New World Datsuns...

Ok So I have a Closed Chamber head sitting on my bench. I also have a ground cam sitting on my bench. The two are begging to be mated.

So I did some thinking... not sure if its correct, but I think its in the ball park. Next would be to just try it out on the head.

The idea... lash pads are needed because reground cams have a smaller radius to make the lobe bigger. Well why not figure out the lash pad size by measuring a stock cam and a ground cam? So thats what I did.

Stock: (210 stamped cam out of a 210 head, need to double check a U20 Cam)
Diameter:
1.300" intake
1.301" exhaust

Aftermarket: Unknown, 470-480 lift... somewhere in there... its a ground 210 cam (no ears like the U20 cams)
Diameter:
1.122" intake
1.131" exhaust

Difference:
Diameter:
.178" intake
.170" exhuast

difference in radius:
Radius
.089" intake
.085" exhaust

Per Racer Brown, Rocker Geometry is 1.48, so...

At Valve:
.13172" intake
.1258" exhaust

Stock lashpad ~ .096"

so I would need...

.096 + .13172 = .22772" intake
.096 + .1258 = .2218" exhaust

Tempted to just order some .190" .230" pads and mill them down at work... after double checking of course.

Already found an error in my thinking... This is difference at the cam lobe, which is different than at the valve.


And edited the math... should be better now. Hmm...

Fucking smart people and your math.

flatcat19 wrote:Fucking smart people and your math.

Right.. I couldn't figure that shit out, even if you explained it to me like a retard. I'd still make a thread and ask wtf should i use

Really? It would make sense if I explained in person...


Basically you first have to understand how a regrind cam works. A ground cam has material removed to make the lobe appear bigger. Well when you do this think of it like your valve lash now got really big! Well the rocker adjuster only does so much, and you want to keep the cam contacting the middle of the rocker arm, so to space the rocker up to meet the cam, a taller lash pad is used.

Now since the lash pad sits on the valve, we have to translate the difference in cams to the valve; the rocker is a lever. So if the cam pushes 2/3rds the distance from the pivot to the valve, you multiply the cam difference by 3/2halfs or 1.5.

And since this is a difference, we have to add to what is stock, or the stock lash pad.

I understood it. I just dislike math.
Math needs to learn to solve it's own problems.

Thats, um, like 2nd grade math, with "decimal places" and "real world" examples. Ok maybe 3rd grade... but its just basic addition and multiplication. And a bit of geometry if you want to understand exactly how it works, or just take a number as reference to skip the geometry part.

flatcat19 wrote:I understood it. I just dislike math.
Math needs to learn to solve it's own problems.

Fuckin lolled....

I'm sure I could figure it out if I actually sat down and read about it... But if someone were to come up and ask me I would be lost.

Tho I may be able to pull an engine apart and put it back together, tune shit, turn wrenches, replaces transmissions, bearings, ball joints, and do all that shit... I don't understand certain things.

So... I have torn down and put more motors than I can count back together.. But crunching numbers isn't a strong point for me. I failed basic math in school but passed algebra and another class after that in college when I was going for my AWS certificate. It's all been deleted from my head, and 2 stroke motor shit has taken its place

I just had to redue my lash pads, as we spoke about, new cam is different so I set my #2 intak and exaust valves up with the inner spring only, and installed the old lash pad, along with some non drying blue maxhinst dye, the old cam lift/duration made it hard to guess because it actualy ran the whole face of the rocker during opperation, wich I suspect your will also, new xam doesnt use that much of the rocker face in comparison so I was able to get it closer the first time, what I did is install a .190 and it was too short, the wipe pattern was towarss the tip of the rocker, so I snipped a small peice of a bent old .010 fealer guage and put it ontop of the valve stem and reinstalled the lash pad, re blued the rocker and rolled the cam over a few times. It was just alittle closer so I stacked 2 more peices in ther for a total of +.030 on my .190 lash pads, wich got me just to the inside of center on the rocker face,
I cant remember who gave me the idea about cutting a fealler guage for spacer, but it helped.
I could explain better in real word probably, not an articulate writer.

Sealik has mentioned it a few times on ratsun.

Lash pads go in the purple things... and the purple things sit on the spiral things...

Mmm shiny. Thank you. Pictures help us understand.

Good info. I have been reading up on how to set up the valve train. Looking forward to doing it when I get the head back.

So I found your thread.


Your math says less than .230 for the lash pad.
Nissan comp catalog says these retainers are to be used with .250-.340 pads.

So what part of the retainer needs to be machined off? And by how much?
And I'm guessing, at this point, that a .210 to .220 lash pad would be needed.


As for the cam-I'm guessing mild to high street cam. Mid to high range increase.

mill the top off. spring to bottom of lash pad clearance distance shouildn't change from stock... ask your machinist about lash pads, they kinda seem like they might be universal? my readings seem to make that conclusion.

im buzzed/tired.

Nissan comp catalog has the L7 cam. Close to this one in specs. .475/.270.
They list it as needing .160 lash pads, I'm guessing on stock retainers.

Trying to wrap my mind around all of this.
Comp springs against stock retainers seems like a ton of pressure.

Thoughts?

May call Isky at some point throughout my day. Very busy.

I think the difference is that the Nissan Cams are not regrinds....