SLIGHTLY larger A series engine

[Birchall]

Hi,

I am restoring a 53 series 2, split screen.
I am not planning on keeping it totally standard but it would be nice to keep it looking reasonably standard at least.

I am about to start work on the engine and it is currently a 948, what are my options for a larger A series (so it still LOOKS standard), I realise that I could go 1098 or even 1275/1300, but do they all use the same block?

If they do, then could I not just bore out my 948 and fit the relevant crank and rods?

If they do use a different block then what modifications would I need to make to fit a 1275/1300 A series?
Do I need to modify/buy different engine plates? As for the gearbox I am tempted by the type 9, 5 speed box conversion (I had one on a traveller). But what would the other options be for a gearbox, I am assuming that the 948 would have to be replaced as well? WOuld I fit a 1098 or even a 1275 (if thewre is such a thing?)

And are the clutches different?

Sorry for all of the questions, but I have searched for similar topics without success.

Thanks
Steve B

[chrisryder]

A series blocks are inherently the same, but you can't make a 948 into a 1275 as the crank main journal diameters are different. you would have to get the main caps line bored out to the larger diameter, and you will probably find not enough 'meat' to remain strong.

You can bore out a 948 to take 998 mini pistons, and then use their oversized counterparts. With one of our cars, we took the worn out 948 and bored it to take 998 + 10 thou pistons. We also used a camshaft and head off a 1098 engine.

We chose to fit a 1098 minor gearbox, so we had to fit the engine with a backplate off a 1098, and a flywheel off a 1098, to use the 1098 clutch. The backplate and flywheel both bolt straight on.

Having changed the flywheel, it seemed sensible to get the whole lot of spinnng bits balanced as a set, to make the engine as smooth as possible. Crank, flywheel, clutch cover, and front pulley. £50 got it all balanced.

No idea what sort of power it produces, but it's a happy little free-revving thing. With a 4.5 diff it certainly accelerates, but would probably benefit from a 4.2 diff out of a later minor.

If you want to keep the 948, you will have to fit a 1098 backplate and flywheel to fit a 1098 minor box, a 1275 midget box, or a ford 5 speed.

Most A series blocks look pretty similar, so you could fit any A series and fit the ancilleries to make it look almost right. We did that with our split screen minor, changing its 803 for a 1098, but fitting the original oil bath air filter. It looks the part, but that air filter must suffocate the engine somewhat!

[Birchall]

Wow,

Thanks for a very helpful reply, much appreciated.

Steve B

[bmcecosse]

As above - BUT - the 948 block only has the front cam bearing in 'white metal' - the other two run directly in the block. So - it's much better to use a 1098 block straight off - with the 948 crank and 998 Mini pistons (and the matching rods of course) if you want to go that route, or use the 1098 pistons/rods - overbore if necessary, but the power increase from any sensible overboring will be poor in relation to the cost. I can say a 1098 with a 940 head goes very well indeed - for low cost. A 1275 Spridget engine still has the side mounted felt oil filter - so it 'looks' more like your 948 than say a Marina/Ital 1275 block which has high mounted screw on canister filter. However - your car should really have an 803 engine - which has a distinctive low block mounted (useless bypass type) oil filter.... None of the other blocks will look like that. 5 speed box if you can afford it - but really a different ratio final drive seems to do a good enough job for most folks at very much less cost.

[Birchall]

As above - BUT - the 948 block only has the front cam bearing in 'white metal' - the other two run directly in the block. So - it's much better to use a 1098 block straight off - with the 948 crank and 998 Mini pistons (and the matching rods of course) if you want to go that route, or use the 1098 pistons/rods - overbore if necessary, but the power increase from any sensible overboring will be poor in relation to the cost. I can say a 1098 with a 940 head goes very well indeed - for low cost. A 1275 Spridget engine still has the side mounted felt oil filter - so it 'looks' more like your 948 than say a Marina/Ital 1275 block which has high mounted screw on canister filter. However - your car should really have an 803 engine - which has a distinctive low block mounted (useless bypass type) oil filter.... None of the other blocks will look like that. 5 speed box if you can afford it - but really a different ratio final drive seems to do a good enough job for most folks at very much less cost.

Hi Thanks, very helpful, I will see what engines are around for sale, I have already had the 1275 engine and 5 speed conversion in a traveller and it was a great combination. The ratio change on the axle is much cheaper, but I must admit that having synchros on 1st and reverse are a real bonus, not to mention quieter. The other thing to bear in mind with the axle ratio change is that you are changing the ratio of all gears, whereas the 5 speed conversion gives you (basically) the same ratios for 1st to 4th and then an optional 5th gear (if you see what I mean)

Cheers
Steve B

[bmcecosse]

We see ok - but 1st and indeed 2nd are far too low anyway........ My Trav will now do 50 in 2nd, making it a very useful gear! A 5 speed conversion is likely to cost ~£1000, way way beyond my budget for Classic car spends!