O320 Cylinder Swap Question

0-320 A1A Engine
Can you swap out low compression cylinder assemblies 05K21423-A 150hp and replace with high compression 05K21101 160hp?
Both the 05K21423-A and the 05K21101 are narrow base cylinder assemblies for a 0320

Found the answer:

If you have a wide deck case you can up the compression no problem using the 160 hp pistons however if you have a narrow deck case you need the cylinder base plates and longer thru studs in the case.


Thanks Guys

Do some searching on this site. Lot of past discussion on the subject including input from Mattituck and other engine gurus.

If the -A1A is an early narrow deck engine then bumping up the compression ratio to 8.5:1 for 160hp may not be quite as simple as a piston (or piston + cylinders) swap. The case thru studs and cylinder studs might have to be replaced with longer ones to accommodate extra cylinder base hold-down plates. Some discussion of this, including part numbers for the longer studs needed, can be found in this thread on the Shortwing Pipers forum: http://www.shortwingpipers.org/forum/archive/index.php/t-5684.html

Neal@F14 said:

If the -A1A is an early narrow deck engine then bumping up the compression ratio to 8.5:1 for 160hp may not be quite as simple as a piston (or piston + cylinders) swap. The case thru studs and cylinder studs might have to be replaced with longer ones to accommodate extra cylinder base hold-down plates. Some discussion of this, including part numbers for the longer studs needed, can be found in this thread on the Shortwing Pipers forum: http://www.shortwingpipers.org/forum/archive/index.php/t-5684.html

Click to expand...

My Parts manual shows that hold down plates are not used on the 150 and the through studs are 3/16" shorter on the A series engines. While there may be tricks, I don't believe that those studs can be removed without splitting the case. A series engines are 150 and B series are 160. The other numbers and letters are related to configuration elements like induction style, carb prop flange, etc.

Larry

One more thing to consider is that higher compression pistons might also need wrist pins that are thicker-walled. Of course this also means that you need to take into consideration the piston weight to compensate for the additional weight of those heavier wrist pins to keep all the reciprocating mass balanced correctly. I *think* most makers of the high compression pistons reduce their piston weights to compensate, but this is something important to consider. This might only be a concern when going to more than 9:1 compression or higher but it's something I've encountered in my preliminary research for possibly bumping up compression on my wide-deck O-320 to get more HP out of it.