I read a thread on this a year or so ago but I couldn't find it, so here goes.

My car has an l20b fuel injected and turbo. contolled by a microtech, running about 10psi on a pretty safe tune.

I recently got some pretty bad fuel and before I knew it had some detonation at high revs. I would have heard pinging on 4 or 5 separate occasions before I really knew what was going on.

I put in some fresh fuel and it seemed fine. It wasn't. Water loss and oil in the water. No water in the oil so it must have been pumping it out the exhaust.

I took the head off. I was expecting a blown head gasket, but discovered a head bolt with 0 torque on it. I tried tightening it up but as it tightened it span loose. Upon inspection the thread is fine on the bolt but stuffed in the hole on the block.

so my question is what options do I have for repair?

Obviously I'd like to avoid hellicoils.

Can I cut a bigger thread and put in a bigger bolt? I assume this would involve drilling into the head also and I'm not sure if it'd hit a water or oil passage (it's the middle hole on the passenger side)

Can you buy studs that have a short section of m12 and then go to m10?

I think the correct way is to take the block out, weld over the hole and re tap at the original thread size but I'd like to avoid this.

any other suggestions?

Finally would this have been less likely if I was using head studs instead of bolts?

Cheers

See if time sert are available .

Not sure if they can be torqued that high for a head bolt but means drilling and taping block.

Contact and engine reconditioner or similar perhaps too.

I've had heli-coil inserts done before, they seem to stand up just fine

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Thanks Nissanman. Is your motor NA or boosted?

Anyone have any idea why the threads let go in the first place?

It was on my sons L28 which was boosted.

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

ok interesting.

I'm still interested in other options though. Anyone know if it's safe to drill out that bolt hole in the head and use a bigger bolt?

+1 for HeliCoils. If done *properly*. I had one in my L20B track engine for many years. Not boosted, but was an all out race engine. (Custom conrods, pistons, etc etc etc). It had ARP studs as well. I did it with the block still in the car, but if I did it again, to ensure alignment, I would tare the engine down and put the block in the mill for boring the damaged thread out.

Jeff