QUESTION: My Lycoming IO-360-B1E engine will be majored sometime early next year and I am trying to educate myself. The facility I plan to use for the overhaul says that a reground cam is just as good as a new one. Could you please explain how a cam is reground. I don’t understand how if it is reground that you still have the original lift and duration, etc.
ANSWER: It’s been quite some time since this subject has crossed my desk, even though I’m sure it comes up when people get to the point where you are. I’m impressed, by the way, with the fact that you are beginning to gather your important information now with your planned overhaul sometime early next year. It allows you to see just what’s out there and do some good comparison shopping and, most important of all, it gives you lots of time to get answers to all of your questions. If you still aren’t certain about something, you’ve got time to do additional research. I wish more owners had that foresight.
I’d like to throw one thing out that may add to your decision making process and that is the fact that it is typical for factory prices to increase at the turn of the calendar year, so depending on what that increase might be, it may pay you to consider having the job done sooner.
Now to your question: there are still a few overhaulers that will have a camshaft reground if required. I personally don’t think this is as common these days as it was, say, 10 years ago. I would suggest you review Lycoming’s Service Letter L206A for additional information on this subject.
Lycoming offers some very competitively priced service kits that provide a factory new camshaft and tappet bodies. Just in case you’re not aware, you must install new tappet bodies whenever the camshaft is reground or replaced (no, I’m not going to mention those field “”reground”" tappet bodies even though I’m certain I’ll get letters regarding them). This information is found in the Direct Drive Engine Overhaul Manual in Section 6, Page 11, reference 6-43.
To answer your question regarding the lift and duration: If the camshaft is reground, it does not change. The regrinding process follows the same profile of the original grind and only removes any discrepancies on the lobe. If my memory hasn’t failed me, I believe when the factory used to regrind camshafts many years ago, you were allowed to take up to .006 inch off of any individual lobe and still be within spec. Keep in mind we are dealing with a hydraulic tappet and plunger, so the proper dry tappet clearance when installing the rocker arms is accomplished by different length pushrods. On your particular engine, the dry tappet clearance is .028 to .080.
In my humble opinion (and opinions are like belly buttons — everyone’s got one!) I think it’s hard to beat the factory kit deal where you know you are getting all new parts that carry the standard factory warranty.
Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.