Bored l24 block vs l28 block

[240z71]

Hey guys

 

I have recently taken my l24 apart that was in my 240z to find that the old owner had turned it into an l28 by boring it and changing the crank and other internals. As for the block he has bored it out to 86mm which is more than reccomended from what I've been reading. As the car had been in storage since the 90's I assume he had done this for cost reasons and l28 was in a reasonably new car back then?. In today's market thought I was thinking to just start with an l28 block. What could go wrong with the old block if I were to run it? Other thing is if I change to l28 it's considered an engine change so do I have to have it engineered or do I just hope whoever inspects the car doesn't notice ? Can you source just the block and what $$ am I looking at? Should I just have the old block sonic tested and if it gets the green light use it?

[dat2kman]

Send old blck off for hot tank clean and sonic testing.

Dont be too worried if test comes back with all kinds of varying wall thicknesses, this is due to core shift in the moulding process.

Prob wouldn't go much further, maybe give it a Flexhone, and new rings, bearings etc.

 

Be aware that hot tank cleaning will not thouroghly and completly clean a block, use long stem rifle brushes and cleaning/flushing fluid, and compressed air,

Then do it again.

 

[d3c0y]

Does it have any trick internals or is it all just stock? If the engine was used for racing they might have done it to keep the car in a specific class.

 

 

A stock L28 will set you back at least $500. I just don't see bare L28 blocks around anymore, they are starting to become a sought after thing.

You don't have to get it engineered.

Yes just get what you have sonic tested for piece of mind.

[240z71]

Thanks guys

 

Think I will just get it tested and cleaned. All internals are standard although it was used at the track ( it's luke Mcalisters old car (lukes run) ) I was thinking of putting l24 crank and rods I have sitting around and replace dished piston with flat top standard l28 Pistons. Anyone reccomended this setup. I also have a e30 head that my dad used on an old 2 door 240k that's had a lot of porting and larger valves put in it back in the day. This setup sound alright I plan to  do a lot of track days/ targa and only club reg. sorry if this is a bit of topic

[gav240z]

A stock L28 will set you back at least $500. I just don't see bare L28 blocks around anymore, they are starting to become a sought after thing.

Yes just get what you have sonic tested for piece of mind.

 

And even then it's a punt as to weather or not you can actually give it an overbore. The l28 out of my car came back as being only good for a 1mm overbore not much else. Have a second block, going to see what it's like then decide which to use.

 

How viable is it to resleeve a cylinder these days?

[dat2kman]

Very viable.

Use CDC thick walls, to a bottom step ( to stop sleeve being dragged down into bottom end)

The higher Specific Graphite content of the CDC sleeves means pistons run with less friction = more HP!

 

Did a 4 cyl a while back, no other changes, all items like for like, it gets run in on a engine dyno,

It picked up 9hp just from sleeves.

 

To OP, fit new ARP rod bolts to the stock 240Z rods (133mm long) have a look at/for Isuzu G200 ?, pistons these you then knock top off to get deck height you want.

Otherwise stock cast Datsun flat tops will be fine, but will finish at just under deck.

E30 off a 240k, ported and valved should be the tits,,,

[240z71]

Very viable.

Use CDC thick walls, to a bottom step ( to stop sleeve being dragged down into bottom end)

The higher Specific Graphite content of the CDC sleeves means pistons run with less friction = more HP!

 

Did a 4 cyl a while back, no other changes, all items like for like, it gets run in on a engine dyno,

It picked up 9hp just from sleeves.

 

To OP, fit new ARP rod bolts to the stock 240Z rods (133mm long) have a look at/for Isuzu G200 ?, pistons these you then knock top off to get deck height you want.

Otherwise stock cast Datsun flat tops will be fine, but will finish at just under deck.

E30 off a 240k, ported and valved should be the tits,,,

 

Is it a problem to finish just under deck height? The thought of combustion in the cylinder not completely in the combustion camber doesn't seem good to me. With my e30 setup I will be getting quite a high compression ratio so will need big cam but will i then be getting into piston to valve problems?. I know this has been covered but can't find anything about it for my type of setup with e30 and so on. Calculated theoretical displacement at 2575 roughly along with 37cc chamber on e30. How big of a cam would you think I could run if I got it flush with deck height ?

[d3c0y]

 

I guess it depends what your CR ends up with that E30 head, but having a negative deck height will lower the compression. Depends how big you go on the cam with the valve clearance but we just put a .526" lift 300 duration cam in a stock L26 and it clears.

 

I would definitely keep the L28 crank it in, all you are doing by putting the L24 one back in is making it slower. Use the L24 rods and find a piston that has the correct pin height (5.3mm less, 32.8mm overall) and aim for around 10:1 CR.

 

 

There is a simple program called Lengine that has been around for years that lets you put different combinations of engine parts together and it calculates all the values of the setup. Shoot me a pm with your email if you would like a copy.

[gav240z]

You can CC the engine head to determine compression ratio.

http://www.jegs.com/i/JEGS-Performance-Products/555/80950/10002/-1

 

Found this kit the other day, good for doing a 1 off rebuild.

[240z71]

If it's reccomended to keep the l28 cranks I will do so. What do I now do about the E30 head as if I keep it a 2.8 the CR will be too high won't it. Should I opt to keep the dished Pistons with the e30 would that give ideal CR or could I run flat tops ?

[d3c0y]

Depends on what has been done to the E30 and how many CCs the combustion chamber is now. Standard, L series are pretty low compression so it's not a big deal usually, but check it out. No point putting a motor combo together and just guessing.

[gav240z]

Depends on what has been done to the E30 and how many CCs the combustion chamber is now. Standard, L series are pretty low compression so it's not a big deal usually, but check it out. No point putting a motor combo together and just guessing.

 

Yep, that's why I said use the buret kit above to determine cc of the chamber etc.. I think the E30 might be smaller than E31 or E88 but I wouldn't trust what you read on the internet as it's hard to verify this information and it's source. Much better to measure yourself and know for sure.

 

I think "too high" compression is a bit of a misnomer, people tend to think anything above 10:1 is too high on a street car, but it really comes down to the engine set up and camshaft you're running.

 

This article is quite good.

http://www.hotrod.com/events/coverage/0606em-understanding-compression-ratio/

 

I'll admit I didn't fully grasp it all yet, it is the kind of thing that needs to be read more than once.

 

I think the biggest draw back of the early cylinder heads is their chamber design, they are more likely to suffer detonation. The P90 is apparently good for reducing detonation which will allow for more adv. timing etc..

 

The other thing about the E30 is it has smaller valves than the later L28 heads like (N42) but it's not all about valve size anyway. There are other ways to get more flow than simply sticking big valves in it. Much better to blend the valve seats and get a good port job done and possibly un-shroud the valves. Sometimes smaller valves give better port speed. 

[d3c0y]

Wasn't disagreeing with you Gav, especially since this head has been 'done' and larger valves installed you won't know what CC is. E30 is smaller than E31 which is smaller than E88.

 

 

11:1 is the limit on pump fuel in my opinion, even with a really big cam.

 

 

 

 

 

[NZeder]

As for the block he has bored it out to 86mm which is more than reccomended from what I've been reading.

what and where have you been reading? I have a copy of the sports option catalog of the period and Nissan sold pistons for the P30 blocks aka L24/L26 that where 87.8mm spec. It does have a foot note that states new blocks only. So that is more than your current 86mm. I have seen 2 P30 blocks here in NZ taken from their stock 83mm to 86mm and not fail...well one did but not the block, the crank snapped in that engine

[240z71]

Thanks for the replies, I think I'm going to stick with the dished that are in it to save cost but also as with E30 it gives around 10:1 CR depending on gasket which I think will go alright for my application. As for the head it's an old yella terra unit that's was fully gone over at the time (valves, springs, cam and a lot of porting but don't think it was shaved so should be stock cc chamber. but as for the metal it's done one weekend of abuse on a bit of a rally course my dad set up on his farm way back in the day and then has sat around, I'm yet to pick it up as it's at his brothers.another reason for dished was so I've  got plenty of valve clearance with what cam I pick, was thinking of checking out the cam in it as it was a new billet and was a race one. As for where I read that was recommended only to bore 2mm I just read that on various forums,if its safe to go 3mm that good news  and I'm happy to be wrong on that one 

[Riceburner]

Very viable.

Use CDC thick walls, to a bottom step ( to stop sleeve being dragged down into bottom end)

The higher Specific Graphite content of the CDC sleeves means pistons run with less friction = more HP!

 

Did a 4 cyl a while back, no other changes, all items like for like, it gets run in on a engine dyno,

It picked up 9hp just from sleeves.

 

How expensive is it to sleeve a block in this way?

[PZG302]

Last time i looked at it for my hemi 265 was looking around $150-$200 per pot.

[Riceburner]

That sounds pretty reasonable.