6 replies to this topic

[booton]

ok i'm rebuilding a 998 engine. its total stripped at the momment.

going to replace pistons with these ones
http://cgi.ebay.co.u...e=STRK:MEWAX:IT

fitting a 1275 head. that i will port and polish.

not sure what cam to use. was thinking maybe a 1275 one.

replacing all seall and bearings.

should hopefull produce over 60bhp.

any tip on the parts. steve

[Guess-Works.com]

first question, what are you using 1098 pistons, I assume with a 998 crank and rods ?

[Cooperman]

Will those 1098 pistons fit a 998? Is the piston wrist height correct for 998?
Dont forget to either pocket the block or recess the valves into the head to fit a 12G940 head onto a 'small-bore' block or the valves will het the block deck.
Also be sure you do the compression ratio calculations correctly as the combustion chamber volume of the 940 head is much smaller than a standard 998 head.
I'm sure you know this, but you must get all the geometry correct and measured/calculated or it won't work.

[booton]

yes i'm going to use a 998 crank and rods.

i was wondering weather these would fit correctly once bored out.

can't see no reason why.

[Guess-Works.com]

apart from they are meant to be used with a longer stroke crank, therefore will give absolutely shocking compression when used with a 998 crank... basically the pin to crown height on the 1098 piston is shorter than that of a 998 piston...

There is someone on here who has a set of 998 +20 pistons, which were advertised as 1100 pistons, maybe you could do a swap ???

http://www.theminifo...x...=144458&hl=

[Cooperman]

To be blunt, why would you fit the wrong pistons when you can buy the correct ones off-the-shelf and know that you'll have no problems?
Presumably you know how to do compression ratio calculations and measurements and the issues with fitting 12G940 heads onto small-bore engines.
Get it all wrong and you'll have wasted more than the additional small cost of buying the right pistons and getting the block pocketed or valves recessed.
A 1275 standard cam will give no gain over a standard 998 one.

[In-a-mini]

minispares sell a really good piston for the 998 that is stronger than the original and last well. a set will cost about £150 an mg metro cam is ok if ya got one sitting around if not go for a fast road one. Get the compression up around 10.5-1