question about lapping barrels to head

[hoodsy]

okay I have done alot of rebuilds big and small but have never done a aircooled VW. question is I know that you guys are very insistent on lapping the barrels to the heads, but are you guys just setting the barrels metal to metal to the heads or are you also using sealing rings. my 1.7 had sealing rings between the cylinders and the heads, so I am puting new ones in when I reassemble, now just to be safe I have lapped the cylinders to the head anyway but not to the extreme that I would lap valves. the only reason I ask the question as to wether you are using the seal rings or not is that one of my books says that some VW's don't have them, and also the only time I ever had to lap a cylinder to a head before was on a engine that was a metal to metal fit with no seal what so ever. I just feel that the lapping seems irrelevent as soon as you add seal rings. Ray or anybody want to enlighten me.

[raygreenwood]

Lapping is done so you can get rid of the sealing rings. The object...is to first make sure you have smooth tops on the barrels. They are lapped ...just the barrels...on a sheet of glass with fine valve lapping compound. Then...they are lapped into the heads...so each one is "mated" to the head. Check it with machinist dye.
There was a factory bulletin...long ago....saying that the factory deleted the gaskets. They are not consistant. Generally, they will always leak at some point.
Personnally, I have never had one really leak on me, but then again...I replace them like clockwork to lap the valves....between 50-60k miles. Do not use the gaskets. Just lap the cylinders to the heads. Ray

[Guest]

Thanks Ray. I was kinda thinking along those lines but needed the clearification . thanks again.

[vwbill]

Did you read Jake's site info?(In the engine room forum) He talks about the head gasket/shems. He has issue with the different materials and the expansion of adding another material to that! Ray knows his stuff! I think lapping and working with sealing two surfaces vs four has to be better! I missed it the first time and it hurts having to do it again! My only concern with the lapping is about the issue of the total jug length and the issue of causing a pivot issue? Do you need to get both jugs to match exactly in lenght so you dont get a high side when bolting the head down? bill

[MGVWfan]

Lapping takes off an infinitessimally small bit of metal from the heads and the jugs...it's mainly polishing at a microscopic level, so I wouldn't worry about changing seated lengths.

I would check deck heights and seating surface depth on the heads to be sure things are OK there from whatever machining's been done in the past. You've got to check deck height anyway to be sure you've got enough piston-to-head clearance. I'm trying to figure out how to do the above measuring on my 412's engine with my limited precision measuring tool set...I may have to spring for a depth foot for my vernier caliper.