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My 620 build thread.


J's 620

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This was on the 78. I’d like to put it in. My 76 CA truck already has El dizzy but it’s like the pertronix type, but it is factory hitachi. In CA they did put that in for 76(first year of smog). 
 So doing some searching, I need to check that this matchbox is good, no vacuum leaks, and the bearing is good. 
 But to wire it up? I can’t find the T connector so I’ll make one, but what about my remote igniter under the dash? Is it as simple as the diagrams I’ve seen, wire it to the proper  coil and keep the resistor using a strip of 14awg connecting whatever terminals those are, or even decide to bypass the resistor. 

0D403474-27BF-4105-863F-E103C784A8EF.jpeg

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I also took the opportunity to snag the coolant overflow bottle from the 78. I mounted it to the driver side fender well right next to the horns. It fit nicely there. I have a cluster of wires and relays to tidy up on the passenger side....... the 78 has a very nice bracket and cover for that. 

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On 9/17/2020 at 3:24 PM, datzenmike said:

Find the temp sensor from inside the old air filter and get the ATC working. You'll never have carb icing again.

I now have 2 factory air filter housings, I can try to get that sensor fit in somewhere. Right now it’s cold as **** in the mornings and the truck warms up fine, but I’m sure having this will be a great addition. 

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1 hour ago, J's 620 said:

Well here’s what I worked on today.

8C245569-C9B6-4E59-8C9F-6A813F167B9E.jpeg

This is the 5spd with the z series bell housing. This set of yellow wires, is that the speedo drive or something else? I didn’t get under my truck today to look for what that looks like so I guess I’m ignorant to what I’m looking for.

 

The yellow wires are the neutral switch used by the emissions system. The speedometer drive is that bump just below these wires. So I guess this is a 2wd 5 speed unless it's got a plug in the hole.

 

 

 

1 hour ago, J's 620 said:

I now believe I have 3 5spd transmissions.....

 The trans on the tailgate seems to roll through 6 gears and has the same ratio as that z series bell housing transmission . I think the casting says L4

 the 5spd hook to the L20b I’m assuming is a 5, it says L8 but I haven’t tried to shift through it yet.

82741933-36A5-492F-AEF4-58F2A22778C4.jpeg

 

Unfortunately the bottom transmission is a 4 speed. Looks like it's from a Z car as early as '71 ish and will have the same wide ratio gears. It's not from the 810 or Maxima as they only used 5 speeds. Probably you can swap it's front case onto the Z series 5 speed to make it an L series compatible transmission BUT SEND ME A PICTURE OF THE REVERSE LIGHT SWITCH TO SEE IF IT WILL.

 

 

 

 

53 minutes ago, J's 620 said:

I’ve been hearing some annoying noise this past week...... I narrowed it down to the alternator. I noticed some red dust on the pulley and fan. Well.....

306F870B-20B4-448E-8805-8D212D37734F.jpeg

4F33F6C1-89AF-45FA-8675-520156F6B396.jpeg

 

Is the fan just on backwards. Facing the other way would work.

 

 

 

 

38 minutes ago, J's 620 said:

This was on the 78. I’d like to put it in. My 76 CA truck already has El dizzy but it’s like the pertronix type, but it is factory hitachi. In CA they did put that in for 76(first year of smog). 
 
 But to wire it up? I can’t find the T connector so I’ll make one, but what about my remote igniter under the dash? Is it as simple as the diagrams I’ve seen, wire it to the proper  coil and keep the resistor using a strip of 14awg connecting whatever terminals those are, or even decide to bypass the resistor. 

0D403474-27BF-4105-863F-E103C784A8EF.jpeg

 

 

 

That's a '79-'80 matchbox.

 

Unplug and or remove the remote igniter box under the dash. You won't need it.

 

You need a '78-'80 EI coil from any L series engine. This is crucial to getting the higher output spark.

 

On the '76 find the Black/White wire AND the Black/Red wire that both go to the ballast resister. You can now remove the ballast resister, it's not needed now. Remove the the B/W and B/R wires and join them together and connect them to the coil + terminal and the B terminal on the matchbox as in the diagram below The C terminal goes to the coil - terminal. Remove the Blue wire that is on the - coil terminal and tape it up out of the way. IGNORE THE OHM RATING ON THE COIL

 

ZOkbBht.jpg

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16 hours ago, datzenmike said:
17 hours ago, J's 620 said:

306F870B-20B4-448E-8805-8D212D37734F.jpeg

4F33F6C1-89AF-45FA-8675-520156F6B396.jpeg

 

Is the fan just on backwards. Facing the other way would work.

That’s how the fan was mounted when I bought both alternators, I sure hope they aren’t built with backwards fans! 
 I ended up adding another washer to shim it farther off the front housing. 
 On the truck the pulley doesn’t have a warped/wobbled rotation, on the bench spinning by hand it looks as if my pulley is warped or something, either of the fan blades wobble along with the pulley( hence why I wonder if it’s the pulley)....

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16 hours ago, datzenmike said:

That's a '79-'80 matchbox.

 

Unplug and or remove the remote igniter box under the dash. You won't need it.

 

You need a '78-'80 EI coil from any L series engine. This is crucial to getting the higher output spark.

 

On the '76 find the Black/White wire AND the Black/Red wire that both go to the ballast resister. You can now remove the ballast resister, it's not needed now. Remove the the B/W and B/R wires and join them together and connect them to the coil + terminal and the B terminal on the matchbox as in the diagram below The C terminal goes to the coil - terminal. Remove the Blue wire that is on the - coil terminal and tape it up out of the way. IGNORE THE OHM RATING ON THE COIL

 

ZOkbBht.jpg

Thanks for this. It’s what I’ve been looking for. I’ve found similar diagrams in other discussions so this helps a lot.

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16 hours ago, datzenmike said:

The yellow wires are the neutral switch used by the emissions system. The speedometer drive is that bump just below these wires. So I guess this is a 2wd 5 speed unless it's got a plug in the hole.

 That is a plug in there..... I think..... damn. I’ll look closer when I get back home. 
 So if it’s a threaded plug, useable? Wouldn’t have a speedo but *could* work?

I’ll have to look at this a little later today too.

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What they usually didn't do is machine out the speedometer pinion hole on 4x4s because the speedometer is run off the transfer case. It's very possible that this was machined and a plug put in. Remove the 8mm? bolt and wiggle straight out, don't twist it. Post a picture of it. If a blank plug then 4x4 but oif it has a colored plastic gear on the end then 2wd.

 

Tu0tY8g.jpg

 

J0uxMW8.jpg

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Ok this is all from the trans with the z bell housing. I couldn’t get that to budge, it was covered in an undercoat I think. I’ll give it some penetrating fluid tonight. What’s the cover plate on its driver side in the bottom pic???

FE0BAFEB-3C07-47BA-9E6B-D313E7173387.jpeg

F5A4CB3A-141A-41F1-B970-89406E88BE47.jpeg

4E88CD2E-7FEC-480B-AE3F-F7EDEA858F84.jpeg

Edited by J's 620
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CACD7943-2635-4B22-B4FF-4FE4A498EC39.thu

 

This definitely has a speedometer pinion installed so 2wd transmission.

 

4E88CD2E-7FEC-480B-AE3F-F7EDEA858F84.thu

 

This is the reverse check sleeve used on all '80 and up 71B transmissions.

 

 

6FC440B3-B312-443F-8E7B-EC3FEC29F391.thu

 

L to R top gear, 4th gear and reverse lamp switch

 

 

9C33AC43-A0F4-4EB1-A0CC-6742B19516B4.thu

 

Fill hole and reverse lamp switch. (note: that it's to the left and not under the L4. almost all other transmissions has the reverse switch to the right under the L4.)

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I’ve been searching for the tag with rear axle info. I can’t seem to find it. The tag inside the door jamb gives me nothing, neither does the one under the hood by the hinge. Is there one I can’t find that was painted over? 

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That started after the 620 and with the 720. Basically the 620 was as follows (unless swapped later by owner)

 

All standards were 4.375 except the '79 which was a 4.11 but with 4.375 as an option.

Automatics were 4.625 for the '73 L16 and 4.375 for the '74 L18 and '75 and up L20B engines.

 

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  • 3 months later...

I've recently lost low beam function. I've downloaded an FSM using the search, but its not helping. the wiring diagram just isn't doing me justice. It seems like I'm not actually getting 12V to the relays. Im definitely not getting 12V between the black and red/black at the low beam plug. when I pull the light switch I can hear the relay, its the one with all the red wires plugged into it. I have tried another factory relay out of my '78 parts truck and swapped the relay with the black wires thinking this relay should be kicking on(?) but it's the same story. there are 2 relays correct?? at least that's what other "my headlights won't work" threads tell me. high beam works though so to get to work tomorrow I've just unplugged the highs and will run the high beam switch on. I've had a lot going on lately so I may just be easily defeated right now.

 

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Really though the 620 has been running ok, rich at idle but pretty damn good around town and on highways. at least it feels ok. however the vacuum gauge tells me I've got some worn valve guides. it bounces at idle and steadies out upon higher revs, its just what I've read on vacuum gauge tuning. I think the machine shop that did my cylinder head work boned me. they said it was all good. I'm ready to call it a night here though. 

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Top of the morning. Monday’s are always good in some ways. Seems like I have a misfire, which I can’t see why. I mean the truck sounds like a Subaru and not in a good way. I checked plug wires, dizzy to make sure it’s still in position, various ground connections, I’m a bit confused. I must have unplugged something somehow while chasing electrical issues. 

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 RE-vacuum gauge reading and mis-fire...

 

Check your valve clearances. A tight intake may prevent it from closing tightly and leak intake vacuum.

 

 

 

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valve lash need adjustment. fauled plug plug wire bad. I never had a plug wire go bad myself with the NGK wire sets.

 

one way to ck is pull a plug wire and it it gets WORSE then that wire is good. till you pull one off and it stays the same then its that cylinder bad..

I have had distrubots worn out and notice power loss in the higher RPM range, the bushing is worn causeing dist shaft wiggle

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I run the ngk wires. They looked good when I checked, I just need to be thorough and take some time this evening. I trust the valve lash adjustment suggestions. I’ll definitely look into this. Thanks. 

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Well when I was dropped off at where we carpool, I started the engine, let it warm up a little and then started with checking plug wires. Sure enough cylinder 3 is the culprit. Here’s what’s odd to me.... when I pull the wire and then get it close enough to make contact with the arc only, it runs fine. When I fully seat the plug wire it goes to shit.

I looked at my wire set really well and figured there must be a hairline fracture or something. So I went and picked up a cheap set at autozone just so I could get it home. Well same deal, fully seated it runs like crap, pulling the wire off and just letting the arc find it’s path it runs well again. 
 So I went back in and bought a set of spark plugs and I will try that. 
 I always run ngk plugs and wires. 
 So I’ll try swapping those, and adjust valve lash tonight. 

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Plug is fouled and spark leaking down the porcelain nose to ground. Holding the wire away there isn't time to drain away and the spark jumps the gap and all is right. This is on an extremely short time scale... the spark doesn't start out at 20,000 volts but builds up to that over time. An extremely short time but enough for it to leak away to ground. With a small gap the voltage has to sit on one side and wait till it has enough voltage to jump it and the plug gap. I don't know if they still make them, but there used to be plugs made with a very small air gap inside that does the same thing.

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Yeah good call, that plug looked nasty. In fact they all do. Looks like my choice of synthetic oil is not a good one. I’ll have to switch to a conventional possibly? I’ve been running 10-40 mobil1. What oil do you guys run in your l-series?

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