rocker geometry with pics

doorpz · Post by **doorpz** » Sat Jan 28, 2006 6:20 pm

so i started mocking my motor up today and i thought i'd see if i could use my old push rods as they only had a couple hundred miles on them. everything seems to fit all right but this whole geometry thing kind of confuses me. i get the concept behind it i just don't really know what is good or bad. does this look okay?

the left is no shims and the right is a .045. there wasn't really that much difference in between that i could tell except for just how far i had to move the adjusters to get the right valve clearance.

VGM · Post by **VGM** » Sat Jan 28, 2006 6:32 pm

You need a longer push rod in either case to align the adjuster parrallel with the valve stem at 1/2 lifft.

doorpz · Post by **doorpz** » Sat Jan 28, 2006 6:40 pm

oh well i just thought i'd try. somehow i kinda know whats going on now that i just sat here and looked at it for awhile. so i shouldn't need that much longer of a push rod cause the one with no shim on the left looks pretty close. i'll have to see if i can find one of those adjustable push rods around town that i can use for a day.

doorpz · Post by **doorpz** » Sat Jan 28, 2006 7:37 pm

how close does it really need to be? cause the more i look at the one on the left the more it seems to be good. at no lift the adjuster cap is facing down a bit, at half lift its pretty close to parallel and at full lift the cap is facing slightly upwards. i just don't want to buy a whole new set of aluminun push rods if i don't really have too.

Tom Simpson · Post by **Tom Simpson** » Sun Jan 29, 2006 5:58 am

The left set of photos looks better than the right side...
This means that you need less shims under the rockers. Since you already don't have any, you are about at the limit of what you can do...
Installing longer pushrods won't help anything. It will only make it so you run out of adjustment on the adjusters. It won't fix any geometry problem.
From the look of the left set of photos, I'd say that your pushrod length is just right (your adjuster is in the correct position).
The only thing you can do to make it better is to shorten the rocker stands and shorten the pushrods. Other than that, I'd say run it...

VGM · Post by **VGM** » Sun Jan 29, 2006 10:24 am

Are those ACE rocker arms you are running?They look like good units.
You decide if your adjuster IS parallell with the valve stem, and then act accordingly.If you run a mild lift cam, then imperfect alignment won't be too much of a problem.If you run it a is,you probably will be just fine.
If,since you cared enough to ask, the goal is to align the adjuster with the valve stem at 1/2 lift,a longer push rod and some clearancing of the rocker arm will get you there.Shortening the rocker stands would also require rocker arm clearancing for the adjusters to work.
The elephant foot adjuster often requires the rocker to be clearanced so it can be adjusted out far enough with longer push rods( or shorter rocker stands).This can be done with careful use of a bench grinder and a minimum removal of metal(about .060").The rockers are tough and can stand a bit of metal removal in the under adjuster area.
Good luck with the mockup.

Eaallred · Post by **Eaallred** » Sun Jan 29, 2006 10:53 am

Agreed. Backcut the rocker arm for the elephant foot adjuster and you'll also need a longer pushrod.

Time spent getting the geometry dead on will pay off in the long run.

doorpz · Post by **doorpz** » Sun Jan 29, 2006 10:59 am

yep they are the ACE rockers. Art also did my heads, manifolds and rebuilt my carbs. i'm only running an engle 110 so its a pretty mild cam. it might actually be closer to parallel at half lift too as my measurements are far from perfect, i was just using a ruler and eyeballin it. yeah i was looking at it when i first put the 911 adjusters on and then i compared it to a old rocker set with stock adjusters and i could tell difference. i bet i would only need .060" to be dead on cause i'm using the same cylinders and base shims i just added a .060" copper head shim.

doorpz · Post by **doorpz** » Sun Jan 29, 2006 11:14 am

all right so as far as back cutting i'm pretty much just grinding off the lip that stick out past the rocker arm, right?

also since i know how much length i added should i still get an adjustable push rod or should i just get .060" longer pushrods.

gcorrado · Post by **gcorrado** » Sun Jan 29, 2006 12:50 pm

measure twice, cut once.

definitely definitely definitely get an adjustable pushrod and mock it up before you get new rods cut.

doorpz · Post by **doorpz** » Sun Jan 29, 2006 1:05 pm

yeah i found a shop in town that will let me use their adjustable push rod, i'll have to go and try and get it tomorrow. i hope to have this thing in and running by march but i still have to put the new tranny in and put the front end back together so i have quite a bit of work to go.

HotStreetVw · Post by **HotStreetVw** » Sun Jan 29, 2006 2:07 pm

hows the Vw crowd out there in boise?

Do you know Steve Arndt? I think he lives out there. He would be a good guy to become friends with.

doorpz · Post by **doorpz** » Sun Jan 29, 2006 2:23 pm

there's alot of ACVW's around but i don't see a whole lot of hi-po ones. i've seen a few but i probably just don't know the right people. there is quite a few vw shops in town though so i have resources when i need them. thats half the reason why i moved up here. i have a long commute now to work but i can get parts and services easy so its worth it. i've seen steve around on the forums but i've never met him in person. thats one thing that i really need is some local Vw friends to help me out since this is my first build. i'm moving to phoenix at the end of april so that is the absolute deadline to get this car done, haha its only taken me 3 years to get this point.

Joe vw · Post by **Joe vw** » Sun Jan 29, 2006 2:32 pm

doorpz wrote:all right so as far as back cutting i'm pretty much just grinding off the lip that stick out past the rocker arm, right?
also since i know how much length i added should i still get an adjustable push rod or should i just get .060" longer pushrods.

You do not want your adjusters hyper extended, it will put too much stress where it narrows. Please think about how far a "stock" adjuster protrudes from the rocker. While this is not possible with these large tips, LESS is better.
I use a ball end die grinder to clearance recess the end of the rocker.
The order I do rocker geometry is:
1-all valve stem heights close to equal height
2- all valve adjusters in a neutral position ( room to back off adjustment without swivel foot to rocker interference, but close as possable to the rocker) LOCK the jam nuts.
3- Test fit rockers and measure total lift with an indicator and "adjustable push rod" for base-line total lift. do NOT touch adjusters, use adjustable push rod adjustment to meet up to rocker
4- At half lift note angle of adjuster to valve stem without moving adjuster. Add rocker shims to correct angle, again, do NOT compensate with valve adjuster- Use adjustable push rod to compensate.
5- Test all other valves with same adjustable push rod to make sure all will fit without backing off adjuster significantly and possible rocker-arm interference.
6- Recheck full lift of valve (geometry can change it) and again check adjuster angle at half lift. If angle is off, repeat steps 4-6.
7-cut push rods to size, install tips.

rcb78 · Post by **rcb78** » Sun Jan 29, 2006 3:59 pm

You might want to add that when using rockers with the adjusters on the pushrod side there are oiling holes in the adjuster shafts. Your 'baseline' adjuster position needs to be such that the position of these holes align with the oiling holes in the rockers themselves. Failure to do so can result in no oiling to the rocker shafts and severly reduced splash oiling to the valve stems. The adjusters usually leave room for about 4 rotations, +/- 2 from the center point to allow for future adjustment, but only provided you were at the center point to begin with. --Ryan