Nissan 720 help please.

[ready2hunt]

Hi fellas! Well, I have hit a wall, and have no idea where to go from here. I have an 86 720 I have been working on. Great truck, have put TONS of work into her. Ran great, but did have some valve clatter around 4k. Well my parts truck had brand new heads on it, so I decide to swap, and you know it, the tensioner popped. 

 

I have replaced the timing set before without any issues. This time, I decided to pull the motor, and clean it up, replace every gasket, retorque all the bolts and whatnot. I set TDC prior to removal. I lined up the colored links with the punch marks on the cam and crank sprocket as seen in the photo. Now it wont run for crap. It will only start with the choke on, "manual choke, weber carb" and runs at like 4k for 7-8 seconds, then dies. I moved the oil pump a tooth each direction, with no avail. Funny thing is, if I put the crank at TDC compression, my dizzy is pointing at #1, and my cam sprocket key is at 12 o'clock. I have even manually spun the crank, and all the valves appear to be operation correctly. 

 

I'm half way back into the timing, but dont want to break the case, because then what do I do? You can see in the picture, I have everything lined up properly..... What gives???? Maybe someone didn't rebuild the head properly....? Thanks in advance guys.

 

http://i1109.photobucket.com/albums/h422/me5150/20140430_171210.jpeg

 

[datzenmike]

 

Crank must be turned clockwise up to TDC using the notch on pulley and the zero on the timing plate on the timing cover. Both cam lobes on the first cylinder should be pointing downwards with the first one (exhaust) at  8 o'clock and the intake at 4 o'clock.

 

This picture look ok IF you are at TDC compression stroke on number one cylinder. Cam sprocket should be in the #2 hole, so that looks good.

 

Now position the oil pump and distributor drive spindle so that when lookling down the distributor hole you see the top of the spindle in the 11.28 position. Note that there are two half moon shapes. The smaller one goes to the front like this picture...

 

 

Distributor goes in and should be close to correct timing.

 

Distributor should be wired this way, be sure to check ALL wires...

[ready2hunt]

Thanks for the info Mike! If what your saying about the cam lobes, that's my problem. My lobes are in probably the 5 and 7 position. Now does the cam have 2 rotation to complete? Beings it's keyed, if I disconnect the sprocket spin it 360 degrees, will the lobes be pointed up?

 

I just double checked, and yes, they are pointing downwards. A 360 rotation would put them right back where they are wouldn't it? I i spun it 180 degrees, the key would be at the 6 o'clock position.....

 

My oil pump shaft is at the 11:25 position, but from the oil pump side... But it still put the distributior pointing at the #1 contact...?

[datzenmike]

Sorry 4 an 8 would be better for the Z series. 10 and 2 is the L series.

 

Z series lobes downward.

[ready2hunt]

Well dang... I got a little excited! 

 

I'm wondering about the the oil pump again.. I have it at 11;25, but on the oil pump side. That would put the dizzy side at around 12:25.. But that's how it was the last time I replaced the timing chain.... The rotor is point at #1 on the cap.... My cap sit's a little different, not sure if that matters. Compairing it to the photo above, my #1 starts where #2E is, but goes in that order... The cap is actually stamped with which one is which.

[datzenmike]

As long as the TDC on #1 cylinder points to the two #1 plugs it doesn't matter much.

[ggzilla]

As long as when the engine is turned to TDC, the distributor rotor points to the two #1 plugs it doesn't matter much.

[ready2hunt]

Should the oil pump shift be at 11:25 on the pump side or dizzy slide? I have it set to the oil pump side. If I set the dizzy side to 11:25 and advanced my plug wires one spot it might Change things. Like I mentioned the cap is stamped 1I,3E and so on. Right now the stamp is to the right of the plug location, so it might make since to move the shaft, and move the plug wires on spot. That would put the stamp to the left of the plug location. Doesn't make since though, truck ran before and I haven't removed the plug wires from the cap.

[ggzilla]

It should be exactly like this

 

[ready2hunt]

How would ya'll read these marking's that are on my dizzy cap? Right now I have the positioned to the left of the markings, with the oil pump shaft at 11:25 on the oil pump side. 

 

Now if I moved the shaft to 11:25 on the dizzy side, and moved my plug wires to the "right" of the markings, it should line up with #1 also... 

 

But would that even make a difference?? 

 

[ggzilla]

Try it and see

[ready2hunt]

Just throwing this out there, would it matter or effect anything if I cut out the automatic choke harness? I'm running a weber with a manual choke and wasn't using it, so I cut it out... Just a thought. 

[ready2hunt]

Well, switch the dizzy and pump shaft around, nothing changed. Turned the key, I cranked and cranked for 7-8 seconds, fired up with the choke on, and reved up to around 5k and stayed there, so I shut it down.

 

My buddy is a mechanic, and offered to come look at it this weekend. He thinks by looking at the photo, that it's timed properly, but it's a vacuum leak causing it to run lean, hints only with the choke on... So we'll see.

 

Quick question, what lines can I delete, and is it worth it. I would really like to simplify the motor. It's not a daily drive, but a snow runner. I have lifted it 3" and 3". 32" tires and whatnot for hound hunting.

 

I have a weber on it, so only lines I have are the EGR, solenoid on the passanger finder, solenoid on drivers finder, and the canister.... Any advice on what can/should be removed? 

[ggzilla]

Wow somethings wrong, that is way too fast for a cold motor.

 

fired up with the choke on, and reved up to around 5k and stayed there

Yes, it needs the choke to start easily, although in warm places it may start without it.

[ready2hunt]

I understand. Issue is, I have driven this truck for months, with all the mods, weber carb and whatnot. Decided to do a head swap, and pulled the motor in doing so. The timing chain go away from me, so I cracked the case, fixed the tensioner, and timing chain, which I have done before. Put it all back together, put the engine in, and it wont run other than with the choke on, and then it rev's up to 5k on it's own, and stays there. I have dicked with the dizzy every which way, and the oil pump shaft, no avail. The truck ONLY runs with the choke on, and when it does, it runs up to 5k on it's own, and stays there. All while backfiring out the exhaust.

[ggzilla]

Revving to 5k at idle cannot be caused by timing. It is caused by air getting past the throttle blade, either by the throttle being too far open or by air getting into the engine some other way. For example large hose not connected or air jet loose.

 

And all that air needs more fuel - is why it only runs with the choke on.

[ready2hunt]

Bam! Now we're getting somewhere. That's what my mechanic friend thought. Should the intake gasket have been rvt'ed? I did not rvt the air intake gasket, it didn't look like it was before...

[ggzilla]

Put no sealer of any kind on the gasket. If it is old and damaged, replace it.

[ready2hunt]

Ok now is see not to use rvt on intake. I will start looking at the carb. Would that also result in exhaust backfire?

[ggzilla]

Yes. Air leaks can be caused by a leaking gasket, but its not the most common cause.

[ready2hunt]

Wow I have be beating my head against the wall trying to figure out how I screwed up the timing. I will start looking at ways air is getting in. Could it be vacuum related? Thanks a bunch for your help!

[ggzilla]

Air and vacuum are the same thing, just depends on your perspective.

[ready2hunt]

Turns out, the pvc valve hose came unhooked behind the motor. Seems to run Ok, but not sure if I'm happy with it. Had a piston slap when I started it, and it seem to sound a miss out the exhaust. It's kinda hard to explain. Anyways, I have another block, and am seriously considering staring from ground 0. Thanks for all the help guys!