Do you happen to have the Lycoming Service Bulletin number, that describes process for checking cam using cam lift measurements? How about a web link to the service bulletin?Originally Posted by WLIU
Also, about how long does this procedure take if being done for the first time?
About how long should the procedure take, assuming one has done it a few times already?
Thanks, Wayne
First, some of how Lyco suggests that the valve tappet assemblies should be handled is described here - http://www.lycoming.com/Portals/0/te...0Lifter....pdf
The procedure that you are interested in is mostly described here - http://11hc.44rf.com/manuals/engine-prop/lycoming/aerosportspower-library/360_series_ops_manual/sec_5-maintenance.pdf
How long will it take? If you budget a half hour per cylinder you are unlikely to be disappointed. Someone who has done it a few times can likely do it much faster, but I think that a half hour is a safe guess.
Best of luck,
Wes
N78PS
Thanks. I probably should have mentioned that I have a Lycoming 0-235. I am not sure if it has hydraulic lifters. I think it has solid lifters. If solid lifters, then using a dial gauge to "map" the lift on each cam lobe should be fairly easy, unless I am missing something. Is anyone aware of Lycoming data sheets that specify the allowable limits on the cam lobe lift profiles? Is there more to this than I am thinking?
if the 0-235 has hydraulic lifters, then I need the procedure on how to deal with the lifters, so the hydraulics don't impact the dial gauge when mapping each cam lobe. I can't find this procedure in the referenced materials. Any additional ideas, references?
thanks, Wayne
The docs that I linked to speak to hooking hydraulic lifters out with some safety wire (never a magnet), collapsing them, and putting them back. You then reassemble the valve train on the cylinder and put a dial gauge on the rocker arm. Rotate the prop and measure the lift. There is an SB tha has the limits. Google should find it for you.
For an O-235, even if you do not know the exact tolerances, what you can do is check all of the valve lifts, then compare all of the exhaust and all of the intake valve numbers. Typically one lobe fails but the others are OK. It is unusual for them all to wear down at the same time. So by checking them all and doing the comparison you can get a good idea whether you have a problem.
It sounds like you do not yet own a parts book and overhaul manual for your engine. Both books have lots of useful information in them. Highly recommended that you have them on your shelf.
Best of luck,
Wes
N78PS
One thing that I do when trying to leave the piston in the cylinder by removing the wrist pin, and it usually works, is once you get the pin exposed to the point where it can be pushed out is to heat the pin bosses of the piston and the end of the rod with a hot air gun. By doing this I have seldom ever had to resort to applying force to the wrist pin. It does get hot so you will need some gloves. Even if you plan to leave the pistons in the cylinders it is a good idea to have the ring compressor handy. Things don't always go according to plan.
Not checking dry tappet clearance with a hydraulic tappet engine is the most common error in field cylinder replacement. Do not mix pushrods because the dry tappet clearance is adjusted by installing push rods of different lengths.
As Wes mentioned, you should not attempt any of these procedures without the appropriate manuals/parts list.
If the engine is not making metal particles in the oil filter, do you really need to tear it that far apart?
Of course if there are particles that might mean a problem.
I think it would be an easier first step to run it for 10-15 hours and check the filter.
As an A&P and first hand knowledge, best take a look.
Last annual on my O-360 A4M, I discovered a cracked head.
I pulled #4 cly. Piston skirt was impregnated w/sparkly stuff.
Took a peek at the cam.....SHOT!!!!!
I change oil at 50hr intervals, have a oil filter that is opened and inspected at every oil change and the screen is also always removed and checked for fodder.
NO SIGNS OF IMMINENT DANGER!
When I dismantled the engine, in the bottom of the oil sump (left rear) were the remains (Grindings) of the cam and lifters!
The way the oil sump is designed with the bottom mounted Carburetor, there are webs that are just high enough to prevent the last 1/8 inch oil in that corner of the sump from making it to the oil pump intake port. HMMMMMM.
Lots of stuff sitting in the 1/8" of oil!
Again, IF YOU REALLY WANT TO KNOW, Pull#4 and either #1 or #2 and visually inspect the cam.
If you don't find anything amiss, Great!! You will now feel safe flying behind that engine.
If the cam shows wear and / or the pistons have a little sparkle on the skirts, IT IS TIME TO TAKE THINGS APART.
The parts requiring replacement from pulling the Clys. is a small price to pay for the knowledge gained.
Good luck.
Hope your cam is fine.
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