Oil Return Tube "O" Ring Problem

[jrcotner]

I'm having a terrible time keeping the "O" ring on the oil return tube from sliding down the oil return tube when I slide it into the head. I've tried all of the ideas listed in previous posts with no success. Any suggestions would be appreciated. Photos wouldn't hurt, either. I'm so close to having the motor back together save for this little problem, and it's driving me crazy. I had no trouble with the old style oil return tubes, just the new style.

[Jim LaGuardia]

First, what year is your truck/engine?
There are two types of heads, early( pre 72), late(all others).
Early heads have the O ring in a recessed groove and return tubes dead head against the casting. Later heads the o ring is put on the tube, the tube is inserted into the head and then the head is installed(just like the manual lays out).

[jrcotner]

I've got a 1971 710M with the old style heads. However, the #2 cylinder head was beyond repair so I replaced it with a new style head, which I was assured would be compatible. I placed the "O" ring over the new oil return tube and inserted it into the head, but for some reason the "O" ring keeps coming over the little bulge on the oil return when it is inserted into the head.