Break In schedule

[Marian Claire]

The rebuild on the 65 A4 was a success. Have set the oil pressure and run thru two heating torque cycles. How should I run the engine for break in?. I want to check the valve/ tappet clearance before she goes back in the boat so I am doing this outside the shop. What rpm, rpm up and down, idle time? OOO what a sweet sound.
Dan S/V Marian Claire Soon to be under new power.

[superdave474]

Break in time

I'd be curious to have an expert opinion on this as well. I've had mine running three times, brought up to temp each time, for a total time of probably just under an hour. I've adjusted the oil pressure, reversing gear, and dealt with a minor oil leak.

As for the valves, I have been somewhat mystified by the settings. When I was assembling the engine, I adjusted the clearance to the .10 and .12 specs listed in the manual. The first time I started it, I could hear them tapping. I removed the cover, and about half of the clearances were WAY high, some close to 1/16". How could this happen? Did I dream that I adjusted them the first time? In any case, I re-adjusted them back to the listed specs. The tappet screws are not loose, meaning they won't spin without putting significant torque on them when adjusting, so I don't imagine vibration could throw them out of adjustment. After adjusting them to the recommended spec, the exhaust became extremely smoky. I removed the manifold and cover again, and went down the line, setting the clearances at .13 across the board. Engine started, and exhaust ran clean. But now, the motor will only run for about twenty seconds or so and then shut down. It will restart right away, and do the same thing. I have a theory that I may have a slight leak in the fuel line that causes the pump (electric) to cavitate..? While performing my valve exercises, I did not replace the Teflon tape around the fuel supply line going from the pump to carb, so I am hoping that is my problem there. Does anyone else have any suggestions?

And of course, advice regarding break in time, per Marian Claire's question?

[Don Moyer]

Unless we're looking at a typo, you set your valves at .10" and .12". If this is what you meant to say it would certainly account for your approximate 1/16" clearances. The valve tappet clearances are .010" for intakes and .012" for exhaust. Also, be sure to check the clearances when that particular cylinder is at TDC, just as you would set the number one cylinder for ignition timing.

Don

[superdave474]

Yes, Don, my typing mistake. Set clearances at .012" and .010" the first time, now all set at .013", and engine runs smooth for the twenty seconds after startup. You mention frequently you err on the 'high' side of adjustment. How 'high' would .013" be considered?

[Don Moyer]

I like to have a loose .010" and .012" but not so loose that I can get the next size feeler gauge to go in with a normal feel. A normal feel for .011" or .013" (especially .013" for exhaust valves) will probably result in a bit of valve tap by the time the valves all settle in. I would say though that even in these worst cases (a full thousandths or so over specification), we have never really seen any indication of "peening" of valve seats that you might see in higher compression engines and operating at higher RPM.

Don