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Cracked valve seat.


R.White

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I have just collected my '26  block from the engineers.  They have rebored +040" and this included a liner in one cylinder because of a crack in the cylinder wall. A few other issues like Helicoil two of the stud holes;  skimming the head and block surfaces have been attended to but when they recut the valve seats a crack was discovered in one valve seat.  This was pointed out to me by the machinist when I arrived to collect the block but to my surprise he said that if it was him, he wouldn't worry about it.  

 

I loaded up the block and returned home but ever since I have been worrying about the cracked valve seat.  I have been assured that there is no leak from the seat but it occurred to me that the engineer would have tested the valves with a vacuum gauge on a cold engine.  I worry that if I refit the engine as it is, when it heats up the crack could open up and I would loose compression and eventually, burning would occur.  The consequence would be engine out again and another trip to the shop. 

 

I think I know what I should do but what would you guys have to say?

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Apparently the crack was discovered late in the reconditioning process, but it might have been nice to call you and inform you of the problem when they discovered it, rather than waiting until you picked up the block and were presented with a bill.  I feel your pain.  I'm not an expert, but I would have the same reservations about expansion once the block heats up.  Is repair possible without damaging the seat area?  I'd get it attended to if it were me.  With all the work already done, finding another block is obviously not an option.

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That is disappointing for sure but I wouldn't think machining out the seat area and installing an insert would be too expensive.  If an exhaust valve seat I would be tempted to do all 4.  It shouldn't need to be a hardened seat but they will need to know the correct interference fit.  Having in insert come loose can damage a block beyond repair.

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Thank you for your kind support.  Yes, after having spent over £1000 on repairs and new pistons, valves, springs etc. I am in no mood to start afresh any time soon.  The strange thing is that these particular engineers have done a fair bit of work but they have certainly been dragging their feet despite having come highly recommended.  The machinist may not think there is anything to worry about but I doubt he has considered the vast amount of work involved in getting the engine out of the car and stripping it down to enable him to have a clean sheet so to speak.  

 

Yes, I think I will phone him on tomorrow and find out when it would be possible to have the valve seat replaced.  An insert would be necessary as the crack goes right across the seat and is beginning to intrude into the block .   These engineers are excellent at what they do but I fear their services are in such demand that my job might be considered small fry.  They want to think on... I was told the work would take 3 weeks but I have been kept waiting 3 months.... I may not be Rockefeller but I am quite well know in old car circles.  

 

Ray. 

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Thanks.  That is what I think too. I am an old worry guts at the best of times so I need to feel confident in the engine when it's done.  If I can't get it done in a reasonable time perhaps I should try elsewhere.  This machinist is making some new big end bolts for me (already paid for!) so I don't really want to give him a reason for more delays!  

 

Also, if the valve seat cracked further I fear it might be curtains for the block!

 

Ray.

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Is the crack intruding into the block itself?  I'd make sure installing a new seat will not cause further problems.  As I stated before, I'm no expert, but will forcing the new valve seat in as an interference fit possibly enlarge the crack if it extends outside the machined area?  Sorry, maybe I'm just causing you more angst than you've already experienced.  I swear, it's always something with these old beasts.

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42 minutes ago, cahartley said:

They LET THE BLOCK GO with a crack IN a valve seat?........ :o

Man.........you just can't get a break.

 

 

Yep!  Darn crack didn't show up when I lapped in the valve but they said the seats needed to be refaced so I agreed and the crack apparently became visible during the machining.  I suppose the grinding paste had disguised it before.  Anyhow, the point that has just been made about the crack extending beyond the seat itself if an insert is pressed in might be why the engineer left it alone.  Perhaps he could envisage making matters worse by going for it, I don't know.  

 

Now I don't know what to do for the best.:(

 

Ray.

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Hi Ray,  I would try to find a shop that can demonstrate they are good with magnaflux or penetrant inspection (special fluid that is applied to part, let sit for specified time, washed off and then examined in a dark place with black light; the crack will fluoresce).  The idea is to map the extent of the crack to ensure it will be machined away completely.  Do you know any NDT people at Rolls Royce?  Hopefully the crack isn't too large to allow an insert.  I am surprised the shop didn't check for this condition before going too far since, generally speaking, this is not an unusual area to find cracks. 

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Hi Mike.  Unfortunately the only RR people I know are long retired.   The engineers I have been to are using Magna flux ; they identified the extent of the hairline crack in the cylinder wall with it.  To be fair, the valve facing was in addition to the rebore (and liner) operations but as I said I am now wondering if the extent of the crack makes it too risky to install an insert without worsening the situation.  I guess I will have to speak with the guy - perhaps they could peg it in some way.  Cotterell engineering are a family concern with a good reputation among classic car guys in this area and to be fair Bob Cotterell  did point out the problem but didn't think it would cause a problem.  I beg to differ.

 

It's at times like this that I really miss my Dad.  He was a very experienced development engineer and would have fixed the problem in no time.  He was a senior man at James Walker when they were at Woking and controlled not just the tool room but the garage as well.  Ah well, life goes on as they say.  :mellow: 

 

Ray.

Edited by R.White (see edit history)
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Hi Ray! A quick story; I removed the head of my Model A to replace a very old head gasket years ago, just to know a new one is on the engine. I quickly noticed a fairly good size crack from the #2 cyl. exhaust seat heading to the cylinder. This is from a quick wipe of grime from the block with an oily rag!

  I never even had a remote hint of any problem when the Ford was running for several years with it like that. I ended up finding another valve seat crack and busted off two studs myself. I DID elect to find a better block, Model A's being easy to find, not the old Dodge though! I feel bad for your position now.

 Installing a steel seat can be kind of scary as Taylormade states. I wonder if a repair can be made by heating up the whole block and then welding with a cast iron rod, then machine that down.

Edited by Pete K. (see edit history)
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I welded a crack in an exhaust valve seat in a 20-35 Rumely I once had.

I also welded cracked seats in the head of a John Deere 60.

I welded a crack between the cylinders of a John Deere MT as well.

In a country like yours where preserving history is so highly revered it shouldn't be that difficult to find someone with some expertise and guts.

 

Kind of off the subject but I had some dealings with a substantial collector of OLD tractors in Ireland........in fact I sold him one of mine.

One of the tractors he bought was a teens 30-60 Hart Parr "kit" which is a 20,000 pound machine with a 2 cylinder headless engine of 10" bore × 15" stroke.

He called me to ask about having a cylinder sleeved and I advised him.

He called back saying the shop wouldn't touch it because someone had welded INSIDE the cylinder........ :wacko:

I told him to tell the shop to grind out the weld and have at it since it was being sleeved anyway........which they did.

I was saddened that common sense eluded everyone at that shop........ :( ........still am as far as that goes.

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I have now spoken with the engineers and sorted out a plan.  Tomorrow I will take the block over to a cold metal stitching specialist not far from here.  The guy there should be able to pin the crack before the weekend.  Rob Cotterell will then have the block back in his shop and fit a suitable insert.  They do this sort of thing all the time and the cost will be £45.  I am told it will be done straight away.  (Heard that one before!)   How much the metal stitching will be I don't yet know but it is only a small job so shouldn't be all that expensive. Whatever; it needs doing for my peace of mind if nothing else.

 

I hope it doesn't take too long because I would like to get the car back together in time for our local show this year.

 

Ray.

Edited by R.White (see edit history)
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I have got the block back from "stitch weld" and Brian, who runs the place, has not only repaired the crack so you can't see where it was, he has recut the valve seat as well!  Apparently, the metal is a bit on the thin side for an insert to be fitted safely, so the best option was to thoroughly repair the crack and cut a new seat into it.  It looks good. Fingers crossed.

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Thanks Ron.  I am spending a fair bit of time getting every bit of Ausie grit out of the block!  I did most of the cleaning before handing the block over to the engineers and they also cleaned it but the sheer quantity of silt and grit that has come out is something to behold!  The pan and oil galleries are now clean but muck is still coming out of the water passages.  I thought it might have been rust but a magnet confirms that it is just dirt. First I used a powerful pressure washer and when it had dried out (using hot air) I got more out with compressed air, using a professional compressor and a suitable raking tool.  I think the job is almost done now.^_^

 

Ray.  

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It's amazing the amount of crud that accumulates inside an engine over the years.  I had similar experiences with my 29 and 48 Plymouth engines and my current 32 Dodge Brothers.  The Dodge got a good cleaning at the rebuilder's and only needed air pressure to get some dusty dirt out.  I used your pressure washer and compressed air method on the other two at home with the freeze plugs/casting plugs out.  A virtual river of mud flowed out of both motors for what seemed like hours.

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Good to hear you found a solution.  I also used a pressure washer to clean out my block which had a lot of the (missing) upholstery material in it.  Mice had set up shop in there since the radiator hose opening on the head had been exposed for who knows how long....  It took a lot of flushing before coming clean.

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