Educate Me

[mack]

At the risk of placing myself in the, " what kind of oil do you use on your spark plugs", category, I have a general mechanical question. I read someplace that the valve seat and the shims are made from the same aloy. Presumably the valves themselves are all made from the same material, (different from the shims & seats), my question is what makes each valve train wear differently. Is it that the combustion chambers are not uniform, or each cylinder breaths a bit differently because of the flash in the ports. I dig that shims would require replacing , but I'm curious why they all wouldn't require replacing at the same time and theoretically, by the same amount?

[b.walker5]

Gooood Question..

Gotta be the same reason why the valve lash in the ole 350 is never the same, dunno what the reason is but it's gotta be the same, Right? Everytime I adjust the tappets in the V8 they're different. It has solid lifters and adjustable tappets and theres alway one thats a few thou out from the rest, and never the same one. (over long periods).

This probably gets down to the pyhsics of metal, heat and pressure etc so I'm going to watch the replies with interest on this one.

[xswilly]

metal has different levels of hardness.
even a little difference will cause different wear
and remember when you replace a shim you generally are only changing it
by a couple of thousands of an inch
a human hair is 3 thousands of an inch, so having 1 thousands wear on one valve and 3 thousands wear on another valve, the difference is less that a human hair

just my 2 cents

[petejw]

the way the engine is run can also
make a difference to how things wear,
the faster the rpm the harder parts are opening and closing.

also different valve train configurations,
with over head cams (as in our bikes) valve clearances usually close
up do to wear from the valve and seat, with older
style engines that had push rods, rockers, cam followers, these parts
would wear faster resulting in the gaps being larger.

[Ken Talbot]

I dig that shims would require replacing , but I'm curious why they all wouldn't require replacing at the same time and theoretically, by the same amount?

It's a feature?

[mack]

curiosity

Pete, seems to me that I read that the reason the shims and valve seats are made from the same material was so that they would wear the same, negating the need for frequent shim adjustments.
I was just wondering about the different wear per valve train was related to mixture differences in each cylinder as I don't believe "color tune" was available 20 years ago. One cylinder richer or leaner than the next making one train work harder than the next.
As I've said before, my mechanical expertise is minimal so I'm trying to learn as I go. My usual route is to get a handle on the macro before I tackle the micro.
It certainly is a feature Ken. Last time I was in Revelstoke was to shoot down avalanches along the highway. Stayed at Rogers Pass. It was a fun couple months. Loved the scenery.

[Ivan]

Chaos Theory.

There isn't a good explaination. Why is it that my Okuma Horizontal Machining center is accurate to less than .0001" but one part will be perfect and the next .002 over nominal? Why does one stock engine in a Ford truck run 250k with only oil changes and another wear out in 30k? Why are there 20 slices of bread in a SAE ISO 2009 loaf of bread, but bologna comes in packs with 22 slices? HOW MANY LICKS DOES IT TAKE TO GET TO THE CENTER OF A TOOTSIE POP?

The world may never know.

One thing is for sure, its a damn good think FIAT didn't make out valve train. If that were the case, you'd have to carry a full shim set with you to go to the local Sonic Drive In for a cherry limeaid. You'd have the valve cover off three times. At least that was my experience with my 78 X-1/9.

[cywelchjr]

One thing is for sure, its a damn good think FIAT didn't make out valve train. If that were the case, you'd have to carry a full shim set with you to go to the local Sonic Drive In for a cherry limeaid. You'd have the valve cover off three times. At least that was my experience with my 78 X-1/9.

Dunno, how far away is your Sonic? Ours is 15 miles (east or north two choices) away, so how many valve adjustments would that mean?

[mack]

OK enough

10W1000 you say?