4 replies to this topic

[minisilverbullet]

Researching some things for a specialist components k head conversion. 

 

I have the build book and I have spent an hour or so searching but I can't find any info on piston choice (dish size) and/or ideal compression ratio.

 

Any information out there?

[Alex_B]

Researching some things for a specialist components k head conversion. 

 

I have the build book and I have spent an hour or so searching but I can't find any info on piston choice (dish size) and/or ideal compression ratio.

 

Any information out there?

I haven't done any final part selection yet, but I believe the cc of the head is very close to the mini head so I think the options are suited to standard mini choices. But the pistons need valve pockets cutting in for the 16v head and obviously this needs to be accounted for. I would probably hit SC with an email asking about ideal CR and what they would recommend piston wise. I am aiming for 10:1 CR as I want to use 98 octane minimum. 

[minisilverbullet]

 

Researching some things for a specialist components k head conversion. 

 

I have the build book and I have spent an hour or so searching but I can't find any info on piston choice (dish size) and/or ideal compression ratio.

 

Any information out there?

I haven't done any final part selection yet, but I believe the cc of the head is very close to the mini head so I think the options are suited to standard mini choices. But the pistons need valve pockets cutting in for the 16v head and obviously this needs to be accounted for. I would probably hit SC with an email asking about ideal CR and what they would recommend piston wise. I am aiming for 10:1 CR as I want to use 98 octane minimum. 

 

Yes that will be one of many questions to SC. 

 

Looking at Omega die cast 11cc pistons (only 330 at MED) , though as you say the cut outs need to be accounted for. 

[Spider]

I'd probably look to the likes of Omega or Ross pistons for a build like this, most likely, but not set in stone, that I'd consider a forged set.

 

Being an Alloy Head, and if working to static CRs and have the rod / stroke ratio less than ideal (if going to a 16 valve set up) you'll want to set the CR 0.5 to 1.0 'point' higher than you would for an Iron 5 porter.

[Streetscreamer]

Before choosing the piston start to calculate the total unswept volume needed for your ideal (static) compression ratio. (remind BMW used 11:1 static CR)

 

- combustion camber

- headgasket volume (BK450? or MLS 0,6 or 1,0 mm of SC..?)

- ring land volume

- deck height volume

- valve pocket & dish volume

 

Then also check which type of camshafts you use: LT is much tamer than RS.

Considering the camtiming as indicated by SC you should be able to calculate the dynamic compression ratio.

The Holey Grail will be found with dynamic compression of 9:1.

Nevertheless this needs octane boosters. So, a 8,7 :1 is ok for 98 RON.

 

I face exactly the same issue..... have a K100RS head & cams, bought some flat topped but pocketted forged Omega's.

Sure they will need some torture on the lathe...

 

good luck!