15 replies to this topic

[JonnyAlpha]

I am in the middle of deciding on an engine conversion 998 (rebore to 1079) or 1275 (rebore to 1293) but am now considering a 1098 with a 12G295 Head

 

I have been offered an 1100 short engine (Block, Crank and Pistons) and need to know what to look out for before I buy it.

 

I have been advised that early engines were fitted with pinch bolt type small ends and as such will be no good.

 

If they are pinch bolt then the ConRods are no good, but what about the crank? Can the crank be fitted with newer ConRods?

 

If the 1100 block comes with pinch bolt small ends or without Con Rods and Pistons at all, can I use the Con Rods from one of my 998 A+ engines? 

 

The 1100 block has been pocketed so I will just use one of my two 998 blocks.

 

Does anyone have any pics of 1098 cranks for me to refer to?

 

Thanks

 

 

 

[DeadSquare]

Going for the 1100 will be cheaper than machining a 998 or 1275.

 

The 1100 uses the same conrods as the 998

 

As you will have to get a flywheel, and have it balanced, get everything balanced, because the 1100 doesn't like even moderately high revs, which is why the spridget 1100 engine got the crank upgraded to 2" mains.

 

The 1100 was a good swap for an 850.............until the 1300 came along.  More torque for acceleration and less stress on the engine.

 

I hope that is helpful.

[andyapanel]

I had a 1098 with a 295 head; it was VERY torquey, ideal for the lanes where I live. However, I don't think I would have liked to drive a long way in it as it was so noisy. Mind you, it could been because it was in my pick up. It was built on a 998 A+ block if I remember correctly.

Make sure your engineering shop know about the oil pathway in the head, which is likely to be milled through; mine gave it to the apprentice who didn't know. Start up was exciting, and not in good way.

[Minigman]

The 1098 crank fits in a 998 block without machine work. The rods are the same so interchangeable.
If you can measure the big ends and mains journals to know they can be ground again (to a max of +030”) before handing over the money that would be worthwhile. Otherwise just buy a crankshaft, use the rods off the 998 and buy new pistons. You can get dished or flat tops depending on the cc of the head and the compression ratio you’re looking to achieve.

Edited by Minigman, 19 December 2018 - 10:04 AM.

[grizzler73]

Good little torquey engine if done right. AC Dodd is building a 1150cc based on a 1098, you can follow it on Facecrook.

[JonnyAlpha]

The 1098 crank fits in a 998 block without machine work. The rods are the same so interchangeable.
If you can measure the big ends and mains journals to know they can be ground again (to a max of +030”) before handing over the money that would be worthwhile. Otherwise just buy a crankshaft, use the rods off the 998 and buy new pistons. You can get dished or flat tops depending on the cc of the head and the compression ratio you’re looking to achieve.

Where do I need to measure the journals and what size should they be to know if they can be regrouped?

Tks

[DeadSquare]

You need either a 1" to 2" micrometer, or a vernier that reads to .001 of an inch.

 

The main bearing were meant to be no smaller than 1.75" when they left the factory, and the big ends, no smaller than 1.625". They were often as much as .001" over size, and you may find that they are now oval.

 

Even if they measure full size, but you can feel ridges when you run your finger nail across them, they ought to be reground, but being oval is a more important reason to regrind than slight ridges / scratches.

[Spider]

Rather than buy a 'complete' 1098 engine that you'll be ditching the block and possibly the rods on, just but a 1098 crank and use all the other parts from one of your 998 engines. As you'll be having it bored, you'll be needing (1098 comparable) pistons in any case, unless of course, the 1098 engine can be obtained for the price of the Crank.

 

The 1098 Cranks are good, but slightly more prone to cracking than most other cranks, so don't neglect to have it tested. Also, be sure to use a good quality Harmonic Damper or it won't last too long at all.

 

When measuring up a 1098 Crank, the Factory Nominal sizes for the Mains on these is 1.7505 to 1.7508" and the Big Ends 1.6254 to 1.6259". Any re-grinds it may have had will be in lots of 0.010" off these figures.

 

Just going back to your original question though, which is basically " should I go 1098 or 1293? ", I'll just say that the parts you need for reconditioning either engine will cost similar money for either, though to fit a 12G295 head on the 1098, you'd be wise to use flat top pistons here rather than skim the head that much and these pistons are limited for choice and are over priced. I feel parts fopr the 1275 Engines are much more widely available, with a bigger choice. Likewise, machining costs will also be the same. So, apart from the initial outlay for the engine to build, after that, the costs will be a much for muchness. The other aspect of a 1098 vs 1275 is that the 1275 should last way longer as it has lower piston speeds and bigger Crank Bearings.

[JonnyAlpha]

Rather than buy a 'complete' 1098 engine that you'll be ditching the block and possibly the rods on, just but a 1098 crank and use all the other parts from one of your 998 engines. As you'll be having it bored, you'll be needing (1098 comparable) pistons in any case, unless of course, the 1098 engine can be obtained for the price of the Crank.

 

The 1098 Cranks are good, but slightly more prone to cracking than most other cranks, so don't neglect to have it tested. Also, be sure to use a good quality Harmonic Damper or it won't last too long at all.

 

When measuring up a 1098 Crank, the Factory Nominal sizes for the Mains on these is 1.7505 to 1.7508" and the Big Ends 1.6254 to 1.6259". Any re-grinds it may have had will be in lots of 0.010" off these figures.

 

Just going back to your original question though, which is basically " should I go 1098 or 1293? ", I'll just say that the parts you need for reconditioning either engine will cost similar money for either, though to fit a 12G295 head on the 1098, you'd be wise to use flat top pistons here rather than skim the head that much and these pistons are limited for choice and are over priced. I feel parts fopr the 1275 Engines are much more widely available, with a bigger choice. Likewise, machining costs will also be the same. So, apart from the initial outlay for the engine to build, after that, the costs will be a much for muchness. The other aspect of a 1098 vs 1275 is that the 1275 should last way longer as it has lower piston speeds and bigger Crank Bearings.

 

Moke Spider

 

I have been looking for a 1098 CrankShaft and they seem pretty rare, but someone in my local Mini group happens to have a short engine, which I believe is the block, crank and pistons (all for £100). So, if the crank is OK then that's a good price I believe. The Pistons will be replaced and if the rod are OK i'll reuse them. The block has been pocketed for (I think) a 12G940 head, so I may be able to shift it on.

 

I picked up a 12G295 head that looks unmodified so skimming will be OK. 

 

I am planning on getting Kieth Calver to do the work, competitive prices and he knows his stuff. He sells some good 1098 Flat Top Pistons.

 

Harmonic Damper - I had never heard of that before but a quick search and found that it is also the crank pulley for the fan belt - so a good quality one is needed - any recomendations.

 

I need a diagram of a crank shaft identifying all the various parts, before measuring

 

1098 v 1275 - when you say that the 1275 would last longer, this car gets driven on average every couple of weeks (quick spin) and the odd weekend run out (Mini events 2 per year). So if anyone has the statistics of failure rate I'd be interested. I used to work in an vehicle engineering assurance department (I dealt with the supply side not mechanics). We used a Mean Distance Between Failures to calculate how many of a certain component we would need over a specific time period, is there such a thing for Mini components?

 

I have a partially stripped 1275 in my garage and am teetering on selling it, but need to make a decision on which way I am going. I have looked at this for a long time and I have always been one for taking the non normal route - so sticking with Small Bore is where I am currently veering

[Spider]

Jonny, I really didn't think a 1098 Crank would be that hard to come by in the UK.

 

Just thinking about your opening post again, when looking at this 1098 engine, if it is that early that it has clamped little ends on the rods, then it may likely have a 'wet tail crank' too. These used a oil pressure fit Primary Gear and were notorious for getting an oiled Clutch which very soon thereafter, slipped in short time. The parts for the Primary Gear, including the seals, are NLA and as well as needing an odd ball Primary Gear, they also used a particular Flywheel, that takes a Coil Spring Clutch. Many of these Cranks had a 1-3/8" Tail though some did have a 1-1/2" Tail. These (1-1/2" types) can be converted to use a later (proper) Deva Bushed Primary Gear, but I have a recollection that more or less, you would be stuck with the same flywheel and clutch arrangement.

 

For flat top 1098 pistons, you can get them here, the same ones that Keith Calver is offering, only for 1/4 of the price    https://www.precisionintl.com/

 

For a Harmonic Damper - note this is not a pulley, but has a pulley machined in to it. Sorry to be 'picky' on this but they are a very critical item, all too often over looked and mis-quoted, I kinda go in to orbit when they are referred to as a 'pulley' - you could get a standard type as fitted to the 1275 Engines and have it reconditioned, but if you are wanting something better, then KAD, MED and Romac  http://www.vpw.com.a...ry/Index/185874

 

You can get some good results from a 1098 engine, I did quite a few of these years back, as bits (here at least) were plentiful and quite cheap.

[DeadSquare]

Moke,  1098 cranks dried up here, on ebay about 6 or 8 years ago.

 

Do you have Microfiche of the early 1100's?   I never came across any in UK with clamped little ends or thin tailed cranks.

 

The 997 had clamped little ends and the first conversion that I did, blocking the oil hole etc: was on a 997, which might have had a thin tail.  I know that I went in two days before Christmas to get a new clutch plate and came out with a free box of goodies to fix things.

 

The guy gave me a small box of Cadburys Dairy Box for my trouble.

[Cooperman]

I can't ever recall seeing a 998 with clamped small ends. I know the 997 did as I rebuilt one about 4 years ago.

 

There is a lot of talk about the fragility of the 1098 crankshaft. It is not all that fragile so long as it is not revved much over about 6200 rpm. it is a good idea to balance everything if building a 1098, fit a good harmonic damper (as Moke... says), run a sensible cam, such as an MG Metro or Kent 266 or Evo001.

[Spider]

Hehehehehe,,,,,, the early 1100 series was well before they went to Fiche, but none the less, I do have part of an 1100 engine parts book. Sadly, the pages with the cranks and rods is missing but it does have the primary gears and yes there was thin tail cranks. Yes, the first of the 997's had thin tails too.

 

Cooperman, likewise, I've never seen clamped little ends in an 1100 and definitely not in a 998, but given when the 1100 engine came out (61-ish?) I'm keeping an open mind that some of the early ones may have had them. In the Minis, only the 850 and 997 had these rods, though other engines used them like the 803 and 948 engines.

 

Jonny, there was at least 4 different 1098 Cranks. Have a look on the 5th Web (from the Nose) and there should be a Forging Number or it maybe ground off and a new number hand stamped in.

[DeadSquare]

Boy racers used to get an 1100 engine, saw off the front mounts, and drop it straight in.

 

Great acceleration, but without changing the diff, the cranks got flayed when they hung on in 3rd, waiting to overtake.

 

The cranks certainly used to flex, as you could see from the main bearings, when stripping the engines.

 

Having the flywheel stuck out on a tail didn't help, and there was a special part number for exchange cranks that were full size instead of regrinds.

 

Even with the flywheel tucked up to the rear main in the Spridgets there were problems.

 

The factory tried a few EN40 cranks in 1100's and bored out 997's, but found their answer in upping the mains to 2", which were 'tested' on the public in the Clubman / Mk 3 Spridgets, and so the 1100 was dropped and got replaced by the 1300 throughout the range.

[JonnyAlpha]

Hehehehehe,,,,,, the early 1100 series was well before they went to Fiche, but none the less, I do have part of an 1100 engine parts book. Sadly, the pages with the cranks and rods is missing but it does have the primary gears and yes there was thin tail cranks. Yes, the first of the 997's had thin tails too.

 

Cooperman, likewise, I've never seen clamped little ends in an 1100 and definitely not in a 998, but given when the 1100 engine came out (61-ish?) I'm keeping an open mind that some of the early ones may have had them. In the Minis, only the 850 and 997 had these rods, though other engines used them like the 803 and 948 engines.

 

Jonny, there was at least 4 different 1098 Cranks. Have a look on the 5th Web (from the Nose) and there should be a Forging Number or it maybe ground off and a new number hand stamped in.

 

Moke - I have been advised that the number should be 12G82.

I have now been offered another 1098 crank from a classic car specialist, he is currently removing it from a car. He is a sound all round bloke and will ensure its ok for the job. (£30). I also found a company called SC on the web:

 

https://www.scparts....ft-1-99248.html

 

This is a 12G82 Crank (Is this the style I should be looking for to avoid all the problems you pointed out earlier?

£150 if exchanged.