B18/20 rebore

[Jamie Taylor]

Can I bore a B18 out to B20 size and still use the same crank? but with B20 pistons. Someone has said that the 1967 block would be best for boring. Does anyone out there have any experience of this?

[Andrew (UK)]

Yes in theory, but it is probably not worth the risk. You run the risk of ruining the block and the gain in hp is very small. It's an expensive mod with no gurantees. There are many other ways to increase the power without the risk or the expense.

[jamie]

such as?

[Andrew (UK)]

Performance camshaft coupled with breathing and exhaust mods
Shave the head for a higher CR
Lighten the flywheel
Light-weight pistons and con-rods
Bigger valves
Lightweight push-rods and rocker arms
High lift rocker arms
Port and polish the head
Fueling system improvements

OK some of that will cost more than others, but there are many, many choices to be made.
Do the research, read the books, talk to the suppliers. Find someone who has done it before. OJ Rallye and IPD are valuable resources in the US and there are more in Sweden.

[Tony Barrett]

>Can I bore a B18 out to B20 size and still use the same
>crank? but with B20 pistons. Someone has said that the 1967
>block would be best for boring. Does anyone out there have
>any experience of this?
I've done it more than once , no problem . You run a small risk of a thin cylinder wall , but I have not seen a failure . Be sure to get the early type B20 pistons cos the later ones have a different size gudgion pins , also use a B20 cylinder head .

[jamie]

Finally carried out most of the mods suggested on the dyno at present and waiting for results, will post some readings
Jamie
PS Merry Christmas!!!



Performance camshaft coupled with breathing and exhaust mods
Shave the head for a higher CR
Lighten the flywheel
Light-weight pistons and con-rods
Bigger valves
Lightweight push-rods and rocker arms
High lift rocker arms
Port and polish the head
Fueling system improvements

OK some of that will cost more than others, but there are many, many choices to be made.
Do the research, read the books, talk to the suppliers. Find someone who has done it before. OJ Rallye and IPD are valuable resources in the US and there are more in Sweden.

[Volvorama]

It's a cheap mod if you recycle used standard size B20 pistons. I believe Pete (940Turbo) did this on late B18 blocks on several occasions without problems. I understand that the trick is to use the B18 blocks with alternator mountings as these are the same casting as the B20