nut or top of stud that is stripped.

 

[Gunn]

yes if its a american thread just go to metric and you can get a good tap out of it.For instance if you have a 5/16 x20 also none as coarse thread you can go with a 8mm x1.50 tap and make a good thread and just use a metric bolt here.

Good idea to go the next size up and tap out the hole you have, but don't go metric on an otherwise SAE engine! What a pain that would be...for you and the next guy who owns it.

I've used heli-coils once...on a valve cover! It was on a Chevy 350 small block. It came out perfectly, I fell in love with those helicoils. Easy to do...just be sure to not let any of the debris from drilling out the head get amongst the valve springs and end up inside your engine. I had wished I had done it years earlier...

 

[OldSkool]

The Timeserts are a great product and the threads are sealed once installed. This makes for great water jacket type repairs.
Heli-coils are a great product but can leak through the threads as you now need to seal two sets of threads in the same hole.

IMO.

 

[Paladin]

Hi, Thanks for the good advice and the timesert link.
On my engine they are bolts (not studs), I got that one partially out. I'll look into the time sert thing.
As far as the cotter pin idea goes, I was thinking also a soft wire or piece of thin solid solder to just shim the hole, and then carefully rethread it. It doesn't move or bear weight or pressure, so maybe that would work until I could get it "right".

just be sure to not let any of the debris from drilling out the head get amongst the valve springs and end up inside your engine.
woo.. didn't really think of that.
Paladin

 

[Happy Hour IV]

There are a few places on an engine where I would use JB Weld. This would be one of them. figure out a way to keep constant pulling pressure on the bolt while turning it until
you get it out. Clean out the whole. fill with JB. Cure drill and retap to the original size.

 

[Paladin]

What a great idea. These are all such good ideas, I love it. I agree i wouldn't use the "fake" measures too much, but sometimes they really do work well. I even have some JB weld on hand. Thanks!

 

[JUST PULLIN MY DINGHY]

yes anything softer then the bolt would work it's not the ideal fix but when you can't get in there and do it the proper way it really works and holds just as tight as a helicoil i even done it and was still able to torque to proper spec .

 

[Paladin]

Hi, Thanks. Pretty amazing that it works that well!