4 replies to this topic

[dotmatrix]

Just a thought experiment. With the standard stroke length of the 998, a 5-port head and obviously a lot of work everywhere in the engine could a 998 do 10000rpm do you think?
 
I guess the piston speed would be acceptable for short sprints, and with enough money I guess the bottom end could me made to handle it, but can you flow enough through a 5-port head to get to those rpm on a 998 or what problems do you see?

I Guess pushrods operating at That speed would also be a problem

Edited by dotmatrix, 25 March 2018 - 12:05 AM.

[Spider]

I'm quite sure the bottom end would well stand up to 10 000 RPM with little worries, including the Push Rods (970 S Engines frequently were taken to 10 000 RPM), but as you've identified, the head would be be the resrictor in this set up.

 

In regards to getting a head to flow for these volumes, the issue as I see it is the small bore itself - that pretty much limits the size of the valves that can be fitted. I'd say you'd have to boost it in some way.

 

Turbo Phil would be the guy who'd be able to shed more light here.

[dotmatrix]

If using a 1275 head with its standard valve sizes. I think You would need to Pocket the Block a Lot as the cam needed to be fitted for Those rpm would have a Lot og lift and the head would need to be skimmed to bring Up the compression

[OzOAP]

998 Mini 7s are getting there. Many going to 9500rpm.
+020, 940 head, 35.8x29 valves, MG Metro cam. 4.6cwp.
I'm currently building one with a few changes from last season.
Changed the piston crown shape and a lot more development on the valve train.
This season could see the 1000cc, 100hp, 10000 rpm.

Edited by OzOAP, 25 March 2018 - 06:58 AM.

[dotmatrix]

Impressive. Especially with a mg metro cam