valve shim thickness

[Wfolland]

After assembly of my 2L rebuilt head and cam housing I haze zero clearance between valve shims and camshaft. I have new oversized valve installed, by a local machine shop, and rebuilt cams, from megacycle, out of California. My question is has anyone used valve shims with a thickness less than .130 which is the thinnest ship available according to the shop manual.My concern with a thinner shim is possible contact of the cam lobe with the bucket that the shim sets in. I really do not want to grind the valve stem to achieve the necessary cam to shim clearance if there is another option, your thoughts please. BTW according to Megacycle the cam to shim clearance for the camshafts that they reworked is,Inlet @ .010 and exhaust @ .012 .

[FiatMac]

Per Croft, the minimum shim thickness you should use is 3.25 mm (.128") or you risk contact between the nose of the cam and the edge of the cam follower bucket. He also says that 3.3mm (.13") would be safer.

[124JOE]

I thought shims were set at .17

[narfire]

Per Croft, the minimum shim thickness you should use is 3.25 mm (.128") or you risk contact between the nose of the cam and the edge of the cam follower bucket. He also says that 3.3mm (.13") would be safer.

I'll second this.

[bobplyler]

Autoricambi has 2.55 (.10 in) shims.
http://www.autoricambi.us/product/CH9-2 ... -Shim-255/

With the following warning:
"when using valve shims below 3.50mm, verify that the cam lobe does not strike the shim bucket"

[engineerted]

So do you have custom cams, or reground and you are at the min for shims? You can install two cam box gaskets, this is acceptable to do, Guy C. Has done this also. 0.010 and 0.012 gaps are fine and is required on some performance cams with aggressive ramp rates.

[So Cal Mark]

did Megacycle regrind your cams? What specs did they use?

[Wfolland]

Yes, megacycle reground the cams after welding material onto existing cam lobes in order to maintain base circle. I have the spec sheet that shows the result of their grinding, quite different that OE spec's. Put a lot of faith in the shop that is building my engine although I did contact megacycle direct and asked what was their regrind spec's based on, they told me it was based on similar 124 grinds that they have previously done, not the best answer but I'm told they are a very good shop. BTW it was not cheap.

[Wfolland]

Decided to grind valve stems to get required clearance, this is the advice from the shop that is building my engine, I agree this is the best route considering the $$$ I,m putting into this build.

[So Cal Mark]

I'm curious about Megacycle. I visited their site and they only offer motorcycle cams. My cam grinder won't weld more than one lobe. If Megacycle welds the base circle, they'd also have to weld all of the lobes. Welding the base circle would reduce lift and duration unless the lobes were welded also.

[Wfolland]

Believe all lobes were welded, here is the spec sheet I received after they ground my cams, your thoughts on the outcome. Yhey also included TDC lift with lash specification which I have not included.


Intake Exhaust

Open 19 degrees BTC 51 degrees BBC

Close 47 degrees ABC 15 degrees ATC

Valve .405" .405"
Lift


at .040" 246 degrees 246 degrees
duration

Lobe
Center 104 degrees 108 degrees

Lash of
Running .010" .012"
Clearance
(cold)

[Wfolland]

Do not understand why my last post was truncated. Hope you can understand the post.

[So Cal Mark]

yes, no problem. I misread your earlier post about welding. I see they welded all 4 lobes. That's a fairly radical grind they did. Did you have the head ported?

[Wfolland]

Yes heads are, along with the intake manifold,have been ported. Block has been bored out oversized and have Ross forged pistons that , according to my engine builder, will result in a compression ratio of 10:1. Have not decided on carbs or ignition system as of yet although I have duel Weber IDF's, the old type with fuel enrichment tube, and thinking of installing an ignition system that runs off the 26-1 tooth crankshaft pulley that I purchased from Millers Mule. Still making up my mind as to what will be best option for my driving habits that are weekend only driving thru the back roads of CT. in my 1970 Euro Spider.

[So Cal Mark]

sounds like it will be a beast. What's your exhaust?