new AeroVee seems tight

[jwd3ca]

Greetings...

I had my first engine start yesterday, and I have a couple of observations/questions. My engine seems quite tight and not very easy to hand turn via a prop tip. I've been hoping that it would loosen up after running a few minutes, but that seems not to be the case. It runs OK, nice 900 rpm idle, good oil pressure, but it needs a honking big auto battery to get it to turn past the compression strokes and start. There's no way the little Odyssey PC680 battery would start it at this point. I'm worried there's something amiss, but don't know what it could be. I wish I had plasti-gauged the big end and con-rod bearings during assembly, but I didn't. Not sure what other possible factors could be contributing. How hard/easy should it be to hand prop through a few revolutions? Have others had tight engines? Will it loosen up? Thanks.

[Rynoth]

Shouldn't be that tight, and may indicate an improperly seated main bearing that was more or less "squished" when the case halves were mated. Was it always this tight during assembly?

It's surprisingly easy to have an improperly seated main bearing, I almost did it myself with the thrust bearing. Everything looked perfect, I put the case half on and it didn't want to seat the last 1/8" on the aft side, and the crank was more or less locked. Pulled the halves off, doublechecked bearings and found the thrust bearing wasn't fully aligned on the dowel pin.

Unfortunatly, the only remedy at this point would be to split the case halves. Maybe it's a different issue though.

[Bruce593SX]

I have not run mine yet, but this may or may not help you....

In my case I had 2 mistakes in a row, both which gave me a tight engine... easy to know if you have an engine that is too tight, take off the prop and one plug out of each cylinder, can you turn the engine at all with just your hands on the prop hub? No? then too tight...

the first time I assembled my engine I had a HELL of a time with the bearing keepers (those damn tits I called them and still do!) Couldn't get them to all line up for anything... assembled the engine when I thought all was good. turning was tight, tight, tight. no way could I move the prop hub with just my hands. After a bit of research, thought better of it, dissembled the engine completely including new bearings (which of course means having the prop hub pressed off and re-assembling the crankshaft!). Saw definite evidence of round "dents" in one of the bearings where the bearing alignment pins where not in the right place when it was assembled. Got everything back together this time being excruciatingly careful of THOSE DAMN TITS! But guess what... still pretty tight... not as much as before, but pretty tight... Still plane not complete and engine not run.

Fast forward a year or so while other real life gets in the way of plane building and I get back to my engine. Something's not right, here we go again lets tear it down, including press off the prop hub (bought a new one for piece of mind since this was the second time the first one got pressed off. Probably didn't have too, but it was worth it to not have it nagging my brain later.)

After much head scratching and some reading on this forum, I discovered the problem this time. The bearings I had purchased where not radiused enough for the big ass racing crank that we run in our aerovees. Particularly at the main bearing nearest the flywheel (in the rear of our engine) where the crank needs to be pushed up against the bearing all the way. that rear bearing gets sandwiched between the crank and the thrust washers and my aftermarket bearing that I replaced to correct my LAST screw up wasn't butting up to the crank because it wasn't clearanced enough on the inside of the bearing for the crank radius!

So here is my advice. I believe you almost certainly have one or the other of the 2 conditions above. either way you are looking at a complete engine tear-down to diagnose and/or correct. I believe you are looking at a teardown either way as if it is issue number one above, the only way it will loosen up is by making metal, if it is symptom number 2, then it will also make metal but once it does, you will have incorrect end play on the crank causing all kind of other havoc.

Once you have bitten the bullet and have the bearings exposed, first look for the obvious signs of THOSE DAMN TITS making a depression in the bearings. You will see the pressed in little round dents that made me feel stupid.... then look at the inside edge of the rear main bearing, Does it fit tightly against the crank? is there a very narrow shiny polished area right on the edge of it where it was rubbing against the crank radius?? I have seen another report on this forum where the Sonex supplied bearings did the same thing. if that's all it is, and there is no evidence of the bearing keepers having been installed incorrectly, just file a radius into the main bearing until it will fit tightly against the crank, DON'T FORGET TO RE-DO YOUR END PLAY! and you should be good to go.

If its the keepers, then obviously it's new bearing time.... with all of the unpleasantness of pressing off the hub etc. For my it gave me a good excuse to buy a nice 20 ton press from Harbor Freight, so at least I got a new tool out of it....

When re assembling the engine, use the technique pointed out by another contributor to this forum, after you have the crank all settled in to one side of the case half, take the other half of the middle split bearing and rest it on top of it's mate. if you can rock it back and forth, one of the bearings is not completely seated. if it doesn't move, you are good to go. Now like me, you are quite adept at tearing down and re-assembling a Volkswagen engine!

[Rynoth]

Here is my blog post regarding my crank case assembly and seating the bearings:

http://www.rynoth.com/wordpress/waiex/2 ... -assembly/

And here's the video that shows the best way to be sure the bearings are properly seated. Watch the first 2 minutes of this video for a great demonstration using the split bearing to test proper bearing seating as mentioned above.

https://www.youtube.com/watch?v=wTCKMUAWl4o

[kmacht]

I would also triple check your end play now that everything is assembled. You wouldn't be the first person to end up with the end play too tight following the assembly manual steps.

Keith
#554

[jwd3ca]

Thanks to all for your experiences and typical expert advice. I should have questioned the tightness earlier rather than thinking it was normal and would loosen up as it was run in. Sounds like I need to have a look inside. No big deal :-) One thing the long Canadian winter is good for B-)

[mike.smith]

I would also triple check your end play now that everything is assembled. You wouldn't be the first person to end up with the end play too tight following the assembly manual steps.

Keith
#554

That was going to be my suggestion as well. You can get a rough check by just pushing and pulling the prob hub in and out. Even the minimum .003 is easy to detect visually. If it moves slightly then you're probably OK with the end play (not too tight, anyway). If you get no movement at all, then that's the first (and easiest) thing to try fixing.

[jwd3ca]

OK, so I'm starting to investigate the tight engine issue. I've seen a post where someone recommends leaving the accessory plate behind when removing the engine. Sounds like a good idea, any opinions one way or the other?

[Rynoth]

I found it easier to install/remove the engine by unbolting it from the accessory plate. Just be careful not to knock around the alternator stator.

[Bruce593SX]

OK, so I'm starting to investigate the tight engine issue. I've seen a post where someone recommends leaving the accessory plate behind when removing the engine. Sounds like a good idea, any opinions one way or the other?

That's what I have done the three or four times I've taken it off for this issue