Is there something intrinsically inferior about the L24 block? I've heard about the siamesed cylinder bores of the F54 block but does that really make that much of a difference?

An L26 is a stroked L24. An L28 is a bored-out L26. So why not just keep your original engines and just rebuild your original engines already in your cars? It follows that this would be a good idea for the car's resale value as well.

The L24 is an extremely tough, good engine. All the above reasons are valid, but there is nothing wrong with an L24.....remember they raced it.

Why? Aren't your cars, though very nice, somewhat modified in a few other ways like wheels, 'da twin stax', etc.? Do you really have intentions of someday turning either or both of them back to completely stock?

You're absolutely right........no I don't plan to do that, but you always need a couple of spare engines to futz with! I love both the L24 and the L28's for different reasons.....that's why I have 2 of each. I really want to build a motor using the L28 block, L24 crank and rods and the L28 pistons and E31 head.....big displacement with high revs.....I've always been biased toward the L24's.......maybe it's just me, but I think they're more fun to drive!

If you build that destroked L28 you'll give up displacement and not really gain any usable rpm above and beyond what you can do with an stroked L28 on a "street" engine. If you're talking about revving to 9K, you're going to have a motor whose life is measured in hours, regardless of which one you build. You will however be giving up displacement and thus power vs the longer stroke.

It would be an overbored L24......you're right about giving up cubes with the L24 crank, but you would pick up displacement over the 24 block........ but seat of the pants, the L24 just feels like more fun to drive to me. Also, the E31 on the big bore block should give you much better compression .....right Jon?

My understanding is that you cannot bore an L24 to L28 size, so you would start with an L28 block. In that case it would be a destroked L28. You could bore the L28 to gain back a little displacement.

I'm a little confused on the pistons and rods, I know you can't run L24 rods with L28 pistons on the L28 crank because they come up above the deck a lot. It may be that you could run L28 pistons on L24 rods with an L24 crank, I don't know, but I can tell you that most machinists won't reuse a pressed piston, so I think you'd be in for new pistons regardless, in which case you might as well bore the block and get back some of that displacement. The E31 will give more compression. E31 with dished L28 pistons is like 8.5:1, and I think flat tops gives 10.x:1, can't recall the specifics.

As a general rule of thumb I would suggest not running "the maximum" compression you can manage on a street motor. You hear of guys retarding the timing to run pump gas from time to time, and there is A LOT of power in those last few degrees of timing. I'd rather have the 9.5:1 L engine that runs with the timing set for optimal advance than the 10.5:1 compression motor that can only run total advance in the mid 20s.

Pin height is the same on L24 and L28 pistons.....so you should be able to run the L24 crank and rods with new .040 over L28 flat-tops to give what equates to a big displacement L24......anyone ever built this motor?

the only substitute for cubic inches is cubic dollars.

And/or rpm. Stock for stock the L24 will spin to a higher rpm then the 2.8 and SCCA ITS builds (stock internals) consistently show the 2.4L making more horsepower then the 2.8L. None of this matters for a street car. I just posted to show that the Internet Rule of Thumb isn't always right. :-)

The L28 (280Z) cylinder heads have larger intake and exhaust valves. You can machine these larger valves and seats into a 240 head but the cost is greater than just using the L28 heads. The L28's have a larger bore and longer stroke so they don't turn as much rpm as the L24's, hence the need for larger valves. For me unless you have 100% numbers matching car in pristine condition I have no problem adding L28 to a 240 for increased hp and more importantly torque. Back in the 70-80's Jim Fitzgerald used early E88 heads, 280 valves and opened the ports up on his race heads. This gave him the higher flow and compression for racing. His heads flowed better than anyone's and Z power is all the heads whether it is on the street on on the track.

BRE also used E88 heads in their race cars. When I was a kid in my early 20s, my brother and I went to the shop in El Segundo a few times. I remember seeing a couple of their race heads. They were things of beauty!!

I think a lot of it, like many many other automotive mods, is hear-say. The cliche' that there is no replacement for displacement has led to generic ideas that a larger engine automatically means higher performance without consideration of the rest of the vehicle. My '72 came with an N42/N42 L28 already installed, and it feels fast more becuz it also has a 3.90:1 R200 in it than becuz of the engine itself. It wouldn't feel as fast if it still had the stock 3.55:1 R180.

On a different note, the torque increase resulting from the longer stroke and larger bore of the L28 compared to the L24 may be enough to make some drivers on a tight budget happy: they probably were able to buy that power increase for a few hundred bucks and an afternoon of work rather than spending weeks tearing down/rebuilding an L24 and a couple grand on parts and machinist time to bore/stroke the stock engine. More power probably from the built up L24, yes, but would it be enough of an increase to justify several times more money?

As for resale value, I do not, and will never, buy any fun-to-drive vehicle with resale as even a small part of the deliberation process. There's precisely zero chance that I'll ever come close to getting the money out of my 240z that I will have put into it by the time I consider it finished, and I truly don't care. I don't care if my toys are or will ever be worth to someone else what they are to me. That's why they're mine

I think a lot of it, like many many other automotive mods, is hear-say. The cliche' that there is no replacement for displacement has led to generic ideas that a larger engine automatically means higher performance without consideration of the rest of the vehicle. My '72 came with an N42/N42 L28 already installed, and it feels fast more becuz it also has a 3.90:1 R200 in it than becuz of the engine itself. It wouldn't feel as fast if it still had the stock 3.55:1 R180.

On a different note, the torque increase resulting from the longer stroke and larger bore of the L28 compared to the L24 may be enough to make some drivers on a tight budget happy: they probably were able to buy that power increase for a few hundred bucks and an afternoon of work rather than spending weeks tearing down/rebuilding an L24 and a couple grand on parts and machinist time to bore/stroke the stock engine. More power probably from the built up L24, yes, but would it be enough of an increase to justify several times more money?

As for resale value, I do not, and will never, buy any fun-to-drive vehicle with resale as even a small part of the deliberation process. There's precisely zero chance that I'll ever come close to getting the money out of my 240z that I will have put into it by the time I consider it finished, and I truly don't care. I don't care if my toys are or will ever be worth to someone else what they are to me. That's why they're mine

Wow! :classic: