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| 998 OVER bore https://www.ausmini.com/forums/viewtopic.php?f=2&t=2145 |
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| Author: | ausminis4u [ Sat Oct 02, 2004 7:39 pm ] |
| Post subject: | 998 OVER bore |
ok guys i have 'aquired ' a set of 73mm pistons , can a 998 block be bored to 73mm ? also does anyone have a set of 998 rods to suit pressfit gudeons? need a set I/F the block can be bored to 73mm. please god (kev) let this be possible |
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| Author: | drmini in aust [ Sun Oct 03, 2004 10:05 am ] |
| Post subject: | |
NO way you can bore a 998 or 1098 to 73.0mm. 68.0 will stop it, even to get that you need to offset bore. <edit> 68.0mm Imp pistons cost a fortune now, they gotta come from NZ or UK. 
73.0mm in a 1275 will give you 1360cc, or 1405 if you stroke the crank. Go find a 1275 block... 
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| Author: | 68matic [ Sun Oct 03, 2004 11:59 am ] |
| Post subject: | |
hey Doc (someone obviously rather unreliable) said A-series blocks were ALL the SAME what made a 850 different to a 1275 was different bore different stroke different accessories |
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| Author: | spathi [ Sun Oct 03, 2004 12:05 pm ] |
| Post subject: | |
998 and 1098 blocks are the same, different crank. the bores on a 1275 are physically in different places i believe (ie offset differently). I think an 850 block is the same as a 998 and 1098 but not sure.. |
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| Author: | drmini in aust [ Sun Oct 03, 2004 3:39 pm ] |
| Post subject: | |
Duc, There are 2 basic block families- 850-997-998-1098 (small bore) 970-1071-1275 (big bore) 850 has only 1 cam bearing (front) and main bearings are wider than the others. 997 (rare now), -998-1098 are pretty much the same block. They can all be offset bored to 68.0mm (1220cc with 1100 crank) if you are lucky. 850 blocks & bearing caps need machining to fit a 998 or 1098 crank in. I used to do it, years ago. Not worth it these days. 1275 block is taller than the 970 and 1071, which are both rare now. 1275 S block has side covers, the other 1275s (1100S, 1275LS, 1275A+) have a solid wall block. They can all be offset bored to 1380 (73.5mm) but the S block is a bit thinner in the walls. My spies tell me an A+ block is less reliably overbored than the earlier ones- more crap in the casting. Any 1380 motor is supposedly a bit thin in the walls if you are going to turbo or supercharge the motor. Better to keep it to 1310 bore, stroke it if you want more cubes. Bore centres for these 2 groups are totally different. The small bores have 1-2 and 3-4 siamesed, with a water passage between 2 & 3. The big bores have them more or less equal spaced, a little thinner between 2-3. On all these there is no water passage between any of the cylinders. 
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| Author: | 68matic [ Sun Oct 03, 2004 4:43 pm ] |
| Post subject: | |
answered all my questions with alittle bit left over too
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| Author: | ausminis4u [ Mon Oct 04, 2004 11:27 am ] |
| Post subject: | |
drmini in aust wrote: NO way you can bore a 998 or 1098 to 73.0mm. 68.0 will stop it, even to get that you need to offset bore. spewing drmini in aust wrote: go find a 1275 block... easier said than done m8 
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| Author: | drmini in aust [ Mon Oct 04, 2004 2:32 pm ] |
| Post subject: | |
Alright Ben, go find a 1275 AUTO block then.
Gotta be heaps lying around, nobody wants them. I'll convert it to manual for you if you like.
Or, ping `boostedmini', he has a couple of 1275 blocks for sale at the moment- one auto, one manual. |
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