I am considering an engine rebuild of a B20F engine. This is the 2.0 liter continuous fuel injection engine with over head valves. I have torn down the spare B21F engine I have and found the pistons are worn or were previously replaced with undersize pistons (perhaps from B19??). Replacement B20F pistons do not seem to be available. I have a couple of B21 engines which may or may not have useable pistons. I can buy B21 pistons and rings and could have the block bored to fit the larger (about .125 inch) pistons. My research shows that the stroke and connecting rods are the same for these engines. Deck height may be different - I have not found that level of detail.

Does anyone know if I can safely bore the B20F engine .125 inch over size? Can I use B21 piston in the bored B20F block without piston modification?

I am not looking for more power - just restore lost compression so my faithfull 1975 245 can go on like the energiser bunny............

If your engine is 8-bolt (74 or 75) that is a viable option.
The late B20F (8-bolt) engine was the trial run for the B21 and following
lower ends. The main bearings are the same but the rod bearings and rods
are different as are the wrist pins, compared to the earlier 6-bolt B20.

The B21 standard bore is 3.622 and the B21 standard pistons and rings should
work admirably in an 8-bolt B20 bored to this size. The BIG problem will be
getting a big-bore headgasket. IPD may have one and some of the swedes may
have them. If not, copper gaskets unlimited in Phoenix can make you one.
--
George Downs Bartlesville, Heart of the USA!

Thanks George,
What makes the engine 6 or 8 bolt? Head bolts? Main bearings?
I had not thought about the head gasket problem. Thanks for bringing this up.
By the way did you come to Duncan a few years ago to look for 2 door seats? I now have a pair of real two door seats (with back release). They are rough and need recovered.

Flywheel mounting. Older and B18 engines use 6 3/8"-24 UNF bolts and
74-75 B20s and B30s use 8 10mm bolts.
No, I haven't been in Duncan since I went through there on a bus from
OKC to Ft. Sill in 1961. Don't need any 2-door seats - both my 122s
are actually 220s.
--
George Downs Bartlesville, Heart of the USA!