Deck Height, how close? Options

[worn]

OK using a section of chain saw bar (very nice flat grind - I've been saving that for almost 40 years) I have measured the deck height so things are moving ahead. They range from .062 to .055 inches. Although I have fair reproducibility, these numbers vary a little because I am clumsy with the dial indicator. Fortunately the vernier caliper approach agrees pretty closely and is easier. They may be closer together than that, I doubt they are much farther though. Oh, the feeler gauge agrees too.

My question: close enough to each other?

Thanks again.

[ArtechnikA]

Issue isn't really the deck height.
Unless you believe the crank throws are off 0.01" or your total rod length is off by that or the pin heights vary ... (all unlikely, but ya gotta check everything...)

The deal is whether all the cylinders are different heights or whether the registers at the case have sunk.

If the cylinders are -not- of identical height, you may be able to play mix-n-match by using a longer cylinder on a more-sunken register.

More than individual deck height variances I believe you need to be concerned about the cylinders on the same side. If the cylinder tops are not identical on the same side, you'll have head sealing issues.

You may be able to tinker with this a little by using different base gaskets, especially if the tall cylinder on each side already has too little deck height.

[SirAndy]

You may be able to tinker with this a little by using different base gaskets, especially if the tall cylinder on each side already has too little deck height.

(IMG:style_emoticons/default/agree.gif)

I'm no expert on the subject, but using various cylinder base gaskets should get you closer than what you have now.

And like Rich pointed out, the height of the cylinders on each bank has to be the same if you want to have any chance of the heads sealing ok.

(IMG:style_emoticons/default/idea.gif)

[worn]

You may be able to tinker with this a little by using different base gaskets, especially if the tall cylinder on each side already has too little deck height.

(IMG:style_emoticons/default/agree.gif)

I'm no expert on the subject, but using various cylinder base gaskets should get you closer than what you have now.

And like Rich pointed out, the height of the cylinders on each bank has to be the same if you want to have any chance of the heads sealing ok.

(IMG:style_emoticons/default/idea.gif)

Ah yes, sealing at the cylinder heads, I was focused on compression. I should more closely examine the bar I have that spans them. And Also they seem to come in two sizes, on diagonals, so maybe swapping the jugs will be worth trying. The problem is, I already wrote position numbers 1-4 on them with a marker, so I will likely confuse myself.

Not saying I won't floor it, but this is meant as mostly stock. Thanks.

Oh, I forgot to add. My gasket kit didn't come with base gaskets or shims. I think. I got some individually wrapped Victor Reinz rings that look like cylinder head seals. i got another bag of 4 identical pieces 8 thousands thick. I think this is another set of head seals correct? Or are these meant to go below the cylinder - I would have expected paper.

[76-914]

You may be able to tinker with this a little by using different base gaskets, especially if the tall cylinder on each side already has too little deck height.

(IMG:style_emoticons/default/agree.gif)

I'm no expert on the subject, but using various cylinder base gaskets should get you closer than what you have now.

And like Rich pointed out, the height of the cylinders on each bank has to be the same if you want to have any chance of the heads sealing ok.

(IMG:style_emoticons/default/idea.gif)

Ah yes, sealing at the cylinder heads, I was focused on compression. I should more closely examine the bar I have that spans them. And Also they seem to come in two sizes, on diagonals, so maybe swapping the jugs will be worth trying. The problem is, I already wrote position numbers 1-4 on them with a marker, so I will likely confuse myself.

Not saying I won't floor it, but this is meant as mostly stock. Thanks.

Oh, I forgot to add. My gasket kit didn't come with base gaskets or shims. I think. I got some individually wrapped Victor Reinz rings that look like cylinder head seals. i got another bag of 4 identical pieces 8 thousands thick. I think this is another set of head seals correct? Or are these meant to go below the cylinder - I would have expected paper.

They'll have to be ordered separately.

[yeahmag]

You are on the outside of the spec a bit. Typically you want to see less than .005" and ideally less than .003". I've made an inexpensive tool that you can order to help a bit with accuracy. See this post: http://www.914world.com/bbs2/index.php?sho...;hl=deck+height

This will also allow you to measure any differences in height for cylinder to cylinder on one side of the case. All cylinder should be measured from the shoulder to the top of the jug prior to checking your deck height to be sure they are the same height.

[worn]

You are on the outside of the spec a bit. Typically you want to see less than .005" and ideally less than .003". I've made an inexpensive tool that you can order to help a bit with accuracy. See this post: http://www.914world.com/bbs2/index.php?sho...;hl=deck+height

This will also allow you to measure any differences in height for cylinder to cylinder on one side of the case. All cylinder should be measured from the shoulder to the top of the jug prior to checking your deck height to be sure they are the same height.

Thanks much. The plate I made covers both cylinders but I need to bore a few holes. Not as nice as yours though, but it should produce results. My biggest problem was maneuvering the silly magnetic base around between the studs! Not the base at issue I am afraid. When I switched to a caliper depth gauge it got a lot easier.

[McMark]

Shims must be added in pairs on the same side of the engine. So cylinder 1 and 2 must have the same shims and 3 &4 can have different shims, but 3& 4 must be the same. If you add shims to only one cylinder your heads won't seat/seal correctly.

[Cevan]

Not saying I won't floor it, but this is meant as mostly stock. Thanks.

All the more reason to floor it. (IMG:style_emoticons/default/beerchug.gif)

[Cap'n Krusty]

You may be able to tinker with this a little by using different base gaskets, especially if the tall cylinder on each side already has too little deck height.

(IMG:style_emoticons/default/agree.gif)

I'm no expert on the subject, but using various cylinder base gaskets should get you closer than what you have now.

And like Rich pointed out, the height of the cylinders on each bank has to be the same if you want to have any chance of the heads sealing ok.

(IMG:style_emoticons/default/idea.gif)

Ah yes, sealing at the cylinder heads, I was focused on compression. I should more closely examine the bar I have that spans them. And Also they seem to come in two sizes, on diagonals, so maybe swapping the jugs will be worth trying. The problem is, I already wrote position numbers 1-4 on them with a marker, so I will likely confuse myself.

Not saying I won't floor it, but this is meant as mostly stock. Thanks.

Oh, I forgot to add. My gasket kit didn't come with base gaskets or shims. I think. I got some individually wrapped Victor Reinz rings that look like cylinder head seals. i got another bag of 4 identical pieces 8 thousands thick. I think this is another set of head seals correct? Or are these meant to go below the cylinder - I would have expected paper.

The thin ones are base gaskets.

The Cap'n

[ArtechnikA]

If you add shims to only one cylinder your heads won't seat/seal correctly.

This presumes that the cylinder spigot registers are the same distance from the crankshaft centerline and that the cylinders are all exactly the same height.

Which is a nice presumption, and I agree that if they're not like that, they all need to go to a machine shop and be made like that.

But if for some reason you wound up with a cylinder top that was, for some reason, just a little bit shorter than its neighbor, and if that cylinder also had less deck height (which should be the case, but we are measurung and verifying everything...) then one might be temped to use a 'big enough' base gasket to _make_ them be the same height. That is - it's the tops that matter, the bottoms less so.

And for completeness, we'll mention that you only get that complete perfect seal if the cylinder head mating surfaces are _also_ in exactly the same plane. There are those that claim they can be lapped to this standard, but I'm skeptical, and without putting words into the Capt'n's mouth, he's already on record as being skeptical as well...

[wndsrfr]

They'll have to be ordered separately.

If you do go the route of ordering any base shims from your parts source....you'll find that they have huge burrs on them from the stamping operation and likely will find significant variation in thickness within a package as well. I de-burred mine carefully by brushing them at an angle against a fine grinder wheel so that the edge burr got ground off but didn't touch the flat surfaces. Then measured the thickness--found that a set labeled as .040" actually mic'ed out at .036". Another set had three at .038 and one at .043!

[mrbubblehead]

i lap my barrels to heads. i just use regular ol valve lapping paste. i have also used the steel base gaskets that come in the gasket kit for shims. i havent used more than 2 base gaskets per barrel tho.....

[sean_v8_914]

cylinder length is fairly consistent. measure it.
sounds like the case deck is off

[worn]

Shims must be added in pairs on the same side of the engine. So cylinder 1 and 2 must have the same shims and 3 &4 can have different shims, but 3& 4 must be the same. If you add shims to only one cylinder your heads won't seat/seal correctly.

Thanks. But this is confusing to me since the only reason I would be shimming here would be to equalize the top planes of the adjacent cylinders. If one is lower than the other and I shim it to equal, would that not be reasonable? I see less need to use shims to make the heights exactly equal on cylinders that do not share the same head.

I spent last night looking, and the smallest shim I could find was I think 20 thousandths. I am off by 5 thou at the most between any two cylinders, so shimming seems moot unless I get out my shim stock and make my own.

One last thing - is the use of the gasket ring at the head something that is largely agreed upon?

Edit: I am assuming if I am *shimming* it means at the base of the cylinder.

[McMark]

No, you and Rich are right. If you're trying to equalize deck heights on the same side you can use mismatched shims. Resurfacing the cylinder bases is the best way to go.

[yeahmag]

You really need to be measuring deck height and the differences in cylinder height as they may only be loosely related. Variances in piston, rod, case, and cylinder all make up your deck height. Variances in cylinder and case make up the collinearity irregularities. Ideally you need to measure both.

Point being you can't rely on your deck height to true your cylinder height.