Valve clearances

[Mike Stevens]

I've just lapped in all the new valves and done a first measurement of the clearances using a 91 thou shim. From that I have worked out the shims I need, and (of course) are having some problems getting the exact sizes.

The question is - when the engine runs and beds in, will the clearances open or close? Should I set them to be at the upper end of the limit or the lower?

If I can't get the sizes I need, I can see some valve stems being shorted by 10 thou or so!

TIA.

Cheers,
Mike,

[Andrew S]

Hi Mike, the valves should bed in so the clearance will slightly be taken up after mileage, bit not a lot.

[Seaking]

Try these i brought the exact sizes i needed no connection ect http://qedmotorsport.co.uk/qed-shop/...tappet%20shims

[mjheathcote]

I got all my shims from my local Lotus specialist.
The shims are the same as used on the Lotus twin cam engines.
Just a possibility for you!

[Motorcycle mad]

Hi Mike
I had this problem when I did my valves, my solution was to get the shim nearest to the size I required (slightly thicker then required), then rub it down on a piece of fine emery cloth and or wet or dry, (I put the emery cloth on a wide flat file and gripped the file in a vice to ensure the emery cloth was kept flat) also to save wear on the fingers, I made up a holder which I placed the shim in, so that I could grip it easily.

Ken

[elvimto]

Mike,
I had the same problem after doing a top end overhaul, I had the engine machine shop grind the tops of the valves then I was able to set the clearance.

Stuart

[cosmicwheels]

I've just lapped in all the new valves and done a first measurement of the clearances using a 91 thou shim. From that I have worked out the shims I need, and (of course) are having some problems getting the exact sizes.

The question is - when the engine runs and beds in, will the clearances open or close? Should I set them to be at the upper end of the limit or the lower?

If I can't get the sizes I need, I can see some valve stems being shorted by 10 thou or so!

TIA.

Cheers,
Mike,

Hi mike, paddocks stock many sizes ,if i didnt buy all of them as ive just done mine.John

[Gresley]

Hi Mike,

I got nearly all the sizes I needed from Paddocks too, IIRC I had to set one of the clearances a thou bigger than I wanted as I could not get the exact shim. I don't think a thou makes much differance...

Brian.

[paulbell6]

Hi Mike, I will soon be going through this process, what is the 91thou shim for, does it ensure that the bucket does not sit directly onto the spring cap thus giving a known datum point from which you can calculate the correct shim size?
Thanks

Paul

[new to this]

Hi Mike, I will soon be going through this process, what is the 91thou shim for, does it ensure that the bucket does not sit directly onto the spring cap thus giving a known datum point from which you can calculate the correct shim size?
Thanks

Paul

paul

i think so, im going to be doing the same thing when i get my head back from the machine shop

dave

[Mike Stevens]

Thanks for all the replies. I had a good search on 'tinternet and found that I could get Lotus twin-cam shims OK in the correct thicknesses so I've ordered some of those as well as a whole load from Paddocks. It appears that Imp shims also fit.

I used a 91 thou shim to measure all the clearances as it was the thinnest I had and that meant that there should have been a measurable gap for all the valves. Actually, one valve I couldn't even get a 1.5 thou feeler in, but I hope I've made a correct allowance for that!

Rather than bolting the cam down each time I was recommended to just fit one shim and bucket only on the valve I was measuring. Then you can hold the cam tight down with that valve on the heel of its cam lobe and all the others not touching. Measuring this way meant that each valve was done in turn with the same 91 thou shim moving from one to the next and it was much quicker than having to tighten down the cam each time. With all the gaps noted, you can then work out what shim you need for each one. Mine ranged from 78 to 101 thou.

I shall, of course, check them all on final assembly!

Hopefully the bits will come today or tomorrow and I can report back.

I'm being chivvied to get the car off for paint next Monday, so I hope to get the engine running over the weekend - for the first time in 20 years!

Cheers,
Mike.

[paulbell6]

Hi Mike, all seems clear to me and I will follow your lead regarding not bolting cam shaft down. I am glad to hear that one of your clearances was 1.5thou ish, as I have had a similar problem with at least two of my valves on a trial assembly, it always makes you feel better in a perverse sort of way when someone else comes across a similar problem/situation. Good luck

Regards

Paul

[Mike Stevens]

Hi Paul,

Good luck with your shim setting. The bits didn't come yesterday (I was busy in the evening anyway), but hopefully today. Then it'll be back to careful measuring again!

Hopefully, I'm still on for running the engine this weekend. Must make sure the video camera is ready first!

Cheers,
Mike.