Just thought I'd mention that since you're going through all the trouble of taking your top end apart, it wouldn't hurt to put new valves (Manleys) and springs (stock VW). You'll want to bead or soda blast your heads to clean them up and if you really want to finesse it, index the plugs. If you're going to put new valves, you'll want to cut some three-angle seats using the Neway cutters . . . although, looking back at things, the stock seats are so soft that the fancy three or five-angle seat you were so careful to create will soon become a one-angle seat after a few hours of flying. That's okay though. As long as the valve is perfectly concentric with the seat and your guides were perfectly installed originally and you have no guide wear, you'll maintain a perfect seal. As the seats wear and the valve sinks into the seat with time, flow will decrease somewhat and a little power will be lost. A back cut on the valve will help compensate for this but unless you replace the seats with some really hard metal, this wear is inevitable.
Please reference Mark Langford's Corvair top overhaul site: http://www.n56ml.com/corvair/valvejob.html Neway recommends NOT lapping the valves once you cut some new seats although Mark is shown doing it anyway. Using Dykem, I have to admit I did a little bit of lapping too, just to confirm I had no leakage. When I say "little bit" that's what I really mean. Just enough to confirm to myself that I had a perfect seal. When I top-overhauled my GP 2180 I was careful in replacing the pushrod seals and had no leaks. I used high-temp silicone and pulled out (just a little bit) the flex part of the tubes to give them a little more tension when re-fitting. I figured I would have to re-do at least one or two of them but I was lucky. Didn't have a drop of leakage after reassembly. If you don't have swivels on your rocker arms, you really should. They save your guides from wear. I had just under 500 hours on my engine when I took it apart and the guides were still like new, thanks to the "elephant feet" (swivels). If you DO put some new Manleys or other stainless valves in, put them in a lathe or valve grinder and make sure they are "true." Even new valves from Continental and Lycoming can sometimes not be true. It's an easy check and if you do it on a valve grinder, you're set to true them up if it's necessary. I had one or two out of the eight Manley's which needed touching up. I got that advice from an old & very experienced A&P who was letting me use his wonderful old Sioux machine. Over the years he had run across many brand new valves in his work that were not straight and sure enough, one or two of my brand new valves were not straight. Using his Sioux, I cut backcuts on the valves to help with flow. Thanks to Don Hall who let me use his valve grinder and to the wonderfully detailed info on Mark's site, I learned a lot, to put it mildly. I would suggest you use new springs, since you've got it all apart. Also, don't go for the extra strong racing springs - just the stock VW springs. Stronger than necessary springs will just cause cam lobe wear. If you really want to do it right, use Mark's set-up for measuring the resistance on each spring and then match them when putting the heads back together. I didn't do that, but should have. What I did do was use genuine German VW stock springs. No dune buggy stuff. My GP 2180 sure appreciated the attention I'd given it. It felt like it had an extra ten horsepower after the top overhaul. I didn't hone the cylinders or put new rings. The engine wasn't using oil so I left cylinders and pistons alone other than cleaning the tops of the pistons. Have fun! Mike KSEE ____________________________________________________________ We Say Goodbye To Lara Spencer risingstarnewspaper.com http://thirdpartyoffers.juno.com/TGL3141/5b2fe7f3d5c8b67f3131ast04vuc _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
