Z24 Turbo charging

[NicktheMillwright]

Afternoon everyone

 

A leak down and compression test have shown I have worn rings. So while I gut this engine and have it out of the truck; what kind of turbo kits are available for the Z24? I'm looking for a modest power increase, nothing that will compromise the reliability. I dont plan to tow anything with this truck. It's going to be a show truck when it's restored

 

Cheers

Nick

[Stoffregen Motorsports]

We were just talking about this in another thread. Here's the kit, but I wouldn't waste the money.

 

- http://turbodatsun.com/Z24 T3 Turbo Kit.htm

- http://turbodatsun.com/Blow Through Carby Kit.htm

[NicktheMillwright]

30 minutes ago, Stoffregen Motorsports said:

but I wouldn't waste the money.

 

Are there any options for getting more power out of this motor without a turbo then? Swapping cams? My motor already has a 32/36 Webber on it. I'm not looking to make a monster, I would swap in a LS4 if I wanted that.

[Stoffregen Motorsports]

Older carbureted engines do not benefit from add on stuff like a modern EFI motor can. Sure, you could install a cam, build a good exhaust system with a nice header, but without getting into the block and cylinder head, there's not a lot to be gained. It has roughly 100hp now. Adding a cam and exhaust will bring it up to about 115-120 with some tuning work (carb jetting, ignition curve). Porting the head and doing a really good valve job will help, but then you're limited by the single Weber carb. To gain more than the 15-20 hp, you're going to spend a couple thousand, at least.

 

KA24 swap for about $3500-$4000 if you do it yourself and you're already ahead of the game. You've now got 135hp, in stock form. Tune it up a bit and you can get 150-180 pretty easily.

 

I know, not what you wanted to hear...

[datzenmike]

 

Here is an L series intake port location. Notice that it's quite high above the block at 1.75". The intake air falls more directly down and into the combustion chamber.

 

 

 

Below is a Z24 intake side. Notice how the ports are 3/4" above the head gasket surface? This means air flows in horizontally and then there is a sharp bend at the valve where the air is forced to slow to change direction. Not a big problem at low speeds but as the engine revs it has to divert more power into actually pulling air in and less is available for moving the vehicle. This is a built in impediment that porting and cam can't remove entirely.

 

 

 

 

32/36 is a good  improvement over the stock carburetor. The exhaust manifold is good enough if you get rid of the Catalytic converter and add a low restriction turbo muffler. If you get a cam, go for more lift and similar duration and overlap. Aim for low RPM power and torque.

 

The Good....

 

1/ The Z series have a cross flow head with the hot exhaust ports on the opposite side from the intake.

2/ They have a much more efficient hemi combustion chamber that is more detonation resistant.

3/ They have dual spark plugs that shorten the burn time and also reduce the chance of pre ignition.

4/ They have larger volume water pumps.

 

Perhaps if the engine is ever rebuilt swap KA24E pistons in to replace the stock 15cc dished ones. This will bump the compression to 9.87. 

[NicktheMillwright]

4 hours ago, datzenmike said:

 

Here is an L series intake port location. Notice that it's quite high above the block at 1.75". The intake air falls more directly down and into the combustion chamber.

 

 

 

Below is a Z24 intake side. Notice how the ports are 3/4" above the head gasket surface? This means air flows in horizontally and then there is a sharp bend at the valve where the air is forced to slow to change direction. Not a big problem at low speeds but as the engine revs it has to divert more power into actually pulling air in and less is available for moving the vehicle. This is a built in impediment that porting and cam can't remove entirely.

 

 

 

 

32/36 is a good  improvement over the stock carburetor. The exhaust manifold is good enough if you get rid of the Catalytic converter and add a low restriction turbo muffler. If you get a cam, go for more lift and similar duration and overlap. Aim for low RPM power and torque.

 

The Good....

 

1/ The Z series have a cross flow head with the hot exhaust ports on the opposite side from the intake.

2/ They have a much more efficient hemi combustion chamber that is more detonation resistant.

3/ They have dual spark plugs that shorten the burn time and also reduce the chance of pre ignition.

4/ They have larger volume water pumps.

 

Perhaps if the engine is ever rebuilt swap KA24E pistons in to replace the stock 15cc dished ones. This will bump the compression to 9.87. 

 

So here's what I'm getting from this very valuable information:

 

- Aim for low rpm power and torque

- Piston swap for more compression

 

Is the L series head compatible with the Z24 block for better air flow? If it were you, would you put a turbo on this motor or keep the webber? Forgive my ignorance, just trying to make the most of this motor.

[datzenmike]

I would put a U67 L series head on a Z24 before I would turbo it.

 

 

Timing chain needs 4 extra links added to an L20B timing chain because the Z24 block is 2cm taller

 

Needs a 4 spark plug L20B distributor.

 

L series intake and exhaust manifolds to match the head.

 

Needs L series engine brackets a suitable truck L series oil pan.

 

Use a Z24 head gasket with some alterations.

 

Dip stick is on rear driver's side so swap to right side or check oil when engine is cold.

 

Above. L20B block vent should work on Z24 block.

 

Head optional mods. Stuffing 20% more displacement into a combustion chamber made for 8.4 compression will raise it to 9.5 so you can afford to open up the shrouding around the intake and exhaust valves where they are closest to the outer edge of the combustion chamber. Use the Z24 HG and scratch the outline of the fire ring on the head and smooth out to meet this. The Z24 cylinder is 89mm or 4mm wider than the L20B

 

 

 

[NicktheMillwright]

Well, sounds like I'm going to be tracking down a U67 head plus components.

 

Know of the bat where I'd find anything locally. We are both BC boys

 

And for clarification, all the water jets line up correctly? Did Nissan try to make this as modular as possible?

[datzenmike]

There are differences in the head gasket holes but generally the block and the head holes are the same. The gasket selects what are or are not used. The L series is not a cross flow head so there are more cooling holes used on the left side of the head where the manifolds are. 

 

The L16 was the first L series and over 13 years it grew to a 2 liter L20B in size. For the '80s a new low emissions Z series head was designed and the L20B block and crank were basically unchanged in the Z20. The Z20 became the Z22 and finally the Z24 in '83. It was used till EFI was added in '86 and was around another 3 years. The KA series was much changed but a KA head will still bolt to an L or Z series block.    

[Crashtd420]

9 hours ago, datzenmike said:

I would put a U67 L series head on a Z24 before I would turbo it.

 

 

Timing chain needs 4 extra links added to an L20B timing chain because the Z24 block is 2cm taller

 

Needs a 4 spark plug L20B distributor.

 

L series intake and exhaust manifolds to match the head.

 

Needs L series engine brackets a suitable truck L series oil pan.

 

Use a Z24 head gasket with some alterations.

 

Dip stick is on rear driver's side so swap to right side or check oil when engine is cold.

 

Above. L20B block vent should work on Z24 block.

 

Head optional mods. Stuffing 20% more displacement into a combustion chamber made for 8.4 compression will raise it to 9.5 so you can afford to open up the shrouding around the intake and exhaust valves where they are closest to the outer edge of the combustion chamber. Use the Z24 HG and scratch the outline of the fire ring on the head and smooth out to meet this. The Z24 cylinder is 89mm or 4mm wider than the L20B

 

 

 

Mike wouldn't he also need to swap the transmission bellhousing to an L series....

[datzenmike]

Very good, yes indeed. Being an '85 the 62mm counter bearing will have to come off and a 56mm put on. Easy to do. Or mill the L case to 62mm.

 

Nick, you will be converting a Z series engine into basically an L series and everything that entails. Still cheaper than a turbo or KA swap. If an L20B makes about 95 hp and the displacement increases by 20% then the hp should be around 115. With Weber and compression maybe 120. A header would be better than a stock L20B manifold for the increased flow. Now if you were to put a mild cam in the results would be much more apparent but the new longer stroke does lower the red line to just over 6,000 RPMs so no sense getting something that comes on at 6K. You have the displacement of a KA engine but I don't think the L head will flow as much so 130 hp is quite possible.

[NicktheMillwright]

Wow that's a lot of information. Hope there's not a test later.

 

I'll toy with this idea some more. I like that there's a plan to follow here and the parts are obtainable.

 

Say if I wanted to go the turbo charging route, which yes would cost more. What would I need to do to prep the motor.

 

I'm not disregarding the L series head and comp swap, I'll probably head down that route regardless. Just weighting my options

[Icehouse]

17 hours ago, datzenmike said:

I would put a U67 L series head on a Z24 before I would turbo it.

 

I would go the opposite way.  Frontier KA.  Plug and play.  The L sucks for exhuast gasket blow out.  All the turbo L's I've done it's been an ongoing issue.  Just really hard to keep the seal.  Any of the crossflow heads would be better as there is a better sealing with more exhaust studs in better places.  Since you are already going to have to mess with converting to Mega Squirt or some sort of stand alone might as we go with the better engine that is plug and play.  Also pick and pull is full of them.  I haven't seen a L in pick and pull in a long time.  

[datzenmike]

Nick, the other L20B head, the W58 is also alright to try. It has round exhaust ports with steel liners that can be removed. Otherwise it's the same as the U67. The W58 has a better intake and exhaust manifold.

 

If you have a running Z24 and can find a scrap L20B with it's engine brackets, it will have all the parts needed. Preferably from a truck so the oil pan will probably fit your 720 and preferably a '78 or '79 so you have the EI distributor. Bonus if it has a 5 speed but the front case from a 4 speed can be swapped onto the Z24 transmission to convert it to L series use.  

 

IF I were to turbo I would do the Z24 because easier, I would imagine. Lots more room on the exhaust manifold side. But again unless you rebuild with hardened parts and all the extras you are limited to 5-7 PSI and about 135 hp.

[NicktheMillwright]

Just out of curiosity, how much power can the 5 speed manual coupled to my 85 720 handle? 

[Icehouse]

4 minutes ago, NicktheMillwright said:

Just out of curiosity, how much power can the 5 speed manual coupled to my 85 720 handle? 

 

My buddy ran his SR20VET at 12PSI through one with a welded diff and autox tires.  He tried to avoid hard launches but it didn't die.  I would say it made 300 flywheel HP.  I'm sure the right guy behind the wheel it wouldn't last a day.  

[Icehouse]

4 hours ago, datzenmike said:

IF I were to turbo I would do the Z24 because easier, I would imagine. Lots more room on the exhaust manifold side. But again unless you rebuild with hardened parts and all the extras you are limited to 5-7 PSI and about 135 hp.

 

 

I wonder why some Nissan pistons die and some don't.  KA pistons don't like over 7psi but other engines are fine.  I had a CA20E with a turbo at 10 PSI I was beyond abusive to in my youth and it never died.  The SR20's don't mind 10psi.  I wonder if the Z limit is really 7.  

[datzenmike]

40 minutes ago, NicktheMillwright said:

Just out of curiosity, how much power can the 5 speed manual coupled to my 85 720 handle? 

 

That would be a 71B and was used in the normally aspirated 280zx so better than 150 hp....

 

 

 

 

36 minutes ago, Icehouse said:

 

 

I wonder why some Nissan pistons die and some don't.  KA pistons don't like over 7psi but other engines are fine.  I had a CA20E with a turbo at 10 PSI I was beyond abusive to in my youth and it never died.  The SR20's don't mind 10psi.  I wonder if the Z limit is really 7.  

 

The 71B was used till '86.5 on the S12 (I have an '85 CA18ET 5 speed in my 710) If the CA20 was from '86.5 or newer it would be a 71C transmission and they were much much stronger than the 71B.

 

Hyper eutectic pistons are 12-20% silicon (basically glass) and very brittle. They don't expand much with the heat so have a quieter cold start up. All N American turbo cars.. 2.3 Mustang, 2.2 Chrysler, 2.8 zx Datsun and more were all hyper eutectic pitons and were regulated to 5-7 PSI and did very well. Can't say the same for the 2.2 head gaskets but the engines stayed together. Even had warranties. Heat messes them up. End gaps close and rings break and/or ring lands. Auto ignition like a diesel melts them.    

[Stoffregen Motorsports]

It's my experience that turbo pistons are thicker in the right places. The wall thickness of a standard KA piston (which is much more advanced than an old L or Z series piston) is only about .100" at the skirt, maybe less even. The domes are thin too. The area around the ring lands is particularly vulnerable to cracking because of the ring oiling holes drilled (or cast) into the skirts.

 

Some pistons have a piece of steel cast into the skirt.

 

I had a piston break off completely at the oil ring and pulling the head revealed nothing, until I rotated the crank and that one piston didn't move. Luckily the skirt remained intact so the rod did not contact the cylinder wall.

[Stoffregen Motorsports]

20 hours ago, NicktheMillwright said:

 

Say if I wanted to go the turbo charging route, which yes would cost more. What would I need to do to prep the motor.

Custom forged and CNC machined pistons would be the starting point. They would be custom built with math already done to get the right compression ratio.

 

The block needs little prep, except maybe o-ring grooves machined into the deck, and then o-ring wire installed in the groove at assembly time.

 

Oiling is a bit of a concern too. To get more oil to the rod bearings, drill the #2 and #4 main oil galleys to 1/4" and also drill the holes in the corresponding bearings. Have the crank journal oiling holes chamfered to aid in oiling.

 

Bearing can take a beating, so nice tri-metal rod and main bearings would be required. Aluminum bearing tend to flake apart under high stress.

 

ARP rod bolts would also be a good idea.

 

All this stuff you can do in your home garage, except the o-ring grooves. With a bit of searching online, you can find out how to do the things I mentioned. Maybe the couple Nissan engine books show these mods. I can't remember if they do or not.

[datzenmike]

You can buy the tool for O ringing and do it yourself. Probably cheaper than paying for it to be done. Sell the tool after for half price.

[Stoffregen Motorsports]

Really? I never would have thought it would be a DIY thing. I'm gonna look into that one for sure.

[datzenmike]

 

https://www.summitracing.com/parts/isk-100-grm?seid=srese1&gclid=Cj0KCQjwvLOTBhCJARIsACVldV10fJDdHXlc3QFVHqlnxH6MFFLjWfZT498Ay-QsPFQPVYm8qC6ZUJkaApl7EALw_wcB

 

I think you set it up with the correct shim for depth then remove the shims and you cut down till it bottoms on the block surface.