NAPS engine questions?

[RacnJsn95]

I read it somewhere before, but what is the purpose of having 8 plugs? Everything burns better? Do both the plugs in a cylinder fire at the same time? I've never seen a NAPS rotor, so I dont know...

 

I picked up a Z22 long block for $200 bucks. It's in pretty decent shape... I've decided to stick it in my 510, so my crazy engine mounting project is kaputz...

 

What's a stock Z22s have for compression? It came out of an 82 720 2wd auto. I'm wondering if maybe I could make blocking "plugs" and plug off 4 of the spark plug holes on either side of the engine? Then just use the NAPS head, and take advantage of the cross-flow design. Would that make a difference running on 4 plugs instead of 8?

 

Or maybe rig up a Megajolt system for one side, and run a stock L distributor on the other... I wonder being able to control when the second plugs fire would make any power increase, depending on when they fired?

 

Just some ideas...

[RacnJsn95]

Double post... delete this :)

[datzenmike]

The NAPS system is designed to run large amounts of EGR, so much in fact that a single plug engine would run very rough at idle when properly set up. Dual plugs shorten the burn time so less advance is needed, just look at the timing for a NAPS it's 3 degrees on your Z22 compared to the L20B's 12 degrees. This lessens the time when oxides of nitrogen are produced. Two plugs are always better than one, even race engines have this and there is a slight MPG increase as a side benefit. Both plugs fire together, all the time, except Canadian models that have a vacuum switch to run single plug under heavy load/high speed. All manuals say this is to reduce engine noise??? I don't get it. Americans don't get noise or they don't care??? When in single plug mode the distributor also adjusts the timing ahead to compensate for the now longer burn time.

 

The Z22's compression is 8.5 to 1. Don't use single plug for the reason above. Make sure that the cap/rotor/wires/plugs are new or good. This system relies on everything working correctly just like an L series. There are 8 plugs on the cap with very little room for them and poor cap and wires will cross fire. The EGR can be disconnected but keep the dual plugs. The Z22 produces almost 120 ft. lbs of torque at 1,800 RPMss. The L20B has to rev to 3,200 to make just over 100 ft. lbs. This Z22 will have all it's torque at low speed. It should out pull the L20B but run out of steam sooner in it's stock configuration. Many truck (720) use the Weber carb to improve on this.

[RacnJsn95]

Thanks for the info mike! Man... Almost makes me want to just put this z22 in my 620, and pull that L20b out for the 510.

[datzenmike]

Don't forget the NAPS motor is tilted more to the driver's side than the L, so you will need a NAPS tranny too.

[pl521sss]

The NAPS system is designed to run large amounts of EGR, so much in fact that a single plug engine would run very rough at idle when properly set up. Dual plugs shorten the burn time so less advance is needed, just look at the timing for a NAPS it's 3 degrees on your Z22 compared to the L20B's 12 degrees. This lessens the time when oxides of nitrogen are produced. Two plugs are always better than one, even race engines have this and there is a slight MPG increase as a side benefit. Both plugs fire together, all the time, except Canadian models that have a vacuum switch to run single plug under heavy load/high speed. All manuals say this is to reduce engine noise??? I don't get it. Americans don't get noise or they don't care??? When in single plug mode the distributor also adjusts the timing ahead to compensate for the now longer burn time.

 

The Z22's compression is 8.5 to 1. Don't use single plug for the reason above. Make sure that the cap/rotor/wires/plugs are new or good. This system relies on everything working correctly just like an L series. There are 8 plugs on the cap with very little room for them and poor cap and wires will cross fire. The EGR can be disconnected but keep the dual plugs. The Z22 produces almost 120 ft. lbs of torque at 1,800 RPMss. The L20B has to rev to 3,200 to make just over 100 ft. lbs. This Z22 will have all it's torque at low speed. It should out pull the L20B but run out of steam sooner in it's stock configuration. Many truck (720) use the Weber carb to improve on this.

 

So Mike, converting a Z22 to single plug is not a good idea due to EGR.

Can the EGR be disconnected then use L20b dizzy to get away with dual plugs?

Or how about those non California model Z22 that came with single plug cylinder head. Are those much less EGR on them to run single plug?

[datzenmike]

The dual plug is not a bad thing with, or if you prefer, without EGR. There are some advantages to dual plugs and many makers would love to have them if they could fit them in. Faster burn time, cleaner more complete combustion, less advance. Forget EGR, just disconnect it and run without.

[Bamadawg]

Don't forget the NAPS motor is tilted more to the driver's side than the L, so you will need a NAPS tranny too.

 

Can you clarify the "if you use X, you gotta use X transmission"

 

If I have a Z-block in my truck now, but I wanna add the L head to make a LZ/hybrid... can I keep my Z tranny, or I have to find a L-series tranny. Tranny should match the head... either Z or L.

 

Thanks...

Nate

[datsunaholic]

Tranny (and motor mounts) should match the head- the head dictates how you "lean" the engine (with an L-series you lean it towards the battery side because all the manifolds are on the driver's side... the NAPS-Z has almost no lean due to the intake being on the battery side. If you mix/match you end up putting excess stress on the mounts as they fight each other, and if you don't lean it properly the carb won't be level.

[RacnJsn95]

That's good to hear... So if I dump an L head on it, I can use my same L trans, and motor mounts. Luckily I also ended up with the motor mounts for the Z engine, but here lies the problem with using a Z trans: They're few and far between here. I would have got the one that this engine came from, but it was an auto.

 

Next problem: Would the Z truck 5 speed be longer than my L truck 4 speed? I thought I read that they are. If so, anyone know how much? Problem with that is if I swap to the Z engine/trans that I will either have to shorten the drive shaft to the transfer case, or if it's a lot longer I may have to move the transfer case back, and shorten the rear drive shaft.

 

Possible solutions? I would actually like to get rid of the divorced transfer case all together, and just run the trans/transfer case from a 720 4x4, but I' can't remember if the 720 front diff is offset, and if so, which side is it off set to? The only downside to ditching my current transfer case, is that I will loose the 2-low capibility, which I really like, and it comes in handy.

 

I was also doing some reasearch, and it looks pretty hard to get a header for a Z series engine... But it looks like you could possibly use a header from a KA24e, flanges & bolt pattern look the same to the naked eye, but I dont have a head or gaskets to measure... Can anyone confirm this?

[datzenmike]

Next problem: Would the Z truck 5 speed be longer than my L truck 4 speed? I thought I read that they are. If so, anyone know how much? Problem with that is if I swap to the Z engine/trans that I will either have to shorten the drive shaft to the transfer case, or if it's a lot longer I may have to move the transfer case back, and shorten the rear drive shaft.

 

The 720 and 620 5spds, are the same length at about 31 1/2" so measure your 4 spd. I have seen one short 720 tranny but don't remember if it's 4 or 5 spd, about 26" long.

 

Possible solutions? I would actually like to get rid of the divorced transfer case all together, and just run the trans/transfer case from a 720 4x4, but I' can't remember if the 720 front diff is offset, and if so, which side is it off set to? The only downside to ditching my current transfer case, is that I will loose the 2-low capibility, which I really like, and it comes in handy.

 

ALL the 720 transfer cases I've seen were divorced and at least up here in Canada the combined trans/transfer were only available with the D-21 Hardbodys. The 720 front diff is offset to the pass side for the '80 and offset to the driver's side for all other years.

 

I was also doing some reasearch, and it looks pretty hard to get a header for a Z series engine... But it looks like you could possibly use a header from a KA24e, flanges & bolt pattern look the same to the naked eye, but I dont have a head or gaskets to measure... Can anyone confirm this?

 

It 'looks' close. I have a Z24 gasket and can compare to a KA head next w/end.

[Z-train]

To fit the Z-22 with a minimal of problems,you use the Z-22 block,L-20b head,oil pan & timing chain cover & L-20b motor mounts.This gives you the extra cubes but gets rid of the piece of schit NAPZ head,which by the way flows like the affore mentioned schit.

[RacnJsn95]

Thanks for the info mike! I'll have to check out my truck when I get it back and measure the trans. I'm pretty sure my front diff is offset to the pass side. I figured the 720 trans/transfer case was a married unit, guess there is no point in changing my transfer case then.

 

Z-train: You have flow numbers for an L head vs a Z head? I would think that because the Z head is a cross flow unit, it would flow better than an L head.

[Z-train]

The NAPZ motor was designed for emissions from the get-go.The head info WAS posted on The 620.com site.I just looked but couldn't find it.

[datzenmike]

The NAPS and the L20B valves are the same width (the NAPS are longer) so it's not the valves. Both ports on the NAPS come in at a low angle and turn sharply into the bottom of the valve seat. And there's the problem, the air does not like to bend around this sharp corner. Below 5K this isn't a problem, but with bigger carb, cam, header, etc the engine will struggle more and more as it tries to rev into the higher ranges where real power is made. It probably flows the same as an L at low speeds. I've been worlking on a Z24 and a Z22 head trying to increase the port size in an attempt to lower the air speed so it will make the turn on the short radius with less turbulance. I've lowered and smoothed this radius and blended the port into the valve seat itself. I'll have to try it out this summer. The springs are supposed to be weak, they look identical to L springs, but may be, as they dont have to rev over 5,500 and the valves are slightly longer (heavier).

 

There's not a lot you can do about this design, a design that was not intended for high RPMs in the first place anyway. If you look at an L head port you'll see that the ports enter at a steeper angle and blend more smoothly into the valves.

 

On the plus side, the cross flow design frees the driver's side of the intake allowing room for a turbo. The chamber is almost a HEMI shape, the valves are tilted off center, dual plugs and the motor is larger and cam profile favors low end torque.

 

just some thoughts