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#21 wayno

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Posted 20 November 2017 - 02:52 PM

I talked to my machinist today and when I said 11 to 1 he made a face.

I also mentioned compression test and he said the same thing, one cannot get the compression ratio from a compression test, all you can get is knowing your valves are good and that the cylinders are even.

He told me to buy a small amount of premium gas(92) and drive it to see if it knocks, if it does drain the tank and buy better gas(100ish), repeat, if it knocks again buy better gas again(110), repeat, if it knocks give up as the gas they sell isn't good enough anymore.


 

 


#22 datzenmike

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Posted 20 November 2017 - 03:18 PM

Pinging is pretty much the same as dieseling. I'st heat induced So anything the reduces heat will help.

 

 

A colder range spark plug, but not so cold it doesn't 'self clean' itself. Read the plugs.

Reduce the timing slightly, try 10 BTDC

Cold air inlet from in front of the rad support to the carb or air filter. AVOID rad warmed air.

Reduce radiated heat from the exhaust manifold. Paint intake and exhaust manifolds silver, use a heat shroud.

Fuel return line to keep cooler gas from the tank circulating past the carb. Cooler gas will need to absorb more heat to evaporate. 

Oil cooler will lower oil temps and draw away heat from internal engine parts that the cooling system doesn't reach like the undersides of the pistons and the valve stems.

Cautiously try a 175 F thermostat. This is not the correct way to tame pinging but it works. The engine is more efficient closer to 195F. But pinging is worse.

Water injection. Windshield washer bottle (with cheap tap water) and hose with restriction to carb opening, with on switch set for full throttle. Or after market. Heat is absorbed by evaporation into steam. Use washer anti-freeze for winter or for extra cooling effect from the alcohol. Added benefit is the steam cleaning of the combustion chamber removing carbon and deposits that can cause hot spots.


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#23 wayno

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Posted 20 November 2017 - 03:49 PM

Has anyone ever blew the engine spraying water into the carb with a window washer bottle while driving the vehicle?


 

 


#24 datzenmike

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Posted 20 November 2017 - 05:27 PM

It would take a lot of water to hydro lock a running engine. This is why I also said 'restriction'... like a carb jet. You would have to trial and error to get just enough to tame the pinging.

 

I've done the 'coke bottle tune up' before. Get the engine super hot, even put cardboard in front of the rad. Rev it up and dribble water from a coke bottle into the carb. The engine will slow down quite a bit so open the carb more and more as you slowly pour it in. I noticed the temp gauge dropped down to the bottom of the warm area. So let it warm up and continue. You've all seen piston tops when a head gasket has blown. The piston looks like it just came out of the factory.


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#25 flatcat19

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Posted 20 November 2017 - 08:41 PM

Is there any real definitive answer as to which Z20 came with what piston/rod combination?


I just got a PM from a member that stated he had a Z20 from an 81 200sx. 8 plug model.

I've been thinking about this ever since PM was received.
Thinking about switching plans if this is in fact a long rod/flat top motor.

You can't hang if your nuts haven't dropped...it's physics


#26 datzenmike

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Posted 20 November 2017 - 08:55 PM

I have had an '80 and an '81 200sx. Sold or gave away the piston/rods long ago. They were the 6" or 152.5mm long rods.

 

Only the California emissions equipped 200sx got the 8 plug head in '80. For '81, all engines were 8 plug. In Canada they were all 4 plug till the engine changed to the Z22E in '82.


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#27 wayno

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Posted 20 November 2017 - 09:08 PM

The more I talk to people that know about engines the more I am thinking that building mine was a waste of time.

It is sounding like I will not have any more power than an L20b, but I really don't have much money into the engine, just time.

The machinist wasn't really impressed about it being a longrod block when I talked to him, he said the race guys build a chassis, then they put the largest block that will fit into the chassis, then they put the guts into the block that will give them the most power, basically I walked away with the age old saying, "there is no substitute for displacement", more CCs mean more power, all I really have is a Z20b.


 

 


#28 datzenmike

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Posted 20 November 2017 - 09:33 PM

A long rod may move the torque range around a bit but really? it doesn't mean much. Long rods allow the piston to decelerate approaching TDC and accelerate away faster but travel past TDC more slowly taking some of the stress off the parts. A slower moving piston right after TDC might capture more of the expanding pressure of the burning fuel/air when it's at it's highest. But this is no real gain for the average guy who expects it to be 'faster' or 'more powerful'. It might be worth more than a few hp if you raced.

 

With an L head you do have built in compression increase. The fuel burns faster and the explosion more intense. For every point of compression increase maybe 5% more power extracted form the fuel.


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#29 wayno

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Posted 20 November 2017 - 10:12 PM

With that thinking my 10.9 compression ratio LZ20 with flat top pistons should have 10 percent more power than my 8.9 compression ratio L20b block had with dished pistons and the same head, but I have a feeling it is not going to turn out that way.


 

 


#30 flatcat19

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Posted 20 November 2017 - 10:30 PM

Long rods are less prone to vibration.

Vs. an L20B? Minimal, I'd bet. But it is still what it is.


Higher comp, even if slightly, is still more efficient. Except you may be using a fractional amount more of gasoline.

You can't hang if your nuts haven't dropped...it's physics


#31 datzenmike

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Posted 21 November 2017 - 06:10 AM

Higher compression extracts more usable work from the stronger 'explosion' of the fuel air as it burns. Peak cylinder pressures are much higher and push down on the piston more. But you have to be on the ragged  edge of pre ignition. Gas is gas... but higher octane allows you to compress it more without it self igniting. That 5% is considered as being 'on a good day' and under ideal conditions. As you get closer and closer to perfect that 5% becomes 4% and then 3% and so on.   

 

Long rods also reduce frictional side loading on the piston. All these are small but actual gains that added together total significant amounts..... for a race engine, where any advantage can get you into the winner's circle. For a street engine? it's hard to justify for a 5% gain you can barely feel on the ass dyno. You know it's there but it doesn't show like bolting on SUs.    


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#32 Stoffregen Motorsports

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Posted 21 November 2017 - 08:47 AM

Why install a modern stereo when my original AM radio works fine?

 

Why upgrade to modern radials tires when the old bias ply tires still hold air?

 

If long rods are only good for racing engines, then why did Nissan make the switch in the 80's?



#33 datzenmike

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Posted 21 November 2017 - 12:30 PM

I'm not aware they did but it was likely pollution related to lower emissions than the blinding amounts of horse power released. In the same decade they had to switch over to EFI and crank angle sensors to refine the combustion process even more. Next would be better economy through reduced friction. Remember these were car and truck engines used for town and highway driving not driven much above 3-4 K. Actual power gains, if any, would be very small.

 

As the Z20 and the L20B block and crank shaft are identical it would be interesting to see a Z20 long rod compared to an L20B with flattops using the same head and cam.  


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#34 wayno

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Posted 21 November 2017 - 02:58 PM

I for a fact will be able to tell if it is different, but different than what it was before when it was on the L20b block, not sure as it has an RV cam in it, and the cam was likely timed wrong, that fact alone throws a wrench in the gears, when I removed the head I now have on the LZ20 and then I put a 219 head on it, it didn't seem like there was that much difference, then I went out later after I seen them photos of a properly timed cam and timed the cam properly, it did have more power, but the engine might have had more power with the head/cam that was on it before if the cam had been timed properly.

I did this LZ20 because I thought the longrod/RV cam might be a good combo/revver, when the issue likely was the cam being timed wrong.

What I planned to do was start the engine in my future work truck frame/chassis using this engine to sort out the motor mounts, ect. to get it ready for the LZ23, but it appears that I will need to drive the LZ20 to know anything, that will slow things down and make them harder, I planned on dropping the cab onto the chassis while the engine/transmission were in place, now I will have to remove the LZ20 engine to put in the LZ23 that it has in it now as I need the grunt/torque it has.

This LZ20 was just a build for fun engine to see what would happen as I had every part needed for the most part already, even the headgasket.


 

 


#35 distributorguy

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Posted 22 November 2017 - 05:45 AM

Wayne, you have a great recipe, but like any recipe if you don't follow through with ALL the ingredients, its not going too turn out well.  This is one that won't work if you put a stock worn distributor in it.  A heavy stock flywheel also won't allow it to perform as it should.  Shave that flywheel down to 16 lbs and have it balanced.  Then you need a distributor set up to run at 14-16 degrees BTDC at idle with an advance curve that won't ping like crazy at 2700 rpm.  Unshroud the valves in the head so they can breathe clear out to the cylinder walls.  Remove anything remotely close to a sharp edge on the valves, in the chamber, and lightly bevel the edge of the bore.  Make the edge/head of the exhaust valve round.  Then time the cam to 107/108 Intake CL and you'll have a strong puller without needing race fuel.  You will likely need premium or at least non-oxy real fuel.  



#36 Stoffregen Motorsports

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Posted 22 November 2017 - 02:22 PM

I'm not aware they did but it was likely pollution related to lower emissions than the blinding amounts of horse power released. In the same decade they had to switch over to EFI and crank angle sensors to refine the combustion process even more. Next would be better economy through reduced friction. Remember these were car and truck engines used for town and highway driving not driven much above 3-4 K. Actual power gains, if any, would be very small.

 

As the Z20 and the L20B block and crank shaft are identical it would be interesting to see a Z20 long rod compared to an L20B with flattops using the same head and cam.  

You're not aware they did? The Z20 came with long rods, proof that even the economy minded, middle of the road, pencil pushing engineers thought it was a good idea.

 

Long rods themselves are not the answer for every engine, but when taken in context of rod to stroke ratio, sometimes longer results in better cylinder filling and more horsepower, and, as you say, better economy.

 

I've said it before, but I guess I'll say it again, long rods in most L motors make more horsepower across a broader RPM range than otherwise identical engines. It's the flattening out of the curve that makes them worth it.

 

And this term "race engine". What does that mean? I bet a third of the guys here on Ratsun have what you might call a race engine in their street cars. The 2200 in my last 510 street car made more than double the original horsepower, and almost triple what the 510 came with, but that didn't make it a race engine. It was very well mannered around town and ran well on pump gas.



#37 wayno

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Posted 22 November 2017 - 04:32 PM

Wayne, you have a great recipe, but like any recipe if you don't follow through with ALL the ingredients, its not going too turn out well.  This is one that won't work if you put a stock worn distributor in it.  A heavy stock flywheel also won't allow it to perform as it should.  Shave that flywheel down to 16 lbs and have it balanced.  Then you need a distributor set up to run at 14-16 degrees BTDC at idle with an advance curve that won't ping like crazy at 2700 rpm.  Unshroud the valves in the head so they can breathe clear out to the cylinder walls.  Remove anything remotely close to a sharp edge on the valves, in the chamber, and lightly bevel the edge of the bore.  Make the edge/head of the exhaust valve round.  Then time the cam to 107/108 Intake CL and you'll have a strong puller without needing race fuel.  You will likely need premium or at least non-oxy real fuel.  

The head on it has less than a couple thousand miles on it, the block has unknown miles but I listened to it run in a shop, it sounded alright as a Z20 with a carb, the guy had nice cars in that shop, one was a 1970ish GT 6 cylinder Triumph as I recall.

I am just going to see if it will run, I will be out some gaskets and time, the rest was just sitting around here taking up space, now it is all in one spot as the engine is fully assembled and has been for a few weeks now.

I didn't understand half of what you said above, I believe that having the distributor advance less than stock is likely a good idea, but how to do that is rocket science to me, likely it has something to do with stronger springs(a guess), I will not lighten a flywheel unless I know it is going to work, then I might spend money on that.

As for the un-shrouding of things, well that's more rocket science to me, it has the stock valves with hardened seats, it has a brand new RV cam in it, my machinist told me not to do it, but I thought it might breath better, he was right, I lost torque which I needed, so I had him rebuild my first super head(big valves/stock cam/port matched to SU manifold) and I put together my first LZ23, this head stayed on the L20b engine and that was installed in my 520 ute project, didn't like the cam in that either, so I had the shop rebuild the 219 head I had and I installed that on the L20b, it then was slightly better off the line, but then DMike posted that photo of a properly timed cam, so I went out and re-timed that cam and the engine has more power now, and it drives better all around, I also re-timed the cam on the work truck, it has slightly more power, but it uses WAY LESS GAS, that is what I have noticed the most, way better mileage.

When you start throwing numbers at me about cam timing, well that is French to me, I don't speak French, if I can get it to run at all I then will start changing things, if it will run and move the vehicle down the block and back, I will then think about doing more to it, I have no idea what timing the cam to 107/108 intake CL is.

This is the engine.

DSCN7275.jpg

 

DSCN7276.jpg

 

DSCN7277.jpg


 

 


#38 datzenmike

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Posted 22 November 2017 - 06:48 PM

You're not aware they did? The Z20 came with long rods, proof that even the economy minded, middle of the road, pencil pushing engineers thought it was a good idea.

 

Long rods themselves are not the answer for every engine, but when taken in context of rod to stroke ratio, sometimes longer results in better cylinder filling and more horsepower, and, as you say, better economy.

 

I've said it before, but I guess I'll say it again, long rods in most L motors make more horsepower across a broader RPM range than otherwise identical engines. It's the flattening out of the curve that makes them worth it.

 

And this term "race engine". What does that mean? I bet a third of the guys here on Ratsun have what you might call a race engine in their street cars. The 2200 in my last 510 street car made more than double the original horsepower, and almost triple what the 510 came with, but that didn't make it a race engine. It was very well mannered around town and ran well on pump gas.

 

 

If long rods are only good for racing engines, then why did Nissan make the switch in the 80's?

 

Nissan switched? or they tried a few?

 

Because the Z24 and the KA series has the same rod/stroke ratio of the old L18.

 

The L20B is 1.7 and the 'long rod' Z20E (same crank shaft) is 1.77.... hardly anything to write home about.

 

The 'long rod' Z22E rod/stroke ratio is lower than the much much older L18. It only 'looks' like a longer rod, but they used the L20B rod first when they should have gone with the longer to begin with. All they did was put the correct length rod on it.

 

Only the L16 has a rod/stroke of 1.8 with the Z20 and L20B next closest.

 

 

Everyone says that long rod stroke ratios make more top end power but fail to say how much. This is probably true of 'racing engines' that are quite modified and at high RPMs but Nissan does not build them for that. They build car and truck engines that run around 3K. Just how much extra does a long rod engine make at these levels 3 HP? 

 

A third of Ratsun members have 'race engines'? If you mean a Weber and a closed chamber head, then yes. Far and away the majority of members have close to stock engines, they run the best. If there are 'race engines' out there (other than a swap) it's more like 3% (we have, and have had, lots of members)


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#39 Stoffregen Motorsports

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Posted 23 November 2017 - 08:00 AM

I'm not going to win this argument.

 

I won't claim that long rods are the answer to world hunger, but when building an engine package that dots all the i's and crosses all the t's, everything needs to be addressed. A Ford exec famously said about the K-code 289, something to the effect that these are for people who want no stone left un-turned in the hunt for power.

 

Don't knock it til you've tried it. More importantly, don't discourage others.



#40 Stoffregen Motorsports

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Posted 23 November 2017 - 08:10 AM


I didn't understand half of what you said above, I believe that having the distributor advance less than stock is likely a good idea, but how to do that is rocket science to me, likely it has something to do with stronger springs(a guess),

 

This mod is probably the most important to ensure a long engine life. It's very easily accomplished by shortening the slots in the distributor cam so the mechanical advance is limited. You can weld the holes a tiny bit and file them smooth to get the proper total advance.

 

Springs should not be the only thing that limits total advance.

 

I don't know what Jeff charges to go through a distributor, but I bet it wouldn't cost more than a hundred bucks to get the advance limited.  If you can find a SSS distributor cam, that's a bolt in operation. When I was at Rebello, we charged about $150 for a full distributor recurve and rebuild.