Shimming Solid Lifters

[LuckyX2]

Hey guys, I have the tomei solid lifter kit and some jwt s3 cams that I am in the process of shimming currently.

If I understand the process correctly, I have to:
1.) take my measured clearance and subtract the desired clearance from it
2.) multiply that number the rocker ratio of 1.43
3.) add that number to the thickness of my test shim to find the thickness of the shim needed

I was hoping someone could explain the rocker ratio to me though. Will that always be 1.43 with tomei solid lifters or does it change depending on the lift of the cams?

Also, how does the rocker ratio fit into all this? I don't quite see why I have to multiply that in... To me it seems that if I want .006" clearance and have .005" clearance then I would need a .001" thinner shim. But with the rocker ratio taken into account I would need a .00143" thinner shim, correct?

I'm just not seeing why...

Also, it doesn't make sense to me that with this method, loosening clearances become even looser and tightening them becomes even tighter when multiplied by 1.43.

tl;dr: why and how does rocker ratio factor into shimming?

[compactfean]

Ok, think if it this way. When you are measuring, are you measuring between the shim and the rocker? No, you are measuring between cam base, and rocker. Well because you are measuring at the top of a "triangle" instead of at the tip the geometry is different. Think of a triangle that has a 90° and two 45° angles if you change one of the 45° angles is the other 45° still 45°? No. if it was possible to measure between rocker and solid lifter than yes you would just claculate the difference and shim accordingly. But you cant so therefore you have to calculate the geomtry difference (which tomei has done for us) which is where you get your 1.43. If you have any troubles I can guide you through it. Ive done many solid lifter conversions for sr's and other engines.

[LuckyX2]

So if I'm understanding this correctly, to shim you measure clearances between the cam and rocker but what is actually desired to be changed is the clearance between the rocker and shim which is not easy to measure.

Where the 1.43 comes in is that for every 1 unit change in clearance between the rocker and shim, there will be a 1.43 unit change between the cam and rocker. Is that correct?

So to use my previous example; if I measure .005" clearance between cam and rocker and want .006" clearance between rocker and shim, then I have to add .00143" clearance between rocker and cam to produce a .001" change between rocker and shim.

If this is the case then, thank you, I understand now. One last thing; this ratio is independent of cams and is a result of the height of the lifter, not the lift of the cams so it will always be 1.43 with tomei lifters right?

[compactfean]

1.43 will be the same no matter what. Let me check your math tomorrow and ill get back to you.

[compactfean]

K so you have your math backwards. Take your measured amount, (.005) and subtract your desired amount (.006) and you get -.001 then multiply that by 1.43 and you get -.00143. So the shim needed would have to be .00143 inches smaller than the test shim. Get it? I had too many beers last night and am glad I didnt tell you it would be all good! Lol.

[compactfean]

A little trick I noticed is take .001 inch, multiply that by your rocker ratio and you get .00143. Well shims are not sold in "inches" there sold in mm. if you convert .00143 inches into mm you get .010 mm. hhhmmmm! Shims are sold in .010mm increments! So that means for every .001 inch you need, a .010 mm bigger or smaller shim will get you where you need to be. Now tell me that nissan didnt think ahead on that one! Lol oh by the way if you want to save some money dont buy the shims from fr sport or wherever. Harley davidson makes shims that are excactly 10mm OD like ours are and are in whatever size you need. You can rather get them online or the dealer but I paid like $1.50 per at my harley dealer. The guides you WILL need to order from frsport or where ever. Or if your real broke you can use a piston ring file and hand grind your stock left over shims if you have a good micrometer.

[LuckyX2]

Yeah, I meant to say measured minus desired but good catch and that's cool that the inch/mm conversion works out like that.

And yeah, I spent a while sanding down the stock 3mm shims today but the whole thing is done. I'm just waiting for my rocker arms to return from the machine shop and my head will be going back on!
Good to know about the Harley ones for the future tho; there's a dealership right by me.

Thanks for the help!

[compactfean]

Lol! I ground my rockers with a bench grinder. Way cheaper. Hurry to no more collapsed hla's!