When Valves Don't Measure Up!

[vairmech]

You say what?????? Is this about the quality of the valves? NO! This is also not about any one vendor because even my source of aftermarket valves have the same issue.

So, what am I talking about? Valve spring height. I used to never give this a thought and like a lot of old school people I would just add some kind of an extra shim not knowing what I was really doing. Back in the day you could get by with it and not even think about it. With today's new valves like anything you better start thinking about it!

You say, so what is it going to hurt? Well if you go far enough you get what is called coil bind in the spring and if it is enough you will bend or break something you don't want to. Even if you don't get that far then you are over pressuring the lifter and the cam and you can have accelerated wear on the lifter and cam lobe(s).

Like I said this NOT vendor bashing but I happened to have a set of the Clark's GN Tuftrided valves, the same thing has happened to my valves I source but I thought nothing of it until I used a different manufacturer's valve. So what is happening?

First off I now measure all of my valve spring heights, I have a tool that I modified to work on the Corvair heads. Once you get a number that is larger than the valve spring height that you want those keepers and retainer become paired with that valve.
You think this is a simple number but there are many factors that go into what you set the spring height at. Some of the factors are lift, the brand and style of spring you use and what spring pressure you are after. All the while keeping in mind never to exceed the coil bind height at full lift.

Here is how the tool is set up.



I also check all of my valve springs that I get, I order bulk springs! I measure all springs at 1.7" and I get anywhere from 80-100 lbs pressure. I bag and tag the springs according to the height and pressure at that height, those of you that have gotten springs from me can attest to that fact. That is NOT a service you get from anyone else. I can play with the spring pressures a little a little and my spring heights are from 1.65-1.75". Mostly I can do 1.7" and use close to stock spring shims. OH, BTW, the stock shims are not all the same thickness!!!! I measure each one again to know what I have.
With that here is the first measurement of the spring height of the valve. That number is 1.702, good to go you say! Nope. The thinnest shim is .015", take away the .015 and what do you get? Another day older and deeper in debt! (Some of you will get the reference to the pun.)



I have a lot of retainers and keepers to try to mix and match to help and again they are not all the same! Do you see a common phrase recurring here? If I am close I can sometimes get another .005 length that way but with needing about another .015" length what can you do? I have the tools and machinery to cut the pockets deeper but it is easier to just cut the valve face. Let it be known that I have had to take several of the valves to the minimum edge thickness on the valve to get enough length so I could put at least the .015" shim in.
Below you cn see what I am talking about.



So it seems that a simple job becomes very complicated and time consuming because manufacturer's tolerances have changed. With everything I did, cutting the valve and mix/matching the keepers and retainers here is the number that I ended up with. 1.724" and the only shim I could get in there was a .015" making the spring height 1.709". Again measuring my shims I think I found a .017" shim. That spring is probably only running about 80# seat pressure, Just acceptable for what I was after in my engine for the van. If it had been the race engine I would have done something else.

[chris]

Interesting notes Ken. I appreciate your in depth photos too, as that does a great job of illustrating the concepts.

[66vairguy]

That was interesting, BUT I've always wondered about valve seat height variation affecting the height of the valve stem to head spring seat, and of course spring height.

So are you saying the valve seat to valve stem retainer groove varies among the valves, or are you saying depth of the valve seat to valve varies with rebuilt heads???

Excuse my confusion, just asking.

[vairmech]

That was interesting, BUT I've always wondered about valve seat height variation affecting the height of the valve stem to head spring seat, and of course spring height.

So are you saying the valve seat to valve stem retainer groove varies among the valves, or are you saying depth of the valve seat to valve varies with rebuilt heads???

Excuse my confusion, just asking.

I probably should have said that I did not change the seats so this is a pretty stock head. I did cut the seats in the head but that is only a minimal change.
The big variable is the aftermarket valves themselves. There is some variation in the keepers and retainers and I was able to get about a .005" change just mixing and matching and in a couple of instances I needed that little extra.

Anytime I put seats in a head I sink them between .010 to .015" deeper and I have had no issues with valve length and shimming.

[66vairguy]

That was interesting, BUT I've always wondered about valve seat height variation affecting the height of the valve stem to head spring seat, and of course spring height.

So are you saying the valve seat to valve stem retainer groove varies among the valves, or are you saying depth of the valve seat to valve varies with rebuilt heads???

Excuse my confusion, just asking.

I probably should have said that I did not change the seats so this is a pretty stock head. I did cut the seats in the head but that is only a minimal change.
The big variable is the aftermarket valves themselves. There is some variation in the keepers and retainers and I was able to get about a .005" change just mixing and matching and in a couple of instances I needed that little extra.

Anytime I put seats in a head I sink them between .010 to .015" deeper and I have had no issues with valve length and shimming.

Keepers and retainers -- that is disconcerting, but I'm not surprised nowadays. I have had issues with the new rocker nuts being either too tight or too loose. I sort them and swap them until all have the same tension on all the rocker studs.

[vairmech]

SNIP
Keepers and retainers -- that is disconcerting, but I'm not surprised nowadays. I have had issues with the new rocker nuts being either too tight or too loose. I sort them and swap them until all have the same tension on all the rocker studs.

Why would that be disconcerting? They come from different manufacturers and even then the same machine has production tolerances. Look at my pictures and the look at the differences in the retainer caps.

[vairmech]

OK, I have to re-evaluate what this post says in the beginning.

If you look closely at my pictures of my gauge tool, look at how it is in the pocket. I think it was bottoming out before in the raised area around the spring pocket. Since that time, today I readjusted the brass position and recalibrated the tool. It now sits fully in the pocket so I will take the springs back off the heads I just did and report back in a day or two.

[KenHenry]

Anything wrong with using a telescoping bore gauge and calipers for this measurement? It seemed to produce pretty repeatable results when I tried it a couple of years ago with a set of Isky springs… Ken

[vairmech]

I've used a straight edge and calipers for the longest time. Doing similar to what you mentioned. I have found that when this tool work it can be very fast to get the numbers. The longest time is doing the math and then figuring out what combination of shims gives me the most correct number.