You could sleeve it.

 

I agree, sleeving is probably your best option. I doubt you'd be able to find new B21 pistons, and you would need to use the F head from an '72-on injected B20 and also modify the connecting rods to take the larger wrist pins. There is an Elring gasket for that bore, but it's over $100. I did build a few B20s like that, but the last one was in 2007 or so due to the lack of pistons.

 

I'm sure I still have new B21 pistons and they are still available

 

I was looking at sleeving a B20 myself when I found a crack in number three cylinder. However I ended up finding an AQ130 Penta boat motor for 60 bucks and useing that block. The trick is finding some hillbilly with a yard full of old boats. I got lucky and found one on craigslist in about five minutes.

 

thanks for all the help. we have found b21 pistons and hopefully the machining will start soon. still looking for the head gasket. I contacted Elring but have not heard back from them.

 

Am I wrong in thinking you need an 8 bolt crank for those pistons? Of course that could be an 8 bolt motor.

Anyway if you need the 8 bolt crank and rods let me know I have the 8 set up from the AQ131. I just want the cost of shipping to send it to a good home.

 

I may have a need for that as I have another motor to rebuild for my 123

 

Ill check tomorrow and let you know

 

If you are running a 6 bolt crank, have your machinist remove the pin bushings from the con rod small end, and ream them for a press fit of the 24mm pins.. JohnMC on turbobricks is running one tis way over on turbobricks without issue, and from the sounds of it, its been running for a good while.

 

It's best to have the pins able to rotate in the rods, rather than just in the pistons. I'd ream the rods for .0006" clearance, and use the retaining clips on the pins. I've built a few engines like that, and they've held up fine.

 

I have an 8 bolt crank, so hopefully things will all work together. Thanks again for the advice.

 

Okay, then the pistons will fit your rods without modification.

 

The piston arrived today but work will only strat on monday. Will update with progress