Deck Height yet again
 

I'm in the middle of a stock overhaul on my 2.2T engine and again unexpectedly baffled - this time over deck height. The Hynes manual says nothing about it. Wayne's book says .144 - .285 (his spec for "cylinder top outer diameter to cylinder head").Most posts talk about a minimum of 1.0 mm. That's quite a difference! What to do? :confused:

Thanks

You really want 1.0mm.

I got 1mm on my 3.3 rebuild...bearly!

and ... another question
 

Thanks Steve. I'm having a heck of a time measuring from the extreme outside edge of the 2.2 T piston as the tip of my vernier is too wide. As far I as I can tell the reading is .6 mm with .75 mm of shims onboard. This way, I would have to use 3 shims - seems not right. Is there another way to measure other than the crush method? Can't do anything until the puzzle is solved. Thanks much.

Dave

JMHO,.....

The crushed-solder method is not an accurate nor reliable method of measuring deck height and not used by professional engine builders. To get accurate measurements of this very critical value, nobody else should use that either.

I use a dial indicator mounted to one of the head studs and 2 knurled screws made for this purpose to hold down the cylinder. This allows one to accurately measure the distance between the top of the cylinders and the "deck" around the perimeter of the piston domes.

Dave, I have the exact same issue (posted in 'deck height in 2.4S'). What I was just thinking of is to file the tip of my vernier to the shape of the dome where it meets the cylinder wall. I guess that the best I can do

Dennis

THat's where Steve's dial-indicator mothod can help. Small touch point, repeatable, simple.

Great idea. Thanks much. I'll do it! What was very confusing to me is why you would only measure the difference between the top of the piston at the outside perimeter and the top of the cylinder when some of the domes are so high? Probably not an issue with my lowly T pistons. So, I will do as Steve suggests. I'll report back. I assume I'm still looking for a min of 1.0 mm.

Thanks to all

Distinguish between "Deck height" and "piston to cylinder head clearance." The two are only the same with a flat-top piston.

Deck height is the distance that the THEORETICAL flat top of a piston protrudes beyond the edge of the cylinder wall. In our engines it is negative and as Dr. Ing. Weiner says, you want it to be 1.0mm.

This is not the same as the distance between the top of the dome and the cylinder.

In order to measure deck, you must have a specification for the dome height of your piston. You can either get this from the piston manufacturer, or measure it as Bruce Anderson does in his book with a height gauge. Either way, if you use the bridge method or a dial indicator, you deduct the dome height from the measured height at TDC to get you the deck height. See below.



http://forums.pelicanparts.com/911-engine-rebuilding-forum/422025-assembling-1966-901-05-engine-phase-ii-sealing-up-short-block.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/387496-setup-measuring-deck-height.html

An update. Thanks for the great information. I used a dial gauge set-up and started by finding absolute TDC. I then measured the diff between the piston top at the cylinder wall and top of the cylinder; the two ridges that will border the top sealing rings when installed. With a .25mm shim installed I got readings all over the map, all low and some even negative. I attribute some of this to a rather sloppy dial gauge setup and a dial gauge end that was very much on the bluntside. I will re-equip tomorrow and try it again. Just in case, I'm ordering some 1.0mm shims

Interesting that when I earlier tried the solder method result didn't in any way compress solder as thick as 2 mm. If my deck height is near zero, I would have expected some potential interference with the heads. Re: deck height only, there is no visible machining on the bases of the cylinders, so it must be the case?

You should be able to tell by eyeball within 1mm. Certainly you can tell by looking if you have zero deck height. I've also used feeler blades to get an approximate value. For a street engine all you have to do is make sure you have at least 1mm and no more than 1.5mm.

-Andy

I am a bit confused about this. Is this the piston edge to cylinder top measurement or the piston to head clearance?

I'm putting together a 2.0S and it seems I have tons of clearance above the piston dome, maybe as much as 4mm while the deck height is close to zero (but will increase with base gaskets.) I can't see how the factory would have ever got a 1mm deck height given the 0.25mm base gaskets I removed during disassembly.

The cylinder to head gaskets may add a little but if I understand correctly they should squish down to allow the cylinder top to meet the shoulder of the head dome adding no additional deck height. If otherwise, how is this additional deck height measured?

andy

Deck Height is the space between the piston dome and the combustion chamber, at top dead center (TDC).

And that cylinder to head gasket does add to the deck height and should be in there when you take your measurement.

It does not.
Or how do you explain the markings of the cylinder on the cylinder head recessed surface?

This is 2.0S, early design where the cylinder tops sit in a groove around the dome.

Here's a picture, the groove is red arrow and the gasket surface is the green arrow.

http://forums.pelicanparts.com/uploa...1362445978.jpg

andy

Known and true.
But the thread owner was asking for a 2.2L with CE rings.

No. Deck height is the difference between the theoretical deck of the piston and the top of the cylinder.

What you are describing is piston-to-cylinder clearance.

Also incorrect. The 2,0 liter head gasket sits around the cylinder wall and does NOT add to deck height. It's there as a backup to the cylinder wall to head interface but does not compress.

With all due respect, I disagree with your assessment.

"Competition Engineering - Easy Deck Height"

Your definition is different which makes you just as wrong as me in my opinion.