shims

[coldstreamer]

hi boys ,

in need of some help and advise, i am rebuilding my cylinder heads and have tried feeler gauges on between the cam and the buckets , i have all different readings , the book says inlet between 008/010. and exhaust between 016/018. if i have a reading of 016 on my inlet , would i need a shim of 008 to make the correct reading , or can i buy the shims to the thickness described in the book and just fit them , robsport have the shims in stock ,

sorry for sounding a bit thick but i havent done this before , i have only worked on a shortblock chevy with hydraulic lifters ,

cheers andy

[marshman]

imported post

Hi Andy,

As you have correctly worked out you need to close the gap by 0.008". To do this you have to take out the old shim, measure its thickness, then add the 0.008" to it and then get a new shim that thick. e.g. old shim = 0.091"

add 0.008"

shim required = 0.099"

It is a real pain to do because unless you have 16 shims of every size you cannot guarantee to do the job in one go. It is even worse if some of the old shims have worn a bit and are thinner in the middle as it is much harder to accurately measure them and when you fit the new ones the gap is often still not correct.

The thinnest standard shim is around 80 thou I beleive. One only 8 thou would literally fall out the moment the engine is started.

In my opinion it does not matter too much if you are a few thou further out than the manual says, 2 thou is a bit on the tight side and you can spend forever trying to get all 16 clearances spot on.

hope this helps

Roger

[Thurlo Squire]

imported post

Andy

You need to make a note of all of the clearances. Then remove the cams. If you then remove each valve bucket you will find a shim underneath. You will need to adjust the difference from your original measurement vs required clearance by adding to or subtracting from the shim thickness and change the shim accordingly.

Nigel


To slow but Roger's explanation is better anyway

[coldstreamer]

imported post

thanks guys ,

i think i have got it , luckily i have the heads off the engine , which makes it easier.



regards ,andy

[Scotstag]

imported post

Dont just rely on adding shims,Check what shims are on the engine,check what clearances you need and instead of obtaining extra shims shift around shims and grind the end of the valves that are too long.