530803 Camshaft Specs

[Jason]

Hi everyone, first off I'd like to mention how valuable I consider this association, well worth the price of admission for sure. A question - I have torn down the bottom end of an O-300-A and I'm measuring all the parts before I send them out for inspection, but I'm obviously missing something in the table of limits regarding the camshaft. The only specs I see are for allowable bearing clearance and endplay. Also from the overhaul manual...

"(g) Camshaft and Hydraulic Valve Lifters.
(1) Stone light scores on cam lobes, journals and
valve lifter bodies.
(2) Replace camshaft if lobes are pitted or if lobes
or journals are excessively worn. Replace complete
hydraulic unit if any part is worn or damaged. (Refer
to Section 16.)"

How do you determine if a lobe is "excessively worn" without a spec? Like I said before I am sending out everything including the cam and lifter bodies for inspection, but it would be nice to know minimum lobe lift to see if it can be reground. This is what I found on the front most lobe/lifter body. All the other lobes/bodies looked perfect. As embarrassing as it may be, I really hope the answer in the manual somewhere and I missed it. It's driving me nuts!

Jason

[T. C. Downey]

I'd send them off to Aircraft Speciality services and have them reworked.

0-200/0-300 lifters are not flat where they touch the cam. they are domed, and do not set centered with the cam. When they need to be re-surfaced they will show a wear tract all the way across the cam lobe. and a wear tract on the lifter, like we see on the lifter body you show us.

[Jason]

Thanks for the explanation and recommendation for repair shop. Just looking at the flat spot at the apex of the lobe makes me wonder what the cutoff point is for trashing the cam. This lobe measured 0.342" lift, all remaining 11 lobes measured between 0.356 and 0.353". Anyway its purely out of curiosity that I ask the question, at the end of the day the repair shop will be making the call on its servicability.

[Sixracer]

I have ask and ask that question and no one will give Specs, as in opening and closing and overlap and lobe centerlines. I have found 2 cam numbers for the 0-300D that I have and all I can get is they are both Legal.
In building race engines for 44 years I have a vast wealth of cam design knowledge. I've also built a very large data base of different cam profiles for automotive race engines. I also have a program called Cam Pro Plus that I use eveyday to check the specs and identify cams without identifying numbers or marks. Some people are familiar with a Cam Dr. The Cam Pro Plus has a few features the Cam Dr. doesn't. All of the flat lifter cams, Hyd or solid have a thing called taper ground into the lobes. That is what helps spin the lifter (if the lifter doesn't spin or rotate the cam usually goes flat) when it 's convex surface contacts the cam. It also helps keep the cam pushed into position back into the block. Most non roller automotive cams have 1 to 2 degrees taper ground into the lobes.There are a lot of things that can be worn on a cam and there are also problems with the "Grind" that can not be seen with the naked eye. Problems can go all over the place, I've even had a cam grinder install the master lobe wrong and reverse the flanks on the cam lobes. I've even had cams that didn't match the cards specs. I've also noted that the diameter of the grinding wheel can vary. The master is usually set up for a 18" grinding wheels. New wheels come @ 24" diameter. What happens, you ask?, when the big wheel is used on a master lobe designed for a smaller wheel? The came lobes don't match the master lobes specs. My point is if you don't have all the specs leave it to someone else check it out.
This aircraft industry is real closed on giving specs like I am familiar with to the general public. The only way I can see to build a Data Base with "Real" Spcs is for me to buy new cams and check them. OR:
I will make an offer to anyone wanting to know the "Real Specs" to send me their cams and I will roll them and build a data base by part number. This info will be for the club to use.
BTY: Jason in the automotive world you would have a lobe going flat or a real poor grinding job.
With the computer program I can tell base circle run out and lobe centerline variations by laying all the lobe profiles on top of one another. I can also see when one lobe, or multiple lobes don't match. Usually wear or a bad grind job.
FYI: I've sent back brand new cams from major performance grinders because of QC problems. There is one supplier I do't even bother buying from because his QC is non exsistant and his grinders are worn out.
Adger Smith
Adger Smith Performance Engines
2802 W 7 th St
Texarkana, Tx 75501
shop 903 794 7223
cell 903 824 4924
adgersperf@aol.com