9 replies to this topic

[Mini118118]

Hi everyone i have a 1275 block that i am looking to get bored to a 1380 i have read various things about wether to offset bore or not can i have a few opinions please.. its never going to see a race track but it going to be turbo charged and i already have the 73.5mm 11cc Powermax pistons..
your thoughts would be appreciated..thanks

[Cooperman]

You really do need to offset bore to go to 1380 (if you must go to 1380 - 1330 is just as good and doesn't require offset boring). Without offset boring cylinders 2 & 3 become very close and it's difficult to get the head gasket to last..

[Carlos W]

Is your 1275 on standard bore? I've got a +0.030 which needs a rebore and you could have cheap, then you could keep your standard bore block!

[mike.]

The downfall is that once offset bored the block is scrap once its bores are worn. If you have a 1275 block it can be rebored 2 or 3 times before its scrap.

If you go straight to 1380, then the bores get worn (which could be quite quickly in a high revving engine) then the block is scrap and you'd need to find another one. 1275's are getting harder and harder to find now too.

[Cooperman]

The downfall is that once offset bored the block is scrap once its bores are worn. If you have a 1275 block it can be rebored 2 or 3 times before its scrap.

If you go straight to 1380, then the bores get worn (which could be quite quickly in a high revving engine) then the block is scrap and you'd need to find another one. 1275's are getting harder and harder to find now too.

Anth no more new ones are ever going to be made!
If you are building it for out-and-out competition it's a different matter as 1/10ths of seconds on a lap time count, but for road use the difference between 1330 and 1380 will really never be noticed.

[86mayfair]

NAYY!!! Save the A-Series!!

[Pigeonto]

1330 is just as good and doesn't require offset boring

+ 1 on that

[Pigeonto]

The downfall is that once offset bored the block is scrap once its bores are worn. If you have a 1275 block it can be rebored 2 or 3 times before its scrap.

If you go straight to 1380, then the bores get worn (which could be quite quickly in a high revving engine) then the block is scrap and you'd need to find another one. 1275's are getting harder and harder to find now too.

the difference between 1330 and 1380 will really never be noticed.

and that !! .....well I didnt any way

[JimmyB]

This topic has come up many times and I have often wondered why a 1380 cannot be sleeved back down to re-life it. I believe AC Dodd has a solution to be able to re-use blocks bored to 1380 according to ML motorsport website. Link below

http://www.mlmotorsp...id=83&Itemid=30

[ACDodd]

Just out of interest I offset bore every block that need to go big enout to allow it. Ie if I bore from STD to +0.060" it is offset. If I bore from STD to +0.040" I offset a smllaer amount. This extends the useful life of a block. With aftermarket liners it is easily possible to resleeve back to stock to give more life, it just costs £££.

Offset boring should be considered the way to go to conserve block stocks.

AC