Deck Height Variance

[msaltz]

I have spent all morning meticulously measuring me deck height on my new 2180 build (92 tw pistons/cylinders, 82mm crank), all new parts including case and come up with the following:

#1,3 & 4 = 0.0425"
#2 = 0.0440"

I am using the deck heght tool torqued to 18 ft/lbs. (8mm studs), attaching my dial indicator to the plate to get TDC and then using my caliper to measure down from the plate then subtracting the plate thickness. I am taking several measurements in the same location, although I do get some variation, although the measurements are repeatable. My worst case was 3 repeatable measurements out of 5. I keep coming up with 0.0015" greater deck height on my #2 cylinder. I have switched cylinders, wrist pins & pistons and my 0.09" spacers (all the spacers measure exactly the same).
I also used the screw that came with the kit and although I cannot decern the exact measurement it turns slightly (very slightly) more on my #2 cylinder. I also used feeler gauges and come up with the about the same result.

Since this is my first air cooled engine is the 0.0015" variance enough to worry about?

If so I am not sure what is causing it other then the case deck being off, which I do not have a good way of measuring, although it seems odd that just the #2 hole would be off. Should I take the case to the machine shop and have them check my case deck? Or is there something else I should check?

Any advice would be greatly appreciated.

[vwracerdave]

[esde]

IF it is the case deck, it could effect cylinder sealing. Even if it is something you can live with, I would want to know what it was.. I would suggest changing the different piston with another, and if the problem doesn't follow the piston, then change two rods. Does the problem follow a particular piston, rod, cylinder, or always show at that position on the case?
FWIW, I have had a short rod (snicker) and a piston that was too tall.
SD
_________________
modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that.

[bugguy1967]

When checking decks, I use one cylinder and piston to check all. Then I verify that the others are all the same length. .0015" is within allowable tolerance. Beyond .003", you need to worry.
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[jason]

Put both cylinders in and check with straight edge, if it’s flat I wouldn’t worry about it.

[msaltz]

Thanks for the info. I think I should be good to go, I am definitely not more than 0.0015" out. I was mostly worried about the head sealing on the cylinder if everything wasn't spot on (I'm not use to no head gaskets). Again thanks for everybody's input.

[msaltz]

Just checked the 1-2 cylinders with a straight edge. I can get a 0.0015" feeler gauge between the straight edge and the top edge of the #1 cylinder (inside edge closest to #2 cylinder) a 0.0020" wont go. Everything else is tighter than the 0.0015". So they are definitely not totally level. It sounds Like I should still be ok or is it worth taking it back to the machine shop and having them see if they can get it closer?

[bugguy1967]

If you're worrying, do a little cylinder to head lapping in that particular area.
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[slalombuggy]

[I Ride Sand]

i bet the cylinder sealing area is fine. hit it with a straight edge. more than likely it was the case not being perfectly flat when it was machined, so the deck is out of square to the crank. also did you verify the cylinder length is the same height between the mating surfaces?
_________________
Just a dirty coyote playing in the desert.
now where'd that dirty badger run off to?

[VW_Jimbo]

FWIW

I just built an engine and the case sealing surfaces were pitted from water damage. I drove it to Brothers machine shop in Ontario, CA, and had them surface the case, based off of centerline of the crankshaft. I think it was $150. Don't quote me on that because they balanced rods, and pistons, too.

Took about a week to get done, but sooo worth it! Downside. I had to add a few shims to get my desired compression ratio. Guess I could have had them machine the tops of the pistons, but no big deal!
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[maui]

I do what Brad said. Or leave it cuz it's not a big deal.

[modok]

[nsracing]

Modok, when he gets it down to half-thou then he is bragging.

Under 0.002" is very good. A lot of VW machining available cannot get down to those numbers as far as tolerance.

Most bore work are worse than 0.010. Leveling the deck -most people do not care to measure the crank axis tilt in the case. The case will get flopped on the milling table and cut. BAM!

There was a bore job once posted here and the cut was done in one pass. And that was a new case.... It was hard to watch.