32 replies to this topic

[CdnAustinAmerica]

Doing a rebuild on my 998, it was time, got a good 1098 crank (is cross drilled as well) and nos Karl Schmidt/Kolbenschmidt  1100 .20 over pistons (had a 1100 motor in my first car, really liked the torque curve). It is also getting a fresh metro grind cam and lifters. Gearbox is being gone through as well, was pretty good, upgrading to a cross pin diff. Have a rebuilt 998 head on it from a few years back (got rid of Canadian smog head)

 

Was wondering if anyone has done this and has any info on how much one could deck it safely? I might just clean up the top of the block. Also is .0025 piston to wall clearance a good number for these?

 

Will also have a AAA needle in the 1.5 HS4 at least for now, have access to some other needles if need be, at least for run in.

Edited by CdnAustinAmerica, 20 September 2024 - 05:35 AM.

[CdnAustinAmerica]

One other thing I've noticed is that these pistons have four rings, is it two compression and two oil rings? Also noticed the top of the piston says "Sp 0.03" "15k" "65,088"

[Spider]

To make it worthwhile, you'll want a slightly better cylinder head, the stock 998 one (which is also common to the 850) will strangle it, even a stock 1098 head would be better than nothing. You'll also need to run it on a rolling road once you have it bedded it to properly sort Ignition and fueling requirements, these engine are more sensitive than most others in the tune dept.

[DeadSquare]

One other thing I've noticed is that these pistons have four rings, is it two compression and two oil rings? Also noticed the top of the piston says "Sp 0.03" "15k" "65,088"

 

 

One other thing I've noticed is that these pistons have four rings, is it two compression and two oil rings? Also noticed the top of the piston says "Sp 0.03" "15k" "65,088"

I doubt that your pistons have 2 oil rings.  The oil ring's groove is always at least twice as wide as the compression grooves.

 

It probably doesn't make any difference, but I arrange the gap in the rings alternately 180 degrees from each other, to make any escaping gas have to travel further.

 

My grandfather's Lanchester had recessed pins in the grooves that located the back of the ring gap so that the rings were arranged in this manner and could not rotate, and for many years I had assumed that this was just Frederick Lanchester's attention to detail, but it was probably something to do with the sleeve valves.

[ACDodd]

Do it, 1098 based engines make great road units. The graph below shows what can be done when squeezing a 1098 crank into an overbored 850 block. This was 1150cc used my RT cam with my 1.3rockers, it ran twin hs2 carbs breathing through a Calver modified 295 cooper head. The engine still idled like a factory engine giving the impression it was standard in actual fact it pack more than double the power of a stock 850! And basically equalled the power of a stock 1275 unit.

Ac

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Edited by ACDodd, 20 September 2024 - 10:07 AM.

[DeadSquare]

Do it, 1098 based engines make great road units. The graph below shows what can be done when squeezing a 1098 crank into an overbored 850 block. This was 1150cc used my RT cam with my 1.3rockers, it ran twin hs2 carbs breathing through a Calver modified 295 cooper head. The engine still idled like a factory engine giving the impression it was standard in actual fact it pack more than double the power of a stock 850! And basically equalled the power of a stock 1275 unit.

Ac

I thought that the centre main bearing of the 998 / 1100  crank was too narrow to fit in the 850 block.

[PoolGuy]

 

One other thing I've noticed is that these pistons have four rings, is it two compression and two oil rings? Also noticed the top of the piston says "Sp 0.03" "15k" "65,088"

 

 

One other thing I've noticed is that these pistons have four rings, is it two compression and two oil rings? Also noticed the top of the piston says "Sp 0.03" "15k" "65,088"

I doubt that your pistons have 2 oil rings.  The oil ring's groove is always at least twice as wide as the compression grooves.

 

 

He wouldn't be the first person to see the parts that make up the oil control ring and notice that it's two rings and an expander.

[Shooter63]

Karl schmidt used to make a lot of 4 ring pistons back in the day, the same as other companies, ring pack technology has come on a long way since then. Very good pistons all the same, and still available ( not for A series though as far as I know).

Shooter

[ACDodd]

It is, you have to machine the centre main wider to fit th crank, you also have to shorten the crank a little to make it fit, and relieve the rods but it can all be made to fit.


Do it, 1098 based engines make great road units. The graph below shows what can be done when squeezing a 1098 crank into an overbored 850 block. This was 1150cc used my RT cam with my 1.3rockers, it ran twin hs2 carbs breathing through a Calver modified 295 cooper head. The engine still idled like a factory engine giving the impression it was standard in actual fact it pack more than double the power of a stock 850! And basically equalled the power of a stock 1275 unit.

Ac

I thought that the centre main bearing of the 998 / 1100 crank was too narrow to fit in the 850 block.

[CdnAustinAmerica]

Do it, 1098 based engines make great road units. The graph below shows what can be done when squeezing a 1098 crank into an overbored 850 block. This was 1150cc used my RT cam with my 1.3rockers, it ran twin hs2 carbs breathing through a Calver modified 295 cooper head. The engine still idled like a factory engine giving the impression it was standard in actual fact it pack more than double the power of a stock 850! And basically equalled the power of a stock 1275 unit.

Ac

 

Thanks Dodd!  Your videos are invaluable.

 

Anyone have any thoughts on decking the block? How much could I safely take off? This block has never been apart and made it to nearly 200k km despite a couple misaligned oil holes from the factory, still had 60 psi too. 

 

 

 

 

One other thing I've noticed is that these pistons have four rings, is it two compression and two oil rings? Also noticed the top of the piston says "Sp 0.03" "15k" "65,088"

 

 

One other thing I've noticed is that these pistons have four rings, is it two compression and two oil rings? Also noticed the top of the piston says "Sp 0.03" "15k" "65,088"

I doubt that your pistons have 2 oil rings.  The oil ring's groove is always at least twice as wide as the compression grooves.

 

 

He wouldn't be the first person to see the parts that make up the oil control ring and notice that it's two rings and an expander.

 

 

 

Karl schmidt used to make a lot of 4 ring pistons back in the day, the same as other companies, ring pack technology has come on a long way since then. Very good pistons all the same, and still available ( not for A series though as far as I know).

Shooter

 

They are NOS pistons

 

[Cooperman]

I have Karl Schmidt 4-ring pistons in my 1310 'S'. They are super and take very high revs with no issues. I run my rally engine at 11:1 CR with a 286 cam and it's very competitive in its historic class.

 

I. too, have always liked the 1098 engine and it's great unless you want to really rev it, like a sustained 6200 rpm plus. In fact, it produces a lot of torque so with the right cam giving good torque from around 3000 rpm you never need to use a lot of revs. In terms of a head, it's possibly best to use a 12G940 and pocket the block.

[CdnAustinAmerica]

I have Karl Schmidt 4-ring pistons in my 1310 'S'. They are super and take very high revs with no issues. I run my rally engine at 11:1 CR with a 286 cam and it's very competitive in its historic class.

 

I. too, have always liked the 1098 engine and it's great unless you want to really rev it, like a sustained 6200 rpm plus. In fact, it produces a lot of torque so with the right cam giving good torque from around 3000 rpm you never need to use a lot of revs. In terms of a head, it's possibly best to use a 12G940 and pocket the block.

 

 

 

How about a 12A185 head?

Can't find too much info on it other than they came on 948cc spridgets and possibly 997 coopers?

its the 9 stud one. The intakes look a little more square on it, I can port the exhausts a bit bigger on it. Metro camshaft going in it

 

Thats what I had on it, going to have to put some guides and maybe some new seats, it came with a  ECAM 4004(?) originally which was the standard Canadian smog head, no real info on that anywhere. Assuming its not great, it had the ports for the air pump.

 

I decked it 5 thou as when I dry assembled it #1 was 9 thou but #4 was about 17-18, measure the block and its square so I guess rods+crank variance, is that going to be alright? Putting a balancer pulley on it too.

[CdnAustinAmerica]

So an update - its going to end up with a ported and skimmed12g202 head, with the 295 intakes, and some cooper double springs, nothing too heavy, it'll be around around 9.5:1. I also was able to get the crank and rotating assembly professionally balanced (crank to 0 grams out!). Two conrods were out by 7 grams too. I know that won't "make" any extra power but I view it as insurance for longevity.  Also considering the price they're at, I would recommend getting the Calver lifters as well, can't be too careful with flat tappets. Some other modifications and getting the tolerances nice as well, been doing this at a friends place who is very knowledgable on minis. Just have to degree the cam next and its all going back together!

No idea how much power it'll make, ha.

[whistler]

Mine made 78bhp.

[miniGTS]

Would this 1098 be different to the South African big bore 1098 that used the same cylinder block as our 1275 but different pistons and crank?

 

I think all our big bore 1098 engines had the same 12G940 head as the 1275E but with 11 studs and also used the 1275 GTS block to match the 11 studs. Though, the extra 2 studs don't really add anything other that the extra effort to torque the extra studs to a lower setting than the rest.