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+--- Thread: Valve reseating (/showthread.php?tid=966)
RE: Valve reseating - Stuart Giles - 21-03-2018
(21-03-2018, 10:28 AM)Mike Costigan Wrote:(21-03-2018, 09:35 AM)David.H Wrote: Worth remembering that valve seat recession is unlikely to be much of a problem when using modern non leaded fuel.....no lead in the fuel back in the day! ...
But don't forget, once upon a time regrinding the valves was a regular maintenance routine; my father reckoned on doing it twice a year when he was doing around 10,000 miles per year!
And that, rather than exhaust valve seat recession is why you find so many valves, including inlets, sunk in to the cylinder head; or of course, the block on side valve motors. You can see that the valve seats on this motor are a reasonable width but only after I had machined about 20 thou off the block face. Even then you can still see some evidence (bottom middle to left) of the damage caused by the gorilla who used a big cold chisel to separate the head from the block at some time in the past.
![[Image: 29572171894_388478ce77_k.jpg]](https://farm9.staticflickr.com/8407/29572171894_388478ce77_k.jpg)
RE: Valve reseating - Ruairidh Dunford - 21-03-2018
Valves are made of very different material these days - most I use last in excess of 80'000 miles before needing any work at all.
Stuart - do you find you need to put a spacer under the block, when taking off material from the top?
RE: Valve reseating - Stuart Giles - 21-03-2018
(21-03-2018, 01:14 PM)Ruairidh Dunford Wrote: Stuart - do you find you need to put a spacer under the block, when taking off material from the top?
It's rare in my experience to have the pistons actually coming above the block face after a skim on an A7 motor, but obviously that can happen, especially where the block has previously been skimmed. When this does happen, I just skim the piston crowns. Here's the jig I made for this job. I have knocked up several sets of the grips from guage plate so that they are always a snug fit in whatever the ring groove width happens to be.
![[Image: 36409488175_3e2974c2cd_k.jpg]](https://farm5.staticflickr.com/4369/36409488175_3e2974c2cd_k.jpg)
Apologies for the non A7 piston in this photo, but you get the idea.
![[Image: 39129256530_089a302b56_c.jpg]](https://farm1.staticflickr.com/797/39129256530_089a302b56_c.jpg)
One of my abiding memories from when I was 12 or so, was one of my elder brothers skimming a piston which was held in a 3 jaw chuck on our prehistoric Brittania lathe at home. The lathe tool must have dug in, and when the chuck spat the piston out, it ricocheted around the garage for what seemed like forever. Unfortunately, the skirt was a most peculiar shape when Chris retrieved the piston off the floor.
RE: Valve reseating - Ruairidh Dunford - 21-03-2018
Very nifty Stuart - thanks for sharing.
RE: Valve reseating - Terrytuned - 21-03-2018
John Barlow does block base shims in aluminium in two thicknesses if pistons are too high in the block
saves having to machine pistons.
Terry.
RE: Valve reseating - Ruairidh Dunford - 21-03-2018
I have seen those.
RE: Valve reseating - Ian Dunford - 21-03-2018
(13-03-2018, 02:21 PM)P J Quinn Wrote: I need the valve seats recut and new inserts fitted in my Austin big7 engine block. Can anyone recommend a workshop to do this please.
Many thanks
![[Image: huh.png]](http://www.austinsevenfriends.co.uk/forum/images/smilies/huh.png)
I’m sure their people willing to advise you P J Quinn but they really need to know roughly where you are.
RE: Valve reseating - Ruairidh Dunford - 21-03-2018
PJ is based in Ulster.
RE: Valve reseating - Colin Wilks - 29-03-2018
I am sorting some sticky valves and apart from some strange grooves in the valve's sealing faces, which I'm putting down to somebody lapping them in by rotating them in one direction with a sucker on an electric drill, a couple of the exhaust valves (4&5) are sitting slightly below the level of the face of the block. I do not want to get the block refaced at this stage and intend starting afresh with some new valves, but how far into the block do people feel is "too far" for exhaust valves to recede before there is a serious impact on exhaust gas extraction?
RE: Valve reseating - Chris KC - 30-03-2018
(29-03-2018, 06:28 PM)Colin Wilks Wrote: I am sorting some sticky valves and apart from some strange grooves in the valve's sealing faces, which I'm putting down to somebody lapping them in by rotating them in one direction with a sucker on an electric drill, a couple of the exhaust valves (4&5) are sitting slightly below the level of the face of the block. I do not want to get the block refaced at this stage and intend starting afresh with some new valves, but how far into the block do people feel is "too far" for exhaust valves to recede before there is a serious impact on exhaust gas extraction?
Colin, I reckon most people nowadays try to build their engines as good as they can be, in the hope that they won't have to touch them again for a long while. If you're in this camp you'll know what to do.
On the other hand, if you only take the car out on summer Sundays and peak performance doesn't bother you it'll probably keep on running for years. The day will come though when you have to strip it all down again.