First 25hrs

[Loki9]

I now have 25hrs of run time on the A4 I overhauled last summer. Things have mostly been great, starts right up, runs smoothly and quietly, and cruises 5.5 knots @ 1500rpm.

The one problem has been an excess of blow-by gasses coming from the oil fill. To combat this, I installed a PCV system, which reduced but did not eliminate the problem. The motor has new rings and valve guides, installed during the overhaul, so I don't understand why I have this problem.

I guess I did something wrong or missed something important during the overhaul, but I can't think what it could be. Help me Afourians!

[Marian Claire]

I would not worry to much after only 25 hrs. If the problem exists after 50 to 100 hrs then you may have a problem. Remember that it is not just about the hrs run. You need to make sure the engine is running at a good operating temp. You need heat to seat the rings. If you suspect that the rings are stuck a few MMO treatments along with running at suggested temp will help. I made the mistake of running to cold when I was breaking in the A-4 after I rebuilt and some of the rings actually got gummed up and stuck.The rings seated just fine after I started running at proper temps and a few MMO treatments. Dan S/V Marian Claire

[Dave Neptune]

Two things

Loki9, as Dan stted don't worry yet!!! Are you using anything in the gas like MMO? If so stop as the additive will hinder the rings seating a bit.
My first suggestion would be to back the timing off a few degrees. If the timing is a bit to advanced "blowby" can be exagerated considerably.
You could do a compression check to see how much variance you have, but that will just give you info, if one or two are lower it is most likely more time is needed for seating of the rings. No need to consider worry until after a lot more hours.

Dave Neptune

[sastanley]

I think you need to get the RPMs up too. 1,500 RPM is probably lugging pretty bad and putting extra pressure on the rings as well!

Any idea what prop you are running?

[Sony2000]

I'm not recommending this, but to redirect the blowby towards the PCV or flame arrester, and less out of the oilfill, I did the following. Place wax paper over the opening of the oilfill, then fill the cap with a high temperature gasket silicone, and close it down on the opening. Let it dry. Now the iol fill will be less open to the atmosphere. The blow by can go (redirected) to the carb or front bearing vent.

[Loki9]

I would not worry to much after only 25 hrs. If the problem exists after 50 to 100 hrs then you may have a problem. Remember that it is not just about the hrs run. You need to make sure the engine is running at a good operating temp. You need heat to seat the rings. If you suspect that the rings are stuck a few MMO treatments along with running at suggested temp will help. I made the mistake of running to cold when I was breaking in the A-4 after I rebuilt and some of the rings actually got gummed up and stuck.The rings seated just fine after I started running at proper temps and a few MMO treatments. Dan S/V Marian Claire

Thanks Dan. It sounds like my favorite type of problem, those that go away on their own. My A4 is FWC and runs rock steady at 180 degrees, so it's not too cold.

[Loki9]

Loki9, as Dan stted don't worry yet!!! Are you using anything in the gas like MMO? If so stop as the additive will hinder the rings seating a bit.
My first suggestion would be to back the timing off a few degrees. If the timing is a bit to advanced "blowby" can be exagerated considerably.
You could do a compression check to see how much variance you have, but that will just give you info, if one or two are lower it is most likely more time is needed for seating of the rings. No need to consider worry until after a lot more hours.

Dave Neptune

No MMO in the gas. I will try backing the timing off a little. I power timed it to peak RPM, maybe that was a bit too aggressive.

[Loki9]

I think you need to get the RPMs up too. 1,500 RPM is probably lugging pretty bad and putting extra pressure on the rings as well!

Any idea what prop you are running?

I'm running a 12x7 folding prop. The 5.5 knots @ 1500 RPM I quoted is not the max, just a comfortable cruise. She will get up to about 6.25 knots at 2150 RPM max.

[sastanley]

Jeff, OK.i was worried that 1,500 was getting close to max RPM. I am no expert, but if it were me, I'd be running it up some to try to get the rings to seat.

A completely different motor, but I had a Honda Civic engine I rebuilt that burned oil for 6,000 miles before the rings finally settled in. - I guess the rings finally stopped letting oil through...so YMMV.

Carry on, sir.

[Dave Neptune]

Timing

Loki9, I have always been a big suporter of "power timing" for duty engines. BUT whenever setting the timing in this manner once "max" is achieved at your "max" cruise, let it set for a bit and then back it off a tick, just a couple of degrees to the point at which it starts to drop off ever so slightly and then leave it. Setting in this manner avoids the error of a bit to much timing and will reduce blowby considerably especially at the lower RPM's. This will also make for a much smoother engine as to much timing will max out in a low compression engine however they "RUN" better just a tick back from max advance. Engine life and bearings will be better too.

Dave Neptune

[Mo]

Very good bit of info Dave...I too will keep that in mind.