M20 Engine Blocks

[kimbo]

Apologies in advance if this has been covered before, but could anybody tell me if the M20 2.0 litre and 2.5 litre use the same basic casting for the block, so that I can bore a 2.0 block to 84mm to make it into a 2.5.
I know that this sounds like a daft question, but I promise you there is a very good reason for asking.
Thanks
Kim.

[maxfield]

Yes, you can bore a 2.0 block to a 2.5.

[kimbo]

Thanks for that, Maxfield.

Ki

[march109]

Why would you want to tho when the 2.5's can be had for around £250, by the time you add up the cost of machining and taking the car off the road your probabyly better off just buying a 2.5

[Jhonno]

if you were doing a proper 2.7 it would make sense..

[Andyboy]

I have a 2 litre block here, free of charge to first collector!

[Turbo-Brown]

Good idea if you want maximum cylinder wall thickness.
I'd be interested to see a sectioned 2.0 block though, don't think I wanna cut mine up.

[Andyboy]

Why would you want to tho when the 2.5's can be had for around £250, by the time you add up the cost of machining and taking the car off the road your probabyly better off just buying a 2.5

Because unworn 2.5 blocks are getting harder to find, and boring a 320i block is cheaper than boring a 2.5 block and six new pistons.

It's been done a few times, it works. Plus you keep a 320i engine number and the '80' cast in the side that tells an insurance assessor that you still have a 2 litre.

[swindy]

I have s FULL 325 engine for sale and it can be heard running............

£200.

[kimbo]

Andyboy, where are you based?
Offers of free stuff are few and far between!!

As to the why, its a long story, but we've got a 325 racer on which the engine lost compression on two pots (after three wet laps of snetterton - not happy).
However, on stripping it down weve found that there is some damage to the front three bores due to stuff being drawn in through open inlets (airbox now fitted by us but too late) but the big problem is that one section of the oil control ring was twisted round and running between the piston and bore, thereby reducing said block to scrap. I am guessing this was an assembly error by the previous owner of the car.
Anyway, we are now figuring that the cheapest way forwards will be to save five of the pistons (Mahle high compression slipper type), buying one new one and equalising the weights. Then overbore a 2 litre block to give a 'standard' size bores for said pistons to go into.
We've still to check whether the block has been decked at all, but obviously this will be done if necessary.
Then its just a matter of checking what cam is in there, replacing if necessary with Schrick or Catcams super wild profile and Bobs your uncle.
Told you it was a long story - this is the abridged version.
Kim.

[Ant]

Kim

no idea if its what you're looking for but I have an Alpina block, pistons and rods in the unit going spare, add the 2-7 crank and away you go, new rings all included.

B20 goes out to 84mm easy, done 7 strokers this way over the last 11 months.

[jaffro]

ive got a full 320 engine a auto box going free 2

[kimbo]

Thaks anyway, Ant but we're looking to stay at 2.5 for now at least, due to regs.

Which Catcam would you recomend - looking for power between 4 - 7500rpm?

Kim.

Jaffro - thanks for kind offer but we're down south so probably a no no.

Kim

[Ant]

I feared that might be the case

1300525 gets my vote, power band just as you've asked for

Wont see much over 6/5K though, M20 has given its best by then in almost all cases.

[kimbo]

Thanks for that Ant.
We'll see about the revs - this head has had some SERIOUS porting work done on it and it's breathing through triple 45DCOE's.
Originally built by Griffon Motorsport (so we were told) - ring any bells with anyone & do they still exist?

Kim

[Simon13]

muchos respect for griffen! they have gone bust years ago, but the blokes who worked for him started up again on their own. I don't know who they trade as though!