Last fall I picked up a spare AeroVee. A few weeks ago I was having problems with valves and I pulled a head off the spare motor. This motor had Empi heads from Sonex and they had about 20 hours on them. As I started looking at the seats and valves, they were really not great. I was considering a head swap but held off.
We know the purpose of the hobby is to buy tools. So I ended buying a Neway valve seat cutting set. I’ll talk more about that over in the tools section. But in playing with the new toy, I made a discovery.
The Neway tools use a tapered pilot that jams into the valve guide. Cutting is done concentric to the guide. What I found is that both exhaust seats in this head were not very concentric with the guide. It cut on one side at first and I had to cut a lot to clean up the opposite side.
I have a new set of CB Perf heads that I’m going to put bottom plug holes into. I have to get the Bridgeport to my hangar and tool up first. But I’m also going to do a 3 angle valve job on the brand new heads and see how good the machining is.
I am thinking that a valve job on new heads will improve the sealing and longevity of the valves. Stay tuned.
Wow, Bryan, you must be my improved better brother. I also picked up a spare Aerovee last fall. It’s a 2.1 with Empi heads. My current engine is a 2.0. Note of interest, I’ve had both heads on my current engine rebuilt with new valve seats. The first one I had rebuilt with new Empi valve seats. This is now on cylinders #3/4. Since installed I’ve been loosing my exhaust valve clearance at around 10 hours flight time on #3. Still have fair compression on that cylinder when pulled through cold and hot, although I’ve not done a leak down. The second head I had rebuilt I had CB exhaust seats installed, it is now on cylinder #1/2. I’ve had almost no valve clearance loss on those exhaust valves. I wonder if the CB seats are harder material than the Empi seats.
I think that is a possibility. It’s also possible the machining is better on the CB heads. It was discouraging how much material I had to remove to get the seats to cut all the way around. I really think they are not centered well on this particular head.
I’ve got all 4 seats cut in this head and they look really good. I’ll have to check the valve geometry as I think they may need another shim under the rocker blocks. I’ll be curious if this head has better valve lash stability when I’m done, just because of better concentricity.
I’ve posted this in the old forum but worth another broadcast I believe. The heads I’m working on now probably have the best casting quality I’ve seen, but still not good enough. Check out the casting flash in what is probably the most critical cooling fin location:
For those that have had their vw heads rebuilt, was it locally or did you send them out? I cant seem.to find options close by. My need is not immediate …just looking to the future.
I have had mine done at a local engine shop. Just make sure you tell them it’s for a dune buggy or performance car. Some machine shops will refuse to do them if they know it’s for an airplane, especially an experimental one . Ask me how I know.
Most small engine shops have a guru VW guy, you have to ask around, you’ll be surprised.
I’ve got a buddy from Ohio, not on the forum, who uses a local machine shop. All of the coolest AeroVee guys have a second set of heads ready to swap on. That lets you rebuild the first set at your leisure.
" …the coolest AeroVee guys have a second set of heads ready to swap on. That lets you rebuild the first set at your leisure. "
Back in the day, a bud said essentially the same thing about the XKE. Gotta have 2 to always have 1 that’s drivable. Followed by “I love 'em, they breakdown just when you feel like working on them.”
The super cool guys even have a complete spare Aerovee engine
I’m in the midst of my annual. I lost an unbelievable .055" total exhaust valve creep on cylinder #3 over the last 100 hours since rebuilding that head. Leak down is still acceptable at 70/80. I was going to pull that head this spring for rework, but will wait until fall now since we’re going out of country for 2 months. Rule of thumb is to pull the head if you loose more than .035".
I don’t know exactly what is going on with RevMaster, but rumor has it that they intend to spin the aviation branch back up once some sourcing issues are resolved. So, I assume they would have retained the means to add the second plug.
I don’t know much about their engines, but I seem to remember that the second plug was in an odd location. Couldn’t the second plug hole be added by anyone who drills the bottom holes for other brands of heads?
I have another non-EMPI set of heads that need holes drilled. Because it’s a different casting, I’m going to carefully figure out where the holes need to go and make tooling for the Bridgeport. Those combustion chambers look different than any of the heads I have, so you would need to carefully figure out where to put the holes.
The original Revmaster 2100 heads had the bottom plugs in a tough to service location. You had to remove the rocker arm assemblies then two special made caps to access the plugs. Pain in the derriere! The later 2300 heads had the plugs in the same location as Aerovee and Greatplains heads. Made sense.
I know Mofoco has a jig and tooling to drill bottom plug holes, but doubt they’ll want to drill other manufacturers heads.
Back in the day when we had 4 Revmasters running at our airport, a machinist buddy built a metal jig to mount the heads so anyone with a mill could machine them. Me and others would borrow the jig and have machine shop drill the bottom plug holes into our CB044 heads. Wish we still had that jig kicking around. I think someone else posted one on the internet built out of wood a long time ago. Basically it tilts the head at the right angle for the machining bit to stay vertical.
Bryan Cotton looks to be very handy at machining and building jigs
A guy gave a presentation at AirVenture on “How to Drill a VW Head for Dual Ignition”. He posted the notes from his presentation on another forum. I uploaded them here, see attachment. The presentation was not recorded, but for those considering this, there might be some information of interest. The gentleman also said he would answer questions, via email, for anyone truly interested (address in the notes).
To follow up on my Jan 23 post.
I removed the 3/4 head this weekend, the one that had the constant valve clearance loss every 10 hours. 107 hours on this head since rebuild with Empi seats. There is a definite issue with the Empi seats. I lost 0.057" on the #3 exhaust valve over the 107 hours. Interestingly it still had good a good leak down number at 70/80.
I’ve not experience this much clearance loss and valve seat recession on any previous VW head. Crazy! Head was always run within temp limits and typically saw 325 deg F in flight on #3 and below 375 deg F on climb out.
Was also dismayed to see the mushrooming on the #3 intake valve stem. I will make removing the rockers and inspecting the valve stems an item on my annual inspections.
. Ask me how I know.
