Getting Ahead

I was so excited to get past this hurdle - heads are finally (almost) in shape. I figured the best way to CC my heads was to install the valves and valve springs - turns out I was wrong*, but that's how I did it to start. Got them in pretty easy, once I figured out the tool:

I'm really, really opposed to buying single-purpose tools. However, there's really no way around this one - it was either this or some kind of press with a few hokey jigs, and I didn't have space for that nonsense.

Once I got the valves installed, I started prepping for the CC measurement process:

Ok, the first step is always to get the heads level. I figured the easiest way to do that was to set up the heads, then add shims until they were level. This turned out to be a huge project, because even with the heads just about perfect, air bubbles would still show up *not* directly under the hole in the plexiglas. So I'd have to start tipping the head, and by the time I got the bubbles where I needed them, the shims would have walked out of position and now the head isn't level anymore, and the bubbles zip off to some corner of the chamber. I spent more time re-stacking shims than I did on any other part of this project!

I failed to take pictures of the entire CC process - call me impatient, I just didn't want to stop what I was doing and get my camera out. I went through the process at least 3 times for each chamber, then averaged my results - which wasn't hard, considering my syringe only had 1cc graduations. I was still able to guesstimate quarter-cc accuracy though.

Final volumes were 56cc, 56cc, 56cc, and 55cc. I'm still not sure about the last one - but it was consistent, all three measurements showed 55cc on the dot. That was easy enough to fix with a rotary tool and a cutter, followed by a sanding drum to smooth away chatter marks. Now I've got about a quarter cc spread between all four chambers, which is definitely good enough for a VW.

I cleaned the heads and valves really well to make sure no shavings or abrasives remained, and then put them away for now. I need to measure the valve spring forces, but after that I can reassemble the heads and bag them for now.

Aside from matching all the chamber volumes, CCing the heads gives me the last unknown for my compression ratio equation. I've got 94mm cylinders with a 78mm stroke; that's good for 541.2918 cubic centimeters. I've got 56 cc's in the heads, and I want a compression ratio (CR) of 8:1. CR is calculated by adding the volumes of the cylinder, head, and deck height, and then dividing by the sum of the head and deck height. When I go through all that, I get a necessary deck height of 3.06mm, or about 0.120". Back in an earlier post, I made mention that with the cylinder shims that were on the engine, the deck height was 0.114"..... which is pretty close to what I want. I can add .01" by going with the next size up shim; if I felt really crazy, I could chuck up the cylinders and turn them down .004" to get exactly what I'm after. However, I'm so close to final assembly of all of these components, I don't want to risk damaging something - and I think being off a tenth on my CR is probably ok; the math I'm finding looks like I'd be splitting hairs over less than half a percent of my power.

*The easiest way to do it is smear just a little grease on the valves and on the valve seats, then push the valves in and give them a little turn to hold them in place. No leaks this way.

More surprises!

Curiouser and curiouser! I spent a fair amount of time during disassembly taking measurements and writing things down, and then promptly forgot to worry about any of those numbers. When I was sold this engine, it was sold to me as a 2180. There was some mystery behind its history, but I didn't think too much of it. However, as I was ordering parts today, I realized that the numbers didn't match up.... specifically, the cylinder and crank numbers. 

A Volkswagen 2180 engine begins life with around 2/3 that displacement, and then a bit of machine work is down. The crankshaft, which comes stock with a stroke of 69mm, is replaced with a crank with a stroke of 82mm. In addition, the cylinders and pistons, originally in the 85-90mm bore range, are replaced with 92mm sets, which gives the final displacement of 2180cc.

My Volkswagen "2180" engine no doubt had similar beginnings, but the end result is a bit different - the pistons are not 92mm, but 94mm. The crank stroke, likewise, instead of 82mm, is 78mm. The engine I'm working on has, in fact, a displacement of approximately 2165.

What does that mean? I'm not sure. Obviously the parts for it are different. As far as power and reliability, those depend a lot more on quality of workmanship than they do on any other factor. Bottom line, I *may* have a little more torque, or I *may* not, and at the end of the day it's still up to me to build a solid engine. 

This does cause some complications, though. The main one I've run into so far is that nobody sells cylinders for a 78mm stroke... only 69mm and 82mm. That being said, some folks sell the 82's as "78-84mm," and don't give any other dimensions. There are three possibilities, as I see them (in order of most preferable to least preferable from my point of view):

1. The cylinders are short enough for 78mm stroke, and you add shims to use them for longer strokes

2. The cylinders are long enough for 84mm stroke, and you cut them down on a metal lathe if you need shorter cylinders

3. The cylinders are somewhere in the middle, and we don't really expect you to worry about compression ratio that much.

I'll know better once they show up and I can measure them. One way or another I'll get this engine built.... but if I have to custom cut each cylinder, it'll probably cause me to wait a little longer before the next rebuild.

On a more normal note, I finally got my crankshaft ready to send out for NDT (Non-Destructive Testing). Here's the key in the slot:

Partway removed:

All the way out:

I hope to spend some time this weekend cleaning the parts I intend to reuse... we'll see if I can pull myself away from this guy long enough to get any work done.