I am lingering on the same notion of an L28 N/A upgrade for my mr30 skyline.
my friend has a 240k, as said before their heads have small ports and their compression is high but their flow is crap.
here are some random facts;
*going efi will straight up make a noticable difference, although i'm not sure whether efi is compattible with earlier l24heads such as e30-31 heads. they come stock with e88 heads on mr30 skylines.
*p90, p92 and other heads of the same type were used on the turbo model 280z's. they have a compression of around 7.00:1 i think.
*e-series heads usually have high compression but have really bad flow.
*n-series heads such as n42 and n47 are ideal for non-turbo setups because they have high compression and high flow. when looking for an N-series head go to U-pullit and look through all their Mr30 skylines, most have e88 heads- what mines got(they're still better than e30,31 heads), but you should be able to find some n42/n47 heads amongst them. i think it costs about 80-110 for a block or head individually from lonsdale and elizibeth U-pullits. and there should be plently of mr30's there.
Blocks:
L24- alright for a bodge turbo setup
L28- excellent for N/A. if you're looking for a straight on conversion with an L28 head, then get one WITH FLAT-TOP PISTONS. -even higher compression.
*an L28 block with flat-top pistons and an n42 or n47 head will get you a whopping compression level of 9.5 to 10.5 depending on how it's setup. which is so high you'll be running premium.
*'apparently' there isnt too much difference between the restriction of L28 manifolds to L28 extractors, but i cant comfirm this.
*the efi used on L24 and L28 engines should be interchangable.
*if you go with an N/A setup consisting of an L28block-flat-top pistons and an N47 head-ported, with a 2 & 1/4 exhaust and EFI'd you'll be looking at about 180-190hp at the flywheel i think. maybe more.
if you play your cards right you shouldn't be paying too much for this upgrade assuming that you do it by yourself.
EDIT: also as stated before you will also want the cam grounded, i think 2x1000rpm - 7x1000rpm would be an ideal powerband.
*although this all seems well and good, the hardest thing to get your hands on would probably be an F54 block. they are sought after by datsun enthusiasts.
Goodyear Eagles Dry - 4 Wet - 0 - these tires are absolutely dangerous. it's nearly impossible to steer with them on the front in the wet. i was running 205/65/r15's. they're not even fit for daily driving.