5 replies to this topic

[ollydc5]

Evening all,

Right after good advice from you guys the other day I managed to convince the old man out of buying a running metro turbo engine and that a 1275cc unit would be more suited, many thanks to all

Right I've brought a decent known running 1275cc engine tonight and will be collecting next week. So this brings me back to my original plans for a fresh engine build from a bare block, so I'm taking the bottom end to start with once dissasembled.

Without sounding thick, excuse me I'm a bit new to this lol

After a little reading am I right in thinking the 1275cc bore is 70.6mm ?

If so what would you be having the block machined out to ?

So if looking for new pistons I'm presuming the + 0.020 would be my component of choice ?

[ollydc5]

After having a quick search through the site I can see a few have asked similar questions.

From what I can gather if I buy the pistons my local machine shop should be able to sort the cutting and honing to match.

Only other thing I've noticed is there are dished and flat top pistons, my Dad said the flat tops are what he'd go for performance wise. Is this true ?

[Cooperman]

Go from standard bore to +0.020.

You will need high-compression pistons part number P21253-20 which have 8.4 cc dish and they are ideal for all 1275 blocks.

Before doing anything, measure everything very carefully including crankshaft, and bores.

Have the rods checked for straightness.

After the initial machining do a trial build to establish the new dimensions, then strip & machine the block deck to bring the tops of the pistons to within 0.005" of the block deck level at TDC.

If it is a pre-A+ block, crank & rods, you will find that the rods have 'lumps' on the big end caps. These can be partly removed or a set of the much better A+ rods acquired.

Set the crankshaft end float to between 0.002" and 0.005" using thicker thrust bearings as necessary. They come in +0.003" extra thickness so you can increase the total thrust bearing thickness from standard by either 0.003" or 0.006".

 

Come back for more advice when you need it

Edited by Cooperman, 19 February 2015 - 11:15 PM.

[ollydc5]

Excellent buddy many thanks, such a massive learning curve. So good to have these forums

I'll probably be replacing the rods anyway, if I can get away with keeping the crank that would be great.

Looking forwards to going shopping

[Cooperman]

Try to get a set of A+ rods as they are so much better and lighter too.

[ollydc5]

Fantastic thanks cooperman,couch appreciated