Building a "nice" 1098 engine

[linearaudio]

The old girl is starting to smoke quite alarmingly, time to think ahead!
There are a couple of 1098 engine/boxes on the farm, and the farmer owes me for fixing his washing machine, so.....
What suggestions? A rebore to start, are there any better/worse pistons to go for? I was thinking of maybe decking the block and balancing piston weights, crank etc. Any thoughts appreciated. I know balancing won't add more than about 10bhp but I'd like to feel I've got the engine as near as I can to ideal. Anyone got an MG Metro cam going spare?

[bmcecosse]

Balancing doesn't add anything to the power output! Especially unimportant on a 1098 engine - which must NOT be revved above 6000 rpm for any length of time. But - it will make for a smoother engine - and can give personal satisfaction in a 'job well done'! If the bores are good - may not even need a rebore/new pistons - depends if you want an engine to run for a year or two - or something that will last for 60,000 miles or more. Crank regrind is highly likely - and new oil pump of course (make sure it matches the cam!) . MG Metro cam is good! Especially as it works very well up to that rev limit of 6k - and it doesn't lift the valves any higher making it easier to use the excellent 940 head. You can buy very expensive pistons fom OZ - which will allow up to 120 thou overbore - but I don't see the point (in UK) because 1275 engines are relatively plentiful. These big overbores are popular in OZ because they got lots of 1098 engines in Minis - and very few 1275s!!

[RobThomas]

Start with a post-63-ish Midget 1098? Stronger crank and you can rev the guts out of it without it going pop. Same pistons etc but better crank.

[bmcecosse]

Not easy to find! It was the pre-cursor of the Cooper S engine. Certainly stronger - but still the longest stroke engine of the range - so be wary about revving it too much!

[linearaudio]

Really, BMC! I thought you would have seen through my "10 BHP balancing boost"

[MarkyB]

I'd intended to build a nice 1098 but ended up just changing the head from standard and replacing rings and shells.

I was going to smooth and lighten a spare set of rods that are in stock and balance them up, same with the pistons.

Bmcecosse said recently that he had lightened up pistons, exactly how would be nice to know.

Vizard condemns split skirt pistons but new pistons, especially fancy ones tend to be the most expensive part of any engine rebuild.

My thinking is that we have we have time to do things better than they had when putting them together in the factory.
One look at how the crudely the crankshaft balancing has been done, more for speed than accuracy I suspect.

[bmcecosse]

My lightened rods and pistons were for a 'full race' 998 Mini engine - which was intended (and did) to be revving to ~ 9000 rpm. There is no point lightening etc an engine that won't see beyond 6000 rpm. You can do it - and there is of course some satisfaction in doing the work - but little to show at the end. I lightened the rods as much as seemed sensible - polishing away any roughness on the shanks - and then balancing them end to end using accurate scales (at Uni). The pistons were first trial assembled - and found be surprisingly accurate in their distance form the top of the block - so nothing had to be taken off the crowns. They were machined away on the skirts - right up to the gudgeon pin bosses - and then balanced on the scales - extra metal removed from the skirts with a file. They were run with 2 compression rings and one oil ring. I couldn't do anything sensible with the crank - but i did lighten the flywheel by machining great lumps out of it! It was then assembled to the crank with the damper - and the whole assembly was then set on two large rods of silver steel - clamped to a machine table (sticking out) and set perfectly horizontal. The crank was then gently rolled on it's two end mains - and noted where it settled as it rolled back and forth. This then checked by turning it 90 degrees - and the 'heavy' section would roll down to the bottom. Drilled a few holes in the flywheel rim until there was no more obvious 'heavy' side. It's the best i could do (static balance) - with no money and limited facilities. I did get access (through a friend) to Lloyds Training skool on saturday mornings to do most of this!
Head for that engine was full Cooper S (so large inlets and exhausts) - with massive pockets gouged out of the block - and was run with a 544 cam (I tried a 649 - it was better overall with the 544) and twin 1.5" SUs (scavenged from an MG in a scrappy) on a home made inlet manifold - two 6" long tubes with flanges - no balance pipe. The head was flared out to match the tube diameter. All was done following the excellent guidance of the great Mini God - Clive Tricket - way before Vizard came on the scene.