Discussion in 'S30 (240Z,260Z,280Z) Engine' started by Turn & Burn, May 17, 2017.
The front end is quite nice, but those rear wheels/track and arches are seriously vile.
Sorry, I don't know this off-hand. I'm away at the moment but when I get home I can scan the detail of a Z Car magazine article of a similar build done by a friend of its previous owner at the same time. See if there any clues.
I read 20R pistons have a pin height of about 31mm.
With L24 rods on a 83mm stroke crank and L28 block that will give you pistons 2mm or more below the block deck.
If you had those 135mm L20 rods then you’d be in the right area.
Are the 20R pistons attractive because they’re cheap and 88.4mm?
I'm trying not to get too carried away with this engine as it's really easy to keep adding extra bit "while its apart". I don't want to lose sight of the fact I was just going to put in a refreshed L28 with a bit more compression and use a ported head I already had. As I now have a LD28 crank it seams a shame not to incorporate it in the build. I was hoping to use all the bit I have and just add another couple of grand worth or parts to it. I wasn't trying to reinvent the wheel and just wanted to go down a tried and tested route. Pistons seem to be the main stumbling block if I cant just use the KA24's. Are there alternatives that work with the normal L28 block, LD28 crank and L24 rods? without having to come up with your own design sheet.
KA24 pistons are fine on deck height with L24 rods if you can go to 89 bore.
Or you could use LD28 crank, L28 rods and L28 pistons and have 1mm or so taken off the top of the pistons.
Ur right, I’m finding the pistons the difficult bit, whereas even custom rods are easy n relatively cheap. I haven’t spoken to JE yet but suspect they’ll cost about a £1k.
I may have a look in more detail at the R20 piston, but it will need more rod work as they are 24mm pin. The compression height is also nearer 42mm than 30mm i think.
Rod ratio for the L28 rod would not be all that good. I had considered this.
Anyway, I thought about this for far too long so now I'm going to bite the bullet and just order some custom pistons from JE. I have just looked at their order for and it looks a little scary. A lot of it I can work out but I could do with a little help. What should I be asking for with regard to valve cutouts to cover myself if I go for a higher lift in the future? All assistance welcome
I'll be going for the 240z maxspeeding rods. Actually ordered them this morning and they are on their way. Looks like I've got a roadsports .460"/300 duration cam coming so need to think about springs and lash pads.
Rod ratio for L28 rods results in less than 1/2 degree worse angle.
I suspect it makes naff all difference in the real world.
How about these pistons, hardly any mods req’d...
I believe you’re ok upto .480 ish lift with stock springs.
The kameari pistons have 2.7cc cut outs for the valves.
I happen to have one with me - I could measure them if you like.
32mm pin height and 22mm pin diameter for the VG30 pistons, so good for the L20 rods if you rebush the little end. On my spreadsheet anyway
This is an 88.5 bore kameari piston for L28 rods.
Clear as mud eh?
you need to work out your head first?
I picture of the top of your piston, looking down would help.
Maybe this is a stupid question but are the valve positions and angles the same on all l series heads?
Pretty sure they are, yes.
Kameari don’t call out any particular head for those pistons.
Fwiw, I reckon the angle of those cut outs is about 70 deg to the surface of the piston, but I suppose you can qccurately measure from the ‘spike head’.
Oh and remember the valves are in different orders on different pistons
EI IE EI IE EI IE
if you know what I mean
3 are like the one in the photo and 3 are a mirror image.
Have you thought about going to kameari direct and ordering form them, removing the guess work and getting a decent product. That way your only unknown is the head, then get my cheap crank checked over
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