43 replies to this topic

[N/A-PWR]

Hi zooma355,

Maybe try welding and re-tapping the thread (although welding distorts the casting properties) first.

Re-coils are not a ridget type of thread for Torquing up. Dave I

[S pack]

Well i think this engine build has finally defeated me! While waiting for my manifold to be machined i thought id throw my heads on and torque em up... easy! Apparently not!

After cleaning out the threads, bitta spray glue on the gaskets, lube on the brand new ARP headbolts and at the last stage of the headbolt torque up the bolt nearest the back water jacket/driverside let out a loud crack.

After thinking id first broken the bolt, then that id broken my torque wrench i found that the thread in the block had let go! On closer inspection i found marks that look like they have thrown a helicoil in there and that it has snapped.

 

Ive had a gutfull of this engine! It hasnt given me a break on any single part of the build!

 

Anyway these are my options as far as i can see

1. drilling it back out and Re coiling or thread fastening the thread, what are my chances of success given it may have already been done and the closeness to the jackets? 

2. stripping it all back down and sending it in to get done professionally

3. cutting my losses and getting a new block and starting again

 

What do u guys think? Have u guys heard of this happening and any possible remedies?

I would be seeking the advice of a professional on this one. The block may have suffered some hairline cracks around the bolt hole that can't be easily seen with the naked eye.

[rodomo]

Studs? With a stepped stud in THAT hole.

[S pack]

Yeah mate i probably wont go down that track as heating up that area is bound to cause dramas. Cheers

 

Yeah bud thats the way im leaning, i wouldnt have thought helicoils would be a solid enough thread for torque on cyl heads. Are there any other options u know of?

No other options that I can think of if the thread has been damaged once before and helicoiled to repair it other than scrapping the block and starting from scratch.

[TerrA LX]

If the helicoil have just failed you maybe able to bond a new one in place.

I have done this on lower tension studs, around the 30~40 pound mark but never tried on a 75 pound head bolt.

I would consider gaining ARP's advice (do they have a tech service?) and possibly bonding a stud in place so as not to stress the block thread again.

[ls2lxhatch]

A stepped stud will use a larger thread at the block end so you can drill and tap the block.

 

A stud can have more thread engagement (longer threaded section) and therefore they can be stronger than a bolt.

[neglectedtorana]

Hi Zooma Instead of a helicoil you could try a locking threaded insert They are stronger than helicoils and the sort of thing you can still do yourself with simple tooling. http://www.mcmaster....inserts/=n8hqr9 Sorry the link is from a company in the States but surely can be found in Oz not sure if it is suitable but well worth a look once you have decided if you continue or get it welded, studded etc Cheers, Tom

[Struggler]

The noise you heard was probably the deck around the bolt hole cracking/splitting. I'd be checking it very very closely.

 

This is sad but may well be true.

 

The end head bolt holes are close to the bore and can and do crack to the bore. I have seen low performance engines repaired with a sleeve and thread insert but I wouldn't run that way.

 

Get the head off, have a good look and report back.

[warrenm]

Have you got a pic?

[TerrA LX]

PM Tiny if he is still doing the thread service kits, he maybe able to shed some light on a suitable repair, if the block is not cracked.

[S pack]

At a guess, you missed it because the thread was all there before you put the the bolt in.

Can't say for sure from those pics but looks to me like it is the original cast iron thread that has stripped not a helicoil.

 

No visible cracks so you might be in luck.

I would still advise taking it to a professional and get their opinion on the viability of a repair, and you could also discuss machining the head to inlet manifold faces to make your manifold fit properly.

Edited by S pack, 18 June 2013 - 03:31 PM.

[ls2lxhatch]

Have you checked the length of the head bolt?

 

It seems odd that only a couple of threads are damaged, maybe the bolt was too short to start with and that's what caused the failure.

[Struggler]

Have you checked the length of the head bolt?

 

It seems odd that only a couple of threads are damaged, maybe the bolt was too short to start with and that's what caused the failure.

 

I thought the same, looks like you screwed one of the 4 inner bolts into that hole when it should have been about a half inch longer. Check your head bolts, there are 3 different lengths.

[Bernie]

Use a Caterpillar  style thread insert repair .They are much stronger than helicoil and are keyed so they don't move .

Bernie