engine questions

[nickbean]

my borther and I have been rebuilding the engines in our z cars, his for the fun of it, mine because it started leaking water into the combustion chamber (still not shure if it's a cracked block, head, or bad gasket) my question is this; both cars are suposedly 1971's but my engine has flat top pistons and his has valve recesses, both engines had E-88 heads on them and the bores seem the same (haven't accually measured) so you can understand my confusion. any info would be helpful

[2ManyZs]

Check the block casting number. Sounds like one is not the original block. His may have been changed sometime during it's "previous life" and is now an L-28 block. Look for the casting number behind the alternator and compare the two.

The heads will work on any of the L-series blocks, so that is no indication of anything, it's the block number you need to check.

[Royce]

Admittedly, I haven't taken apart and compared the internals of the motors of various years of 240Z but I believe '70 - '73 originally had the same pistons (corrections are welcome). I am of the impression that compression and emissions changes during these years were done in the head and the intake/carbs. I do have several engines around and expect I may do some comparisons of them one of these days. But even then I think it is safe to guess that after 31 years it is possible that the engines have been rebuilt and may not have their original pistons. On drivers right the engine is stamped with a casting number this will give you a good place to start determining which blocks you have but without measuring the bore and stroke you still wouldn't really know what you have. I think it is time to get out some dial calipers and start measuring.

Have fun!

[nickbean]

the block says L-24 on it so now I'm even more confused, unless someone replaced the pistons, did any engines overseas get recessed pistons? due to money restaints my brothers project is on hold so I have choice of either block, is there any advantage to his pistons as opossed to my flat top pisons? also I have a 1970 parts car with an E-31 on it (dumbass sold the complete car to me for 100 bucks) should I get this head rebuilt for use on the street or save it for a race motor or something special?

[Royce]

What 2manyZ's and I were refering to is the casting number on the drivers side on the bottom near the motor mount. But the casting number isn't really important unless we are talking L28 motors.

Most likely the dished pistons with the notches for valve clearance are replacement pistons. It is possible that they are lower compression, equal or even higher compression pistons than your stock pistons. You should crank the engines over and get both so that number piston number one is all the way up, then see how the pistion height compares. If the difference is not obvious you would probably have to take it to an engine expert to find out what the differences are. Another thing is to clean the piston top surfaces as some manufactures will stamp a number, usually the bore or overbore, or other info into piston. Also, measure the cylinder diameter because it sometimes can be hard to visually see the difference between a stock engine and one that has been slightly overborred. Especially if they have both been overborred.

One more thing, I would check the diameter of the valves on the motor with the dished pistons and compare to the other engine. They may have used those pistons because they installed larger valves?

Have fun! Hope it helps!

[Z Kid]

E 30 heads come out on the datto 240K's over here from what i have been told.

[Mr Camouflage]

Take a look at the Georgia Z club's Cylinder head referance

http://www.georgiazclub.com/tips/ztech/cylinderhead.htm

hmmm. actually its not much help when it comes to pistons.

[dohc]

E30 was the smaller head for the 240K and 240C's in Australia. Not a particuly good head from what I've seen.

R.

[CoastGuardZ]

Forgive me fellas...I'm not accustom to all the datsuns down there in OZ.

What are 240c's and k's.

Nate

[dohc]

This is a 240K four door from the local wreckers... As you can guess an L24 with a single down draught carby. Not too bad in two door GT form.

[dohc]

Here's the back

[dohc]

Here's the two door