I currently have a '71 that I'm building up, and I plan on buying a mild cam/spring/rocker kit and forged pistons... I see L28 pistons all over the place and not much on L24's. I've heard that an L28 piston will give you a lower deck height, thus reducing compression and increasing valve clearance. My questions are this: Is what I'm being lead to believe true? If so, how much lower is the deck height over an L24 piston, and what would the new compression ratio be?

Thanks

Steve

Edited May 13, 200915 yr by Thrasher

L28 pistons wont fit in an L24 block.

I'm having the block bored out to fit the new pistons

You can bore an L24 1.5mm.... go 3mm and you are most likely into the water jacket. There is a reason that the L28 was a new casting.

FWIW,

Carl B.

A set of 6 L24 pistons with rings are in the $200 area, i got mine from Northern Autoparts.

Chris

've heard that an L28 piston will give you a lower deck height, thus reducing compression and increasing valve clearance.

Where did you hear or read this?

You can bore an L24 1.5mm.... go 3mm and you are most likely into the water jacket. There is a reason that the L28 was a new casting.

FWIW,

Carl B.

I've heard 2mm is the max overbore an L engine should ever have... I thought a stock L28 piston was only 0.040 larger than a stock L24 though? Please correct me if I'm wrong.

A set of 6 L24 pistons with rings are in the $200 area, i got mine from Northern Autoparts.

Chris

I would do that as well, but the walls have been bored out .020 already, and It looks like Northern only has stock sizes.

Edited May 14, 200915 yr by Thrasher

The L24 (and L26) is 83mm while L28 is 86mm,

The L24 (and L26) is 83mm while L28 is 86mm,

Thank you

Still wondering on the pin height differences though, does anyone know about that??

>_<

Edited May 14, 200915 yr by Thrasher

I'm having the block bored out to fit the new pistons

Now you know why L28 pistons don't fit a L24 Block.

L24 & L28 pin height is the same: 38.1mm

Thank you

Still wondering on the pin height differences though, does anyone know about that??

>_<

Where did you get the notion that the pin heights were different? Whoever you're getting your Datsun info from....you need to fire them!!

Guessing here, but he's probably seen custom L28 pistons on L24 rods. You can put these in an L28 block with the L28 crank. The purpose is to get a better rod/stroke ratio, and I think it's a pretty common upgrade for racers. The custom pistons have the wrist pin higher in the piston to allow for the stroke difference at the crank so that the pistons don't come out of the bores (more than usual).

Here is an example:

http://www.arizonazcar.com/piston.html