[rjcthree]

Is dry tappet clearance measured with the pushrod forcing the tappet to bottoming, or it at contact(tappet pushrod seat at contact) with no pressure?

My understanding was that it was with some pressure (against the tappet internal spring), then measured between at the valve stem and rocker contact point when the tappet internally bottoms out.

It doesn't make much sense to have clearance (lash) on the pushrod at just contact - the pushrod risks falling out of position. But I've been wrong for reasons I didn't fully understand before asking before!

H2AD if it matters, but I don't think it does - just a different hyd lifter.

If it's at contact, LOL, I'm going to need a LOT of shims. The case machining took ~.015" a side out.

I've seen the A&P consensus is that clearance shrinks as the engine breaks in - that the valve seating depth grows (and decreases clearance) more than any break-in of the pushrod/lifter/cam break-in.

Thanks, RIck 90432

PS: anybody have a clue how to TDC @1 a D3000 mag?

 

[N162RV]

If my memory serves me correctly, you check it dry against the spring in the lifter. Thats the way we did it on my O-320 A1A a few years back. We used a go- no go gauge...

When all said and done, you will have zero lash.....

 

[airtractor8]

Make sure you measure dry tappet clearance with lifter leaked right down. You can do this easily on the H2AD by removing the clip in the top of the lifter, disassembling it and then washing all the oil out and re assembling. They remove easily from the engine using a piece of lock wire with a small bend on the end to pull them out. When you reassemble them back into the engine with pushrods and rocker arms make sure the rotor caps have not fallen of the exhaust valves and got lost. To check the clearance, push down on the pushrod side of the rocker arm to depress the spring in the lifter and measure between the valve and rocker arm. If you have somewhere between .028 and .080 clearance you are good to go. The pushrods aren't available in different lengths for the H2AD like the other Lycomings to adjust the clearance, this is achieved by shims under the rockers instead. This clearance or "lash" as you call it, is taken up by the oil pressure to zero clearance when the lifter pumps up with oil. The pushrod cannot fall out then.

My engine has the D2000 mag but as far as I know the D3000 is timed the same. I think you are asking how to initially time the mag to your engine?

Get cylinder 1 coming up on the compression stroke and stop when the 25 BTC mark on the ring gear lines up with the small drill hole on the starter motor. Remove the 2 inspection plugs on the left and right side of the mag and rotate the mag so the red painted tooth on the nylon distributor gear in there lines up in the middle of the hole. If the mag "E" gap is set correctly you should see a red tooth lined up in the middle of the other hole as well. Put a little grease on the mag drive coupling so that it does not fall of into the engine when you try to insert the mag. If you have a tail dragger you may want to lift the tail up level. That makes it easier to insert the mag into the drive gear in the engine and helps stop the drive gear falling down in the engine. The mag is orientated with the right side a few degrees lower than the left when viewed from the rear of the engine. To do this it may take a little trial and error to get the internal drive gear lined up correctly with the drive on the mag. It is removable from the engine and could be sitting in there no were near the right position. Make sure you put your new gasket on before pushing the mag home! Lightly tighten the 2 hold down clamps so you can just move the mag for final timing with your "buss" box. Don't forget to "fire" the impulse coupling before final timing of the mag to the engine.
You may also want to check your mag has the newer circlip type impulse coupling installed otherwise you will be subject to 100hr inspections per AD. Click here for some info about it from Sacramento sky ranch magneto knowledge base http://www.sacskyranch.com/aircraft_magneto_troubleshooting.htm

A long description but I hope it helps.
If you would like an overhaul and parts manual for the H2AD just PM your email address to me and I'll email a copy to you. I have them in PDF format.

Cheers
Graham
RV6 with H2AD

 

[rjcthree]

Thanks

Yes, I have the O/H manual, and have all new shims and whatnot - it's that I didn't find the manual all that clear on the lifter state/position for adjustement. It's a new OH, new cam and lifters, new Lyc Cyls.

As far as the D2000/3000 timing, oddly, non of that info came with the Lycoming information ($400 subscription), and since I had the mag rebuilt by a shop, I expected some form of info (CAUTION MAG at #1TDC firing postion) on it, but it appears it was tested and boxed. I'm a little afraid of blowing coils rotating it.

I think I'm good here, thanks everyone, as always. Rick 90432