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How much valve recession is too much?
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AndrewA60



Joined: 12 Mar 2025
Posts: 3

PostPosted: Tue Apr 29, 2025 7:58 am    Post subject: How much valve recession is too much? Reply with quote

I've just started cleaning up the head from the 1622cc B series engine from my 1959 Australian Austin A60 Cambridge.
The head looked nice until I had a close look at the exhaust valve seats which have worn down around 1mm. The inlet seats look like they were machined yesterday. The engine was running OK 30 years ago this car was taken off the road, so do I just clean up the seats as is, or get them re-cut, or get inserts fitted?
By the way I think the Australian Austin A60 Cambridge is an A55 Mk II elsewhere.
Any advice appreciated.
Andrew


Last edited by AndrewA60 on Tue Apr 29, 2025 1:21 pm; edited 5 times in total
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badhuis



Joined: 20 Aug 2008
Posts: 1467
Location: Netherlands

PostPosted: Tue Apr 29, 2025 9:17 am    Post subject: Reply with quote

Even with recessed valve seats an engine will run pretty good. Not as effective maybe as an engine without the recession because the compression will be lower.

When I daily ran my Triumph 2000, and installed LPG, valve recession went in very fast. This is typical of running LPG, it wears out the valve seats much faster if the original "soft" metal valve seats are still in the engine.
OK - I drove a lot then (2002, approx 700 miles per week) and I needed to adjust the exhaust valves every weekend.... until it could not be adjusted anymore. I removed the cylinder head and the recession was very visible. New hardened seats and no more problems.

The valve heights should be the same but the exhaust valves stick out a lot more meaning recessed valve seats:




The smaller valves are the exhaust valves. The recessed seat is clearly visible:


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Ray White



Joined: 02 Dec 2014
Posts: 7077
Location: Derby

PostPosted: Tue Apr 29, 2025 10:22 am    Post subject: Reply with quote

Personally, I would cross that bridge when I came to it. If you don't have a problem, why try to fix it?

Last edited by Ray White on Tue Apr 29, 2025 11:25 am; edited 1 time in total
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AndrewA60



Joined: 12 Mar 2025
Posts: 3

PostPosted: Tue Apr 29, 2025 11:13 am    Post subject: Reply with quote

That exhaust seat is more than twice as deep as mine. Maybe I'm good for a few more miles! Was getting new seats straight forward? (and cheap?)

badhuis wrote:
Even with recessed valve seats an engine will run pretty good. Not as effective maybe as an engine without the recession because the compression will be lower.

When I daily ran my Triumph 2000, and installed LPG, valve recession went in very fast. This is typical of running LPG, it wears out the valve seats much faster if the original "soft" metal valve seats are still in the engine.
OK - I drove a lot then (2002, approx 700 miles per week) and I needed to adjust the exhaust valves every weekend.... until it could not be adjusted anymore. I removed the cylinder head and the recession was very visible. New hardened seats and no more problems.

The valve heights should be the same but the exhaust valves stick out a lot more meaning recessed valve seats:




The smaller valves are the exhaust valves. The recessed seat is clearly visible:

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badhuis



Joined: 20 Aug 2008
Posts: 1467
Location: Netherlands

PostPosted: Tue Apr 29, 2025 12:34 pm    Post subject: Reply with quote

I am with Ray. It depends on how much you plan to use the car. If only for shows or the Sunday drive, I would not bother.

However if you plan to take the head off it is something I always would do (especially if the seats already have some recession). Valve seat inserts are cheap and the cost for a shop to do this also not too much - I guessed I paid around 200 pounds altogether maximum. That was 23 years ago! But I cannot imagine it will be expensive as it is an easy job that is done frequently at machining shops.
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alastairq



Joined: 14 Oct 2016
Posts: 2117
Location: East Yorkshire

PostPosted: Tue Apr 29, 2025 1:22 pm    Post subject: Reply with quote

My only concern [since it happened to me once] with valve seat inserts is, if the workmanship or quality turns out to be 'dubious,', the seat will drop out!

Not a concern for those with sidevalve engines, of course.
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Ray White



Joined: 02 Dec 2014
Posts: 7077
Location: Derby

PostPosted: Tue Apr 29, 2025 2:03 pm    Post subject: Reply with quote

alastairq wrote:
My only concern [since it happened to me once] with valve seat inserts is, if the workmanship or quality turns out to be 'dubious,', the seat will drop out!

Not a concern for those with sidevalve engines, of course.


That would be my worry. According to the engine stitching expert that I went to with a valve seat crack in the Dodge Brothers block, seat implants are prone to fall out.

He was able to stitch right across the crack and machine it back to standard . I was impressed - to say the least - as the crack never reappeared.
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badhuis



Joined: 20 Aug 2008
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Location: Netherlands

PostPosted: Tue Apr 29, 2025 2:52 pm    Post subject: Reply with quote

alastairq wrote:
My only concern [since it happened to me once] with valve seat inserts is, if the workmanship or quality turns out to be 'dubious,', the seat will drop out!


Everything is possible of course. But I have never heard of it in the last 40 or so years.
It helps to go to a reputable shop, but does that not apply to everything?
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Ray White



Joined: 02 Dec 2014
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PostPosted: Tue Apr 29, 2025 3:12 pm    Post subject: Reply with quote

Probably just the way I look at things but if the seat is 'overhead' would it not be more likely to fall out than a side valve insert?
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alastairq



Joined: 14 Oct 2016
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Location: East Yorkshire

PostPosted: Tue Apr 29, 2025 4:05 pm    Post subject: Reply with quote

Quote:
It helps to go to a reputable shop, but does that not apply to everything?

That's the problem today. Who, or what, is reputable?

Does 'reputable' mean, they do the job right in the first place, and that's it?

Or does it mean, they do a job, and if it goes awry within a reasonable space of time, they'll 'put things right?' {Hopefully, without argument or question?]

Given how we are often strapped for time, and there can be quite a number of months or years between having seats [as an example] done, and actually starting to use the vehicle on a regular basis, it can be quite some time before indifferent workmanship rears its ugly head.

Maybe even, only for a new owner?

Reputable or not, it's still a gamble...as with so much else these days?

{Like, buying a brand new car in the vain hope that it'll be reliable, & if problems arise, the dealer will fix them, without faltering? I imagine some folk on here will be thinking, ''oh yeah, dream on!'']
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Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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Vintage Fly Guy



Joined: 27 Jun 2024
Posts: 170

PostPosted: Tue Apr 29, 2025 11:52 pm    Post subject: Reply with quote

OK, let's look at this logically and honestly. How many years and miles did it take the exhaust valve to recede 1mm? How old are you now, and how many more miles do you realistically intend to drive the car?

Sorry if that sounds a bit brutal, but it's a point of view I've had to face myself recently. I'm 61 this year, so, realistically, that probably gives me another 15 years or so of reasonably active life and driving classic cars for pleasure, rather than modern cars for necessity (such as getting to the shops). Anything after that will be a bonus for me... and given the way that Christmases seem to be coming around quicker and quicker, I'm under no illusion as to where I am time wise!

If you're thinking about it from your point of view, then a simple regrind and reassembly might be the right choice? If you're looking at it from the car's point of view, then it probably depends on factors such as what the budget is, how structurally and mechanically sound the rest of the car is, and where refurbishing the cylinder head sits in the list of priorities with those factors in mind.
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AndrewA60



Joined: 12 Mar 2025
Posts: 3

PostPosted: Wed Apr 30, 2025 12:38 am    Post subject: Reply with quote

Good point. I'm 63 with hair receded much further than my exhaust valves! I think a simple regrind will see me out.

Vintage Fly Guy wrote:
OK, let's look at this logically and honestly. How many years and miles did it take the exhaust valve to recede 1mm? How old are you now, and how many more miles do you realistically intend to drive the car?

Sorry if that sounds a bit brutal, but it's a point of view I've had to face myself recently. I'm 61 this year, so, realistically, that probably gives me another 15 years or so of reasonably active life and driving classic cars for pleasure, rather than modern cars for necessity (such as getting to the shops). Anything after that will be a bonus for me... and given the way that Christmases seem to be coming around quicker and quicker, I'm under no illusion as to where I am time wise!

If you're thinking about it from your point of view, then a simple regrind and reassembly might be the right choice? If you're looking at it from the car's point of view, then it probably depends on factors such as what the budget is, how structurally and mechanically sound the rest of the car is, and where refurbishing the cylinder head sits in the list of priorities with those factors in mind.
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Rusty



Joined: 10 Feb 2009
Posts: 272
Location: Bunbury, Western Australia

PostPosted: Wed Apr 30, 2025 12:46 am    Post subject: Reply with quote

badhuis wrote:
But I have never heard of it in the last 40 or so years.
It helps to go to a reputable shop, but does that not apply to everything?


It happened to "me" in a V8 International truck and scrapped the engine, I had to get a replacement engine.

There are a great many good engineering shops and with the amount of inserts done I wouldn't be scared of getting them done, but like the others have said, how much driving will it be doing ? I did an "economy" rebuild on a neighbours 318 powered Dodge truck engine and it needed inserts far mor than your B series but the owner couldn't afford it so we put it back together without them and it worked for five more years and was still running fine when he traded it.
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alastairq



Joined: 14 Oct 2016
Posts: 2117
Location: East Yorkshire

PostPosted: Wed Apr 30, 2025 9:16 am    Post subject: Reply with quote

https://www.ebay.co.uk/itm/135529848862?_skw=valve+seat+cutting+tool&itmmeta=01JT2VVQYMSBJQNCY424HWVRMP&hash=item1f8e35601e:g:wVIAAOSwlzZktThH&itmprp=enc%3AAQAKAAAA0FkggFvd1GGDu0w3yXCmi1c0Lza%2Fz6nRruaF4AzK06TbXYzTL1hEa88Nw%2B1g8jX%2BQohWnaudxuiCaeZ1ihxQ9VADtdqOJ2esnOUimXPUGuczn0jIcLoIpVCqgBaPlFbizlTMwcS3Z2%2BxYX%2Fh6Zsg0MoURRXGE0QwPmOJkL6MSmaOY2H7RjHExTK2KNhaozdvLTh6O1KAEZREtwlCVZuvdaSExbCv9Qw6GGeqm%2BuaxjTvyehOFaMvwX1OD9nJD5faqLcvspAbSMVCkoHBDPA6efY%3D%7Ctkp%3ABk9SR8j_7tvQZQ


Above is but one example I plucked from ebay.

It's not as if one is going to set oneself up as an engineering workshop, is it?

If the tool lasts long enough to do 8 valve seats, then it has to be worth a punt, eh?

If one can do half a dozen heads with the same tool, one is in 'profit!'

I don't know the actual seat sizes needed offhand, but a trip round ebay for a cheap seat cutting tool must be worth a try?

Who knows, one ight even be able to cut a nice neat three-angle valve seat? Then one would obtain enough power not to dream of fitting an MGB engine, eh?
_________________
Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces.
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norustplease



Joined: 11 Apr 2011
Posts: 825
Location: Lancashire

PostPosted: Thu May 01, 2025 8:36 am    Post subject: Reply with quote

I had always thought that an extreme overheating event was the cause of inserts to drop out, presumably because the head expands enough to release them. If you have cooked your engine to that degree, this is probably the least of your worries.
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