I sacrifice a lash adjuster and shim it solid with close to zero clearance.

If you are measuring at the valve yes the lash adjuster matters since the cam will have to rotate further to make contact.

You can figure out how much milling the heads affected your cam timing by taking the diameter of the crank sprocket and the distance you moved the head closer to the crank ( asuming the tensioner is on the slack side).

( 360/3.14 * the crank sprocket Diameter) * amount milled= retard added

So for a head and deck milling of .008" and a 2" diam crank sprocket the cam would be retarded

(360?/3.14*2)*.008= .46? Of crank rotation.

Also in my experiance the belt should not stretch or change enough to make a differance.

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A general rule of thumb is that 2? or less timing change is very hard to find on the dyno.

The cam should be ground assymetricly to account for the varying rocker arm ratio since the effective arm lenght changes as the rocker amr rotates on the shaft.

I would look at the cam both ways.. opening point VS TDC and finding the lobe center line by taking to similar lift points on each flank of the cam.

For fun you can always plot out the entire lobe profile. <img src="/forums/images/graemlins/cyclops.gif" alt="" />

It takes a while manually... Some day I will have a quick way with a couple of optical encoders and a data aquisition box.

Also since the roller does not take up the entire cam face you should be able to see / measure how much the cam has worn.


Kevin C

This I normally do agree with, some times I wonder if it was a fluke that I had one move. The belt does not particularly stretch, but some of them do not mesh real accurately on the sprockets. They settle in, break in if you choose.
I have enough time in my EVO that I might check it to see if it remained as set.

No problem.. I can be there <img src="/forums/images/graemlins/kewl.gif" alt="" /> Enjoy the game!

That's good info, Kevin! <img src="/forums/images/graemlins/kewl.gif" alt="" /> That's about right for my engine - .003" on the deck and .004" as a result of 2 cuts on the heads.... not enough to put me where I measure these cams, though.

Today, I measured both sides, swapped cam sprockets side/side, changed to another set of sprockets and tried another crankshaft sprocket. I now have both sides the same at 118* ATDC C/L - should be 115* ATDC C/L. What I don't know is if the 3* can be attributed to the geometry change by using a collapsed lifter. I filled one with 30W oil, but it won't hold it without pump pressure against it.

So, I decided to get some adjustability...... thought about machining a slotted circular plate to bolt to the sprocket spokes with 2 sets of bolts - outer and inner circular patterns (outer slotted, inner fixed), then cut the spokes between the bolt patterns so the outer belt-drive ring could be rotated for adjustment. Instead, I'll try something a little simpler and cheaper. I took both cams and sprockets to a friend's machine shop this afternoon. He's going to remove the dowel pins and drill the sprockets to use the GM eccentric bushings that are available in various amounts of change. Since the GM dowel pin is a larger diameter, he'll also make 2 stepped dowel pins for the cams to fit the bushings.

I found a good use for the knock sensor bracket - it's a good place to set up the magnetic base:



The shim idea is a good one. I can probably get a single lifter from NAPA or another auto store for testing. What's the best way to shim it?

Frank

Hi Frank,
Do you have any lash caps. If you install one on the valve top it should bottom out the lifter, the valve may be left open a bit but should not be enough to contact the piston.
On the 2.6 I use Chevy bushings and drill the cam to accept the 1/4" dowel.

Lash caps? Ahhh, the old hot-rodder's top-hat shim. No, I don't, but it does give me an idea of what to look for to shim the lifter.... maybe I can find something similar somewhere around here. I was thinking I might need to pull a lifter apart and replace the spring with something solid like a BB. I've never tried to strip one of the lifters and don't know exactly what to expect if I try it.

I guess another method would be to stuff something into the follower barrel behind the lifter. I measure the lifter compression at .100", so something on the order of .090" should do the trick.

I decided to leave the cam dowel hole as original diameter in case I ever wanted to return to OE condition. The stepped dowel pin will let me do that, although I will blow a pair of sprockets if I go back to the original.... I figured better that than trash a set of Diamante cams.

Frank

Would a 2.6 mech rocker arm fit? Might not have the same slipper/roller contact point, but you can wrench out the slack...

Dunno, Eddy - Ive never seen a 2.6 rocker arm. I should have the cams and sprockets back this afternoon and I'll see what I can rig.

Frank

I thought of that but due to the different radius of the follower the information would be meaningless. I would close the lifter down either with lash cap or washers behind the lash adjuster. I generally set cams working with opening and closing events and that might be warranted here not knowing just how asymmetric the lobes are. Going by centerline will allow that both cams will be the same but might be a degree or two from the book numbers.

The washer shims didn't work very well - rocker angle was way off - so I looked a little closer at the lifter compression during valve movement. The checking springs I'm using are weak enough that one lifter completely overpowers the checking spring - no noticeable compression and no slack. The other lifter I'm using compresses slightly - not enough to worry about. I did buy a spare lifter from AutoZone today and will try something to see if it works. I'm going to inject the spare lifter with epoxy, let it set up and see if it won't give me a solid lifer to work with.... just might work.

The cams are another lesson in learnin'. I brought them home, cleaned and installed them and began trying various eccentric bushings in the driver side sprocket. After a couple of tries, I hit the number on that cam.... 115* C/L, dead on. So, then I tried to dial in the passenger side cam, tried every bushing both ways about 6 times each. I didn't have 2 complete bushing assortments, so I'll need to order some more.

Oh, another finding. When I installed the rear crankshaft seal, the DOHC seal housing was convenient, so I grabbed it, installed the new seal and put it on the block. Today, I cleaned and painted the oil pan, laid down a nice bead of RTV and put the pan on the block. After I had about 4 pan screws in place, I noticed that the holes in the rear seal housing are not aligned with the Montero oil pan rear screw holes. That was a nice mess to clean off the pan and block. <img src="/forums/images/graemlins/baby.gif" alt="" /> ....and another 3.0L lesson learned the hard way. <img src="/forums/images/graemlins/notooth.gif" alt="" />

Frank