3300 lapping heads

[mccool]

I'm reassembling my gen 2 3300 after having the heads reworked at Arion, new piston set, and cylinders honed out. The manual says that if you use used heads, they need to be lapped to the cylinders, but if the heads are new, it's not necessary. I want to know if I can consider my heads to be new since they were extensively machined.
I was going to talk to Nick at Arion to clarify, but they're dealing with their disaster just now, (car crashed in to their offices), and I don't think they'll be prepared to answer questions for a few weeks at least.
Anyone else have any experience with this?

[lakespookie]

My only experience is from machine shop work on non aviation engines, but it should be pretty clear if the matting surface of the head looks like it was machined flat you should be good to go, since you sent these heads out to get worked i would anticipate that they did the machine shop work to the Jabiru specs which would include the necessary lapping of the head(AKA surfacing or decking in some parlance although there is a bit of differences in what those actually mean from an objective perspective although the process is the same the goals are not)

Not to be confused with lapping a valve seat which is to match the two matting surfaces and ensure a good seal.

[flyguy0609]

Resistance is futile....

I once had a dog named Ace,
Who loved to lick my face,
If my face wasn't there,
She didn't care.
She'd lap my head anyplace..

Don't worry, I'm not quitting my day job....

[tx_swordguy]

If the heads are off of all the cylinders, it is a simple job to lap the heads to the cylinders. I would just do it to be safe. It doesn't take much time in reality. just put some lapping compound on and turn the head about a 1/4 -1/2 turn while barely pushing (just enough to get a good solid contact, it doesn't take much pressure at all). I am assuming the jugs are already torqued and in place. If they do not seat properly you will cut the heads with exhaust gas and be in a worse off situation than just spending an hr to lap the heads.
Mark

[builderflyer]

If a Jabiru cylinder has ever been overheated or if the bolts holding the head on have been torqued unevenly, a likely consequence is that the head will be warped. So it is critical that when reworking a cylinder, the head must be carefully inspected for warpage and if found, be corrected. I'd be very surprised and disappointed if Arion had not done this.

Art,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,Jabiru 3300 #261

[Bryan Cotton]

Is there anything bad about lapping the heads? At the very least you would see if both surfaces look to be true.