K-series conversion
Turbo Mini Forums

Looks good!....... Oh how I remember starting out like this!

Haave you guys ever used HLH prototypes or Xometry for any CNC machined items ?

So this week a worked crankshaft from Carl at Force Racing arrived It has been wedged, bladed, back drilled, balanced and hardened.

Attachments:

119.16kb

60.38kb

Shame to put that in an engine, work of art.

Hehe XD thanks mate

So just a little bit of an update ... The pistons and rods have just been bought. Pistons are the 18cc +20 forged from MED with floating pins, and the rods are also forged from John at SC components. They will also be taking care of the valve cutouts. In total this should give me a CR of around 8.9 and planning to tuck in around 20psi boost.

The next thing ahead now is to plan for the main bearing support (just seen the new item from MED), and a decent gearbox.

Do you guys recommend a good read on a box choice ? I've never experimented with different gearbox configurations so far, so before spending any money I wish to give it some thinking.

Evening chaps, looks like Christmas came early this year

Attachments:

97.42kb

Blimey, how much lift are you intending on running? Those are amazingly deep cut-outs...
Actually, I'm thinking they look deep enough to never contact the piston no matter what the timing - about the only thing that will hit the valve is the one across from it!

Yeah to be honest I thought so as well..
I guess SC do it like that to be able to run their big valve conversion ?

Yeah, I thought I had seen somwhere that these can be non interferance, (which I like the idea off despite the drawbacks) not managed to confirm it though.

I need to get a couple of sets of pistons done at some point so was going to find out then.

what are the drawbacks then of having deep valve pockets ?

I assume weakening the piston by having removed off excess material ?

basically that really,

weaking the piston, although not really seen any exidence of them giving issues due to this, also a it of a dead spot for the mixture to sit in.

Yeah yeah that's right. Something that I found a bit odd is that in the piston box there wasn't any info on how much bore-to-piston clearance I should run and from where exactly should I measure the skirt diameter.

yeah that never seems to be included, ehat are they, omega's? forged or cast?

Yeah they are Omegas forged 18cc +20

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=509971

Thanks for that Joe. The thread seems to suggest similar to what MED told me this morning. They told me that I should measure the piston at 6 to 8mm above the bottom of the skirt at 90deg to the pin.

This should give 2.796" diameter. And they recommended a 0.004" skirt clearance for a forged piston. So the ultimately finished bore should be 2.800".

I think the valves will still contact the pistons. Main reason the cut outs are so large is to get round the difference in valve positions in each cylinder, and, the difference in the head location on the various vintage of blocks, one size fits all sort of thing.

For comparison, these are my 18cc pistons machined to match the OEM BMW piston. Somewhat smaller, but the engine block has a significant more machine work done to get to that point!

Attachments:

62.29kb

Those are much smaller. What kind of work needs to be done to the block then in that case ?

moove ALL the holes

Good morning chaps,

Yesterday I started designing the bottom plate for my twinky to get machined this week. However I'm a little bit worried on how to sort out the end float of the camshaft. Also since the camshaft is made of a harder material than the aluminium plate, I'm thinking that it will wear out the plate immediately.

Morning,
This was something that I scratched my head over for for a while. After some careful measurement to ascertain the depth of the hole, I machined a recess/retainer in mine to carry a modified camshaft thrust plate giving the correct endfloat and the possibility to replace the plate if needed.
Bear in mind that the gasket thickness at the oil pump end will alter the cam position, if removed or replaced at a later date this will alter the end float. That said a different thickness gasket could be used on your cover to rectify the endfloat if required.
Regards
Shane

Hmm. Haven't even thought about the gasket thickness at the oil pump side to be honest.

I was going to machine the oil passage at the back side of the plate with a depth equal to the original A-series steel plate, so that it would have equal end float to the original assembly, however if this is done, the oil passage needs to be only around 4mm deep, which I doubt if that is deep enough.

By the way shane, why will the gasket thickness at the oil pump alter the end float ?

The gasket at the plate side will, but I don't think the one at the oil pump changes it ?

generally people use the std triangle plate to set the end float, this there its cheap it works.