Rocker Geometry Woes

[coop]

FWIW, the wipe pattern on your old rockers(way over toward the edge) are displaced from center toward the pivot side of the rocker.  They almost look like the ones in my old ITS motor.  This is a legal way to get extra lift out of a restricted class engine such as a fairly stock ITS motor that uses a stock cam, rockers etc.  The wipe pattern is ALMOST off the pad but just so.  Just noticing.

[rossiz]

i understand about "cheating" the geometry to the back of the wipe pad (towards the pivot end) but these heads were both set up with the cam lobes running right off the back of the wipe pad and hitting the rocker arm itself. what you're seeing that appears to be a thin strip of un-wiped pad area is actually a small bevel at the end of the wipe pad where that sharp corner was worn off by the cam lobe going over it. this fooled me at first until i looked really closely under good light - hard to photograph it.

 

i'm expecting my re-surfaced rockers to come back from delta cams any day now, then i'll re-measure required lash pad thickness, order a new set of lash pads and hopefully be back on the road soon. the z has been sitting headless for way too long...

[Diseazd]

Stock lash pad thickness is just under .120 inches.......they are concave and sit down on the valve stem. New lash pads are usually flat across the bottom. If you were that far back on the wipe pattern, you'll need to start with a thicker lash pad (assuming the builder used a stock lash pad). I'd start by measuring the thickness of what he used ( you have to get inside the concave bottom to the flat top of the lash pad). Then I'd order one of each .130, .140, .150. ......then check the wipe pattern on each valve to make sure they all require the same lash pad. Put rocker and lash pad in an egg carton to keep in order.

[siteunseen]

My N47 had .160"s I'm 99.9% sure.  I can measure them later to be sure, for what that's worth (I don't know).  

[rossiz]

just got my rockers back from delta cams - they look beautiful, like new surfaces on the pad and toe.

perhaps tonight after dinner i can sneak down to the basement and check wipe patterns with my shims to get final lash pad size required...

 

 

[Zed Head]

They do look good.  Did they send the ZPaste along with the rockers?  Wonder if they've always done that or if the recent cam destruction cases have made an impact.  Maybe we should thank Leon and madkaw for their sacrifices, along with yours, re DPLLC.

[S30Driver]

Nice looking rockers....   You need to get that Z back on the road soon, especially with the nice weather of late.

 

FWIW, On Site's recent thread, you asked about machine shops with L6 experience in the Seattle area.  Check with Autosport in Ballard (johnny's machine shop).

They moved from downtown, they do alot of jaguar & exotics, I used to get alot of parts there.  Talk to Brad, he will point you in the right direction.

Their reputation is very good.  Not too far from you.

[madkaw]

Great-your rockers look pretty. Just make sure you check the wipe pattern on BOTH the cam and valve stem. My rockers were supposedly new Nissans and my cam new Schneider. 12k miles later I am rebuilding me head. 99% sure it was the rockers not having parallel surfaces , but there is a chance the cam wasn't right. Very first rocker I checked was not flat side to side by .014 on the cam surface .

The machinist found this using a dial indicator on a machined surface. 

Search you tube for Delta rockers and see.

My point is to make sure you verify the regrind carefully

[Diseazd]

.........use plenty of that zinc cam lube, and any other slick lube you can apply (). It'll protect both cam surfaces and rocker surfaces until that VR 1 arrives to do it's job! They look beautiful!

[LeonV]

Mine looked nice and shiny too, don't let it distract you. Just make sure to verify, like others are saying. Otherwise, say hello to a noisy, self-destructive valvetrain...

[rossiz]

finally got all the measurements done - learned quite a bit.

first off, i was surprised to find that the measurements were all over the place. 

second, this is a job that takes time and patience, as every .010 makes a visible difference on the wipe pattern.

 

i was lucky to have a tiny set of feeler gauges, they've been in my tool set for ages, so i don't know if they're still available but they're practically made for this job - they are just the right width to fit in slot at the top of the lash pad and short enough to avoid hitting the perimeter of the head. i pulled out the following shims: .010, .015, .020, .025, .030 to mix/match as required - this gave me combinations to make increments of .010 all the way up to .1 so i could hit standard size lash pads. i used a piece of solder wire to make a loop to hold them together so i wouldn't lose them - the solder wire is soft, easy to open and close as i had to pull/add shims to set each rocker.

 

the process: black sharpie on the rocker wipe surface, add shims, set correct lash gap, spin the cam, pull the rocker, check the pattern & repeat 'till the wipe pattern is centered, then move on to the next one. it is a quiet, methodical, satisfying project - not difficult or complicated, and it feels good to get the pattern right where it belongs.

 

after i had the amount of shim that needed to be added to each lash pad, i figured i should check the lash pads to be sure they were all the same.

made a little fixture for my digital caliper to allow me to reach up into the recess in the bottom of the lash pads and zeroed it out, then measured all 12.

i measured flat across the top of the wear surface, to avoid mis-readings from the wear divot made by the rocker arm tip - this is consistent with the flat surface generated by the feeler gauge shim stack i used for measuring as well.

turns out the lash pads were not all the same - they ranged from .117 to .121 and although the difference was fairly small, it matters when added to the shim measurements i had.

 

adding the measured lash pad thickness to the shim stack needed to center the pattern and rounding to the nearest .010 gave me the final size of the lash pads i would need. turns out i need 2 pads at .18, 5 pads at .19 and 5 pads at .20 for this head setup. 

 

so this head was set up way off - i can only guess that the valve seats were set high or not ground deep enough, or both.

MSA has the pad sizes i need, but they have a little warning that states:

 

"Application Note: Aftermarket spring retainers are required for any lash pads over .160" thickness."

 

why is this, and what is the issue with going with what i've got? i don't really want to spend even more on this head if i can avoid it...

 

the perfect tool

  

 

pattern set

 

measuring lash pads

 

measurements complete

 

[siteunseen]

So the lash pad is measured from the recess of the valve tip? Good to know I've been wrong all along saying mine were .160s. Schneider says I'm getting .175 -.190s with my regrind.

I've learned a lot through this thread, thanks Geoff.

Check Schneider. Thats where msa gets their cams and componets. Might save some you money.