What is the largest overbore that you can achieve with an L20B block??
Found some HKS 89mm Pistons for L-series
Block would need to be sleeved to use them ?
How much to sleeve a block for that size overbore?

Thanx

Dave

you can bore a L20 block out to 89mm ( stock is 85mm ).
but thats a 4mm overbore!....not much left after that, so I wouldn't be suprised if you had overheating problems....

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damn, 1mm is 40 thou, so you would be boring 160 thou over standard

I just bored my fj20 110thou over standard.

OK , but do you need sleeves fitted after a overbore like that?
Dont mind if you do , just aslong as it aint too costly.

no thats the max bore u can go, no sleeves req.

to do this well, complete motor, is very very expenisve.

PM if u interested in a 2.4 L motor already done.

Cheers,
Mal

what if you used a z22 block? are they the same wall thickness as l20b??
heard something bout the z22s being 'siamesed' and having a far thicker cylinder wall.....anybody know about this?




Aaron

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Cheers,

Aaron

My l20b is running 89mm pistons & i've never had any overheating probs at all, & yes it's 160 thou, takes 4 cuts to take that much meet out of the bore. Was told by the guy who did it that l20b's can go as far as 200thou , but thats it after that, motors really torquey, but still revs to 6 or 7 thousand rpm, so she's not a bad set up. I used toyota pistons tho.

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Vaughan
'70 P130 Super 6
Fiesta XR4 (modified)
Formally: 510 L22B twin webber terror
510 FJ20et (510 FJ)

Z 24s are more prone to cracking. Thats what I hear. be carful of overheated Z24s.

My datsun book says L motors are good for a 2mm overbore after that sonic testing is required. And have to buy the expensive Nismo head gasket that goes up to 89mm.

Nah you don't need to use a nismo head gasket, just use a z24 head gasket, you have to punch a couple of holes for i think 1 oil gallery & 1 water gallery, cut of the bit at the front where the timing cover is a cut the same bit off an L series head gasket to replace it. Simple huh

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Vaughan
'70 P130 Super 6
Fiesta XR4 (modified)
Formally: 510 L22B twin webber terror
510 FJ20et (510 FJ)

cool thanx guys am gonna get the HKS slugs, now I know they dont need any sleeving!

make sure your block is an aussie cast one the jap ones are to thin to go to 89mm.

If you bore to 89mm its best to use a strainer plate, & fit & torque the main caps. Block must be allowed to cool between cuts.
Without the strainer we have measured up to 0.0035 bore distortion once
the head was bolted on. Resleeve job is very expensive if done correctly.
Really only for max effort motors when you do not want bore flex over 7000. Best to get the block scanned first.

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"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

any one ever bored a z22s block before?

if you're going to put 89mm slugs in it you may as well go all out with the rest of the motor. the last L20 i had built had 89mm toyota flat tops, but they "fly cut" the tops of them for some reason, i'm no mechanic. spent $135 on a nosmo head gasket ( this was in 1994!) balanced, shotpeened, full floating gudgeons and a 75 degree works cam. i think from memory it cost me around $2500 ten years ago, but was money well spent. it certainly was one nasty little motor and still is putting down 140hp at the wheels of a 180b wagon. it pays to do it properly once.

With flat top pistons it is very necessary to fly cut the pistons when used
with high lift cams. we dont need valves punching holes in pistons.

_________________
A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT