7 replies to this topic

[Matt Zane]

Hello guys.

 

I've been looking on a well known internet auction site, to accumulate parts for an engine build that I'm going to undertake. 

I have been looking at getting a 1275cc engine and 'box in whatever state I can get my hands on, then stripping it down and rebuilding it.

However, I spotted a block that has already been overbored to accept larger pistons, and I was initially tempted to bid, however, the wall between 2 & 3 looks pretty thin to me, as this is a common failure point, I thought I would check with the great and the good before committing to a bid.

 

 

I know that cylinders can be offset when going for a large rebore, is this something you are able to see with the eye, or is the offset in thou?

 

Thanks,

 

Matt

Edited by Matt Zane, 17 March 2014 - 07:25 PM.

[MrBounce]

I would aim for a block that can take another overbore. Once that one is worn it's not easy to sleeve.

You can bore a 1275 lump +20, 30 &60 without offset boring and can sleeve it back to standard.

[Matt Zane]

Thanks for your opinion about offset boring.
I know the sleeving and reboring is a way of preserving the finite amount of 1275cc blocks available, but I want that displacement, and if I end up having to buy another block in a few years due to wear, so be it.

Don't think I'm being off, I just know what spec I want, and the greater displacement is the way to higher torque.

 

Cheers,

 

Matt

Edited by Matt Zane, 17 March 2014 - 07:48 PM.

[Alex_B]

The extra power / torque developed by a 1380 over a 1293 or a 1330 is negligible, and infact I have heard of some better executed 1330s outperforming 1380s, whilst having better longevity and reliability 

Personally I am planning a 1293cc unit for my next project, not sure on full spec but its likely I am going to go for a 16v head, that should be good for 150bhp provided the lump is properly setup (and it will) 

[KernowCooper]

There is only a marginal gain in bhp/torque and in my opinion not enough to warrant going to a 1380, more will depend on the engine spec and how well its put together.

 

Quote by ACDODD on the subject

I re-space mine by measuring the actual offset in the block then adjusting this such that after boring the space between the bores at the finished size is the same.

 

Edited by KernowCooper, 17 March 2014 - 08:13 PM.

[The Matt]

It doesn't 'look' offset bored to me to be honest.

 

Anyway, I wouldn't buy a block at 73.5mm with the intention of rebuilding it.  I'd be finding one that I knew needed work but was close to standard bore.  There's nowhere left to go with that block other than liners.  I'm not saying it's a write-off, but it's not the best option IMO.

[Cooperman]

I would never buy a block that has been bored to accept 1380 pistons.

First of all it may not have been 'offset bored' in which case there will be constant problems with head gaskets. Secondly it may not be possible to bore further without the expense of special cylinder liners. Thirdly, unless it is a fresh re-bore, it may in fact be virtually scrap as it is.

The risk outweighs the 3 or 4 extra bhp which a 1380 will give over a 1330.

 

You sorta just beat me to it Matt.

Edited by Cooperman, 17 March 2014 - 08:10 PM.

[Matt Zane]

The Matt and Cooperman, thanks for the advice, I was just having a poke around, what you say makes perfect sense - that block is in no way a known quantity, so I'll avoid it. I am going to be building up a unit with the Specialist Components 7 port billet aluminium head and fuel injection system, the specs they have on their site have the head mated to a 1380 block with a CalverST RE13 cam which developed about 120bhp, and 100lbft of torque.
 
Whereas the reduction in BHP maybe nominal for between 1330 and 1380, I don't know what the effect dropping the displacement will have on the torque output. I'd rather stick with the specs that they've put together. 

Edited by Matt Zane, 17 March 2014 - 09:55 PM.