19 replies to this topic

[MRA]

Er no.......

If you bore it out to +0.135" (ish) then you will not get 1251cc ......... which is what you will get if you use the IMP +0.040" pistons

Never bore a block to the size on the box, ie if you bore it to +0.135" then the chances are very high that it will be either too tight or too loose....

Edited by mra-minis.co.uk, 08 April 2011 - 08:24 AM.

[9FDXEH4]

Er no.......

If you bore it out to +0.135" (ish) then you will not get 1251cc ......... which is what you will get if you use the IMP +0.040" pistons

Never bore a block to the size on the box, ie if you bore it to +0.135" then the chances are very high that it will be either too tight or too loose....

You're completly right!

usually when I take a block to oversize never sent the pistons box (as they here in Portugal never, but never have one minute to read instructions.... :S) .so I use a permanent marker on the piston (1,2,3,4) (on the block too) with the right type of tolerance for the right type of use of the engine.when it´s ready to pick up and after to pay the man all bores have to be measured with me and the tolerances had to be right.


Do NOT forget that is usefull read that yellow bible (David Visard) to have the correct offset for the IMP pistons.

for those who like to use diferent pistons it is possible to use Fiat Panda 800cc's pistons ( I think is that) with 12g82 crank....just need to pressfit the piston pin to the rod (WITHOUT that bronze bush) (as this piston has 20mm pin)


I just want IMP pistons +0.040" because is usefull to lower my CR as I've got a Med offset FIS with 28cc's chambers and dont want to use decompression plate and dont want to skim the head.(yes I will Supercharge it with a Vmax Scart (with all that problems we have wordwide solved) Eaton M45 5th Gen Water cooled,with a Omex 500 series 3D ECU and Injection system) S/C drops and S/C ST ratio rod gearbox (just need the pistons , the mini painted and that wonderfull Quaife ATB lsd) hope that works all together

If you like to see some stuff related follow the link!

Cherrs for ALL


http://www.facebook....100001578510369

Edited by 9FDXEH4, 08 April 2011 - 12:37 PM.

[Spitz]

arg...I give up. we're obviously not reading each other

[Guess-Works.com]

If I've got this right....

The standard 1098 ( and 998 ) mini bore size is 2.543in

The standard imp 875cc bore is 68mm or 2.675in

therefore to use a STD imp piston in a small bore mini engine, you need to rebore the block to 0.132" oversize to fit the standard imp piston.

This gives you an overall swept volume of 1105 on an originally 998 block, or 1214 on a 1098.

To use a +0.040" imp piston in a mini engine you would therefore need to bore the block by a further 0.040", or 0.172" from standard.

I've updated my engine spreadsheet with the imp pistons for reference

 engine_sizes.pdf   10.29K   63 downloads

[9FDXEH4]

If I've got this right....

The standard 1098 ( and 998 ) mini bore size is 2.543in

The standard imp 875cc bore is 68mm or 2.675in

therefore to use a STD imp piston in a small bore mini engine, you need to rebore the block to 0.132" oversize to fit the standard imp piston.

This gives you an overall swept volume of 1105 on an originally 998 block, or 1214 on a 1098.

To use a +0.040" imp piston in a mini engine you would therefore need to bore the block by a further 0.040", or 0.172" from standard.

I've updated my engine spreadsheet with the imp pistons for reference

 engine_sizes.pdf   10.29K   63 downloads

Just an off topic question mate,as you are an "gearbox expert" you could give a help.

I'm thinking to use a 3.1FD but my drops are 1.04:1 so this would give me a FD of 3.2 right?
is a good compromise not to short/not to long to use with this Supercharger convertion.


About your spreadsheet you could add for the 998 cranck +0.100" and +0.120" available in minisport.com.au.

Cheers