twin plug z24 head. simultaneous plug firing? any info

[Farshid]

Dear KING RAT

I have a question ,but excuse me that I mention it here,because may be it is out of this topic concepts.

 the question: As you know ,always there is a rang for fastening torque in service manuals,now how should we chose the right and exact torque?and what is the reason for this rang declaration by manufacturer?

thank you in advance

[datzenmike]

I don't know. Easier I guess. Anywhere in the range is good enough rather than going to extremes to try and hit an exact number. Head bolt are 54 to 61 ft lbs. 

[Farshid]

OK.thank you very much.

[Farshid]

dear guys

do you have the z24 engine mechanical service manual pdf file.

thank you in advance

[datzenmike]

Maybe on line or check e-Bay for a  North American '84 720 truck FSM (factory service manual)

[Farshid]

Hi,dear guys

there is a question for me:some guys apply Copper spray on head cylinder and cylinder  and  gasket.

what is your point,about that?

and is it applicable for graffiti gasket like Z24?

or it is just for MLS gasket?

 

thank you very much

[datzenmike]

Copper spray is for filling/covering any small imperfections in the two surfaces being joined with a gasket. Almost always on heads that have had sealing problems in the past. It's also used on solid copper 'gaskets' that are used on high compression engines or with turbos and SC applications that are under extreme pressure. The copper gasket does not compress and seal as well and requires scrupulously clean and level surfaces to seal properly.

 

For a stock low compression engine with clean flat surfaces copper coating is not needed and the gasket will seal any small imperfections. You can use it sparingly if it makes you feel more comfortable but Nissan didn't use it when the engine was put together.

 

 

The Z24 engine is known for blowing the head gaskets every 100K miles. Nissan recommends that every tune up, on a cold engine, that you loosen ONE bolt and tighten to 60 ft lbs then go to the next bolt and do the same till all are re-tightened. Only one bolt at a time and in any order you like. This keeps the gasket properly compressed and less likely to blow out.

[Farshid]

13 hours ago, datzenmike said:

Copper spray is for filling/covering any small imperfections in the two surfaces being joined with a gasket. Almost always on heads that have had sealing problems in the past. It's also used on solid copper 'gaskets' that are used on high compression engines or with turbos and SC applications that are under extreme pressure. The copper gasket does not compress and seal as well and requires scrupulously clean and level surfaces to seal properly.

 

For a stock low compression engine with clean flat surfaces copper coating is not needed and the gasket will seal any small imperfections. You can use it sparingly if it makes you feel more comfortable but Nissan didn't use it when the engine was put together.

 

 

The Z24 engine is known for blowing the head gaskets every 100K miles. Nissan recommends that every tune up, on a cold engine, that you loosen ONE bolt and tighten to 60 ft lbs then go to the next bolt and do the same till all are re-tightened. Only one bolt at a time and in any order you like. This keeps the gasket properly compressed and less likely to blow out.

thank you very much,KING RAT for your information.I appreciated that.

truly yours

[Farshid]

On 6/10/2014 at 5:17 AM, datzenmike said:

It takes a small but finite time to burn the fuel and air. The ignition point is set so that the expanding hot gasses reach their peak at about 15 degrees after TDC. This is the most advantageous point to transfer energy to the down moving piston. On a single plug engine it may be around 10 degrees BTDC. Two plugs mean two points of ignition so the fuel and air will burn completely in a shorter time, so you would time it to light later to hit the 15 degree sweet spot. A dual plug Z24 timing is about 3 degrees. If the timing is set at 3 and one of the plugs isn't firing then you are actually set (7 degrees) too retarded.

 

Most Z24s have an exhaust side plug shut off. When activated the distributor has a built in advance for the single plug operation so that power is not lost.

 

Running single plug won't hurt anything, as evidenced by having driven 100K, but it is very inefficient and would lack power and good mileage. There's no way to know that the exhaust plugs were not firing for the whole 100K. Usually the first fuse on the far left of the fuse box blows and this is what shuts off the exhaust plugs. 

dear king rat

I installed the twin distributor recently and check the white wire logic.

when I connected  it to ground there is not any cut off in exhaust  side coil,but when I connected it directly(with out any capacitor)to positive potential,it works ,mean that shot off the exhaust side.and also there is not any change in timing that i checked by timing synchronous timing gun.

truly yours

 

[datzenmike]

Good to know. I wasn't sure if grounding it was what made this work. The timing should change to advanced with single operation.

[Farshid]

8 minutes ago, datzenmike said:

Good to know. I wasn't sure if grounding it was what made this work. The timing should change to advanced with single operation.

as you know there is already the big question for me exist that how this module can shift the timing lonely,because it need in electronic some delay circuits such big capacitance.and can you send me some electrical diagram more than the previous one that is in this page.

and also I connected the white wire by one and two 0.68 micro Farad capacitor to Batt and ground,Nothing happened.

and how can i send for you some pics?

[datzenmike]

The 280zx matchbox EI distributor has ignition retard. The ECU uses input sensors (maybe a knock sensor) and tells the module to retard or not. Here's what's inside it.

 

 

The Mileage option 720 with the Z20 engine also has an ignition retard circuit with a knock sensor and uses the same distributor as you have.

[Farshid]

14 minutes ago, datzenmike said:

The 280zx matchbox EI distributor has ignition retard. The ECU uses input sensors (maybe a knock sensor) and tells the module to retard or not. Here's what's inside it.

 

 

The Mileage option 720 with the Z20 engine also has an ignition retard circuit with a knock sensor and uses the same distributor as you have.

thank you very much,I will check them all.

[datzenmike]

The timing on the Z24 is around 5 degrees with dual plugs. This is partly the efficient hemi design but mostly the faster burn time from having two plugs. In comparison the L series is 12 degrees. When the dual plugs are switched to single operation the engine will act retarded because the spark is too late. The module advances the ignition timing to compensate for this loss of power. Or is supposed to. I'm guessing 3-5 degrees more, the manual does not say.

 

Myself I would just run dual plugs at all times

[Farshid]

46 minutes ago, datzenmike said:

The timing on the Z24 is around 5 degrees with dual plugs. This is partly the efficient hemi design but mostly the faster burn time from having two plugs. In comparison the L series is 12 degrees. When the dual plugs are switched to single operation the engine will act retarded because the spark is too late. The module advances the ignition timing to compensate for this loss of power. Or is supposed to. I'm guessing 3-5 degrees more, the manual does not say.

 

Myself I would just run dual plugs at all times

thank you in advance dear king rat.yes it seems that if  I can not arrange the auto advance system( ofcourse  if exist and can be performed by single magnet madule in  this distributor) just set it to 5 degree and  permanet dual situation.

I appreciated from your attention.truly yours.bro

[datzenmike]

I'm saying that in the Z24 the timing  is fine if you leave it in dual plug mode at all times. Nissan says single plug operation is "to reduce engine noise under heavy load conditions" so what's a little noise?  

[Farshid]

9 hours ago, datzenmike said:

I'm saying that in the Z24 the timing  is fine if you leave it in dual plug mode at all times. Nissan says single plug operation is "to reduce engine noise under heavy load conditions" so what's a little noise?  

yes you are right.I am agree with you??

[datzenmike]

Good. Sometimes I mix up who I'm talking to.

[Farshid]

hi dear guys and dear king rat

 coming back

 

I have problem about losing horse power of z24  engine in high altitude,is there any compensatory mechanism for that like p40

6 cylinder carburetor,HAC<high altitude compensator????

and so double vacuum advance in distributor.

 

truly yours

farshid

 

[datzenmike]

Hi farshid

 

You have to expect some power loss in the mountains because the air is thinner as you go higher. With less air the carburetor will mix too much fuel and it will run richer than needed. If running at higher altitude for a long time you can put smaller jets in the carburetor to reduce the fuel consumption, but it still won't run the same as at sea level.