Compression Ratio Numbers

[BusBerd]

Does this look right?

I am shooting for a CR of 7.3:1

Bore 94mm
stroke 71mm
CC 66cc

According to the calculator the deck height would have to be 1.76mm to achieve a CR of 7.3:1

Doesn't that seem like excessive shimming??

(Is the stroke the same for all stock 2.0L engines with a stock crank and a 94mm bore?)

Thanks!!
_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

[Wildthings]

Have you figured in the dish volume of the pistons?

[BusBerd]

[Wildthings]

Deck heights of up to .060" are okay, but I would rather have the tighter deck and a bit more compression. YMMV

[SGKent]

1.75260 mm or 0.069". I am running .060 shims water cut steel shims from RIMCO to get 7.3:1 so you are close to what I have. Do not stack shims together to get your number. You need one shim for each cylinder. CC each head in case one is off. Make sure the plugs are all the way in.

Also - you will have to bolt down the cylinders to get the real deck height. You can't just slide the cylinders on and let them sit freely. Use something like this - you can ignore the run out gauges and just use feeler gauges. Look at the hold down clamps:

_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[BusBerd]

I measured the deck height tonight using a feeler gauge because a dial indicator was over $100 at the auto parts store. (But I found a more reasonable one online at Menards and I will get it tomorrow).
However, with a feeler gauge at TDC the deck height measurements were this:

Cylinder #1 .026
Cylinder #2 .016
Cylinder #3 .021
Cylinder #4 .022


I CC'ed the heads and piston dishes again tonight. I got a better plunger type syringe that moves more smoothly. I feel comfortable with saying that these numbers are at least within 1CC of being correct.

Cylinder #1 52.5CC + 15CC= 67.5CC
Cylinder #2 51CC + 15CC= 66CC
Cylinder #3 50CC + 15CC= 65CC
Cylinder #4 49CC + 15CC= 64CC

Stroke= 71mm

So, with these numbers (which I will double check the Deck height numbers with a dial indicator tomorrow), If I use an .030 shim on all of the cylinders, my compression ratio for each cylinder would be:

Cylinder #1 7.3:1
Cylinder #2 7.6:1
Cylinder #3 7.7:1
Cylinder #4 7.7:1


If I could use different size shims on all 4 of the cylinders to get a 7.3:1 compression rate all around (or as close to it as possible). The shims I would need on each cylinder would be:

cylinder #1 .030
cylinder #2 .050
cylinder #3 .050
cylinder #4 .060

But I think you are going to tell me that I have to use the same size shims on each cylinder. right?
_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

[SGKent]

yes - the shims have to be the same so the cylinders are the same height.

Did you bolt the cylinders down with a bar of steel or aluminum like the photos? If not you will need to do that to get accurate measurements. ALSO measure the deck height at the CENTER PIN line on the piston because they rock in the cylinders.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[BusBerd]

[bsairhead]

Unless your case was decked wrong or your cylinders are wrong the difference is in the rods, pistons or both.

[Amskeptic]

[SGKent]

you can lay a perfect flat edge across the cylinders and check for evenness. If they are uneven the case needs to be decked.

You MUST measure at the centerpins. Use your fingers to feel between the top of the feeler gauge and the top of the cylinder. All I use the runout gauge for is to be sure I am at the top of the stroke. Usually just sliding feeler gauges under the tip may move the runout gauge enough that it loses zero. You hands are very sensitive to changes in height.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Ian]

Here's how it's illustrated in the Tom Wilson book. Notice he uses sockets and washers to hold the cylinders against the case. And I would highly advise against skimming anything off the top of the pistons. You need to measure everything again, but more than likely the case needs to be decked.

_________________
All your Buses are belong to us.
Love and good roads!
IN LOVING MEMORY OF ROB CRESS 1968-2012
**ACHTUNG DO NOT USE AA BRAND PRODUCTS OR BUY ANYTHING FROM PACIFIC PARTS INTERNATIONAL IN CALIFORNIA**

[Wildthings]

[BusBerd]

[BusBerd]

anyway, I got the dial indicator today and these are the readings I got. I measured along the line of the wrist pin on both sides of the top of the piston and I got different numbers.

#1 F=.029 B=.020
#2 F=.020 B=.012
#3 F=.022 B=.028
#4 F=.018 B=.019

So I think I am going to add .040 shims to the cylinders to knock down the compression ratio numbers a bit. I'll be left with a compression ratio somewhere between 7.3:1 and 7.7:1
_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

[BusBerd]

can I use valve grinding compound to even out any imperfections in the mating surface between the case and the cylinder in the same way that i lapped the mating surfaces between the cylinder and the heads?
_________________
"The large print giveth and the small print taketh away."
1977 Westfalia Camper Bus 2.0L Fuel Injected Engine, Manual Transmission

[SGKent]

[BusBerd]

[old DKP driver]

The only way you can lapp the cylinders to the case is to pull the studs
and use Automatic dish washing soap like Cascade and make a gritty paste
from it.

You Don't want valve grinding paste inside your engine
_________________
V.W.owner since 1967

[BusBerd]