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Need help.. '79 620


hondaluvr

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Ok so I started tearing my '79 datsun motor down to see maybe why its eating through plugs, and also out of boredom.

 

When I bought this truck, it had a Holley single barrel carb. ghetto rigged up instead of the stock 2 barrel.

I bought a stock L-series carb. from a fellow Ratsun member and slapped it on. Had a problem locating what lines went where since they had all been blocked off.

 

Since I don't wanna go through and trace all the lines I was wondering if there is a way to delete most of that metal vacuum tube going on next to the valve cover. Looking to delete what I can.

 

I may not end up keeping the L20 and trying to swap over to a newer KA, but for now I figured I would look into this.

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get a 620 Haynes manual.

Buy a weber carb.

 

KA swap. if you can handle the cost of a weber the ka cost is going to kill ya

 

I have a manual off of the internet. Didn't ever feel like ordering the manual. I can handle the cost of the weber, but the engine might need some work. I have pulled 3 plus from the cylinder closest to the firewall and they have had mechanical damage.

 

I can pick up a KA swap farely cheap and I think it would run a lot better just have to swap it in.

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Make sure you have the right plugs in there.

sometimes I use the type with the shorter electrode.See what that does.Look at theDatsun spark plugs from other Lmotors and they might list a a shorter one but if its smashing the eleltrode soemthing is WRONG

 

KA are not a 4 hr drop in and if your in a Datsun startved area for parts like the midwest.

Plus the wiring needed to be done is a little more than most people think.

Jeff Hino(Icehouse on here) He can do the wireing. He tell people get harness and everything lined up and hell do it. 9 out of 10 times he never hears back from that person.

 

I say find a another L20 if possible and rebuild it.

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It is smashing in the electrode. The first plug I pulled out of this motor, the electrode was completely blown out and gone. I put in a new NGK plug and it smashed that electrode off to the side. Its only in the back cylinder, all the others are fine.

 

As far as the KA swap I was leaning towards a newer KA out of an S13 or the newer nissan hardbodys. I realize the wireing would be something to figure out and the swap is not just going to be a 4 hour drop in, but that is why this is my project truck and not my daily. The truck needs A LOT of work with rust and the engine was neglected. I may rebuild the L20, but have not decided yet.

I'm still weighing my options.

 

I know finding an L20 in this area will be extremely hard. There are only 3 of these trucks in my town and thats including mine and I can pick up a KA for cheap.

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It is smashing in the electrode. The first plug I pulled out of this motor, the electrode was completely blown out and gone. I put in a new NGK plug and it smashed that electrode off to the side. Its only in the back cylinder, all the others are fine.

 

You likely have a foreign object in there. A small carb piece or a broken piece of piston or valve. Do a compression test. If good pull the head and remove it before too late. If low replace the motor.

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  • 2 weeks later...

It never crossed my mind to check the compression. Hmm I will do that as soon as it warms up a little bit here. I was missing to rocker arm keepers and was wondering where they went. That might be the foreign object. I put probably 150 miles on it with this problem so I'm sure it is gonna need replaced.

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I have a manual off of the internet. Didn't ever feel like ordering the manual. I can handle the cost of the weber, but the engine might need some work. I have pulled 3 plus from the cylinder closest to the firewall and they have had mechanical damage.

 

I can pick up a KA swap farely cheap and I think it would run a lot better just have to swap it in.

 

Then you have the wrong plugs in there.

 

Use only NGK BP6ES11

 

B = 14mm

P = projecting tip

6 = heat range 2 (hot) to 11 (cold)

E = reach 19mm (3/4") threads only

S = standard 2.5mm center electrode

11 = 1.1mm (0.043") gap setting

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  • 1 month later...

If I had the wrong plugs in then wouldn't it smash all of them? Not just one single cylinder?.. It had bosch when I pulled them and I put NGK's in there the two times I changed them.

 

And the two keepers I lost went on top of the retainer, they were round and have a notch cut out for the rocker to sit in and keep it in place. With one missing, the rocker was just sitting off to the side.

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Damage to the electrode means there is something rattling around in the cylinder. If it's braking the plug, think what it's doing to the top of the piston or the soft aluminum head. Can't be the keepers, no way to get in there. Only way for the keeper to fall out is over revving or too much clearance. It it was the cylinder with the plug damage, maybe it caught under a closing valve when it went in.

 

When I bought this truck, it had a Holley single barrel carb. ghetto rigged up instead of the stock 2 barrel.

 

Getto rig single barrel carb???? Who ever did this let something drop in the intake. Pull the head.

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