cam/Valve question

[LITZ]

becaus the sho has overhed cams where does the valve lash come in? there is no rocker assembaly to creat space between the valve and the rocker? i have never taken my top end appart so im shure some of you who have, could anser these questions easaly. how noticable is the valve ticking?

 

[sdpatt]

The valve lash or gap is the space between the heel of the cam lobe and the shim that is located on the top of the tappet. The SHO has inverted bucket tappets where a tappet "bucket" is turned upside down and covers the top of the valve spring. There is a lip on the upper face of this tappet that holds the 29mm diameter shim in place.

The shims are from approximately 2.300mm to 2.750mm in thickness and are available in increments of .025mm to get the gap in the proper range. The range of the cold engine gap for the intake camshafts is .020" +- .005" or .015"-.025" and the range of the exhaust camshaft gaps is .030" +- .005" or .025"-.035".

The view in the images below is looking down on the front bank exhaust camshaft while standing in front of the car so the image is upside down. You can see the camshaft lobes and the upper face of the shim as well as the tappet.

 

[LITZ]

wow that was a fast reply thanks.
How noticable will the ticking noise be? will i hear it in my car or will i have to stick my hed under the hood to see if i here the ticking?

 

[sdpatt]

Depends on how large the gap is and if there is a damaged shim or cam lobe. Even a properly gapped engine such as mine can make ticking noises for short periods of time at various engine temperatures and engine speeds. Some morning startups let me hear the meachanical nature of the SHO's valvetrain with a few ticks as the oil flows around the heads.

 

[pjtoledo]

sdpatt:
The valve lash or gap is the space between the heel of the cam lobe and the shim that is located on the top of the tappet. The SHO has inverted bucket tappets where a tappet "bucket" is turned upside down and covers the top of the valve spring. There is a lip on the upper face of this tappet that holds the 29mm diameter shim in place.

The shims are from approximately 2.300mm to 2.750mm in thickness and are available in increments of .025mm to get the gap in the proper range. The range of the cold engine gap for the intake camshafts is .020" +- .005" or .015"-.025" and the range of the exhaust camshaft gaps is .030" +- .005" or .025"-.035".

The view in the images below is looking down on the front bank exhaust camshaft while standing in front of the car so the image is upside down. You can see the camshaft lobes and the upper face of the shim as well as the tappet.

Hey Scott,,,you just solved the riddle of the two lines on the shims in the other post!!! See the lines on the cam cap bolts?? I'll bet we get 10 more HP if the shims match those bolts.




Perry

 

[Ferendon]

Probably a stupid question, but how many shims are there in the engine? I think mine needs a valve job, or something. I hear the ticking if I stick my head under the hood or near the tire well. Haven't let it run for a while then checked it, just when it's cold idling, or barely warming up.

 

[NotSoSlowSHO]

6 Cylinders.

4 valves per cylinder.

One shim per valve.

So 24 shims total

Dont expect to need all 24 shims. When doing a shim job, you will not know the thicknesses you need, nor how many of each, until you are already checking gaps.

 

[Trojan Man]

sdpatt:
The range of the cold engine gap for the intake camshafts is .020" +- .005" or .015"-.025" and the range of the exhaust camshaft gaps is .030" +- .005" or .025"-.035".

I thought the gap was much smaller than that... last time I did a 60k was in the summer though.

 

[Trojan Man]

Shotimes lists:

Intake: .006 - .010
Exhaust: .010 - .014

 

[Rockledge]

I don't intend to do the Upper 60K until sometime later this Spring, so I'm in no hurry right now, but this thread and another current thread

http://www.shoforum.com/ubb/ultimatebb.php?ubb=get_topic;f=17;t=010091

have me wondering about the measurement part of the valve lash adjustment. I fully understand that there is a little bit of math involved in the procedure, and because of that, it would seem to me that a micrometer would have to be one of the necessary tools on hand. Is that correct?

Due to computer issues, I currently am unable to pull up and refer to the Upper 60K stuff that Scott sent me a while back when I first joined SHOForum (thanks again). I have already looked over that material several times, but currently I can't recall if a micrometer was on the tools list.

 

[Trojan Man]

There really isnt any math involved.

Use feeler gauges to measure the gap between the shim and the cam lobe. If it is in spec, flip the shim and pop it back in (assuming they haven' been flipped before). If it is out of spec, find the correct size that you need and pop it in. All of the shims are marked so there really isn't any math involved.

 

[AutoSHO]

sdpatt:

The shims are from approximately 2.300mm to 2.750mm in thickness and are available in increments of .025mm to get the gap in the proper range. The range of the cold engine gap for the intake camshafts is .020" +- .005" or .015"-.025" and the range of the exhaust camshaft gaps is .030" +- .005" or .025"-.035".

All of those tolerances are in MM, not Inches.

Metric:

.015-.025mm Intake
.025-.035mm Exhaust

SAE:

.006-.010 Inches - Intake
.010-.014 Inches - Exhaust

 

[sdpatt]

The only math involved is after you measure the gap and then remove a shim and see the printed thickness. You can determine the best guess shim to get the gap at the desired value with a simple bit of math. The Valve Clearance Worksheet that I have made available through the Forum can help document the old and new shims and gaps.

The following example is for an intake valve. I usually gap for one feeler gauge thickness less than the nominal gap so I round up to the next .025mm size shim. All values are in millimeters. It is easier for me to use the metric measure because the shims are marked in these units.

1) Gap - As Found---------: 0.229
2) Nominal Gap 0.20mm-: 0.20
3) Old Shim-----------------: 2.475
4) Reqd Shim [1-2+3]----: 2.504
5) Shim Installed----------: 2.525
6) Gap - As Left------------: 0.178

 

[Rockledge]

Excellent info, thank you.

I guess what I am thinking about is the "old" shim itself ...is it OK to assume that the number printed on the shim is accurate? Don't they wear out? Shouldn't their thickness be measured, regardless? shrug

 

[AutoSHO]

If you flip the shim it maintains its original thickness because it uses the entire face as a contact area. The very slight wear in the center will not change its thickness while in use. The numbers printed are accurate.

This is a very, very simple procedure. This level of planning and worry is not necessary! You will realize once you have started that it is simple. A set of metric feeler gauges makes it even easier.

 

[Rockledge]

Very informative thread here thumb It almost makes me want to start tearing into the top end a little sooner than I have scheduled...

 

[sdpatt]

Just be aware that the printed number on the shim matters only when you are trying to pick one out of your collection that should get the gap closest to the target spacing. The only true determination of the correct shim for a given valve is the final measure of the gap.

You can do the math from the old shim size and the measured gap to figure the best choice of a shim to try, but only after you put the shi in place and measure the gap wil you know if it is the right one for the job.

Since the measurement of the gap is made in discreet steps with a feeler gauge set, the measured gap is only a indication that the spacing is greater than the feeler gauge that fits without interference. That is why I shoot for one gauge step thinner than the nominal gap value.

 

[Thurem]

autoSHO
No offense, please, but you're off by a factor of 10.

All of those tolerances are in MM, not Inches.

Metric:

.015-.025mm Intake
.025-.035mm Exhaust

SAE:

.006-.010 Inches - Intake
.010-.014 Inches - Exhaust

It should read:
All of those tolerances are in MM, not Inches.

Metric:

.15-.25mm Intake
.25-.35mm Exhaust

SAE:

.006-.010 Inches - Intake
.010-.014 Inches - Exhaust

The way to do the conversion is :
inch x 25.4 = mm
mm /25.4 = inch

ie: 0.15mm /25.4 = 0.006"

Another note, as a motorcycle mechanic I would always install the shims with the numbers pointed away from the cam, to avoid having the numbers worn off by the camlobe.

Thure