Really screwed it up now!!!

[trenedi2002]

Hey guys I have busted my butt rebuilding my 1983 470 Mercruiser. I was putting in the head today and as I was torquing the head bolts 1 of them stripped out the threads!!! Now I have 9 perfect head bolts and 1 that just keeps turning!!! Is there any halfway easy fix or am I totally screwed???? My manufacturing engineering stepdad said I had to take it to a machine shop and have it bored out and fixed thay way. I really dont want to put that much money in that old 470 so what do you guys suggest??

Thanks for the help
trenedi2002

 

[Don S]

Re: Really screwed it up now!!!

Drop back 20 yards and ...............

Someplace along the line you have to stop throwing money at a loosing proposition.

 

[starsnstripers]

Re: Really screwed it up now!!!

Well, sorry to hear that bummer. I dont know if this is the best idea maybe someone has a better one but being it's an oldy like you say and maybe doesn't have a whole lot of life left. I have three suggestions for a temp/quick fix at your own "risk." You could try installing the same tempered Stud in it by either tapping it out a size bigger maybe metric, or again with a stud use some strong epoxy down in the hole and on the stud threads, and this one i'm not sure but a good fabricator may be able to weld a stud in and smooth around the base of the stud so the gasket seats ok. You could inquire about these options. Myself, I'd tap it out to the next size up even just up to a metric size "as not to oversize it" and install a stud w/a good thread epoxy. Slap the head on and toque er down. I'm sure there will be some interesting feedbacks on this one LOL P.S. Get a kicker motor! Good luck

 

[Coors]

Re: Really screwed it up now!!!

helicoil, but you have a engine that is out dated

 

[TilliamWe]

Re: Really screwed it up now!!!

My dad has a complete 3.7LX out of a 1986 model boat ( I think) that had a bent pushrod and a bad exhaust manifold. He would take $150 for all of it. But you would have to be somewhere close to Central Florida to make it worth it for you.
I would try a helicoil, I think.

 

[watermellonI]

Re: Really screwed it up now!!!

I m with the helicoil idea and then put her in run it as long as you can and while its runnin, be shoppin for a replacement (sounds like a good excuse to power up to me

 

[rodbolt]

Re: Really screwed it up now!!!

pull the head back off, heli-coil the thread and reinstall the head using a NEW gasket as they can only be crushed once,
ditch the engineer, while they can usually design something they normally cant fix it
hence the MCM470
make sure the head is properly aligned on the block, there are no alignment pins like on normal motors.
you will need the tool, or make one, to properly check valve lash once the rocker arms are assembled, they make various length pusrods to adjust valve lash.

 

[a70eliminator]

Re: Really screwed it up now!!!

If your really lucky the bolt threads just pulled, I would run a sharp tap and compressed air blow out the debri, then try a new bolt.
Next time you'll know to chase those threads and clean and oil the bolts first.
Good luck

 

[Bondo]

Re: Really screwed it up now!!!

Ayuh,..... Heli-coil is about your Only Chance of a repair that'll last more than a few minutes....

 

[Jim Graham]

Re: Really screwed it up now!!!

I've done the Heli-Coil thing myself but I had to stack 2 thread inserts in the hole to make it long enough!
Good luck!

 

[starsnstripers]

Re: Really screwed it up now!!!

I am not sure if there is enouph area for a helicoil for this application. A helicoil requires a larger oversized hole than it would be to tap it to the next size up. Would depend on wall thickness and location of stripped hole. IMO

 

[rodbolt]

Re: Really screwed it up now!!!

oh and if ya tap it the next size up be sure to use a galvanized bolt from home depot.
bolt tension and thread desighn are irrelevant on such an application.


trust me, the helicoil wont need that much more and then you can use the correct fastener for the application, helicoils can be purchased in various lengths you just may have to order it as most auto parts places simply stock a standard.
when doing anything with the 3.7 strict adhernce to the FACTORY service manual is a MUST or you wont believe the issues you can create.
ITS not your grannys chevrolet.

 

[CharlieB]

Re: Really screwed it up now!!!

Rodbolt has a sense of humor, you can tell by his first comment!

But he's right on with what else he posted.

Your headbolt itself may be fine but the threads that pulled loose from the block is a very serious problem. Helicoils are actually stronger than the original threads that they replace HOWEVER, you must be sure that you order the correct insert length.

 

[Coors]

Re: Really screwed it up now!!!

And find the local bolt distributor, and get a grade 8 replacement.

 

[Don S]

Re: Really screwed it up now!!!

And find the local bolt distributor, and get a grade 8 replacement.

No, order a proper head bolt for that engine.

 

[Coors]

Re: Really screwed it up now!!!

No, order a proper head bolt for that engine.

Ain't that a grade 8?