Deck Height Calculation for CB Aluminum Raised Deck

[mikelars]

Ok - I am preparing for a 94/86 - 2387 in a CB White Rhino Aluminum Case over the summer. I was calculating the deck height to see which case to buy (which raised deck height). They come in 0, 3.5, 7 or 9.5 mm raised deck (if they ever get some back in stock).

So I am trying to calculate this properly so i need don't need shims or minimal shimming - maybe an experienced engine builder can correct me or verify. This 2387 would technically be my 4th engine build if you count the first bearing failure on an old 1500 case, second 1904, and third 1968.

An 86mm crank with 5.5 inch rods (139.7mm) and "B" 94mm pistons with a CB White Rhino Case with a 3.5mm raised deck would give me a final deck height of 0.452 mm or 0.017795 inches. this is without any shims or spacers. Is that too small? Might it cause valves to hit the cylinder? What is the target deck height for a 2387 given the info below?

(I derived this from some other peoples calculations I found - which is why I am not 100% sure it is correct). In theory I could bump up the rod length to 5.6 inches, and also bump up the case deck height from 3.5mm to 7mm. since 0.1 inches is 2.54 mm, but the case bumps out by 3.5 mm, this would adjust the 0.0178 deck height to be +0.96mm or +.0377 making it 0.055 inches, so I would require 0.04 worth of shims. I read that the 5.5 would be better at low RPM, and also seems to require no shims, so I was planning on going with that.

I just want to decide between the White Rhino case that is 0, 3.5, 7 or 9.5 raised deck, and if I want to use the shorter 5.5 inch rods, it "appears" that the 3.5mm raised deck is the correct one to get.

(I was considering an 84mm crank, but then thought why not go for it on the 86 so I have no regrets...)

Using the CB Performance Engine Calculator - I get:

Bore: 94
Stroke: 86
Deck: 0.0178
Chamber: 66cc
Compression: 9.6
Displacement: 2387
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[UK Luke 72]

17 thou is too little.
Based off that, get the 7mm mock it up and then have the cylinders trimmed to get 40 thou with no shims.
Then order your heads with enough chamber volume to get the CR required for your cam/fuel/elevation etc...
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[mikelars]

[sled]

well, I appreciate the direction you're approaching this build from, but I think you're over complicating a few aspects of it.

this is for a bus right? if so, I highly doubt you're going to end up choosing a cam with enough lift you will run into valve/piston clearance issues. The size of the engine doesn't have anything to do with it, its purely valve lift and valve timing related to deck height.

as far as deck height goes, anything from .040 to .050 is generally the acceptable range (others are soon to chime in and say thats BS )

compression is entirely dependent on the cam chosen and the vehicle it will be installed in.

what "off the shelf heads" come with for chamber volume is somewhat arbitrary as you will most likely need to have the heads flycut for the proper chamber volume for YOUR engine combo. Look for heads with large chamber volumes to start with, that can be flycut down as necessary.


I think before you go making any decisions on heads or cam or compression, you need to think about what kind of performance you want out of this engine for your bus. Realistic ideas that is. And don't forget if you let this snowball and turn into some 180hp+ monster, you're going to need to upgrade other parts of the system. I know your trans builder said the trans would handle it, but a strong 2387 in a bus can, and probably will eat parts like crazy



also just another note...the difference between building with an 82 crank, or an 84, or an 86 isn't quiiiiiiite as easy as it sounds.
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[jeffrey8164]

Also, keep in mind the width of the engine.
You don’t want to have to modify the bay or the cooling tins.
I just built a 2276 so I can appreciate how you are trying to work out the deck to try to avoid a bunch of hassle.
And yes .040 is the minimum unless you’re one of those people that use copper gaskets between the cylinder and the head.

Don’t know if you’ve ever seen these. They’re definitely enjoyable and provide a lot of good information.


Link



Link

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[Pruneman99]

This a nice reference chart I stole from another thread. It was not my work, but it's very helpful when mentally mocking up an engine build.

[mikelars]

Interesting - so to compare this chart with my original calculation above:

86mm crank with 5.5 rods and B pistons gives -0.166 inch deck height which is -4.216mm deck. But with the 3.5mm raised deck White Rhino, that leaves it at -0.716mm deck, or -0.028 inches. So that is the amount the piston sticks out the top of the barrel. That means to get close to a 0.04 final deck height, I would need a shim of width 0.06 inch - that gives me 0.032 actually…

Looks like part 1280 on CB Performance
https://www.cbperformance.com/product-p/barrelshimsa.htm

Seems like it would work, although my limited experience tells me that none of these calculations would actually be correct once assembling - just a good ballpark place to start. Probably need to be ready and buy the CB shims for 0.04, 0.06 and 0.09 as well, just in case. Also the Mahle (older) vs General rows - I mean who knows - I was going to buy Mahle (newer) ones…. Wait - are all 94s considered to be that last row in the tables? If so all my math above can be flushed down the toilet.
_________________
Here is my 1961 Beetle Restoration:
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Here is my 1966 Split Bus - Restoration Channel:
https://youtube.com/channel/UCPBRysmvrJlif2wzwEwiuwQ

2332 Torque Motor Build
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Engine Rebuild 1968cc Playlist:
https://youtube.com/playlist?list=PLW_2wBCs4Ny1JbZ2EgJQQ2awfo0koZRqz

[Pruneman99]

I think all of the 94's including Mahle all have the 35mm pin height now. But don't take my word on it. I'm sure someone here knows for sure, or contact the vendor before ordering.

[[email protected]]

Not wanting to be a buzz kill on 4/20, but do you already have cases in your possession to choose from? The only Aluminum case listing that CB has in stock is a 9.5mm deck that is a standard 85.5 bore without the head studs drilled yet. When/if they get the others back in may be anyone’s guess. I would be tracking down some cut to length 94 cylinders, so you could use basically any case.

Here is something to consider from crank centerline to cylinder top on one side.

Crank stroke / 2 + rod length + compression height of the piston + deck height

A stock 1600 with .055 deck height
(69/2) + 137 + 39.6 + 1.4 = 212.5mm

2386 with a 5.5 rod, Mahle B 94, and .040 deck;
(86/2) + 139.7 + 35 + 1 = 218.7mm

That’s 6.2mm / .244 of a difference. I can’t remember the cylinder lengths off hand of a standard 85.5, and a common 94, but that will enter into it as well.

[mikelars]

[txoval]

I did the math in a similar thread and it got deleted…maybe it was the same poster

I’d by pistons with a 33mm pin height to help with width…they are available

[modok]

43+139.7+35=217.7
103.5+114=217.5

so, .008" in the hole, probably?

it would be easier to check you math If you put it in the form of math.

[mikelars]

[modok]

ACN

[mikelars]

[modok]

yes

[mikelars]

How bad is the gas mileage on a 2387 compared to a 1968? (Not that I really care, but it must go down a bit)
_________________
Here is my 1961 Beetle Restoration:
https://www.youtube.com/playlist?list=PLW_2wBCs4Ny2qXEPvdnfvEzN42T8JA8zO

Here is my 1966 Split Bus - Restoration Channel:
https://youtube.com/channel/UCPBRysmvrJlif2wzwEwiuwQ

2332 Torque Motor Build
https://youtube.com/playlist?list=PLW_2wBCs4Ny2HwsKM9QT4LFpcSqP3QG0p

Engine Rebuild 1968cc Playlist:
https://youtube.com/playlist?list=PLW_2wBCs4Ny1JbZ2EgJQQ2awfo0koZRqz

[[email protected]]

[mikelars]

I am planning to get heads with a 66cc chamber, assuming I don’t get them altered…. This would put me a bit over 9 CR.

Also I need to cough up about 5k just to get the main parts, so it may be mid summer before this really gets going. I would go ahead and get the case and the crank/rods if the White Rhino 3.5mm in-stock alert gets sent to me…
_________________
Here is my 1961 Beetle Restoration:
https://www.youtube.com/playlist?list=PLW_2wBCs4Ny2qXEPvdnfvEzN42T8JA8zO

Here is my 1966 Split Bus - Restoration Channel:
https://youtube.com/channel/UCPBRysmvrJlif2wzwEwiuwQ

2332 Torque Motor Build
https://youtube.com/playlist?list=PLW_2wBCs4Ny2HwsKM9QT4LFpcSqP3QG0p

Engine Rebuild 1968cc Playlist:
https://youtube.com/playlist?list=PLW_2wBCs4Ny1JbZ2EgJQQ2awfo0koZRqz

[txoval]

CSP also sells a really nice set of 33mm pin height 94mm pistons

AA does as well, they are JE race pistons