Cam tower shim advice

[guy72277]

Hi, just got my Euro E88 head back from the machine shop. They shaved off 0.73mm (28.74 thou). Shims come in 0.38mm (15 thou on thezstore) so my question is - is it sufficient to shim by only 0.38mm or should I slightly over-shim to 0.76mm? Is 0.03mm over going to cause excessive component wear or is that nothing to worry about? I'll be installing a new timing chain.

Also, does anyone know the thickness of RockAuto's (much cheaper) Pioneer PF-701 or PF-702 shims? Is 15 thou an engine shim standard? I've scoured Google to no avail.

I don't think I need to shim the valves too as that slack can be taken up by rocker arm pivot adjustment.

Thanks,

Guy

 

[jonbills]

Both / either will work fine. I don't know the size of the Rockauto shims.
Raising the rocker arm pivot that much will move the wipe pattern quite a long way toward the pivot. You will probably get away with it on a standard cam, but definitely worth checking.

 

[Rob Gaskin]

You shim the cam towers to correct the valve timing after a big skim right?

So the best way is a variable cam sprocket isn't it?

 

[jonbills]

You shim the cam towers to correct the valve timing after a big skim right?

So the best way is a variable cam sprocket isn't it?

Yes, if the timing is enough out to worry. you can adjust with the granularity of one tooth on a normal cam sprocket.

 

[Turn & Burn]

I agree with Rob, I think you should be looking to swing the cam sprocket to take up the slack. Otherwise you’re starting to affect the wipe pattern and will have to start adjusting the thickness of the lashpads. If I recall there are 3 settings on a standard pulley, one of these should let you advance the cam. If not an adjustable pulley is needed.

 

[guy72277]

Hi and thanks for the replies.

I think shimming is to correct the timing AND take up some of the slack in the timing chain which otherwise will chew up the timing chain guides or cause the tensioner to over-extend and possibly pop out.

I'll go for the shims from RockAuto and cross fingers they're 0.38mm so the wipe pattern is minimally affected. Rock auto is waay cheaper but I need to buy two sets as they come with only 4 shims per set (for 4 cylinder L-series).

From what I've read, this 0.73mm shouldn't mess the timing up too much or cause valve/piston contact. I do have fly-cut/eyebrow pistons on a spare motor if need be or could get a thicker head gasket.

I'll post the thickness of the RockAuto shims here once I get them so at least the info is somewhere on the web.

Thanks for your help.

 

[Bazzateer]

If a shim is a few thou too thick you can use some wet and dry on a flat surface to rub them down to a thinner size.

 

[Huw]

If a shim is a few thou too thick you can use some wet and dry on a flat surface to rub them down to a thinner size.

I actually WOULDNT recommend doing that.

The chances of getting all the shims to the correct flatness and same thickness is not very high doing that by hand. That will lead to your towers being uneven in height across the length of the cam.

At best you will be able to fit the cam but will have unequal wear on you cam bearing surfaces. At worst you won’t get the cam to fit back in the towers and have to have the towers in-line bored to true them back up.

To reiterate what John said, either probably would be fine for a standard cam.

 

[Bazzateer]

I actually WOULDNT recommend doing that.

The chances of getting all the shims to the correct flatness and same thickness is not very high doing that by hand. That will lead to your towers being uneven in height across the length of the cam.

At best you will be able to fit the cam but will have unequal wear on you cam bearing surfaces. At worst you won’t get the cam to fit back in the towers and have to have the towers in-line bored to true them back up.

You're right of course, I was thinking of valve shims where the slight differences can be adjusted out.

 

[guy72277]

Or I could double up on the shims and double down on the foot pounds of torque! Tight AF might work - Not

 

[Fairlineguy]

From the Zstore
Most valve jobs or engine rebuilds will require some level of machining of the head surface. L-Series heads are designed for specific valve train sizing and geometry, so when the head is milled beyond a certain amount (7 thousandths), these cam tower shims must be installed to put the geometry back into alignment. Each kit includes 5 shims (one shim per cam tower), which will re-align the camshaft on one head by 15 thousandths. In the event that further adjustment is required, a second set of shims will be needed. (Note: The most an L-Series cylinder head should be shimmed is 45 thousandths.) Professional installation recommended.

 

[guy72277]

Yep, I found that zstore info thanks but in my case one shim was not enough and two was too much. I'm pretty convinced now that one 15 thou shimming is going to be enough.

Plus I'm going against their recommendation by going with total amateur installation. Hehe

 

[guy72277]

Actually, I have a question about their advice. "If a head is milled more than 7 thou (0.1778mm) you should add a 15 thou shim". so that would mean it would be 7ish thou higher than standard. Huh... anyone care to explain that one to me, please? Maybe it is better to go for an over shim then rather than under shimming? Or maybe I'm over-thinking things...

 

[Fairlineguy]

Actually, I have a question about their advice. "If a head is milled more than 7 thou (0.1778mm) you should add a 15 thou shim". so that would mean it would be 7ish thou higher than standard. Huh... anyone care to explain that one to me, please? Maybe it is better to go for an over shim then rather than under shimming? Or maybe I'm over-thinking things...

Guess it depends on the state of your timing chain . If you have a new chain and sprocket and only skimmed the head
Slightly you probably won’t need shims
You just don’t want the tensioner being to fair out

 

[jonbills]

you can slot the slack side chain guide to keep the tensioner in range.
if you do that, you're left with the cam retardation. The marks on the sprocket and the plate on cam tower one will show you how far out it is. Each tooth is 18 crank degrees. Each of the numbered holes is 4 degrees. So you can advance it by 4,8 or 18 degrees. Playing with that, I think you can get it within a few degrees either way of the optimal cam timing.

 

[guy72277]

Thanks to all of you. Lots of solid info to mull over.

 

[Don Schmitz]

Hi, just got my Euro E88 head back from the machine shop. They shaved off 0.73mm (28.74 thou). Shims come in 0.38mm (15 thou on thezstore) so my question is - is it sufficient to shim by only 0.38mm or should I slightly over-shim to 0.76mm? Is 0.03mm over going to cause excessive component wear or is that nothing to worry about? I'll be installing a new timing chain.

Also, does anyone know the thickness of RockAuto's (much cheaper) Pioneer PF-701 or PF-702 shims? Is 15 thou an engine shim standard? I've scoured Google to no avail.

I don't think I need to shim the valves too as that slack can be taken up by rocker arm pivot adjustment.

Thanks,

Guy

The advice I've seen is to get within 15 or 20 thousandths without going over. Who knows for sure, some people claim they cut 100+ thousandths and just slot the guide-bolts to compensate (and use an adjustable cam gear to dial in the cam).

I did find a (US) company that makes the shims in various thicknesses so you don't have to stack up lots of pricey 15-thou shims - Innovative Machine & Supply - innomach.com - I don't know if they ship international or how long it may take to get them; they made my parts and shipped them in less than a week.