7 replies to this topic

[Pavel]

Alright well the other thread about stroking a 1330 has given me some ideas and motivation to do something with the 850 and 998 engines that I have lyin around in a field somewhere...
What exactly is involved when transplanting an 850 crank into a 998 and putting 998 pistons into a 850 engine? Which of these options would be the most preferred? Also on a highly tuned 850 using 998 pistons, I assume it would be beneficial to use a big bore head? Not worried about low rpm grunt, will probably run a lairy cam, as this will be a pure fun weekend car (got 2 others to use for normal driving anyway). Hoping for a ridiculous rev limit with a solid power output, and am willing to put up with little road driveability!

If I can get my hands on one, a BINI supercharger will be adapted to this engine (one of these s/cs litterally slipped out of my hands for less than a hundred quid! )

[Jammy]

Thats it, STEAL my idea and work on it before I can finish my Vtec project!

[Pavel]

I'll be able to steal all your ideas and bring them to life by the time you're done with that thing!

[Jammy]

Well then maybe you can guess what idea I have for you with this finger I'm holding up!

[Sprocket]

850 crank in a 998 block requires specialy made thrust bearings as the 850 center main bearing width is wider

[Asphalt]

998 piston will not fit because the have another compression-hight as far as I know.
You`ll need pistons with 850s compression-hight.

You might use +0.60 overbore 850 pistons.
Will give - if i didn`t misscalculate - 936ccm.

BUT: 850 crank & pistons, as well as rods aren`t the strongest
Hardening and machining will be neccesary if you`r going to build a high-rev engine with lots of power-output (especially if you want to superchrage it).
Don`t know if 850 (+0.60) pistons can cope with such high power (they were originally build and developt for 34HP!)

What I`m going to do is a 998 block with custom-forged 69mm pistons on a hardened 850 crank and 12G295 head with 1300 valves (33/29mm).
Cam, isn`t decided yet...
3,76 finaldrive is - for me - a "must be"

If you look at a standart 850`s smmotheness - it will be a godlike engine!!

So go for it!!

best regards,
Jan

PS: Need lots of money... It´s quite a long time until I finally can go build this engine...

[Pavel]

So where and for how much can one get these thrust bearings made up?

And asphalt as for using 998 pistons in a 850 block, couldn' you simply remove material from teh top of the block to make it work? What about using 1098 pistons?

Also it's possible to use 998 conrods on a 850 crank, right?

[Oldskoolbaby]

Take a butchers at page 90 of this months Miniworld. I think it may help. Where do you get specially made thrusts from then???