TheSamba.com :: View topic

Mon Dec 31, 2012 6:58 am

Did a test fit on engine and not happy with deck height.

block cut for 90.5
74mm Forged 74 mm Crank
Mahle 90.5 pistons
Rebuilt clearanced stock rods 5.40 (137mm)
Engle 110 Cam
40 35.5 heads cc volume 60ml

When i assembled everything without sealant or gaskets and checked the deck height i cam up with the following numbers
0.153
0142
0.134
0.137

numbers a little of from using calipers

Question send the case back out and cut the cylinder seats
or get a set of 5.5" h beam rods and shim to specs? other ideas.

DWP

Mon Dec 31, 2012 7:17 am

you must be using "B" pistons. You will be better to get the 5.5" rods and everything should bolt together. If you cut the case or shorten the cylinders then all your tin will need to be trimmed to fit and you'll also have adjustments on your exhaust.

Stock VW rods are 5.394" when they are rebuilt they can be shortened .010"-.020"

Mon Dec 31, 2012 3:37 pm

You have the options of:
-5.5 rods
-A pistons and spacers
-shorten the cylinders .080

Mon Dec 31, 2012 4:26 pm

Go the 5.5" rods.

I know it's not the cheapest option, but you will make the one change and it will be done.

Decking and shortening cylinders introduces more possibilities for stuffups, and you will have to deal with cylinder tin, possible intereference at the head and unimaginable woes if it isn't done perfctly.

Mon Dec 31, 2012 4:45 pm

I plan on new rods. live and learn.
DWP

Mon Dec 31, 2012 5:41 pm

I am building the same set up. I have A pistons with cb super rods 5.325. Deck height is at .040 without any shims.

Mon Jan 21, 2013 7:01 am

Got the new 5.5" rods and did a mock up.
Dry case no sealant gave me the following
.029
.031
.035
.026..
Have not had a chance to shuffel cylinders around to even things out.
What would you suggest as a final deck height
and compression ratio.

Going in a 72 baja bus trans tall tires.

Mon Jan 21, 2013 7:30 am

Ideally, deck height should be .040- .050". With the W110 lots of people run 8 1/2-9:1. With a baja with taller tires I would stay somewhere near the lower side of those figures, but that's me.

Mon Jan 21, 2013 9:14 am

Looks like you are already there w/ the 5.5 inch rods.

Get the proper shims and it is good.

Mon Jan 21, 2013 9:25 am

Looks like a set of .020 shims should do it.
DO I really need the paper gasket???

DWP

Mon Jan 21, 2013 10:13 am

.020" shims and sealant. Do NOT use the paper gaskets unless you want a leak.

Wed Jul 30, 2014 3:36 pm

I'll put this question in here since it fits.
Test assembly and got these numbers for deck height:
1. .014
2. .014
3. .014
4. .013

I added in a .020 shim to each and it gave me a range of .034-.033
Using Berg's engine calculator I get these numbers:
Bore 92x stroke 74x deck height .034 x 60cc combustion chambers =the compression ratio is 8.5:1

That seems fine, but then I ran across a few pages where it was stated, "on 92mm bore, we like to see .060 deck height". I'm not so far in that I can't pull the jugs and pistons and go bigger on the shims. Should I, or is .034 an acceptable deck height. Keep in mind, I need reliability more than anything else!

Wed Jul 30, 2014 4:27 pm

I would run .030~.040 piston to head clearance, and do what ever you want to do to the chambers to get the cr where you think you want it. remember if you have a step that is .060" and .040 down in the hole you now have......100" deck hight/quench distance/piston to head clearance. for me piston at top of cylinder and .040 copper head gadget. or some where withen +-.005" witch cam end up .050 or .030, most gadgets are not what they say they are and spacers arnt either.

Wed Jul 30, 2014 4:29 pm

.034 is a bit too tight IMO. It only gets closer with time not looser!!
If you can get .045-.055 that's be perfect.

Wed Jul 30, 2014 4:38 pm

I set up my 2028 @.033 or .034",cant remember,seems just fine to me.that was years ago.

Wed Jul 30, 2014 4:38 pm

I was just looking at ACN and saw .020 shims, but nothing thicker , like .030, or .040, until you get up to .300" . I saw that last one and thought , "A THIRD OF AN INCH!!"

So, should I stack a pair of .020's under each barrel, or are there .040's available?

Wed Jul 30, 2014 4:51 pm

it may not be on acn, but they do exist.

scat, cb, and bugpack, and empi

Wed Jul 30, 2014 5:37 pm

.040" is the minimum I would run. http://vwparts.aircooled.net/Bugpack-Barrel-Shims-90-5-92mm-Type-1-p/4559.htm

Wed Jul 30, 2014 7:28 pm

Apparently I missed the drop down menu with the other sizes. THANK YOU!!

Vwracer dave, quick question: did you mean you'd run a minimum of .040, or run an .040 shim plus the space I have already?

Also, what's the concensus on running a CR of 8:1 vs. say, 8.5:1 ?

Again, thank you all for the input. Bob

Wed Jul 30, 2014 9:20 pm

Minimum is .040" total. If you now have .014" I would add a .030" shim to get you at .044" total deck.