Need some Z24 info...

[Spades]

ok, so, I am most likely buying a Z24 motor from my boss, and I want some info on the Z24 engine.

 

this motor will be my project motor, and since I have a running z20s in my 510, I have time to build it how I want. Before I take on this project, I want some info!

 

ok, first off, I have heard z24s like to loose head gaskets...is there a solution to this? is there a company that makes a good head gasket thats less likely to blow? or perhaps a copper head gasket?

 

next, does anyone have the spec's on the stock camshaft? he has a reground mild cam in it, and I want to make sure it isnt too radical. the engine isnt running right now, so I wanna make sure the cam will work...that will weigh in on the engines worth.

 

next, it has been machined, and has new OEM grade pistons in it...did nissan make any forged pistons on any of their engines that will pop into a z24? I can get good prices on OEM or stock grade aftermarket parts at the repair shop I work at, but I dont get good deals on aftermarket performance parts.

 

the engine will be built to either run a weber 32/36 on a custom manifold set up for blow through and a intercooled 5 to 7 psi turbo, or I will be using a set of SU carbs and going for N/A...so, I would like forged pistons in case I ever wish to go with small amounts of boost.

 

any info any of the forum gurus can bestow apoun me would be greatly appriciated!

[hang_510]

ok, first off, I have heard z24s like to loose head gaskets...is there a solution to this? is there a company that makes a good head gasket thats less likely to blow? or perhaps a copper head gasket?

 

ive heard this too, but my LZ24 w/stock OEM HG hasnt been an issue w/< 10K mi

[RoadRace]

it was my impression that the head gasket would fail due to a crack from the head bolt hole that propogated to the water jacket along the deck of the block. the root problem being a bad batch of castings.

[datzenmike]

My Nissan FSM recomends loosening each head bolt and re-torqing it to spec one at a time in no particular order at every tune up. The problem is... no one does that!!!! So the gasket blows every 100K miles or so.

 

Re-torque keeps the gasket compressed evenly over time.

[Spades]

in that case I will get a nissan gasket and just re-torque every few oil changes.

 

does anyone know if there are any OEM forged pistons that can be fit in a napsz24? like i said, I would love it if I could use nissan parts rather than aftermarket...did nissan make any forged pistons from the factory that can be machined to fit in a z24?

[Bleach]

I've never heard of factory forged pistons.

 

Also, it sounds like you're building a high compression, long cam duration NA motor and then later on plan to boost it. For any amount of boosting I would say keep the compression stock or lower and use the original short duration cam.

[hang_510]

it was my impression that the head gasket would fail due to a crack from the head bolt hole that propogated to the water jacket along the deck of the block. the root problem being a bad batch of castings.

 

some kinda design flaw...

ive seen cracked L18, L20b, and Z22 blocks in the same location in the search for mine.

@ the headbolt between 2 & 3, which is between the water jacket.

 

i used it w/the crack :rollseyes:

 

that said, this is not where ive ever seen the HG fail.

[datzenmike]

KA24E pistons are same size as Z24s and have smaller dish giving a 9.521 compression.

[Spades]

ok, so they would give me more compression, which would be good for N/A, but, will they work with a shaved head on a z24? or is the dish, rather than top height, the only difference? i wasnt aware they made factory forged ka pistons, i suppose even if they dont, forged aftermarket ka pistons arent too expensive.

[steve g]

the block is the cause of the head gasket issues, the deck distorts easily and sometimes the head bolt hole threads crack. IF you want to know why i can go into mind numbing detail later. MY tryck has over 300,000 miles on the stock head gasket and all the credit is to the first owner who actually did the retorque every 30k or so if i remember. i personally have never done it.

Z24s love boost! i have done it and the end result was mind boggling. If was to compare it to dsomething i would have to say it was close to an early 5.0 mustang. It was done with a turbo from a subaru 1.8 "i think 1.8" and was redneck hacked into the 2wd 720 truck, it was never tuned right by any means and still was awesome so i can only imagine if it was done right what i could have been. I suggest a nice strong rebuild to stock specs and boost the thing!

[NicktheMillwright]

Hate to dig up this post. But how frequent did the Z24's block crack? And where about's did the cracks occur?

Something about a bad batch of block castings?

[datzenmike]

Around the head bolts between them and the coolant ports but even the earlier Z22 and L20B would show up sometimes with cracks. Almost always when someone took apart a perfectly normal running engine to rebuild. Says volumes. The cracks did not impact the running at all and the owner just didn't know they were there.

 

The problem with the Z24 was it tended to blow the head gasket at 100k intervals. The bolts lose their clamping pressure and perhaps this has something to do with the cracking? The prescribed preventative for the blowing head gasket is to re-torque the bolts once a year when the engine in cold. Loosen one bolt only and torque to 60 ft lbs. Only then go to the next bolt. Use any order you like. Water can't get out past the gasket and even if it got into the bolt hole it cant get past the bolt head torqued to 60 ft lbs.  

 

 

One Ratsun member welded them up...

 

 

Then had the block decked...

 

 

 

I don't know about any metallurgy for the Z24 but it's basically an L20B/Z22 block that is 2cm taller right at the deck where the head bolts enter it. I happen to have one from an '84 that when the transmission was removed it had wrecking yard crayon saying D21 Hardbody. So it was a swapped '86-'89 block. I put an L head on it and there were no sines of cracking. There's a bit more room inside for the larger throw crankshaft but an L16 oil pan will still bolt up to it.

[NicktheMillwright]

Well I've done the retorquing to my motor when I found out about that bulletin. So I'm good there. The cracking shown above doesn't seem to be structurally compromising.

Cast Iron has a coefficient of linear expansion of 0.0000104in per degree Celsius, so a 7018 MR welding rod or equivalent would be effective for the kind of heat cycles a engine has to stand up too.

 

I'm planning to gut my motor for a turbo build with forged components. So covering all my basses before ripping into it. Hoping for no cracks.

[datzenmike]

Short of a rod going for a walk outside or coolant freezing there is no known problem with the blocks. You might consider O ringing the block if going to a turbo. Also an oil cooler and (dare I say it) a synthetic oil.

[NicktheMillwright]

10 minutes ago, datzenmike said:

Short of a rod going for a walk outside or coolant freezing there is no known problem with the blocks. You might consider O ringing the block if going to a turbo. Also an oil cooler and (dare I say it) a synthetic oil.

 

That's reassuring. From my research the L and Z blocks are quite robust. I'm still going to give the headers a good wrap and invest in an electric fan conversion and definitely a oil cooler to keep those temps under control. Hood vents for extra style points for sure.

 

Pardon my ignorance, but what do you mean by O ringing the block?

 

Also, thoughts on a copper head gasket?

[datzenmike]

What a machine shop does is cut a ring around each cylinder then tap a round stainless steel wire into the ring. The ring is cut to a depth such that a little less than half of the wire sticks up above the block deck surface. When a gasket is installed and tightened down it severely pinches and seals it making it almost impossible to blow out.

 

A copper gasket can be used and reused over and over with O rings too. An advantage is they can be any thickness. The one below is 0.020" about 40% thinner than a stock gasket which will increase the compression if needed. They are a bit extreme for a street car but they are almost impossible to blow out even without O rings. Both head and block surfaces must be extremely clean and smooth as the copper does not crush and fill any imperfections. A spray on Copper Kote is a good idea with copper gaskets.

 

I made my own out of $5 worth of copper roof flashing. When finished it must be heated with a torch to anneal and soften the copper.

 

 

 

 

[NicktheMillwright]

Huh, you learn something new every day. I'll keep that in mind when I send the block off to get machined. Anything that'll help keep the combustion inside the chamber, especially when adding boost to a head gasket prone engine sounds like a good idea.

 

I'm drawn to copper due to the added heat transfer benefits

 

I'm going to take a crack at it and say that's a KA24 head you have in that photo.

[datzenmike]

KA24E yes.

[Stoffregen Motorsports]

O-ring works fine with factory composite gaskets. Copper gaskets are used when you need thicker or thinner gasket than stock. Also, RTV or copper coat needs to be used on a copper gasket to seal the water/oil passages.