3 replies to this topic

[1963MKI]

Reboring an Austin 1300 Gt engine and can't find the right Pistons to use. Any ideas ?

[carbon]

Any 1275 piston can be used, probably best to go for higher compresssion 21253 type.

 

Crown height on more recent pistons is about 30 thou higher than the originals, but this should not be a problem as long as the block has not been decked. If the original engine number is still on the deck face chances are you'll be OK.

[1963MKI]

My block hasnt been decked but would I be right in saying that using the new 21253 pistons +20 would give me more cc's but not as much as 1293 because i've lost cc's with the taller pistons. Based on my calculations I would gain 18cc from going plus 20 but lose 2.9cc per cylinder from using the pistons for a total of 1281cc. So I would get a 6 more cc with higher compression ?? Forgive me if i'm wrong, I lost my calculator haha.

[carbon]

21253 pistons should work fine in an undecked pre-A+ block. You will likely have 5 to 10 thou crown to deck clearance which is ideal for a fast road engine.

 

These +0.020 pistons will give you 1293 capacity (swept volume) regardless of deck height.

 

The deck height and piston bowl voume don't affect the swept volume, they just alter the compression ratio.