Cylinder head erosion around thermostat housing port

[tyroguru]

Recently I dismantled my 240Z engine (1973 P30 block / E88 head) and while removing the thermostat housing, one of the two bolts sheared. Today I was cleaning up the cylinder head in this area and it looks to have eroded around the port. I guess this allowed water to get under the gasket and over to the thread/bolt.



What am I to do with this situation? I imagine that if I just put another gasket on I'm going to get the same situation over time. I also imagine that getting that bolt out is going to be a challenge...

 

[atomman]

Heat is your friend , use a plumber's blow torch to warm up the area around the snappped bolt slowly , then grab it with a stud extractor or a pair of mole grips and carefully rotate it out .

You could get someone to TiG up the corrosion and machine/file it back ?

 

[Bazzateer]

I repaired similar damage on one of my Imp aluminium heads using JB Weld. Have to ensure the surface is completely clean first of course.
To remove the stud another method is to weld a nut to it. The heat will help free the thread and the nut will make extraction easier.

 

[tyroguru]

Thanks Gents! I'll probably try the JB weld approach first as it's an approach that I can attempt myself. Likewise with the plumbers blow torch for getting the bolt out. I keep putting off getting started with welding but I should really take the plunge some time if only for giving me more strategies with situations such as this.

 

[Bazzateer]

I'm in the same boat when it comes to welding, always have to rely on a mate!
As the JB Weld hardened I used a razor blade to keep the surface flat. Once fully hardened I went over it again with the razor blade and ended up with a perfectly flat surface. This was on the cylinder head and it withstood the pressures of compression, heat etc. Used a dremel to clean out the corrosion.

 

[uk66fastback]

Practice, practice and yet more practice as regards welding. I did a short evening course at the local college and then treated myself to an entry level+ MIG.

TIG looks easy when you see someone do it. But then you have a go yourself and realise it isn’t!

 

[tyroguru]

Practice, practice and yet more practice as regards welding. I did a short evening course at the local college and then treated myself to an entry level+ MIG.

TIG looks easy when you see someone do it. But then you have a go yourself and realise it isn’t!

Yeah, I can well imagine that's the case. I had sorted a days "Introduction to Welding" course out last year but couldn't get to it in the end. I'll try and get on to something again this year some time because I'm sure it would be super useful and also fun (for some strange definition of "fun"...). Probably burn the garage down .

 

[AliK]

Not having had the greatest experiences with JB Weld my money would be on the welding option and you never have to worry about it again - shouldn’t be that costly either.

My concern would be the JBW lump breaking up and working it’s way back into your block somehow and blocking up something vital

+1 for plumbers torch - I use a MAPP gas torch (ROTHENBERGER SUPER-FIRE 2 BRAZING TORCH) which is truly awesome at getting a huge lot of heat in very quickly and accurately.

Also a different perspective on removing bolts like that - I have left handed drill bits that, while drilling out the offender, create heat but are forcing the bolt to turn anti-clockwise at the same time. Taken out many a snapped bolt using this method and without resulting to the gas torch. Especially where there were metal threads moulded into plastic housings - e.g. MR2 pop-up light housing bolts etc ... clearly you use a smaller drill than the bolt diameter but relatively close to it.

https://www.ebay.co.uk/itm/Sealey-5...-Stud-Extraction-Remover-Removal/192087344224

 

[tyroguru]

Not having had the greatest experiences with JB Weld my money would be on the welding option and you never have to worry about it again - shouldn’t be that costly either.

My concern would be the JBW lump breaking up and working it’s way back into your block somehow and blocking up something vital

+1 for plumbers torch - I use a MAPP gas torch (ROTHENBERGER SUPER-FIRE 2 BRAZING TORCH) which is truly awesome at getting a huge lot of heat in very quickly and accurately.

Thanks for the thoughts and tips Ali. I was perusing Screwfix at the weekend and was looking at that one. Seemed a touch pricey but if you say it does a great job I'll probably go for one.

I've actually bit the bullet today and gone to see a machine shop that's reasonably close to me to discuss things. Had a nice tour of the facilities and a long chat about things and they're going to weld it up. I suspect I may well use them to overbore the block to 86mm as well while we're at it - it would be rude not to .

 

[jonbills]

Thanks for the thoughts and tips Ali. I was perusing Screwfix at the weekend and was looking at that one. Seemed a touch pricey but if you say it does a great job I'll probably go for one.

I've actually bit the bullet today and gone to see a machine shop that's reasonably close to me to discuss things. Had a nice tour of the facilities and a long chat about things and they're going to weld it up. I suspect I may well use them to overbore the block to 86mm as well while we're at it - it would be rude not to .

I think you need the details of your new pistons before you can get them to bore it. The pistons might not want 86.00mm.
E.g. The pistons might be 86.00mm so the bore might need to be 86.2mm or whatever.

 

[tyroguru]

I think you need the details of your new pistons before you can get them to bore it. The pistons might not want 86.00mm.
E.g. The pistons might be 86.00mm so the bore might need to be 86.2mm or whatever.

Yeah, thanks Jon. They said that they'd need the pistons and the rings if they bore it for exactly that reason. They also talked through the options for sleeving in case the walls get too thin and they showed me a few blocks that were having sleeves put in them at the minute. Interesting stuff!