I bit the bullet today and started sorting out the noisy tappets on my S-type. Went fairly smoothly but getting the tacho generator off was a patience sapping process, for something that is just three set screws...
Anyway, gaps and shims measured after the cams came out and it doesn't make sense - I'm not sure if I'm adding it up correctly.
The shims had no markings and I had to measure them with my (metric) micrometer. I used a conversion factor of 0.0254 between mm and thous.
Here are the numbers (any excuse for a spreadsheet). The inlet should have a gap of 4 thou and exhaust 6 thou.
Cyl Inlet Shim (mm) (th) Req'd
1 10 1.85 73 79
2 12 2.01 79 87
3 10 2.06 81 87
4 12 2.08 82 90
5 6 1.99 78 80
6 8 2.17 85 89
Cyl Exh Shim (mm) (th) Req'd
1 10 1.92 76 80
2 10 1.82 72 76
3 10 1.88 74 78
4 11 1.86 73 78
5 10 1.94 76 80
6 8 1.92 76 78
As the smallest shim available is 85 thou I think I've made a mistake - I'll remeasure the shims tomorrow just to make sure I read the scale correctly.
Any other ideas and could someone check my maths (never my strong subject)?
Simon
Maths Homework...
Moderators:Aceman, ecosselynx
Table went a bit mad so the spreadsheet can be downloaded here:
http://www.sweller.dynalias.org/docs/va ... rances.xls
Simon
http://www.sweller.dynalias.org/docs/va ... rances.xls
Simon
Hello Simon,
I`ve always found theoretical conversion mm to thou and vice versa potentialy loaded with factoring errors.
Because of this I now have both imperial and metric vernier and micrometers in my tool kit. Reasonable tools are easily available on the market. In fact my best vernier, an electronic one came from Lidl for £9.99p!
In the past, if I`ve only had a metric tool available to me on a job and the work standard was imperial, I would bring feeler guages into play for the correct sizes, them measure with a metric gauge to confirm the value. That having been said, this type of working method is slow and tedious.
Hence holding both metric and imperial measuring equipment. Makes life so much easier under gun fire.
Kind regards,
Mike Kennedy
I`ve always found theoretical conversion mm to thou and vice versa potentialy loaded with factoring errors.
Because of this I now have both imperial and metric vernier and micrometers in my tool kit. Reasonable tools are easily available on the market. In fact my best vernier, an electronic one came from Lidl for £9.99p!
In the past, if I`ve only had a metric tool available to me on a job and the work standard was imperial, I would bring feeler guages into play for the correct sizes, them measure with a metric gauge to confirm the value. That having been said, this type of working method is slow and tedious.
Hence holding both metric and imperial measuring equipment. Makes life so much easier under gun fire.
Kind regards,
Mike Kennedy
The range available is from 85 to 110 thou. Which makes my undersize shims even odder.
It may explain why they don't have letters etched on them.
A little research shows that Saab 900 (8V) shims may fit and come in the required thickness - I need to pop down the garage to do a little more measuring.
It may explain why they don't have letters etched on them.
A little research shows that Saab 900 (8V) shims may fit and come in the required thickness - I need to pop down the garage to do a little more measuring.
Hello Sweller,
the likely reason for the narrow gaps is that the valve seats\valves are worn and sitting low in the head. If you have reasonable compression you will probably be OK getting a thinner shim (s). Do be aware of any wear on the shim from the valve stem as this will affect the adjustment you are trying to make. (As the feelers will give true clearance but unless the micrometer is sitting inside any wear you will get an overthick reading).
Alec
the likely reason for the narrow gaps is that the valve seats\valves are worn and sitting low in the head. If you have reasonable compression you will probably be OK getting a thinner shim (s). Do be aware of any wear on the shim from the valve stem as this will affect the adjustment you are trying to make. (As the feelers will give true clearance but unless the micrometer is sitting inside any wear you will get an overthick reading).
Alec
The worn/over cut valve seats was my guess too. Compression seems fine.
On further examination the shims have been ground down at sme point so I just need to get some thinner than normal but thicker than the ones I have.
I believe SAAB 900 (8v) shims will fit - I need to confirm their diameter, the shims I have are 17.5mm.
I've measured the existing shims at the thinnest point to take into account wear from the valve stem head - it's not too bad but did make a slight difference.
As the tappet gap was too large I don't think the valves are receeding - it's hard to say what's happened to a 45 year old engine in its life. I know this one was rebuilt in the early 90s - how well is another matter! It's still running and returns 24 mpg - so points to being relatively healthy.
Simon
On further examination the shims have been ground down at sme point so I just need to get some thinner than normal but thicker than the ones I have.
I believe SAAB 900 (8v) shims will fit - I need to confirm their diameter, the shims I have are 17.5mm.
I've measured the existing shims at the thinnest point to take into account wear from the valve stem head - it's not too bad but did make a slight difference.
As the tappet gap was too large I don't think the valves are receeding - it's hard to say what's happened to a 45 year old engine in its life. I know this one was rebuilt in the early 90s - how well is another matter! It's still running and returns 24 mpg - so points to being relatively healthy.
Simon
Your tappet clearances have opened up as a result of the previous shims being ground poorly - if they aren't flat or haven't been re-hardened, they'll wear away quite quickly.
The problem with using shims thinner than the standard range is that you risk the bucket touching the valve spring cap rather than the shim, but if theres no evidence of this having happened, and you're putting thicker shims in anyway, you shouldn't have a problem.
In more extreme cases you can use late AJ16 cam followers (Jaguar part no. NBC 2543 AA) which have the advantage of being nearly 60 thou thinner than the original 'buckets'. Obviously, you'll then need oversized shims to get the clearances right..
The problem with using shims thinner than the standard range is that you risk the bucket touching the valve spring cap rather than the shim, but if theres no evidence of this having happened, and you're putting thicker shims in anyway, you shouldn't have a problem.
In more extreme cases you can use late AJ16 cam followers (Jaguar part no. NBC 2543 AA) which have the advantage of being nearly 60 thou thinner than the original 'buckets'. Obviously, you'll then need oversized shims to get the clearances right..
I managed to source the correct (under)sizes from a local engine recon place.
It took a couple of attempts to get the cams in perfectly and lining up the screw holes in the splined cam sprockets was a total.....
Refitting the tacho generator was soul destroying too.
However, the engine is now a lot quieter and idles, runs etc perfectly despite my initial fears I'd managed to bend a valve because I'd not located the sprocket correctly.
Not difficult but it was a job I wouldn't like to repeat!
It took a couple of attempts to get the cams in perfectly and lining up the screw holes in the splined cam sprockets was a total.....
Refitting the tacho generator was soul destroying too.
However, the engine is now a lot quieter and idles, runs etc perfectly despite my initial fears I'd managed to bend a valve because I'd not located the sprocket correctly.
Not difficult but it was a job I wouldn't like to repeat!
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