SonexBuilders.net

I am rebuilding my aerovee engine, *perhaps* as the result of the original builder not assembling the engine with the appropriate amount of shims. As fate would have it I can understand why it was put together that way now.

As shown in the image below:

There is .021" gap that needs to be shimmed so:
.021" - .006" = .015"

The smallest shims that I have seen are .24mm which work out to be about .010" (this explains why the original builder installed just a single shim and thought that they were within building specs)

All the data that I have read suggests that there MUST be 3 shims for proper oil and lubrication etc, but in order to do that I would have to have .005" shims (or some combination smaller than .010", which I have not been able to find)

After some reading and research I ordered the cardboard spacer/shims/gaskets shown below:

They measure about .010" and with a few of them between the flywheel and the crank I believe that I could arrive at an appropriate solution. I have some reservations about smashing a cardboard gasket down to 250lbs and hoping that it stands up for a good length of time. There are metal gaskets that are the same as these (actually what I thought I had ordered but not what showed up). Would those be preferable?

Another solution would be to possibly put the flywheel assembly on my lathe and skim off a few thousands, but I prefer to use the sonex parts without modifying them to that extent and assume that most everybody else doesn't do that either.

So in essence, what solutions do you guys propose?

I don't believe those 'shims' will do anything for end play…. they look like they go over the dowel pins between crank and flywheel and just move the flywheel aft. You want the ones that fit on the outside of the crank journal… Google 'VW crankshaft to flywheel shims'…

I agree those paper shims are probably not the way to go if you want to increase the gap between the flywheel and the thrust bearing. I believe my gasket kit also contained a metal version of these (mine was a 4 dowel pin though) perhaps this is a better option but I don't know.

Regarding the number of shims,
I believe the AeroVee manual states you can have 3-5 shims, however, you will not read this anywhere else. ALL VW literature and forums will state you MUST have 3 shims. No more, no less.
Why? I don't know, I have read it has something to with the number of shim "faces" and lubrication, I don't quite understand, I'm not an expert but John Monnett is so I guess his word is worth a lot more than mine.
In any case, neither Monnett or the rest of the VW world find 1 shim to be acceptable, try and get (at least) 3.

I understand the VW gurus tend to keep shims and crankshaft usually together when rebuilding many engines, suggesting that the case are all made equal, it's the cranks that differ slightly.
Perhaps your crank was not ground correctly?

Talk to Sonex about this.

marsolgp wrote:I don't believe those 'shims' will do anything for end play…. they look like they go over the dowel pins between crank and flywheel and just move the flywheel aft. You want the ones that fit on the outside of the crank journal… Google 'VW crankshaft to flywheel shims'…

They do go over the dowel pins between the crank and flywheel... The issues is that the flywheel is too close to thrust bearing and there is not enough room for 3 of the standard VW crankshaft to flywheel shims that we would usually use.

Putting a shim on the dowels between the flywheel seems to be the only solution I can see without machine work.

I stand corrected..... I didn't fully understand your dilemma, until I re-read your post. Sorry.

I believe this came up before. The reason for a minimum of three shims and the end play is they act similar to a bearing and the oil builds up in between. Paper gaskets simply won't work. I've always been told to use three spacers. No more. No less. I can see how more would work but absolutely not less. Spacers come in all kinds of thickness. VW suppliers don't always sell all of your options. Local VW shops and VW freaks tend to be hoarders and usually have hundreds of these used shims lying around in thickness levels you typically won't find from new vendors. Even I have 15 or 20 of these things rattling around in my garage somewhere and I haven't built many engines over my 20 year span as a VW driver.

jfuerst wrote:

marsolgp wrote:I don't believe those 'shims' will do anything for end play…. they look like they go over the dowel pins between crank and flywheel and just move the flywheel aft. You want the ones that fit on the outside of the crank journal… Google 'VW crankshaft to flywheel shims'…

They do go over the dowel pins between the crank and flywheel... The issues is that the flywheel is too close to thrust bearing and there is not enough room for 3 of the standard VW crankshaft to flywheel shims that we would usually use.

Putting a shim on the dowels between the flywheel seems to be the only solution I can see without machine work.

Are you using the Sonex supplied bearings? I had hell with the bearing keeping pins and ended up replacing the bearings with non-Sonex supplied main bearings, I later discovered that the lack of a big enough relief on the bearings for the large crank radius was causing binding issues, and I could see how it would cause end play issues as well... I'm sure you already have, but check that the thrust surface of the bearing fits tightly against the front side of the rear of the crank.

Bruce593SX wrote:Are you using the Sonex supplied bearings? I had hell with the bearing keeping pins and ended up replacing the bearings with non-Sonex supplied main bearings, I later discovered that the lack of a big enough relief on the bearings for the large crank radius was causing binding issues, and I could see how it would cause end play issues as well... I'm sure you already have, but check that the thrust surface of the bearing fits tightly against the front side of the rear of the crank.

That is indeed a good suggestion, I agree.

Jordan, there seems to be a great variety of manufacturers supplying making these bearings and prices seem to vary greatly.
Like with anything these days, there are cheap (Chinese) ones and more expensive better quality ones to be found.
Perhaps this was one of those cheap sets which were not made with the precision required, see if a VW shop in your area could lend you a bearing to see if it makes any difference. If so, buy a set of "better" bearings.