Cyl head repair

[dxke38]

Hi all. Could anyone recommend an engine machine shop in the Norfolk area. My usual people have just closed up. I'm trying to recon a 3.8 Mk 10 engine as a spare for my Ser 1 and the head needs repairs. It obviously dropped an exhaust valve in the distant past and I'm not sure of the new valve seat that was fitted or the state of the combustion chamber.. See pics.
Any advice appreciated.

[politeperson]

I doesn't look that bad to me.

I sent pictures of this head (below) to a company who do nothing but heads for the trade a few years ago as I had doubts.

It shows obvious erosion in the alloy around the valve seat.

They came back and said on the XK engine the seats are quite deep and it would be OK.

That was about 4 years ago and it has been fine ever since.

I had another head that had imprint marks from a foreign object. Sorry no photo. Looked very much like yours to me. That was fine too.

If you want a second opinion, email your picture to Glen Evans at Autoheads Recon.

sales@autoheadrecon.com

[dxke38]

Thankyou for the reply James. I'm sending over these clearer photos to Glen at Autoheads but I think this head is a lot worse than yours. I'm unsure of the metal the new seat is made of and if it needs to be removed the head will have to be welded and machined for a new seat. Thanks again for the contact.

[PeterCrespin]

For a DIY check in lieu of a pro pressure check, install both valves in there and check for gross leakage with a plug in and the chamber filled with fuel.

Then put the tappets back and a cam and see if the stem height is in normal shim range.

If it’s the original head and passes both checks I’d use it. Even if not, repair won’t be all that bad if you have to factor in buying a correct head. If you don't care about numbers matching, be aware that you or your heirs will lose more than the repair cost in car value. A big valve S3 XJ head is a good option if you are nervous...

[dxke38]

Hi Peter. Thankyou for the reply. The engine was running with this head but it was obviously a very cheap and quick repair and the colour of the new seat seems odd. It also had 5 8 to 1 comp pistons and 1 9 to 1 piston so they just fitted any old S/H piston hence my concerns. Not worried about numbers as I said, it's a spare for my Series 1. My biggest problem is finding a new machine shop, they're scarce in Norfolk.

[Gfhug]

Derek, why not look further afield than Norfolk? There are others further away who can supply an XJ6 head as Peter suggests. I got mine from a restorer in Coventry.

Geoff

[dxke38]

Hi Geoff, it's not that I cant find another head. I tend to work on these engines quite frequently for friends etc and original 3.8 engines are getting harder to find so I like to restore repair where I can. As for the machine shop, I miss the convenience of having a local place to use rather than taking engines all round the country.

[PeterCrespin]

The colour of modern seats is often different from the old tech original cast iron. Instead of being concerned I would be content. The originals were good in their day and will survive unleaded reasonably well, but Stellite or similar modern seats are vastly better.

[dxke38]

Thankyou Peter, that's what I need to know. I'd like to be sure of the material used for the valve seat. It's bigger than the original so is a specially made item do to the damage in the head and I'd like an opinion on what it is made of. You may be right, it's just one of the new metals used now. If I can't find out I'll just smooth out the combustion chamber and use it as it is, see what happens. The engine has run with it till now.

[PeterCrespin]

It's bigger than the original so is a specially made item do to the damage in the head and I'd like an opinion on what it is made of.

Very unlikely to be specially made. Valve seats are consumables/replacement items selected for each job from lists like fasteners, metal stock etc. The work was done by a shop. Taking a wild guess, it wasn't their first valve seat job. Why would they make special seat inserts (other than perhaps modify a close item slightly)? And if for some reason they started from stock material why do so with inferior metallurgy?

It's your head and you are entitled to do whatever you want, no question. But you're working based on feelings, curiosity and least-likely criteria, instead of bog-standard engine reconditioning practice. Occam's razor applies IMO. Hope it all works out for you.

[dxke38]

Yes Peter, I take your point about stock item and you are right I'm being overly concerned. When I see an engine that has had a cheap bodge repair, it does make me think just a little too much. The 9 to 1 piston amongst the other 8 to 1 pistons for example. Thanks again.

[PeterCrespin]

Do you know the piston bodge was done by the same shop? If so, I understand your attitude. Heads are often worked on in isolation from the rest of the engine, though.

If the shims on those valves were both in the normal range, it wasn't a bodged head. You don't get lucky twice on such a specialist criterion...

Good luck. If you want a good machinist near you, call Chris Jones in Dereham - he probably won't do the job, (being more of a fabricator) but he will know who's good. PM me if you want his number.