first 720

[720driver97]

Hi everybody I'm new to the forum, I just got a 83 Nissan / Datsun 720 I plan to restore and I have some questions like what can I do to get more power from the z24 might make it sort of a race truck, also why are they Nissan and Datsun mine only has Nissan emblems

[Lockleaf]

Power - first step people take is usually new carb. Weber 32/36 is a great upgrade that provides more power but is still decent on fuel mileage. Weber 38/38 will provide more power but murder fuel efficiency. Headers are basically a waste of time on these engines because the valves run out of cfm before the exhaust manifold does. But a small step up in exhaust diameter and a high flow muffler would be beneficial.

 

Aftermarket cams are available if you want to go that route. All of this assumes your engine is running top notch. If it's not, spend your money there first.

 

The Nissan/datsun thing is just an element of Nissan history in the early 80s. Nissan was selling cars under the datsun name, decided to sell them under the Nissan name, so they double badged for a couple years then dropped the datsun name completely. Cars and company did not change at all, just emblems. Google will offer the detailed version of that story.

 

Welcome to Ratsun. Post pics or it didn't happen!

[datzenmike]

It was always Nissan but when they entered the North American market in the late '50 it was decided to distance themselves from the WW II Japanese Nissan name and revert to an even older name from the early 30s. By the late 70s this was, in hind sight, probably not a great move and phased the Datsun name out. Many '79s had DATSUN by NISSAN  on the DATSUN emblem and over the next few years replacing it with the NISSAN only logo. The '85 300zx was probably the last year with a DATSUN and a NISSAN (one on each side) of the rear of the vehicle. The '84 Maxima also had this badging. End of an era.... 

 

It's fine with me as I have a car name that is no longer made and some people ask what's a Datsun? It's like a De Soto, a Studebaker or a Rambler and in 30 years like a Pontiac or Oldsmobile. 

[720driver97]

Alright thanks for the info on the Nissan/Datsun thing , as for the power I have the engine stripped down to the block for a rebuild I have the Webber carb but not sure which one I have, what is a good cam to use? I have heard of someone putting in pistons from a 240zx what r the benefits from that and will they fit? PS: sorry I have a lot of questions

[datzenmike]

S13 or D-21 Hardbody truck KA24E pistons are the same size but almost flattops. Just a piston change makes 9.52 compression. This is about one point of compression increase so 4-6% increase. On a 100 hp Z24 that 4-6 hp at full RPM..... hardly worth the bother is it? But you also have to run higher octane and it may ping if the timing isn't retarded.

 

Biggest bang for the buck is a differential swap. I assume you have a 3.70 or 3.889 differential ratio? It's stamped on the engine tag under the pass side hood hinge on the inner fender. On lower right of tag it may say HF37 (3.70) or HF38 (3.889) Search around wrecking yards for the third member from an older truck. The '82 2wd automatic had a 4.11. A higher number will allow the engine to rev higher at the same speed as the lower number gear. Higher revving means you are making more power at the same speed and accelerating away faster. Top speed will be reduced and mileage will suffer but it will with a cam too. You might get one for free or up to $100.

 

Next would be a new Weber 32/36 carb kit just under $300.

[Gradyfest]

Welcome to Ratsun! Always good to here a Datsun fell into good caring hands. As long as your questions aren't too stupid, the "trolls" seem to remain at bay, so fear not my friend. It is however MANDATORY to post photos of your vehicle, or the "war lords" of this site hack your bank account and bleed you dry with charges from questionable businesses. You don't want to go there... I think 72 hours is what's written in the rules that you agreed to while making your account... Can't wait to see it!

[720driver97]

What cams r people using

[Scurrvy]

Welcome to the pack! Pics!!!!'

 

I miss my 84 720 kingcab I had, It had both Datsun and Nissan.

[datzenmike]

What cams r people using

 

I purposly left the cam out. The Z series heads are not good breathers. By design the valves face each other and are laying over on their sides quite a bit. The lower edge of the intake valve is close to the piston top and too much lift will contact either the piston or the exhaust valve. This limits the 'size' of the cam that you could ever find for it. A diff and carb change leaves the engine un-modified so it's reliablilty and drive ability remain unchanged.

 

On the plus side the Z24 has dual plugs and a cross flow hemi head design.

[720driver97]

Is there a different head that would help more that would fit?

[Lockleaf]

Yes, it's quite common to fit an L series head to a Z block. There is lots of info on building LZ motors on here if you search around. Only really worth it if you plan on taking the motor above 4500rpm often. My 4x4 720 never sees those high rpm, so I've never had an issue with it running out of breath. If you plan on running above that mark though it can turn in to a very worthwhile swap. 510 guys love it because it combines the larger displacement and torque of the Z with rpms of the L.

[datzenmike]

It's more common to have an L series engine and simply keep the head and substisute the Z series block. The displacement goes up but not much else needs changing. If you have a Z series, the L head will be leaning to the left and intake and carb off level and there isn't much room on the driver's side for the manifolds and the big forward moounted brake booser. Here's abetter idea...

 

 

Get a KA24E 12 valve head and swap it on. The KA sits with the same orientation as the Z series and is also a cross flow. It is EFI, so either make up a tube intake and run motorcycle carbs or get the truck intake which is throttle body, make a block off plate and drill and tap for the stock Z24 carb..

[720driver97]

so from the sounds of it the KA24E head is the best and the Z24 block is the best , so what about the pistons and crank shaft whats the best there?

[84720FourWheel]

Z24 crank and pistons work fine. Ka pistons raise compression enough to need premium gas but not enough for any significant power gains

[_chiefjt]

I went with the Nismo cam for the z24. The specs are 406/272 and after installing it and driving I can feel the power difference over the stock cam.

 

After break in and a little tuning, the idle was breathing much faster. After driving, throughout the rpms I noticed the powerband moved upwards of around 5k- 5 1/2k as was the stock cam was around 4k-4 1/2k. I didnt lose any bottom end and feels happy when I'm on it. Now the power doesnt cap out at 5k, thats just the sweet spot. Don't bash me but I take it up to 7k when I'm racing. I feel thats the peak output without over revving and still have enough power to pull in the next gear. BUT, just because its Nismo doesnt mean its an all out racing cam. I installed this cam in particular because it was cheap, not too big because I daily my truck everyday, and was an upgrade to stock. I figured since Nissan is the one who made the cam it must be an upgrade to stock.

 

My setup is a stock z24 with a nismo cam, weber 38, 4:38 rear end and everything else is stock. And run on 91 octane

[datzenmike]

so from the sounds of it the KA24E head is the best and the Z24 block is the best , so what about the pistons and crank shaft whats the best there?

 

If going with KA head use the KA pistons. The KA head has larger combustion chambers so your compression would drop. KA pistons have almost no dish so the compression would be retained. The KA head also has an oil drain back hole that must be sealed as it would connect to a water jacket opening in the Z series block. This would basically give you a KA engine.

[720driver97]

OK thanks, another question I have is I have a 4wd truck and I want to make it 2wd I have a 2wd transmission to put in but will the drive shaft be long enough or do I need a longer one?

[720driver97]

Also how far can I lower the torsion bars in the front?

[Rhino13]

I got about 2 inches and there was about 1/8 inch left on the threads. I ended up raising it back up to fit 225 tires that I later got, but it sat really low on the 195's I originally had. Here's how mine sits with roughly a 1/2 inch of threads on 225's

[720driver97]

OK thanks

[datzenmike]

The 4x4 by design sit taller than the 2wd. Cab and body mounts are higher on the frame than the 2wd. The 4x4 frame is different than a 2wd so I don't know how well a longer drive shaft will reach from the transmission all the way to the rear end.... there may be a cross member in the way. It only steers and handles well is a narrow adjustment range because of the front differential and axles, so lowering it is limited. If you want lower, a 2wd is better than trying to make it something it isn't. 

[720driver97]

How far do u think it would drop?

[datzenmike]

You might get it to look like a 2wd truck at normal height..

[Rhino13]

The 4x4 by design sit taller than the 2wd. Cab and body mounts are higher on the frame than the 2wd. The 4x4 frame is different than a 2wd so I don't know how well a longer drive shaft will reach from the transmission all the way to the rear end.... there may be a cross member in the way. It only steers and handles well is a narrow adjustment range because of the front differential and axles, so lowering it is limited. If you want lower, a 2wd is better than trying to make it something it isn't.

I thought the 4x4 had quite a few differences to account for clearances, good to know that's true.

 

Yeah I'd hold on to that 4x4, and get a 2wd to lower if you want it really low. If you're just lowering with torsion bars and blocks, I bet you'd love having that 4x4 to drive a few days out of the week. It gets very bumpy with almost no play in bump stops.

[720driver97]

Guess I will keep it the stock hight then