[idubrov]

This classified got me curious. It says engine was converted from an angle valve to a parallel valve. Is that a thing? What exactly needs to be changed? Obviously, cylinders; possibly things around them like intake tubes, etc. What else? What about the connecting rods, the crankshaft and the camshaft?

I don't know much about engines / Lycomings, but I thought that angle valves have different crankcases?

 

[andoman]

I'm sure someone with more knowledge and experience than I will chime in.
However, I have overhauled an angle valve and done a top overhaul of a parallel valve so I have a little bit to offer to the discussion. Off the top of my head, the major differences are:
-counter-weighted crank on AV
-sump and intakes
-pistons (AV are slightly higher at 8.7:1 iirc)
-cylinders. They are quite different under the rocker covers.
-piston squirters
-I believe the cases are different
-don't know about rods but I bet they are different given the extra stress 20 HP adds
-don't know about cam but I bet it's different to take advantage of what I assume to be larger valves flowing more air
I would bet that the Barret conversion is legit as far as functionality. In other words, I doubt it will Chernobyl...
The major comment I would make is that the IO-360 Angle valve on my -7A seemed to be loafing to make its 200 HP. It was very happy burning mogas and the CHT's always ran cool. Once I moved up one oil cooler size over the stock vans unit I had to work hard to get the oil temp over 200 degrees.
By contrast, any PV making 200 hp is working pretty hard. I'm curious about the 200 hp claim. I don't think that cold air induction and 10:1 pistons will net 20 hp. The IO-370 only gets to 195 and it enjoys increased displacement.
Of course, extra weight is extra weight. In my -7A the extra weight up front was a plus.
I'm really looking forward to the posts by the experts.

 

[jrs14855]

Engine

The mix of components probably started in the aerobatic community with the desire for constant speed configuration with front mounted governor. Angle valve crankcase from Seneca I engine with cylinders and internals from parallel valve 360.
With a fixed pitch prop a hot rod parallel valve 360 turning 3300 rpm is probably producing around 220 hp.