Re: Engine swap (repower)
Dhadley,<br /><br />From the whole thread, it sounds like this engine is running basically OK...just not producing enough power to turn the revs it should, regardless of the prop that's on there. That seems key to me...the lack of a significant difference in RPM with different pitch props.<br /><br />He said the throttles are opening fully. I looked at the diagrams for this engine, and can't find any source for an exhaust restriction.<br /><br />It's running a bit rich, but, apparently, not hugely rich, since fuel economy isn't badly affected.<br /><br />I can see a couple of possibilities, here. First, he's using surface discharge plugs, according to what he says. Plugs can certainly restrict an engine at high RPMs, so that seems like a good, and easy, thing to check. I've seen that happen on automobile engines. Plugs seem to be just fine, until a certain RPM is reached.<br /><br />Second, the lack of a difference in RPM with different prop pitches sounded like the symptoms of a restricted exhaust, but I can't see any way that could happen. What if the restriction is on the other end of the engine? Looking at the diagrams, this engine has four sets of reeds held in blocks. Could there be a problem there? If one set was messed up, somehow restricting flow, the symptoms might well be as described. One cylinder would be starved of fuel/air and refuse to perform at some RPM level...just not getting enough fuel to function properly.<br /><br />I just can't get past the lack of an RPM difference between props. That seems to me to indicate some sort of restriction or rpm-linked failure somewhere in the cycle. I just can't see it being a purely power-related issue.<br /><br />Another issue could be compression. Even though it was rebuilt, I wonder if the owner has checked compression on all four cylinders. I didn't see any mention of that.<br /><br />It's an interesting question. I hope it doesn't go away. I'm really curious.
