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Rocker Geometry
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SeVVenth
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PostPosted: Tue Apr 18, 2006 12:04 pm    Post subject: Reply with quote

nsracing wrote:

The C35 is 286degrees Duration, 0.410" lift @ 0.050" checking clearance.
Somebody correct me on the specs.


ACTUALLY, the lift is only .381, .410 is the C 89. One reason I have this cam is because it barely clears the crank without notching it.
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nsracing
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PostPosted: Tue Apr 18, 2006 5:35 pm    Post subject: Reply with quote

SeVVenth wrote:
nsracing wrote:

The C35 is 286degrees Duration, 0.410" lift @ 0.050" checking clearance.
Somebody correct me on the specs.


ACTUALLY, the lift is only .381, .410 is the C 89. One reason I have this cam is because it barely clears the crank without notching it.


Not according to the data sheet I downloaded from Engle.

Are you sure? Did you mike it? Mike across the lowpoint and then across the tallest point. The difference is the lift.

So you are okay with this Rocker Geometry business then?
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mharney
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PostPosted: Tue Apr 18, 2006 5:39 pm    Post subject: Reply with quote

nsracing wrote:
Not according to the data sheet I downloaded from Engle.


Err, Nick, that cam number is a SCAT cam, not an Engle.

Scat C35 is 0.381 at the cam, 0.419 with 1.1's and 0.476 with 1.25's.

Engle 110 is 0.392, 0.430, and probably close to 0.490 with 1.25's.

Durations are almost identical.
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nsracing
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PostPosted: Wed Apr 19, 2006 6:16 am    Post subject: Reply with quote

Is there a new master list of all cams made for the VW? Laughing

Mine looks like it is outdated.

Link? anyone?

but Sev..the math remains the same. You can Mike the lobes VS. base circle and see the gross lift on the lobes.

Peace.
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mharney
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PostPosted: Wed Apr 19, 2006 6:21 am    Post subject: Reply with quote

Go to http://englecams.com and choose Products link at left. Select NEW catalog, and select VW: 1200-2500 TYPE 1,2,3

Choose solid flat tappet, and there you are.
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SeVVenth
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PostPosted: Fri Apr 21, 2006 3:03 pm    Post subject: Reply with quote

Alright, now tell me what I gotta do, lol. In this pic it has 3 shims underneath it....
http://img191.imageshack.us/my.php?image=picture0130cu.jpg

I know that the valve is supposed to be perpendicular to the center of the shaft. I have so much shit going through my head right now, can someone just tell me about what I gotta do? thanks a lot again.

EDIT: Ok, I just reread the shop talk forums about rocker geometry and looked at the pictures. Judging from mine I think I need to take out the shims, correct? I'll go try it right now and see what happens.


Last edited by SeVVenth on Fri Apr 21, 2006 3:09 pm; edited 1 time in total
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mharney
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PostPosted: Fri Apr 21, 2006 3:09 pm    Post subject: Reply with quote

Yikes!

You need to shoot for the adjusters being screwed all the way INTO the rockers, so that on the back side, there is maybe one or 1.5 threads sticking out MAX. Then, if when you put an adjustable pushrod in there, at half lift your adjuster studs are NOT parallel with the valve, you need to shim for it to get it so it is. Pull ALL the shims out to start.
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SeVVenth
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PostPosted: Fri Apr 21, 2006 3:25 pm    Post subject: Reply with quote

mharney wrote:
Yikes!

You need to shoot for the adjusters being screwed all the way INTO the rockers, so that on the back side, there is maybe one or 1.5 threads sticking out MAX. Then, if when you put an adjustable pushrod in there, at half lift your adjuster studs are NOT parallel with the valve, you need to shim for it to get it so it is. Pull ALL the shims out to start.


Well, i know that i don't want them out all the way, i was just doing that to visualize it.

Here is 0 shims.
http://img182.imageshack.us/my.php?image=picture0323mz.jpg
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mharney
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PostPosted: Fri Apr 21, 2006 4:03 pm    Post subject: Reply with quote

What are those, 1.25? Is that half lift?

Those rockers will have to be cut down to get your geometry right, I think. Look at how high they ride on the valves. Look at how much you have to have the adjusters out to be close to the right angle.
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SeVVenth
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PostPosted: Fri Apr 21, 2006 4:12 pm    Post subject: Reply with quote

I knew this was gonna suck and cost me even more money. they are 1.25s and are at half lift. I don't even know where to get them machined down around here. What EXACTLY do I need for good rocker geometry at half lift? Is it the end of the valve that needs to be perpendicular to the center of the shaft, or the end of the swivel foot? And the adjusters are only out that far because my pushrod isn't long enough to take up the slack, sorry if I forgot to mention that...
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mharney
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PostPosted: Fri Apr 21, 2006 4:56 pm    Post subject: Reply with quote

You can't do this effectively without and adjustable pushrod.

Rocker geomety does not suck.

Building an engine is a lot of work, and taking it on yourself requires that you are able to do the detail work to make sure it is right. You're going about it the right way by trying to make it right. I've seen so many engines scabbed together by lazy asses that didn't want to take the time to get it right, it's not even funny.

What you want with that type of rocker (as opposed to the kind that has the adjuster on the pushrod cup):

1. The adjuster should be PARALLEL to the valve at half lift.This ensures that the adjuster is only pushing upward on the stem during half of the event, and pushing down on the stem the other half of the event. While the adjuster is actually positioned pointing UP with respect to the stem, during the motion, it is actually DRAGGING DOWN on the surface of the stem from zero lift to half lift. And while the adjuster is actually positioned pointing DOWN with respect to the stem, it is actually still DRAGGING DOWN on the stem from half lift to full lift. Now when the valve starts coming up, against the rocker, it drags the step UP from full lift to zero lift. With swivels it's not nearly as critical due to the ball and socket's ability to deal with that, but it is still important.

2. The contact of the tip of the adjuster to the valve should be VERTICALLY CENTERED as much as possible. Look at it when you have it an zero lift, and look at it when you have it at full lift. It's probably hanging off the stem at zero, and nearly centered at full lift as it stands.

3. You want to reduce the amount that the adjuster sticks out of the rocker arm on the stem side. What this accomplishes is a reduction in vertical translation of the stem, i.e. LESS WIPING ON THE STEM. You'll get more than enough of that to distribute the wear even if the rockers are set perfectly.

4. At half lift, if you draw an imaginary line across the face of the valve tip, and extend it down to the rocker shaft, you want it to pass through the CENTER of the shaft, or as close as you can get it. There are some statics implications here that are harder to describe, but when you do it, all this will start to fall into place better.

5. You want the adjuster slightly (only a little, not a lot) off center of the stem HORIZONTALLY (what you'd see as left to right positioning of the rocker looking on from the side). This promotes valve spin, and keeps the seat clean, as well as rotating the wear point of the valve stem to keep from getting a groove or gauge... again, less of an issue with the swivels, as they have a nice contact face that distributes force over a wider area than a stock adjuster.

6. With the swivel adjusters, you have an oiling hole in the swivel stud.. you do not want this out of the range of the oiling hole built into the rocker. It must be in the range. This is another reason that having them sticking out that far is a bad idea. I guarantee also that if they were left sticking out like that, your adjuster nuts would come loose from the alternating moment forces on the adjuster.

Do you have to do all this? No. Will your valve train fail sooner if you don't? YES. Is there more to it than this? YES, but this will be enough to make it last.
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SeVVenth
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PostPosted: Fri Apr 21, 2006 5:33 pm    Post subject: Reply with quote

What about now? If I step back a little bit it looks damn near parrell to the valve. Up close not so much.
http://img175.imageshack.us/my.php?image=picture0335xt.jpg
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mharney
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PostPosted: Fri Apr 21, 2006 5:43 pm    Post subject: Reply with quote

It ain't perfect, but it'll do, as long as your tip on your adjuster never passes the edge of the the valve stem. 1.25's are harder to get right than 1.1's.
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SeVVenth
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PostPosted: Fri Apr 21, 2006 6:00 pm    Post subject: Reply with quote

Awesomo. All I needed to do was take out all the shims and shim up the psuhrod. I thought maybe 1 shim at all might be needed, but then it would probably be the other way.
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mharney
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PostPosted: Fri Apr 21, 2006 6:04 pm    Post subject: Reply with quote

It's probably as good as you're gonna get without machine work.
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SeVVenth
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PostPosted: Fri Apr 21, 2006 6:22 pm    Post subject: Reply with quote

Would you happen to have a good pic of near perfect geometry? O, and thanks a lot for helping me. You sure saved me a lot of time and a lot of aspirin.
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mharney
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PostPosted: Fri Apr 21, 2006 6:34 pm    Post subject: Reply with quote

Only for the other kind of rockers. I don't have one for this kind. But take yours, and imagine if the adjuster were vertically centered on the stem. That'd be close.
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Max Welton
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PostPosted: Fri Apr 21, 2006 7:46 pm    Post subject: Reply with quote

SeVVenth wrote:
Would you happen to have a good pic of near perfect geometry? O, and thanks a lot for helping me. You sure saved me a lot of time and a lot of aspirin.


http://www.thesamba.com/vw/forum/viewtopic.php?p=1304981&highlight=zero+lift#1304981

Max
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mharney
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PostPosted: Fri Apr 21, 2006 8:25 pm    Post subject: Reply with quote

That's pretty good Max, but it still suffers from the same problem which is more related to the rocker arms themselves than the heads and valves.. just that the point of contact is not vertically centered on the stem.

The only way to fix it that I know of is to have the studs relocated down some on the heads. Expensive with no huge return for it. There are things that are more important.
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gabe321
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PostPosted: Fri May 05, 2006 2:05 pm    Post subject: Reply with quote

ya thats right Dancing
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