Deck height, What went wrong? Options

[DavidSweden]

I am rebuilding my 2.0 engine

This evening I installed #4 cylinder & piston (with new rings). I then tightened the cylinder down onto the case to measure the deck height.
The deck height came to 0.2mm which is 0.008". as I understand it the deck height should be about 1mm (0.04").
I have installed new crank bearings, the piston and cylinder are original, the shim under the cylinder is the same thickness as the original shim.

The deck height should be the same as before the rebuild shouldn't it? Anyhow the deck height seem very small.

Advice appreciated

[76-914]

David, sorry I haven't followed your build thread so I don't know your compression, head cc volume, etc. so I don't know your required spacing but you can add or subtract shims to get your desired/required spacing.

[tornik550]

Are the rods also stock? Did you have the spigots checked?

[DavidSweden]

David, sorry I haven't followed your build thread so I don't know your compression, head cc volume, etc. so I don't know your required spacing but you can add or subtract shims to get your desired/required spacing.

Thanks, I do not have a rebuild thread I don't think anyone would be interested in my newbie build as its just a stock engine
Anyhow I have not cc´d the heads yet I will do that tomorrow, but they have not been fly cut so I guess they will be about 60cc

Maybe I have misunderstood the procedure but I thought that there was a minimum deck height so the valves would not hit the top of the piston?

Have I got it wrong regarding minimum deck height if so is is it just the compression ratio that is important?

Thanks

[DavidSweden]

Are the rods also stock? Did you have the spigots checked?

What are spigots? I did not have the rods checked

[SLITS]

Spigots are the holes in the case where the cylinders sit.

[stugray]

How are you holding the cylinder down?
I have a tool made by a member on this forum cant remember who...

Here is a pic:
(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1424307439.1.jpg)

You want to measure on both sides of the piston above the wrist pin.
Measure numerous times and rock the piston in the cyl.
If you are directly above the wrist pin, the meas wont change much as you rock it.

How are you measuring? with the "shim method"?
Or the "solder method"?

Or with a dial indicator like in my pic?

[ThePaintedMan]

Cylinders in the same order? As said before, was the case machined? There are lots of variables.

[DavidSweden]

Cylinders in the same order? As said before, was the case machined? There are lots of variables.

Thanks for all the replys.

The case has not been machined, I have installed new rod bearings and crank bearings. I am holding down the cylinder with 2 steel plate on each side, similar to the pic Stugrays posted. I am using a feeler gauge to measure the deck height and a dial to get to top dead.

I will post some pics of the arrangement within the next few days.

Is there a minimum deck height to avoid the piston hitting the valves?

Thanks again

[Mark Henry]

Cylinders in the same order? As said before, was the case machined? There are lots of variables.

Thanks for all the replys.

The case has not been machined, I have installed new rod bearings and crank bearings. I am holding down the cylinder with 2 steel plate on each side, similar to the pic Stugrays posted. I am using a feeler gauge to measure the deck height and a dial to get to top dead.

I will post some pics of the arrangement within the next few days.

Is there a minimum deck height to avoid the piston hitting the valves?

Thanks again

.040" minimum
You should still do a proper CR check, you just have to figure out the Head CC and then there are CR calculators on the net.

Seen it before, the rods did you have the big end and small end bushings done?
Material was likely removed from one mating surface of the rod and cap then machined back to size, bush may also be a hair offset, making a slightly longer rod.
The new cylinders may also be a hair shorter.

You can stack up to 3 shims under the cylinder. You can get thicker shims from EMW and custom made shims from RIMCO.

[tornik550]

Cylinders in the same order? As said before, was the case machined? There are lots of variables.

Thanks for all the replys.

The case has not been machined, I have installed new rod bearings and crank bearings. I am holding down the cylinder with 2 steel plate on each side, similar to the pic Stugrays posted. I am using a feeler gauge to measure the deck height and a dial to get to top dead.

I will post some pics of the arrangement within the next few days.

Is there a minimum deck height to avoid the piston hitting the valves?

Thanks again

Hopefully someone else will chime in however I vaguely remember 0.5mm as the absolute minimum valve to piston clearance however that measurement isn't the deck height. Deck height often ends up being around 1mm however you really need to cc you heads. After that then decide what compression ratio you want then you can calculate what the deck height should be.

Did you cylinder jugs originally have any gaskets or shims? Did you reuse the same or did you change them?

[ChrisFoley]

The deck height minimum is to prevent the piston from ever hitting the cylinder head. The pistons rock in the bore and the rods stretch at high rpm.
A stock cam won't cause valves to hit pistons even with no deck height.

I say just get a set of barrel spacers that gives you the deck height you used to have and continue assembling.

[DavidSweden]

The deck height minimum is to prevent the piston from ever hitting the cylinder head. The pistons rock in the bore and the rods stretch at high rpm.
A stock cam won't cause valves to hit pistons even with no deck height.

I say just get a set of barrel spacers that gives you the deck height you used to have and continue assembling.

Thanks everyone for the help, it is appreciated

What I don't understand is if I have only replaced the rod and crank bearings and everything else is the same why is the deck height so low. Unfortunately I did not measure the deck height when I dismantled the engine. Maybe it was like that from the beginning.

[ChrisFoley]

Did you eliminate the oem head gaskets?
That could account for part of the missing deck height.

[stugray]

Is there a minimum deck height to avoid the piston hitting the valves?

As Chris mentioned above, the deck height measurement alone governs if the piston will hit the head at temp.
The secondary reason for adjusting deck is to set the compression ratio once you have CC'd the heads.

I recall Jake mention once that a min of .025 is a number that should never be crossed and that requires some extra scrutiny.
So I considered .035 enough when I built mine.

The question regarding the valves hitting the piston has to do with your cam selection and IF you have oversized valves.
IF you are running a stock cam and stock valves, then .035 - .040 deck height would be fine.
This can be checked with the "clay method" once you have the base shims installed and the valve train geometry adjusted (if required).
This pic shows my valve clearance, and I got a secondary check of my deck hegit for free (look on lower right side of clay)
(IMG:http://www.914world.com/bbs2/uploads_offsite/i366.photobucket.com-10819-1420921464.1.jpg)

However your numbers DO seem pretty small.
Even after I had my case machined flat (the machinist called it "decking the registers") I still had over .020 deck height on all 4 with no shims.

[Bulldog9]

I'm about 3 seconds less a rookie than you on Type 4 motors, but my $ is on your measuring method. If you are using the same crank, rods, pistons cyls and spacer, and haven't had the heads flycut, you are straining at a baby gnat. Just bolt & go.

[DavidSweden]

The deck height minimum is to prevent the piston from ever hitting the cylinder head. The pistons rock in the bore and the rods stretch at high rpm.
A stock cam won't cause valves to hit pistons even with no deck height.

I say just get a set of barrel spacers that gives you the deck height you used to have and continue assembling.

Thanks to everyone for the help

I have CC´d the heads and get about 60 CC´s, the piston are the US stock type and the dish cc was 5 giving a total of 65 cc or there abouts.
I remeasured the deck and with a lot of care its about 0.015"

I will be installing a head gasket, the gasket measured 0.028" but I guess it will lose some thickness when its crushed?

I am running a stock cam. so working on the info from Chris that the piston will never hit the valves I should be ok..... or have I misunderstood something?

Using the above data I will have a compression ratio of 7.7

If I put the head on with some clay on the piston as suggested by Stugray and tighten down the head is it ok to then reuse the head gasket after its been crushed?

Will I be ok?

(IMG:http://www.914world.com/bbs2/uploads_offsite/i1300.photobucket.com-17452-1424382228.1.jpg)

[ChrisFoley]

The head gasket crush is minimal.
I recommend going without the gaskets and make up the height with barrel shims instead.

[Mark Henry]

The head gasket crush is minimal.
I recommend going without the gaskets and make up the height with barrel shims instead.

(IMG:style_emoticons/default/agree.gif)

[Al Meredith]

This happed to me once. One deck height was off on one cylinder. I found the rod was refinished incorrectly. I took the case apart and removed the offending rod. I then installed the piston pin into that rod and another rod and could see the big end was not lining up. I have a drawer full of rods so it was easy to find one to compare.
Your .040 is the correct measurement. The stock rods can stretch a little. When we build a race engine with CNC rods we use a tighter clearence. Oh you can remove the rod without splitting the case. AL