Discussion
Yep, I'm a cowboy, but are you really supposed to ring your dealer and tell him you want a shim in any one of about a thousand thicknesses?
As for machining them the work involved would be to make a mounting mandrel which wouldn't be worth the average machine workshops time.
I doubt machining would be easy, as I assume the shims are at least case hardened? I would think a diamond lap mounted in a lathe should do the trick, but what do the rest of you do?
Out of interest my gaps are as follows
inlet exhaust
1 .008 .011
3 .006 .012
5 .006 .011
7 .004 .011
2 .006 .010
4 .005 .010
6 .003 .011
8 .001 .013
I wonder if theres some function of the engine whereby the valve seats nearest the driver wear the fastest?
As for machining them the work involved would be to make a mounting mandrel which wouldn't be worth the average machine workshops time.
I doubt machining would be easy, as I assume the shims are at least case hardened? I would think a diamond lap mounted in a lathe should do the trick, but what do the rest of you do?
Out of interest my gaps are as follows
inlet exhaust
1 .008 .011
3 .006 .012
5 .006 .011
7 .004 .011
2 .006 .010
4 .005 .010
6 .003 .011
8 .001 .013
I wonder if theres some function of the engine whereby the valve seats nearest the driver wear the fastest?
Julian64 said:
I wonder if theres some function of the engine whereby the valve seats nearest the driver wear the fastest?
Could number 8 get slightly hotter as it's the most boxed in of all the cylinders ? (the drivers footwell & pedal box takes up a lot more room than the passenger & wiper motor) ???
Equally, I could be talking utter cr*p !
Out of interest, although not much in this thread 
, the new top hat shims are comming from TVRpower.co.uk as everyone else seems to be pointing me at these people. The dealers I rang just told me they didn't stock any locally which didn't make any sense to me because unless they ARE modifying shims every tappit service would take the length of time needed to order shims which would be about a week in my case.
Now as tappit services don't take a week you have to wonder where they get the shims if they don't stock locally don't you
No one seems to know what car they come off of. No one seems to have ever tried to file their own shims down. All in all a strange subject with more questions than answers.
, the new top hat shims are comming from TVRpower.co.uk as everyone else seems to be pointing me at these people. The dealers I rang just told me they didn't stock any locally which didn't make any sense to me because unless they ARE modifying shims every tappit service would take the length of time needed to order shims which would be about a week in my case. Now as tappit services don't take a week you have to wonder where they get the shims if they don't stock locally don't you
No one seems to know what car they come off of. No one seems to have ever tried to file their own shims down. All in all a strange subject with more questions than answers.
Actually its pretty easy, much easier than a modern engine. I done it twice now and this third time I started making a video of the whole process to post for those who want to do their own tappets to learn from my mistakes on, and for people to poke fun at, but doing the video is actually not that easy to get a decent view cos mostly you're leant over the bit your trying to film.
I actually don't think many people do their own tappets, because there's not much in searching this forum about it, and any thread dies a death early on in a hail of why you doing that?
I actually don't think many people do their own tappets, because there's not much in searching this forum about it, and any thread dies a death early on in a hail of why you doing that?
My guess is that actually you'll only need a few shims to do the adjustment, with the corrections for most of the valves being made by swapping in shims used currently on other valves. If you work out what size shims you've currently got, it's easy enough to work out how to reshuffle things to get the clearances right for as many valves as poss. You should then be able to buy only those that you need, keeping the cost down to something a bit more reasonable. My thinking is that it may be difficult to machine your existing shims down with sufficient accuracy, you're better off keeping the old shims for another service.
The reason why dealers end up with a job lot of shims is you pay them for a full set of 16 for your service, they only need to use two and then they keep the rest. Most punters don't ask for shims that they've paid for, simply because they don't understanding what the job actually entails. I didn't until recently and learnt about this from my college tutor on a bike maintenance course.
Steve.
The reason why dealers end up with a job lot of shims is you pay them for a full set of 16 for your service, they only need to use two and then they keep the rest. Most punters don't ask for shims that they've paid for, simply because they don't understanding what the job actually entails. I didn't until recently and learnt about this from my college tutor on a bike maintenance course.
Steve.
maybe there is a new web based business here - www.shims-r-us.com give them the tolerances that you want machined are entered on the web page, a price given - and then they get sent to you in the post 8-)
I'm in!
I'm in!
what you've seen on your clearances is exactly what happens .. the exhausts hardly ever change and the inlets stretch and close the clearance up. I have a stock of shims, but because you're always moving to smaller shims on the inlets you build up a stock of mahooosive shims and keep using the smallest ones up ..
I've often ground shims down in the past and have no problem doing that at all .. in fact on some older engines like Aston straight sixes you only get 4 shim thicknesses and you're expected to either gring the valves further into the head or grind the top of the valve stem away to get the clearance correct! proper engine
I just offer mine up on the end of my finger to the side of the bench grinder stone .. when the heat through the shim starts hurting your finger you've taken a thou off lol
I've often ground shims down in the past and have no problem doing that at all .. in fact on some older engines like Aston straight sixes you only get 4 shim thicknesses and you're expected to either gring the valves further into the head or grind the top of the valve stem away to get the clearance correct! proper engine
I just offer mine up on the end of my finger to the side of the bench grinder stone .. when the heat through the shim starts hurting your finger you've taken a thou off
lolIt's the valve stem 99% of the time .. it's waisted where it protrudes into the port at the end of the guide to give less of an airflow restriction at a part of the port where high speed air is being asked to chnge direction, something it doesn't like to do.. so they increase the cross section area at that part to slow the air down, and also give less of an "in air stream" restriction.
The thin stem is slightly weaker so it stretches ..
To be fair once they're done about 30k miles they tend to stop stretching and things settle down in the top end
The thin stem is slightly weaker so it stretches ..
To be fair once they're done about 30k miles they tend to stop stretching and things settle down in the top end
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