Hi Larry; If fouled plugs are rare for you, that's a good thing. 100LL is a bit much for the itty bitty engines and using TCP or an autofuel mix is probably a good idea to keep it clean. Too bad autofuel has so much junk in it! I've also heard that Marvel is helpful in both the fuel and oil. Can't tell you how I know but I've seen where a certain aircraft was running it and the CHT's were up all around by about 15 degrees. This was one of those attempts to bring a cylinder back to life on a big bore Continental. Shot valve guide.
If we can rule out that there's been no lead buildup working it's way up the stems and causing guide wear (take a compression test) I would look at the lifters for the cyl. sticking a bit on startup. If a bad guide is there it will rear it's ugly head from time to time, not only on startup. If you're close to an oil change, I'd try a straight weight (Aeroshell 100W or the like) with some Marvel or "Cam Guard" and run the heck out of it for a good long flight, much like your mechanic says. It may just work some magic. Also, check all the gaskets and tubes on your induction system. The multi's are great for engines that run a good deal but if you only fly occasionally like me, you may want to research some of the straight weight oils. Your mechanic should have a borescope to look at the valves with. If he knows how to read the colors, he can see if you have a leaker. The "rope trick" involves removing the plugs and placing rope in the cylinder. The valve springs are disassembled and some light line (maybe dental floss, maybe lacing cord) is tied to the groove on the top of the valve and it's lowered a bit into the cylinder. That allows enough room to coat the valve face with some lapping compound so when pulled back, it can be faced - kinda! Some will say that the same method opens the guide up to reaming, but if the guide is oversized already I don't think it would be of much benefit. If the guide is shot, it needs replacing. After the valve is lapped it's cleaned and reassembled and hopefully will give a nice seal. But, as usual, there are so many variables to consider like the health of the spring, ect., etc. Al DeMarzo Visit the Ercoupe Swap Page Free, Easy and No Membership Required http://www.ercoupeowners.com/swap/swapbook.htm ----- Original Message ----- From: Larry Snyder To: Al Demarzo Cc: Ercoupe Tech List Sent: Friday, August 08, 2008 7:58 PM Subject: Re: [ercoupe-tech] Sticking Valve That's oil temp, I don't have a CHT. I use Avgas. I have not been adding TCP, but I did after the trip home from Wausau. The mixture does work, but I have not been using it regularly, just when I need to clear a fouled plug, which rarely happens. I haven't looked at the plugs yet. The oil is about 22 hours old and it's Exxon Elite 20W50. Larry Snyder [EMAIL PROTECTED] On Aug 8, 2008, at 7:54 PM, Al Demarzo wrote: Hello Larry; The temps you mention, are they CHT's or maybe oil temp? I'll assume oil temp and really have no comment about that but will ask a few questions about the cylinder to determine a possible cause. Are you using auto fuel or Avgas or a mix? If Avgas, do you use TCP in the fuel if avgas? Is your mixture control working and if so, do you lean also on the ground? Have you pulled plugs on the suspect cylinder? How old is the oil and what grade are you using? Thanks Al DeMarzo Visit the Ercoupe Swap Page Free, Easy and No Membership Required http://www.ercoupeowners.com/swap/swapbook.htm ----- Original Message ----- From: Larry Snyder To: Ercoupe Tech List Sent: Friday, August 08, 2008 7:37 PM Subject: [ercoupe-tech] Sticking Valve Dear tech heads, When we flew up to Wausau, we flew with the engine at about 205 degrees most of the way, but it crept up to 215 briefly on a climb. When we started the plane up to leave on Sunday, we were running on only 3 cylinders. After about a minute, though, it cleared up and ran fine all the way home (it's about 5 1/2 hours each way). I went out a few nights ago to get night current, and it did the same thing. I went out today and pulled it through and the last turn showed no compression. I warmed it up (it ran roughly) and suddenly all was well again. I stopped the engine and pulled it through and voila - compression on all 4 cylinders. I talked to the local mechanic, and he said that I should put Avblend in the oil and fly for an hour or so to clean up the valve stems and guides, so I did. I'll go out tomorrow when it's cold and pull it through again, seeing if the valve is stuck again. If it is, I presume the guide needs to be reamed? Is this where the rope is used to keep the valve in place? How does that work? Or is it better to just pull the jug? I understand that the valve stem is sticking in the guide, I guess I'm not sure I understand the logistics of reaming the guide without removing the cylinder. Also, when I landed this afternoon, it was hot, and I would get a backfire when I when from full throttle to idle. What could cause that? Thanks! Larry Snyder N99340
