Using B Series Pistons in the B20A

This is the how to for making B16A Pistons fit your B20A. This is a cheaper way if getting some decent compression from the B20A engine, I used some P20 B16A2 pistons, but i assume PR3 and B18C ones work just the same.

Warning: Using other B Series pistons for example B16B or aftermarket High compression Pistons may not work as they may be too high for the B20A cylinder head and will probably bend your valves. These Aftermarket Pistons have not been tested as far as i know, if you have tested them, and it worked. feel free to contact me.

In this photo you can see the difference between a Stock Honda B20A piston (Right) and the more High compression b16A piston (Left)


The main reason why these pistons do not "bolt" straight on is because of the size of the gudgen pin that holds the piston onto its rod. honda B16A/B18C pistons have a pin size of 21mm where the B20A has a 22mm gudgen pin. Here is a pic of a b20a piston with a b16a pin sitting in it:

b16A pin inside b20a piston 

The way i went about it was to pay someone else to make them fit so i took the B20A pistons and rods and my B16A2 pistons and rods into the engine builder and basically told them what had to happen. The piston needed to be machined to take the 22mm pin, So they did this on all 4 of my B16A2 pistons. The Next thing we found was the rod itself is wider where it goes into the piston.

Heres a picture of the two rods, B20A on the bottom and B16A siting on top. 

 Compare B20A and B16A rods

As you can see the top B16A2 rod is narrower than the b20a rod, All that needs to be done here is measure how much wider the B20A rod is and machine the piston so the rod fits.


 Now the piston should fit on the rod, Press the B20A gudgen pin into the B16A2 piston and check it moves around freely. You now have high compression pistons for your B20A