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1980 Austin Princess - Head Rebuild Commences

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New valves have all been lapped in, this took less time than I was expecting, got to nice clean even surfaces fairly quickly.  This is possibly due to the valves having only just been done before I bent everything, I just expected the new valves to require more work to align.

2002005-23.thumb.jpg.81ba04c7f324b4796c9e8560430311c1.jpg

Unfortunately I didn't have time to do more than fit the camshaft clamp ready for measuring the valve clearances tomorrow, so that's what I did and that's where we leave it for now.

2002005-24.thumb.jpg.c1898791bcf2e26378dfec62ceb907d9.jpg

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Spent some time today trying to get the valve clearances what they should be.  The book states Standard Tappet Clearance to be .30mm plus or minus 0.03mm.  It also states adjustment is only required if clearances are below .20mm.  I was going to do this job in the shade in the garage until I found how frustrating it was to try and turn the crankshaft without everything sliding off my wobbly table, so I improvised with some cardboard and loosely bolting the head to the block.  This made measuring etc. a lot easier.

2002005-25.thumb.jpg.f7e96ec10ddf71af90c2326822011d7e.jpg

After measuring everything I had my first readings.  I hadn't changed the order of any of the shims from how they were previously, the only change was fitting the new valves.

From left to right we had .35mm, .10mm, .40mm, .30mm, .45mm, .05mm (just, this one very tight), .45mm, .20mm

I then did some maths to figure out what size shims I needed along with measuring and labelling all the shims out of the head I was working on so I could figure out what best went where.

2002005-26.thumb.jpg.5524089a66cd15397f3b013c8455d618.jpg

This quickly became quite frustrating as I didn't have exactly the shim sizes I wanted, so I shuffled things around to try and improve and got:

.45mm, .30mm, .35mm, .20mm, .35mm, too tight to measure, .50mm, .20mm

I then robbed the shims out of my spare head to try and improve matters, most of the shims in that head were a good bit thicker, and even with those the only measurement I improved was getting #7 to go from .50mm to .40mm

I ran out of patience at that point.  I was too hot and working in a spot I couldn't shade.  I'm going to have another crack at this tomorrow when I've more free time to devote to it, I suspect if I do a bit of shim swapping I might be able to get the numbers a bit more balanced, moving the .20mm ones into the .45 and .50mm ones might just balance things out so we're more in the .30-.33mm range.

I have a lot of shims that are too big and I was wondering if it's safe to file or sand them down to the thickness you want since they are, on the face of it, just a disc of steel.

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The shims will be quite hard and their surface quality is important, especially if it is the shim surface that faces the camshaft. (I can't remember where the O series shim sits -between cam and bucket or between bucket and valve)

I once tried thinning an Audi 80 shim (about an inch in diameter) using wet 'n dry (on a piece of glass to keep it flat.)  Gave up after a lot of effort had made no measurable difference. Sometimes you just have to give in and buy parts.......

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They go between valve and bucket, sit in a little cup on top of the valve spring.  Hopefully I can get things a bit closer so if I have to buy more shims I don't have to buy too many, for such a little thing they seem quite expensive, especially if you get the size wrong and have to order more.

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42 minutes ago, GBJ said:

Measure them all with no shims. Then work out what you have got to make up the gaps.

 

Not sure the reason this wasn't done innthe first place? Was it in the hope fitting new valves wouldn't change the gaps?

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circa 1994 I assisted with doing the shims on an E series 1750; we thinned the shims by holding them onto the side of a grinding disc in an angry grinder; in our defence we were stupid teenagers, we all retained ten digits each although our fingerprints took a battering and a toasting. A less hazardous means might be to hold the shims with a neodym magnet(with regular water quenching as neodym is very heat sensitive), further hazard mitigation achievable by using a belt sander instead of an angry grinder.

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A bit more maths, old metal tools, and the arrival of some new assembly lube happened today.

2002005-27.thumb.jpg.1975305181dec7d677496bf24ff4bca1.jpg

The shims measure 15.5mm across, and the desired gap is .3mm (give or take .03mm).  After a bit of swapping and measuring and generally reminding myself that I really do dislike the tedium of this particular sort of job, I finally had what is probably the best set of measurements I'm likely to get from the shims I have, without modifying said shims.

  • .30 (4.24 shim)
  • .30 (3.5 shim)
  • .30 (4.20 shim)
  • .20 tight (4.24 shim)
  • .30 (3.19 shim)
  • ? can't quite get my 0.05 feeler in there, and that's the smallest one I have (3.08 shim)
  • .30 (4.31 shim)
  • .30 (3.07 shim)

That leaves me with just 2 to correct and that shouldn't be too difficult.  4 is easy to resolve, I just need a slightly thinner shim than I have available, 6 it's probably best to remove the shim and measure the gap to get some idea of where it ought to be.  Given how much tighter 6 is than all the others I did wonder if the valve was sticking and did check, all appears to be fine and not sticking, so I guess the gap on that one is just a lot tighter for whatever reason.  Ran out of time to do more on this today so tomorrow I'll take a look at what 6's gap is without the shim.

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15 hours ago, keef said:

Not sure the reason this wasn't done innthe first place? Was it in the hope fitting new valves wouldn't change the gaps?

It just never occured to me to do that.  This is only the second time I've done shims, the first time we were doing it after old valves were ground in so since we measured the gaps with shims fitted it seemed sensible to repeat that even with the new valves I've fitted.  Likewise shortening the valve stems, not something I'd heard of doing until you mentioned it, though that's not something I'm planning to do since the thinning the shims is definitely the easier option.

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42 minutes ago, vulgalour said:

It just never occured to me to do that.  This is only the second time I've done shims, the first time we were doing it after old valves were ground in so since we measured the gaps with shims fitted it seemed sensible to repeat that even with the new valves I've fitted.  Likewise shortening the valve stems, not something I'd heard of doing until you mentioned it, though that's not something I'm planning to do since the thinning the shims is definitely the easier option.

Ah well. We never stop learning. ;)

Not sure why you'd think thinning shims was easy, but I'd go on others experience on that, if I were you. ;)

 

 

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I should have said 'comparatively easy', since holding a shim to a moving abrasive surface and getting it flat is probably easier than trying to do the same with a valve, it's also much easier to remove and refit the shims than the valves so there's less labour.  The real easy option is to acquire the correct thickness shim.

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11 minutes ago, vulgalour said:

.  The real easy option is to acquire the correct thickness shim.

Seeing as how you only seem to require one or maybe two, I'd go with that option. ;)

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On 5/21/2020 at 3:57 PM, vulgalour said:

Spent some time today trying to get the valve clearances what they should be.  The book states Standard Tappet Clearance to be .30mm plus or minus 0.03mm.  It also states adjustment is only required if clearances are below .20mm.  I was going to do this job in the shade in the garage until I found how frustrating it was to try and turn the crankshaft without everything sliding off my wobbly table, so I improvised with some cardboard and loosely bolting the head to the block.  This made measuring etc. a lot easier.

2002005-25.thumb.jpg.f7e96ec10ddf71af90c2326822011d7e.jpg

After measuring everything I had my first readings.  I hadn't changed the order of any of the shims from how they were previously, the only change was fitting the new valves.

From left to right we had .35mm, .10mm, .40mm, .30mm, .45mm, .05mm (just, this one very tight), .45mm, .20mm

I then did some maths to figure out what size shims I needed along with measuring and labelling all the shims out of the head I was working on so I could figure out what best went where.

2002005-26.thumb.jpg.5524089a66cd15397f3b013c8455d618.jpg

This quickly became quite frustrating as I didn't have exactly the shim sizes I wanted, so I shuffled things around to try and improve and got:

.45mm, .30mm, .35mm, .20mm, .35mm, too tight to measure, .50mm, .20mm

I then robbed the shims out of my spare head to try and improve matters, most of the shims in that head were a good bit thicker, and even with those the only measurement I improved was getting #7 to go from .50mm to .40mm

I ran out of patience at that point.  I was too hot and working in a spot I couldn't shade.  I'm going to have another crack at this tomorrow when I've more free time to devote to it, I suspect if I do a bit of shim swapping I might be able to get the numbers a bit more balanced, moving the .20mm ones into the .45 and .50mm ones might just balance things out so we're more in the .30-.33mm range.

I have a lot of shims that are too big and I was wondering if it's safe to file or sand them down to the thickness you want since they are, on the face of it, just a disc of steel.

No. They're hardened steel so you'll go through the case hardening. Fit what you have so there is a clearance and run it till hot so it all settles in. Then recheck and order the correct shims.

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Measured the two clearances I don't have the correct shims for, removing the shims entirely to find out what I need.

4 measures .60mm gap with no shim fitted.

6 measures .80mm gap with no shim fitted.

So how do I work out what size I need?  Since the shims I have are 3-4mm thick, give or take a few hundredths, what's my baseline for understanding the size of shim I need to fit here?  A lot of this has been quite difficult for me to work out, I'll be honest, because I'm not great with maths and never have been.

The other confusion for me is that sometimes, the gap size changes.  4 is a case in point on this one, here's how the measurements went as I corrected the other gaps:

  • 3.08 shim giving .20 gap
  • 3.08 shim giving .15 gap
  • 4.24 shim giving .10 gap
  • 4.31 shim giving 0.05 gap
  • 4.24 shim giving tight .20 gap

You can see it's not consistent.  I'd been warned this does happen when you're doing shims which is why you have to keep going back and measuring the gaps until they're all even.  It just made it frustrating to figure out which shim to use when the gap wasn't always what I was expecting.  That said, I'm not great with numbers so it could just be that I'm being a little bit thick.

This also brings me to the next issue.  How do I work out what thickness shim to acquire for number 6?  The gap is too small to measure with the feeler gauges I have when I've got the smallest shim available fitted, and without a shim fitted the number is practically meaningless since it's a fraction of a mm when the shims are usually 3-4mm thick.

The way I'd work out 4 is easier.  The gap is .10mm too tight so I need to reduce the size of that shim by .10mm to open up the gap.  4.24mm minus .10mm is 4.14mm, and since the tolerance is plus/minus .003mm I need a shim that's 4.11-4.17mm thick.

For 6, I know I can almost get a 0.05 feeler gauge in the gap with a 3.08mm shim fitted.  I therefore assume that the new shim I fit is going to be smaller than that.  Do I subtract the .30mm gap I need from 3.08mm? How does the .80mm gap I measured with no shim fitted apply?

 

Advice sought on this one because I don't really know how to work it out.

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33 minutes ago, vulgalour said:

How does the .80mm gap I measured with no shim fitted apply?

If the gap without a shim is 0.8 and you want it to be 0.3, then you need a 0.5 shim.  If such a thin one isn't available then it suggests either the valve is too long, or there is something wrong with the bucket or the cup where the shim sits.   I don't know the design well enough to know if this is possible, but is there maybe already a shim stuck in the cup?

 

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There's definitely not a shim hiding anywhere, the valve isn't sticking, I did check both of these things and checked the gap several times after several rotations of the camshaft to make sure I had an accurate measurement.

I've since discussed this issue variously and there's two opinions on it that come foremost.  The first opinion is that it's a slightly longer valve in 6 making the gap very small and it would be best to remove some material from the top of the valve rather than fitting a very thin shim.  The other is that the design of the shim cup (for want of a better name for it) means that without the shim it's sitting against the bucket and giving an erroneously low reading, especially when you consider how odd a .5mm shim would be when all the other shims are in the 3-4mm range.

Shim 4 is also interested when it comes to measuring with no shim fitted.

  • With no shim fitted the gap is .60mm.  This suggests a .30mm shim is required
  • With a 4.24mm shim fitted the gap is .20mm.  This suggests a 4.14 shim is required.

They can't both be correct, and 1.14mm is quite a large variance in the shim sizes.  It doesn't suggest measuring the gap without shims in the manual, instead recommending measuring with a shim fitted and then working out how much thicker or thinner that shim needs to be, I assume there is some reason for this since measuring the gap without any shim fitted doesn't seem to give an accurate measurement for the shim size required.  I had also brought my tools into question on the measurements until repeatedly measuring and finding consistent results, so it's unlikely to be a fault with the tools showing me the wrong size.

A slightly-too-long valve feels like the sensible reason for the issue.  Rather than trimming the valve stem down, I'm going to sacrifice one of the spare shims to shave it down until I can get a gap measurement with a shim fitted.  This will then tell me, hopefully, what size shim is actually required.  If I then also need to shave the valve stem down I will do so.  I won't then use the shaved down shim if I can get an appropriately sized one since I haven't had a conclusive answer on whether or not shaving shims is practical long term, I can't find out for definite whether or not the shims are hardened in a way that means I can't take material off them.

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Another consideration is @Mr Pastry's hint that the shim bucket or valve spring in 6 could be at fault.  I didn't see anything obviously amiss with the components next to the others that measure fine, so it seems unlikely to be the issue.  It's another thing to consider if I can't get the gap to behave.

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The spring cap may have the end of the valve stem recessed too deep for the bucket to sit on the stem as you said so cannot be used as a measurement datum as it essentially means nothing as all the caps will be an unknown variable

@The Mighty Quinn is 100% right to suggest not doing the clearances on a freshly built head with new parts or they will drift almost straight away in random directions, it wants 500 miles before a proper setup really.

'with a 4.24mm shim the gap is 0.20 This suggests a 4.14mm shim is required'

No idea how to quote on mobile,, but that statement is correct.

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5 hours ago, Mr Pastry said:

How are you measuring the thickness of the shims?

With a micrometer, as previously mentioned in the thread.

 

@Jikovron The spring cap theory makes sense given what I'm reading on the numbers.  I don't want to run the car at all until I've got the clearances at least close, I've got to have at least a base point to work from and then, if things need adjusting once they've settled in I can do it then.  Did I mention I find engine work tedious?  Because I find engine work tedious.

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Progress!

I have mentioned, and will continue to mention, that I'm bad with numbers.  Always have been, probably always will be.  Mathematics is a foreign and very frustrating language to me and what others find simple I find incredibly difficult.  I persist out of necessity.  With that in mind I hope you'll cut me some slack when I tell you how I got on today.

I have some spare shims, an okay bench grinder (that hasn't got a bench to bolt it to at the moment, so that's fun), some very strong magnets, and a stubborness to try and get to the bottom of this valve shimming nonsense so I can put it behind me and never think of it ever again.  Because of a failure with numbers, I went through and rechecked all of the gaps today on every valve, and remeasured every shim.  Happily, what I was doing wrong before was consistent and I can at least read feeler gauges properly, so the gaps I hadn't changed the shims in remained exactly as they were.

  • 2.526mm shim giving .30mm gap
  • 2.550mm shim giving .30mm gap
  • 2.552mm shim giving .30mm gap
  • 2.028mm shim giving .45mm gap
  • 2.518mm shim giving .30mm gap
  • 2.014mm shim giving .55mm gap
  • 2.524mm shim giving .30mm gap
  • 2.508mm shim giving .30mm gap

The good news there is that #6 now actually has a gap, even though it's quite a large one, so it definitely just needed a thinner shim.  Unfortunately, I found it pretty much impossible to not take too much material off a shim to get it to the correct size so rather than burn through all the shims I've got since I won't be using shaved down ones unless I have to anyway, I decided to only sacrifice two to get a measurement on 4 and 6, which are the only incorrect gaps.

The thing that tipped me off that I'd done something wrong was when I was looking at available shim sizes.  The shims in the Princess are apparently the same size as those in Triumph Stag and TR7, so I've a couple of leads on replacement shims now that I didn't have before, one of those leads is in Wisconsin, of all places.  I'm not really sure why I was reading the micrometer incorrectly the first attempts on this because I do know how to read one correctly, I do know how they work, I can only assumed I was getting frustrated and number-blind, I do make some monumentally daft mistakes when I've been trying to do anything with numbers for more than about an hour.  You can imagine what hell doing my self assessment tax return can be for me.

To illustrate, here is a shim I'd previously measured as being 4.3mm thick.  It is not 4.3mm thick.

2002005-28.thumb.jpg.3cb6d532e864ea1aa0357e8590387e0c.jpg

On the micrometer, there's two sets of numbers.  The set to the left are full and half millimeters, full on top and half on the bottom.  The set of numbers to the right are hundredths.  You adjust the micrometer by turning the part the numbers on the right are on, which moves up the shaft the numbers on the left are on, blanking out numbers until you get your measurement.  I'm not sure how to explain what I did wrong without a picture, so here's a picture.

2002005-29.jpg.276e49363ba08e15c8c62d5e6e57a4dc.jpg

So, with that sorted out and every shim remeasured as above, I can now at least shop for the correct shim a little easier.

4 needs the gap created by the 2.028mm shim reducing by .15mm.  Add .15mm to 2.028mm and it gives you 2.178mm.  There's a 0.03mm tolerance larger or smaller permitted.  So the new shim should be 2.148mm to 2.208mm thick.

6 needs the gap created by the 2.014mm shim reducing by .25mm.  Add .25mm to 2.014mm and it gives you 2.265mm.  There's a 0.03mm tolerance larger or small permitted.  So the new shim should be 2.235mm to 2.295mm thick.

That is, providing my maths is correct.  If it is, I'm pretty much 2 shims away from having the Princess running... before I have to do it all again when I check the clearances after a few hundred miles which... yay... great joy.

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Addendum.

So apparently I'm reading the micrometer wrong again because of course I am.

metric3.jpg.289d2d4fac6c784ca482aad34edf3fc8.jpg

Not all bad though, right, because I've got all the numbers written down so I just need to maths them correctly.

2 .5 26mm (2.76mm) shim giving .30mm gap
2 .5 50mm (??) shim giving .30mm gap
2 .5 22mm (2.72mm)shim giving .30mm gap
2 .0 28mm (2.28mm) shim giving .45mm gap
2 .5 18mm (2.68mm) shim giving .30mm gap
2 .0 14mm (2.14mm) shim giving .55mm gap
2 .5 24mm (2.74mm) shim giving .30mm gap
2 .5 08mm (2.58mm) shim giving .30mm gap

Nope, still confused on 2, not sure how I've read 50 since there isn't a 50, maybe it was 49?  Not that it matters, that shim is well within tolerance.

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