What rocker arm ratios do people see? Options

[stugray]

I will get pics of the test rig after dinner, but here is the "cam card" that I got from Jake:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1355965443.1.jpg)

So I guess I am "off my meds"...?

So if I follow Jake's EXACT wording from his valve geometry adjustment, I need to set my valve lift to .368. I'll get right on that (IMG:style_emoticons/default/confused24.gif)

I am currently in the "check valve to piston clearance" step (step 1) and I have 0.73 from the intake valve to the piston (when I plan on removing 0.050 from the heads), but I guess I just "have issues"


I'm done...peace out. (IMG:style_emoticons/default/wacko.gif)


And BTW - I fully profiled the cam myself, and those numbers up there with the asteriks (*) must mean - "or somewhere around that"....
The only number I got that matches is the lift and I measure 0.388 when the card says .368, but I did not have full spring pressure on the lifter, so close enough for now.

Stu

[r_towle]

I am confused.
You have not milled out your heads but you are setting your geometry on the valve train?

[stugray]

You have not milled out your heads but you are setting your geometry on the valve train?

Not exactly - I am measuring how much clearance I have now so that I know how much I can shave from the heads with this cam & rocker setup.
I know that I have to do this all over again after I cut the heads.
I have not cut any pushrods yet.

Right now I have .073 clearance on the Intake valve.
Cutting .050 from the heads will leave me less than .023 on the intake.
So I Plan on relieving the pistons, but only if I have to.
If I change to the 1.3 Intake rockers, I will make it.

if I hadnt measured, I wouldnt have known I had 1.4 Intake rockers....
Stu

[stugray]

Some pics:

Pics of setup to measure deck height:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1355972519.1.jpg)

The valve lift measurement jig:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1355972519.2.jpg)

both lifter & valve at zero:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1355972519.3.jpg)

both lifter & valve at max lift:
(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1355972520.4.jpg)
I know it is impossible to tell from the pic, but that is .384 (CW) on the lifter and .546 (CCW) on the valve.


This is a side view to show that the dial indicator is not touching the rocker:
(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1355972520.5.jpg)

0.546/.384 = 1.42
So 1.4 Intake rockers apparently exist.

I will check the other 4 to see if they are matched.
For those observant ones - I am not using the real springs for this step to reduce hassle, but they are plenty stiff enough to seat the valve fully and be flat on top.

Final geometry setup (after final machining) will be with the real springs.

Stu

[nathansnathan]

My experience with it was that it was easy to get more than advertised lift, but something would always be wrong with it - like your adjusters which are backed out to the point of binding. It looks that you haven't taken enough off the rocker face, too. Is that an adjustable pushrod? Making that shorter and adjusting the foot in will make it not right at half lift. It is better to be too much in at half lift than not enough on account of the increasing pressure of the spring.

[stugray]

It looks that you haven't taken enough off the rocker face, too. Is that an adjustable pushrod?

I have taken ~.060 off the rocker faces and countersunk a little.
In the pics, the swivel feet have enough room to move freely.

It is an adjustable pushrod, from Jake's kit.

Stu

[nathansnathan]

It looks that you haven't taken enough off the rocker face, too. Is that an adjustable pushrod?

I have taken ~.060 off the rocker faces and countersunk a little.
In the pics, the swivel feet have enough room to move freely.

It is an adjustable pushrod, from Jake's kit.

Stu

They are all a little different being cast, but the ones I have with .060" taken off are flat at the face with the supporting bit leading up to the boss - the boss doesn't stand proud of that at all, but sort of smooths into it.

I can't remember if it was 1 1/2 or 3 turns in that is the minimum; they look close in the pic. If the valves tighten, you might run out of adjustment, even if it just barely works now. Also, the further out the adjusters are the more likely you are to hit the covers.

[ChrisFoley]

Stu,
Is it possible the ratio was altered by remachining the pushrod cup?
Can you upload a picture of an intake rocker showing the cup?

Regardless of how it was accomplished, you definitely don't want to use rockers that open the intake valve to .548 for the engine you're building.
For one thing, the supplied valve springs might not be capable of handling that much lift from two perspectives: coil bind & open pressure.

.384 is a lot different than .368.
A good cam grinder would never be that far off.
The cam card appears to be nearly useless.

[stugray]

Racer Chris,

I measured all 4 of them, Valve lift was: .546, .524, .524, 532.
For a ratio of: 1.42, 1.36, 1.36, 1.39

Here are pics of the pushrod seats as you requested.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1356214173.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1356214173.2.jpg)

If you are still interested in trading for a set that are closer to 1.3, I would be willing.
These HAVE been modified for the swivel feet (.060 removed from face & lightly countersunk).

Stu

[stugray]

Ok, so after some measurements, I get the whole "shim the rockers" thing.
I thought the main purpose for shimming the rockers was just to get more clearance for the swivel feet to have room to work.
What previous threads about this topic fail to do is explain HOW shimming the rockers can make a difference in the actual rocker ratio.
It turns out that by moving the pivot arm of the rocker geometry up & down it gives more room to adjust the push rod length.
If the rocker-arms had a fixed rocker ratio throughout their travel then this wouldnt change their ratio.
However, the rocker arms have a very different ratio depending on what the "start angle" & "end angle" is through the "throw".

If the rockers start mostly flat and rotate through ~15 degrees. there will be a totally different ratio than if the rocker started at 15 degrees and rotates to 30 degrees.

Here is a pic to show the concept:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1356308971.1.jpg)

The very top pic shows a perfect rocker, at zero degrees, and a ~1:1 rocker ratio:

The next pic down shows a more represantitive pic of our rocker geometry.
Each pic down represents how the geometry is affected by shimming the rockers UP away from the valve seats.

Now I understand HOW shimming can affect the rocker ratios.

(I Still cannot get to the required Intake valve clearence without changing rockers However...)
Stu

[stugray]

Two more questions:

1 - When some of you have had to shim the rockers, how much is typical.
I want to know what assortment of shims to preorder before the final measurements.
I have shimmed them out to 0.200 using washers and only see a marginal reduction in rocker ratio. However the swivel foot adjusters appear to prefer at least a 0.050 spacing for good clearance.

2 - Who has a good selection of rocker shims?


And nathansnathan

Also, the further out the adjusters are the more likely you are to hit the covers.

How is that possible? Regardless of where the adusters are set, that only changes the position of the rocker up&down on the adjuster. The distance from the top of the valve plus the length of the adjuster foot is fixed and does not change as you adjust them. The absolute maximum is when the valve is closed, so that number can never change even if you shim the rockers.

Confused.

Stu

[stugray]

Quick bump so racer chris doesnt forget about me ;-)

Now that I learned that the rocker ratios vary over their whole travel, do I need to check them throughout their entire rotation? My initial measurement of 1.4:1 was with zero shims under the rockers so the swivel feet were only about 1-1/2 turns away from bottoming out. I can get a smaller number for rocker ratio as I shim them out, but only by a total of 0.020.
0.550/0.388 = 1.42 (swivel foot all the way in - no shims)
0.530/0.388 = 1.37 (0.200 shims under rockers)

And I am still bothered by the statement that based on how they are adjusted, they might hit the cover. I still do not see how adjustment can make the tops of the adjusters any taller or shorter when the valve is fully closed (that is when it would hit the cover).

Stu

[ChrisFoley]

Quick bump so racer chris doesnt forget about me ;-)

(IMG:style_emoticons/default/smile.gif)

Pushrod length should be set so valve half lift occurs when the adjuster makes a straight line with the valve stem.
That means the only important part of the rocker motion range is around that point.
I asked for the rocker pictures to see if there was any evidence of modification.
I haven't had a chance to compare any here yet so I can't comment on that.
Shim as necessary to obtain the half lift geometry and swivel foot clearance.
I've never used more than .120 shim thickness.

I always shorten the stem of the adjusters and cut a new screwdriver slot.
Valve covers come in more than one version/shape, and some interfere with the swivel foot stems.

[tscrihfield]

stu,
if i could lend some advice. I would not advise milling .050" out of the heads. The exhaust stud is below the surface of the chamber. IMHO that far down is just a little too far. The other thing i would add to that is with no releif in your pistons it would be very difffcult to acheive that high of CR with that amount of lift on the cam.

use some sillly putty or play dough and find out what your exact clearance is from the valve to the piston.

Best of luck,
Thomas

just as a small token dont bring up Raby. There are plenty on both sides of the fence and any discussion tends to go the wrong way.

[Todd Enlund]

And BTW - I fully profiled the cam myself, and those numbers up there with the asteriks (*) must mean - "or somewhere around that"....

Those are duration numbers, and the * should be a °.

[ChrisFoley]

And BTW - I fully profiled the cam myself, and those numbers up there with the asteriks (*) must mean - "or somewhere around that"....

Those are duration numbers, and the * should be a °.

(IMG:style_emoticons/default/rolleyes.gif) I think there was a just a hint of sarcasm in Stu's comment. (IMG:style_emoticons/default/dry.gif)

[nathansnathan]

And nathansnathan

Also, the further out the adjusters are the more likely you are to hit the covers.

How is that possible? Regardless of where the adusters are set, that only changes the position of the rocker up&down on the adjuster. The distance from the top of the valve plus the length of the adjuster foot is fixed and does not change as you adjust them. The absolute maximum is when the valve is closed, so that number can never change even if you shim the rockers.

Confused.

Stu

I've been on vacation for a week and let my email go. As I said before, the primary thing you are doing when you "set up valve geometry" is determining the shim height. That is it; the most important factor. The pushrod length is set to account for that. Most say to make the adjuster parallel to the valve at half lift. I've had a conversation with Adrian who used to do Jake's heads back when the bugme Type 4 video was made, and I think he's got a point about making them past "straight" at half lift as I said before. It is more difficult/ harder on the cam progressively as you compress the spring more, and for this reason, it's advantageous to be further in to an "easier" place on the cam at that point.

I've got mine shimmed out by .060". You can get .060 type 4 rocker shims from cb performance, or you can buy a bag of hardened washers - these are typically ground and not stamped. A lot of them will be .060 - use calipers.

As for how the adjusters can hit the head covers? Edit- I've thought what you are saying some more and it really must be just their being slightly longer/adjusted out more. They are pretty close, the slot end of the adjusters to the head cover and they get closer as the engine gets hot with expansion. I've got only .423 lift on a webcam 86 and .060" shimmed stands and 911 adjusters that I haven't shortened. The system has clearanced the covers for me - I really need to do something about it, to be honest.

[wndsrfr]

2 - Who has a good selection of rocker shims?

EMW at Hawthorne has a nice set of shims cheap....
http://www.europeanmotorworks.com/pvw/054-...ometry+Shim+Kit

I used 'em to get my adjusters in-line with the valve stem at half lift..

You've got a good point about shimming not moving the top end of the adjusters up since they're seated on the valve stem +or- lash amount....but you do slightly change the arc of rotation & might bring them closer to the slope of the valve cover...or if you somehow got a thinner valve cover gasket also! Chris's idea of cutting them off seems best....less weight where it really really counts!

[nathansnathan]

I've given it more thought their and edited above about the adjusters hitting on account of the shimming - of course they only go out as much as the valves do plus their own length (IMG:style_emoticons/default/051103-stupid4.gif) - must just end up being out more overall. It has been a while since I've been in there, could be my slightly-over-straight at half lift has them going up a bit at the final in position. Iirc I wanted to shim them out more than I did actually, but was worried about other stuff hitting, like the rockers themselves! I think I was going for .040" clearance with modelling clay tester. Like I said, It's been so long, I want to ct new pushrods with my lathe, take my time with it, as I don't recall getting quite advertised lift - I think this is not out of the ordinary to miss it by some, as they have to be all at the lowest's position. Anyway, it can be a problem, and you know how murphys law goes (IMG:style_emoticons/default/smile.gif)

[stugray]

So I had the engine case "decked", the rods re-bushed and measured, and the heads cut by .020 and I repeat the valve travel measurements and I get:

Intake Valve travel is STILL .525 with the "old" Intake rockers.

Intake Valve travel is .519 with a set of new rockers' (completely different FI 1.8L car)

WHICH Means that MOST of these cars have 1.4 Intake Rockers so I cannot reach the desired intake valve travel with the current cam without getting special rocker arms.

So does anyone have Intake rockers that are GUARANTEED to be what "Some" assume to be 1.3, or do I need to machine my cam to accept the fact that Type-IV Intake rockers are 1.4 instead of 1.3?

Stu