[Tkitchen1]

Grettings all, again having been in the moderatly high end drag racing arena, I do not see much information for breaking in the cam shaft. I do understand that new/reground cams need new lifters(tappets). In a high power flat tappet racing engine, the cam needs a HP lubricant and 25 to 40 minuets initial operation at 2000 to 2500 rpm. The higher RPM reduces the pressure on the nose of the cam until it has a chance to burnish the surface of the cam. All of the information that I have read does not address so I am curious about the proper procedure.
Thank you for all help.

 

[hgerhardt]

The valve spring pressure is significantly lower in a Lycoming than a typical high-RPM hot-rodded V8, and therefore puts much less stress on the cam lobes than the V8 would. Just use HP lubricant on the lobes and lifters (tappets) and run it at 1500 rpm for several minutes. Remember, redline in a Lyc is only 2700 rpm, and that's the primary determining factor in valvespring pressure needs.

Heinrich Gerhardt
RV-6, flying (with a Lycoming that I overhauled)
'66 GTO with a big roller-cammed 428

 

[osxuser]

Typically cam break-in isn't really an issue on our engines. The procedures outlined for break-in regard more for the setting of the rings, and avoiding overtemping the aircooled cylinders.

A couple questions:

Did you have the engine overhauled by a shop, if so, did THEY do any break-in runs? If they did, you are probably good to go already.

If they didn't (or you overhauled yourself), the general wisdom I've always heard, and adhered to is:

A 2-3min 1000rpm run, followed by a complete cooldown

A 5 min or so run, increasing from 1000 to 1500 by the end. Cooldown.

Another 5 min run this time getting up to 1800. Cooldown.

A run (No longer than 10 min) that works it's way up to around 2500 (or whatever you can get). Cooldown.

If no leaks, do a runup, make sure she makes a desired RPM on WOT brakes locked on the runway, and if so, fly! (desired RPM would be either 2700 for a CS prop, OR whatever the prop manufacturer specs the static RPM to be.)

You do not want to get the engine (CHTs or Oil temps) too hot on the ground. Note that the prop really doesn't provide enough airflow to cool the engine in any ground operations above idle (if then...). If you have the ability to use a test stand and a test club instead, that is preferred. Especially if this is going on a untested airframe. It's a risky procedure (In mine and Van's book) to use a brand new engine on a brand new airframe. I used the above procedure on our Cardinal's overhauled motor, but if I was doing it again, i'd pay the shop to do the test cell runs...

Mahlon, any comments on break-in on wing?

 

[goodwoodone]

Proper Cam Break

The above comments are correct as far as initial engine runs go and its what I would do on our engine test at our overhaul facility withut the intermittent cooldowns as we use a calibrated test fan .

As for preventing early cam wear my advice apart from the usual regular oil changes is to fly as often as you can and when you do, make sure you reach a high temperature to boil off any exhaust byproducts usually an hour at 75% power should do it , and DO NOT turn the prop by hand when the aircraft is sitting around as this will just scrape oil of the bores causing corrosion to be accelerated heres a link to a good article on break in
www.casa.gov.au/fsa/2002/sep/36-38.pdf
Hope this helps


Gareth Wood

 

[mahlon_r]

Mahlon, any comments on break-in on wing?

This is what I would use for experimental use.

CYLINDER RUN-IN INSTRUCTIONS FOR CHANNEL CHROME,
CERMICROME, CERMINIL or NICKLE CARBIDE BARRELS

1] Install mineral oil in ALL normally aspirated engines and all Teledyne Continental turbocharged engines. Install AD oil in all Textron Lycoming turbo charged engines.

2] Start engine, run at 800 R.P.M.'s for three (3) minutes, shut down, check for leaks.

3] Start engine, run at 1,000 R.P.M.'s for three (3) minutes, shut down, check for leaks.

4] Cowl aircraft.

5] Start engine, run at 1,200 R.P.M.'s for three (3) minutes, shut down, park into wind.

6] Start engine, run at 1,400 R.P.M.'s for three (3) minutes, shut down, park into wind.

7] Start engine, run at 1,400 R.P.M.'s for five (5) minutes, run up to full power, check all engine parameters, retard power to 1,000 R.P.M. for one (1) minute, shut down.

8] Check for leaks, return engine to service (see Engine Break-In Instructions).

All runs should be made into the wind.

At no time during these runs should CHT exceed 350F.

Between all engine runs, allow adequate cool off time.

Before proceeding to next run, you should be able to hold your hand on a rear cylinder head for three to five seconds.



CYLINDER RUN-IN FOR STEEL,
NITRIDED OR REBARRELED CYLINDERS

1] Install mineral oil in the engine.

2] Start engine, run at 800 R.P.M.'s for three (3) minutes, shut down, check for leaks.

3] Start engine, run at 1,000 R.P.M.'s for three (3) minutes, shut down, check for leaks.

4] Cowl aircraft.

5] Start engine, run at 1,200 R.P.M.'s for three (3) minutes, shut down, park into the wind.

6] Start engine, run at 1,400 R.P.M.'s for five (5) minutes, shut down, park into wind.

7] Start engine, run at 1,400 R.P.M.'s for ten minutes, shut down, park into wind.

8] Start engine, run at 1,400 R.P.M.'s for five (5) minutes, run up to full power, check all engine parameters, retard power to 1,000 R.P.M. for one (1) minute, shut down.

9] Check for leaks, return engine to service (see Engine Break-In Instructions).

All runs should be made into the wind.

At no time during these runs should CHT exceed 350(F.

Between all engine runs, allow adequate cool off time.

Before proceeding to next run, you should be able to hold your hand on a rear cylinder head for three to five seconds.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."