Engine Problems

George Bonney

Hi everyone. I am new to the Forum and have been away from cl stunt for 50 years. So I am rusty to say the least, but I am looking forward to getting back into it. I desire to tap into your expertise.

Here are my immediate problems:

I have taken a ringed engine apart and cannot get the piston back into the crankcase. What do you all use to compress the piston rings so the piston will completely go into the case? There are two rings(Dooling 29).

Also, I wish to inspect the cylinder liner. How do you remove the liner from the crankcase without damaging it? Is the liner a press fit? What is required to get it back into the crankcase?

Thanks in advance.

Usually this can be done by compressing ring, at the point where it is split, with a finger nail or soft (wood) tool as piston enters liner. Or compress ring from opposite sides of the piston, each being 90 degrees from where ring is split.

If that isn't working, very thin sheet metal wrapped once around the piston and rings will kinda squeeze it all into alignment as piston is returned to cylinder bore.

Hi George,

The simplest solution is an ACME Hose Clamp of the correct diameter. Just tighten it enough to squeeze the rings and the piston/rings will slip right in. In fact, you can sompress just the rings and insert them to check the end gap.

**Might I inquire just WHICH stunt plane you're gonna put the Dooling in? <G> **

It's been a (long) while since I ran Doolings, and I don't recall if the liner is a press fit, but I think not. Judicious use of a propane torch, applied as evenly as possible around the circumference of the case should allow you to remove the liner. Be sure you scratch in alignment marks before you remove the liner!

George Bonney

Ralph:

I do not plan to put the Dooling 29 into any stunt airplane. I am just cleaning one of my vintage motors for a possible bench run. Then,I'll place it back on the collector's stand to look at and to remember the old days(early '50's) when I flew it a few times in a Speedwagon. Never tried the Dooling in a stunt airplane.

>George Bonney
>
>Hi everyone. I am new to the Forum and have been away from
>cl stunt for 50 years. So I am rusty to say the least, but
>I am looking forward to getting back into it. I desire to
>tap into your expertise.
>
>Here are my immediate problems:
>
> I have taken a ringed engine apart and cannot get the
>piston back into the crankcase. What do you all use to
>compress the piston rings so the piston will completely go
>into the case? There are two rings(Dooling 29).
>
> Also, I wish to inspect the cylinder liner. How do you
>remove the liner from the crankcase without damaging it? Is
>the liner a press fit? What is required to get it back into
>the crankcase?
>
>Thanks in advance.
>
>George

Ron B.
F4Fguy

George:

The liners on these were what used to be(maybe still is)called a "two thumb push fit". A little heat is generally all that's needed to get one out.CAVEAT!! do NOT use a torch or any other method which doesn't heat uniformly! Put the case and liner in a 225/250 deg oven or boiling water for a few minutes, and the sleeve should drop out. If not try reheating and pushing the bottom of the sleeve with a wooden implement,such as a piece of motor mount stock. If it's still stuck go to a good mechanic and ask him to pull it with a bearing puller.Once the sleeve is out,thorougholy clean both case and sleeve before attempting reassembly.The sleeve should then push into the case easily(be sure the ports are positioned properly).

The best ring compressor(other than a proper ring installation sleeve) is a small hose clamp.If you examine the sleeve you'll find that the bottom has a chamfer. The piston should be installed to the sleeve from this end before installing the sleeve in the case. Piston installation from the top is possible, but there should be a slight taper in the bore and inserting from the bottom is easier. be careful to install the rings with the gaps at least 45deg apart,and positioned so that they don't ride over any port.You really shouldn't reuse rings,but if you must, be sure they're in the same groove and in the same orientation as when you took them out.