Flipping Shims??

[SHO92]

I'm almost positive that you can flip valve shims if the bottom side is not worn at all. Can someone back this up?? My friend is installing his stage 2 cams right now, yes its 1 AM, and he asked me if I knew. If anyone knows I'd really appreciate it. Thanks

 

[gosho89]

Yes, if you must but I prefer to install new. By flipping the shim you will have a fresh wear surface for your cam to ride against and yes its the same hardness as the other side was. Make sure to measure and stay within spec. I don't have much time to explain, but you can use the search feature and find all that information. Time to hit the sack. Have fun sleep

 

[shojuan]

A lot of people do it and swear by it and I even respect some of those people. I myself prefer to install new shims just like Kerry mentioned. The stated thickness is much more likely to match the actual shim thickness that way. With new shims double check your valve clearances when doing the valve adjustment. With flipped shims triple check your clearances.

 

[Yamaha V6]

And be sure to keep the documentation on what shim's in there - the numbers will wear right off if you flip.

 

[Lance Cheney]

Or use a set of calipers to measure.

We needed some thinner shims and didn't want to order them and have to wait, so he took them in to work and ground the 'old' side down. New wear surface and the right thickness. Works fine as long as you've got the right equipment to do it.

-Lance

 

[noSHO]

And for those of us who can't afford buying all new shims... I actually probably COULD have afforded it, but personally, I didn't think it was worth it. I really don't believe it will make that much of a difference, but I'd be happy to see some official documentation to the contrary.

 

[sdpatt]

If you use the numbered side of the shim facing up, the number is not touched by the cam lobe and not worn away. The number will still be there. To measure the shim thickness at the center requires a ball micrometer and does not serve any real purpose since the only true measure of the "right" shim is the final, "as left" gap measurement. The key things to shoot for during the gapping are a fresh shim surface under each cam lobe and all gaps at the desired measure. The cam lobe doesn't care about the condition of the lower shim face and can't read the number anyway.

 

[Mike Kopstain]

sdpatt:
If you use the numbered side of the shim facing up, the number is not touched by the cam lobe and not worn away. The number will still be there. To measure the shim thickness at the center requires a ball micrometer and does not serve any real purpose since the only true measure of the "right" shim is the final, "as left" gap measurement. The key things to shoot for during the gapping are a fresh shim surface under each cam lobe and all gaps at the desired measure. The cam lobe doesn't care about the condition of the lower shim face and can't read the number anyway.

The number is touched by the shim and will be worn away in most cases. The best case scenario I have seen with flipped shims is that the numbers are extremely hard to read, if not completely gone. The lobe makes contact with more of the shim than you may think.

I only flip the shims once and then toss em. If both sides have been used, I don't think they have enough hardening to use for another 60,000 miles.

Also, remember that not everyone knows what you do... I'm sure you don't do it intentionally, but you come off as a bit arrogant sometimes.

<small>[ May 20, 2003, 09:28 PM: Message edited by: Mikeys_Taurus ]</small>

 

[sdpatt]

Hey Mikeys_Taurus,

The cam lobe only touches the center 10mm of the shim. The flow of oil may have an effect on the stenciled number. The number is never in the center 10mm of the shim. I'm not being arrogant, just accurate, so get over it.

Scott

<small>[ May 22, 2003, 12:32 PM: Message edited by: sdpatt ]</small>

 

[SHOMurph]

Mikeys_Taurus:
Also, remember that not everyone knows what you do... I'm sure you don't do it intentionally, but you come off as a bit arrogant sometimes.

Becareful Mikey. Flame at SDPatt and you will get flamed by many a people.

Scott is no way arrogant and knows his SHO stuff.
He is trying to help.

 

[Yamaha V6]

I'm sorry Scott, but the wear patterns extend out farther than ø.400" on just about every shim I've ever seen. I'll be at the shop tomorrow night & will be happy to snap some pics.

 

[sdpatt]

Go right ahead, but the cam lobe is only 10mm wide and touches the shim in a 10mm wide line. No cam lobe contact outside this 10mm spot in the center of the shim unless there is significant wear (damage) to the shim resulting in cupping. The bottom face of the shim can wear because the shim can rotate in the tappet. That can make the numbers fade away. I too have seen faded numbers, but it is not from being touched by the cam lobes.

 

[pjtoledo]

sdpatt:
Go right ahead, but the cam lobe is only 10mm wide and touches the shim in a 10mm wide line. No cam lobe contact outside this 10mm spot in the center of the shim unless there is significant wear (damage) to the shim resulting in cupping. The bottom face of the shim can wear because the shim can rotate in the tappet. That can make the numbers fade away. I too have seen faded numbers, but it is not from being touched by the cam lobes.

Well, I just went down to the basement and looked at my stash of parts. While the shim indeed can rotate on the bucket, it isn't much because of the oil "stiction" that keeps the disk pretty well glued to the bucket. The bucket easily rotates in the head, and as the valves are designed to rotate, some of that motion is transfered to the bucket. Thus the cam lobe will come into frequent contact with almost all the disk surface, the outer 2mm or so not getting much if any action at all. That's why the shiny wear pattern covers all but the outer 2mm or so of the disk. The disk is not a press fit into the top of the bucket, some clearance exists, perhaps less than .001",,so some movement of the disk on the bucket occurs. Since I could still read the numbers on disks that had over 200,000 miles on them (I only change the ones out of spec) the movement/wear on the bottom of the disk must be minimal.

Perry Toledo,Ohio "tinkerer extraordinare"

<small>[ May 22, 2003, 11:07 PM: Message edited by: pjtoledo ]</small>

 

[bradman]

Interesting little debate here. I understand exactly what Scott is saying. The 10mm wide tip of the cam lobe will only create a 10mm diameter wear area in the center of the shim as the shim and/or bucket rotates. However, there is little or no clearance between the SIDE of the cam lobe and the shim BEFORE the tip comes into contact. I just went out to verify this on a set of heads I have in the garage. I tried to insert the smallest gage I have (.0015) between the side of the cam lobe and the shim, and could not get it to go. I only checked two "gaps" like this, but at the very least the clearance is so small that it would cause "polishing" (wear pattern) on more of the shim than the center 10mm. If you examine the sides of the cam lobes you will also see that they are also "polished". Even if there is a 1-2 thou gap, the shims are bound to "float" enough to come in contact with the sides of the lobes.

This just reminds me once again that this is an extremely high quality engine built to very tight tolerances.

Hope this makes sense.

 

[Mike Kopstain]

Hey Mikeys_Taurus,

The cam lobe only touches the center 10mm of the shim. The flow of oil may have an effect on the stenciled number. The number is never in the center 10mm of the shim. I'm not being arrogant, just accurate, so get over it.

Scott

Notice the circled area. This is where the *very* faded size number is. This is a shim that was flipped and used for 10,000 miles in a 93 MTX. The number was almost gone and surely would have been gone after 60,000 miles.

A shim that has never been flipped. Note the number is very clear and easy to read.

This is a regular shim, that has never been flipped. This is the top side. Notice the wear pattern. There is a dark circle in the middle, with a larger, lighter circle outside of that. The lobe spins the shim in the bucket while the vehicle is operating. As such, the part of the shim that will show the most wear will be that center 10mm, but the rest of the shim is contacted, quite frequently by the lobe. There is perhaps a 2mm circle on the edge of the shim that is not contacted bt the lobe.

I'm not a fan of calling people out, but when they display an obvious arrogant attitude and tell someone to "get over it", when they are presenting innacurate information as "gospel" that kind of strikes a nerve. Just remember, none of us know everything. There is no need for any of us to pretend to. That is why the forum is here. I hoped you would have taken my critisism seriously. It wasn't an attack on you, just a observance.

Becareful Mikey. Flame at SDPatt and you will get flamed by many a people.

Scott is no way arrogant and knows his SHO stuff.
He is trying to help.

I'm not trying to be an A$shole . Anyone that knows me knows this. If I'm wrong, I apologize. I don't think there was anything wrong with my statement however. It was a simple observance. I stand by it too.

This isn't my "I hate Scott" post... Farthest from that. I think Scott is priceless to this forum and is most likely the most contributing member, but that doesn't mean Scott is flawless or that he is god and no one can question him. In this case he is undisputibly wrong.

<small>[ May 23, 2003, 03:55 AM: Message edited by: Mikeys_Taurus ]</small>

 

[JoeHoe_SHO]

I dont have a GD clue about all this noise, but I can tell you that SDPATT (Scott) aka SHODA Does not strike me as arrogant...he is the one of the most knowledgeable (spelling) members I've seen on the forum. I'd take his advise/input very seriously...look at his credibility! Almost 280K on his SHO, 2 or 3 60Ks on his SHO, countless other 60Ks, very visual pics, instructions...the guy could more than likely build a SHO...not that others could not, but we are not talking about others here.

Mikey; I don't know you, I dig MIDWEST SHO...I've seen good advise from you..you obviously know whats up, but...you are being a little too blunt in calling Scott arrogant, the man is just trying to help.

If you think I'm just kissing Scotts ass...you can kiss my ass

Keep it real, we're all SHO owners so I guess that puts us all on the same side...what the **** do I know anyway, I can't even be sure I got a bad fuel pump, and its 4:00 AM in the damn morning and I cannot sleep thanks to my lovely work hours(4-4 am/pm)

 

[Mike Kopstain]

It was just my opinion on this one situation. Again, I stand by it.

I do valve adjustments every day of the week, every day. This motor is what I do for a living. I wouldn't have questioned Scott if he could have simply formed his response as his opinion, rather than the gospel, when he was indeed wrong.

I never questioned whether or not he was trying to help. Actions speak louder then words... Hop through this forum and look at 90% of the maintenance posts. There is Scott answering away. Good on ya! But even the best of us get big headed and need to be knocked down a couple rungs on the ladder now and then.

<small>[ May 23, 2003, 04:02 AM: Message edited by: Mikeys_Taurus ]</small>

 

[JoeHoe_SHO]

Mad respect to both of you! Friendly debates are what it is all about...just cannot take tech. debates personally.


Mike- Hope you took no offense to what I said, I shouldn't of even stuck my nose up in here...just trying to prevent another cough*JTvsTom*cough thing...

When I posted my earlier response, I obviously had no idea that you work on SHO engines everyday, not saying that anyone is more right than the other, I have no clue about any of this.

Just for ***** and giggles...the 10mm spot mentions is the dark inner circle correct? Scott is trying to say that the numbers are not worn out due to use right, the ones you showed in the pic look very faded as you said, couldn't the fading be caused by age/heat, over all wear...again, I could be choosing the wrong light at the end of the tunnel over here. *Crawls back into little hole, with the ignorant bunch*

 

[PROPHET]

So in the final analysis is it safe to flip the shims and use them? shrug

PS:Joe get back to work and think someones trying to steal your donuts.

 

[sdpatt]

Ther are plenty of others who have performed more valve gappings than myself. There are very few who do it with the eyes and analytical background from experience with physical metallurgy, mechanical engineering, and nuclear engineering. I stand by my statement that the cam lobe only touches the center 10mm of the shim.

The next time you have a valve cover off, take a close look at the contact area between the cam lobe and shim. As the lobe is rotated from the non-contact region of the heel to the peak of the lobe tip, observe and sample the area of contact.

Use a feeler guage or dental floss and see what area of the shim is actually touched by the lobe. You will find that it is an area the width of the cam lobe (approx 10mm) that is no thicker that a line drawn by a pencil. (Much like a very high pressure, low aspect tire.) The roundness of the wear spot is created only by the rotation of the tappet and shim below the cam lobe and not the shape of the contact patch.

The regions of the shim outside of this 10mm "inner circle" are subject to contact by oil on the top face and oil and the tappet bucket on the lower face. These factors conspire to fade the number stenciled on the shim and not the high pressure contact of the cam lobe.

P.S. I have performed five (5) valve gappings and timing belt change services on my own 273,850 mile, 1991 SHO.