Processing engine block from 1250 cc to 1500 cc

[lookas]

Hello Guys, gretting from Croatia 
I have a question about engine block, is it possible to drill the engine block, actually cilynder in block from 1250 ccm to 1500 ccm ??
Are they the same blocks,with different diameter of cylinder ??
Has anyone tried to do something like that ??

[JoKer]

perhaps grab the head-gasket for each and compare profiles/drawings?

interesting theory tho!

[lookas]

Eh  , that's the problem I have just head gasket for 1250 engine .. Here in Croatia don't have many Avenger on road,and parts for them it's impossible to find.  So that there is no engine block to compare!
I got a brand new set of piston for 1500 ccm engine ... maybe someone has tried to do that 

[JoKer]

get you 1500 pstion, place it over the 1300 head gasket and measure the "meat" wall thickness left behind

I'm not a machinist but I bet someone will say yea or nah, not possible, just logically thinking it out

[lookas]

1250 ccm engine - stroke (64,3 mm - 2.53 in), bore (78,6 mm - 3,094 in)
1300 ccm engine - stroke (66,7 mm - 2,62 in), bore (78,6 mm - 3,094 in)
1500 ccm engine - stroke (64,3 mm - 2,53 in), bore (86,12 mm - 3,391 in)
1600 ccm engine - stroke (66,7 mm - 2,62 in), bore (87,33 mm - 3,438 in)

It means that piston rod and height piston on 1250-1500 engine its equal ... The only difference is the diameter of the piston.

This mean that need hone cylinder 7,52 mm actually 3,76 (half of 7,52) ... I'm afraid if the difference in the block,not to weaken the wall of water or oil channel.


Sorry for my bad english 

[oldschool]

I heard you can't drill out a 1250 to make a 1500 or a 1300 into a 1600 because the blocks have different castings, shown by the SB (small block) and LB (large block) symbols on the side under the manifolds.
That's why they stroked the crank to increase the capacity from 1250 to 1300 and 1500 to 1600 as not enough metal in the blocks to drill them out much further.

[TheMechanicnz]

From what i have looked at there is not enough meat left between the cylinders once they have been bored out. In doing so the head would also have to be re-machined to change the size of the combustion chamber, Would it not?

[oldschool]

I think there's only 2 types of heads, Standard and 'S' with bigger valves. Combustion chamber sizes are the same on all models. The compression ratio was changed as required using flat or dished pistons.

[lookas]

Thank you all for your answers in the thread 
I have only one engine block now, so I would not mess with it,until I find another one. Just in case 

If someone sold a good block and sent there in CRO,
It would be great ... but postage would be too expensive, so it is not worth it 

[Paddy75]

Hi Lookas I guess you want a 1500 or 1600 block and your best bet would be to keep an eye on ebay.it and search for 'sunbeam' or some other listing in Italy.
There was an Avenger in Romania for sale a while back, what became of it I don't know.
I assume your Avenger is a 1250 and not a 1300? If you are not sure the shape of the manifolds is the best clue. The standard 1250/1500 had a single downpipe and the 1300/1600 upgrade had twin downpipes as standard with a more formed inlet manifold.

Just a word on the pistons, only the 1250 had a flat piston crown the 1500 had a dished crown like the 1300 & 1600 pistons.
If you fit a 1300 piston to a 1250 crank the compression will be in the order of about 6.5:1 which is way too low unless you fit a supercharger.
When you find a 1500 or 1600 block there are compression differences also, 8.6:1 and 8.8:1 so be careful if ordering pistons.
Roughly speaking a MK1 Avenger 1600 has a wilder cam than a MK2, but the MK2 has a higher crt of 8.8:1 so if you found a MK1 1600 block needing a re-bore then fit the MK2 +20 or 30 oversized pistons and you have the best of both worlds.

I heard recently that some people bored out the blocks to fit Pinto pistons but probably not on the 1250/1300 bore.

[lookas]

Thanks mate  ..  long before we bought our Avenger, ex owner changed engine but My dad says he has put an identical 1250 ccm engine,
I do not believe in that. So I can not claim 100% that the 1250 engine is in,maybe he put 1300 ccm ... Next weekend I'm going to my car to the countryside,I opened the engine, measure the cylinders, pistons and valves,look for marks on the engine block and photograph them. So we will know exactly what type of engine is inside.

[lookas]

I have no luck