74 620

[mysterymojo]

Hi everyone.

 

I just got my first pickup truck and decided it should be a Datsun. A buddy of mine got me interested in Datsun's when he had his Z, so i thought I would give it a go.

I found this 1974 620 with the L18 motor in decent condition with 85k miles on it. I need something for hauling for now but eventually I want to make it all shiny and clean :D plus its smog exempt. yay

 

There are some dents on the drivers side and a missing panel that was ruined when a neighbor of the previous owner backed into it. It runs well once it is warmed up but for now it has a hard time starting up and staying idle at cold. I need to research what I need to do for this. Maybe the carb? I noticed the weber 32/36 is a common swap. Would this held fix my idle problem? I also need to check the timing and probably some other stuff. Any suggestions? The brakes are a little scary. The first time i pressed down on them they locked up and I skidded a few feet haha. I think i may need to bleed the lines and adjust the shoes and, well... probably just do a disc brake swap. Any suggestions?

 

I am fairly new to this so any help and suggestions would be appreciated. Thanks.

 

Heres some photos:

 

[Rob W.]

Not bad lookin for the most part. The interior isn't horrible. Looks like a good one.

 

As far as your idling when cold check that the choke is working air filter is clean, everything is hooked up to the carb fuel filter clean, is the idle high when its warm or can you turn the idle screw up....

 

Could be lots of things really. You'll probably have to tune a new carb too might as well start tuning the one you have first.

 

 

 

[justin 620]

Weird panel to be missing... ha. As for the brakes, disc conversions are expensive, bleed the brakes and check all the drums and shoes, new ones may be in order. And the carb, Hitachi;s are a pain in the ass to trouble shoot once you get past the basics, and even harder to rebuild, a 32/36 is probably the easiest bolt on conversion you can find, buying a new one is a bit spendy, but it'll be worth it in the long run. Nice looking truck, needs to be a bit lower tho. :P

[Bullet_theory]

ill have my weber up for sale here soon, and congrats on the purchase.... and congrats on doing some homework there on common mods and such... of course like theyve stated above a full disk conversion is expensive... unless you wanna do like some of these guys and grab all the stuff youd need from a later year model and just convert the front brakes to disk and leave the rear drums....

[justin 620]

Getting a front conversion off a later truck is probably your best bet, since most of your stopping power is gonna be needed at the front. And it would probably be cheaper to find the parts to do it that way then getting the brackets and such to switch you current set-up.

[mysterymojo]

ill have my weber up for sale here soon, and congrats on the purchase.... and congrats on doing some homework there on common mods and such... of course like theyve stated above a full disk conversion is expensive... unless you wanna do like some of these guys and grab all the stuff youd need from a later year model and just convert the front brakes to disk and leave the rear drums....

 

ya i may just start with the fronts for converting the disc brakes and do a swap from the newer models. any links to those who have already done it?

 

also id be interested in that weber once you are ready to sell it. I am going to do what Rob W suggested and fiddle with the stock carb but once im done with that I think a weber might be a good swap.

 

 

 

[mysterymojo]

Not bad lookin for the most part. The interior isn't horrible. Looks like a good one.

 

As far as your idling when cold check that the choke is working air filter is clean, everything is hooked up to the carb fuel filter clean, is the idle high when its warm or can you turn the idle screw up....

 

Could be lots of things really. You'll probably have to tune a new carb too might as well start tuning the one you have first.

 

Any more details on this? Im not familiar with tuning carbs. would like to learn how on the stock one before i do any swapping

[justin 620]

Search through the brakes forum, should be able to find something in there!

[Bullet_theory]

oh and heads up with the weber... like from what ive seen about 80% of them are jetted perfectly for a l20b... meaning for an l18 its going to run a little rich (untill you dial it in).... crap i cant remember the users that have done the front brake disk swap...... id search the brakes section, and also look around the 620 section for pre 78 620s... because 78/79's have front disk brakes, and see if you can find any users that have done it, and they can set you on your feet

[mysterymojo]

oh and heads up with the weber... like from what ive seen about 80% of them are jetted perfectly for a l20b... meaning for an l18 its going to run a little rich (untill you dial it in).... crap i cant remember the users that have done the front brake disk swap...... id search the brakes section, and also look around the 620 section for pre 78 620s... because 78/79's have front disk brakes, and see if you can find any users that have done it, and they can set you on your feet

 

thanks will do. just started going through the brakes section.

For that weber you mean that out of the box they are set perfect for the L20b's? just so long as it is tunable for the L18. From what I gathered it seems like those 32/36 webers are a direct bolt on to the L18 engine with some tuning required. from your experience is it a direct bolt on true? or are there any other modifications you have to make before slapping it on? or after?

[Bullet_theory]

thanks will do. just started going through the brakes section.

For that weber you mean that out of the box they are set perfect for the L20b's? just so long as it is tunable for the L18. From what I gathered it seems like those 32/36 webers are a direct bolt on to the L18 engine with some tuning required. from your experience is it a direct bolt on true? or are there any other modifications you have to make before slapping it on? or after?

 

 

personally when i bolted my weber 32/36 down, it ran a little rich... ill call my buddy up in the morning, he has a l18 with the same carb... i dont think it was anything extreme, just leaned out the mixture abit...... also found this... mabey it can help a bit... ive seen it pop up from time to time in here about webers vs hitatchi carbs... and also about l18's and webers

http://dimequarterly.tierranet.com/articles/tech_carb_tuning_guide.html

[Rob W.]

Sorry I'm not real familiar with the carb on your truck.

 

I can tell you how I work on anything I own though. I learned this the first week I worked in a Honda motorcycle shop from one of the best mechanics I have ever known. Get the book for your vehicle and read it before you start doing anything. I have a great one for all Datsuns called "How to Keep Your Datsun Nissan Alive" by Colin Messer I think you can still find it. Without a reference its easy to screw things up fast. A good place to start with any carb problem is a fuel treatment like Lucas or what ever. It won't hurt and it just might knock some crap out of your idle circuit and fix it (unlikely though) but for a 5 spot its worth a try. I will read the section on your carb and see if I can shed some light on your issue. For now though you really need to make sure all the basics are right. Check plugs and filters and so on. Really the best thing to do is just do a complete tune up plugs and wires, filters, and oil that way you know what's right and its easier to figure out what's wrong. Good luck I'll see if there is anything else I can come up with.

 

Oh and it looks like all the vacuum hoses are gone. I know my 77 has a whole lot more and I'm pretty sure I should be able to see some on yours.... But then that's a whole other can of worms. Start with the tune up first

[mysterymojo]

Sorry I'm not real familiar with the carb on your truck.

 

I can tell you how I work on anything I own though. I learned this the first week I worked in a Honda motorcycle shop from one of the best mechanics I have ever known. Get the book for your vehicle and read it before you start doing anything. I have a great one for all Datsuns called "How to Keep Your Datsun Nissan Alive" by Colin Messer I think you can still find it. Without a reference its easy to screw things up fast. A good place to start with any carb problem is a fuel treatment like Lucas or what ever. It won't hurt and it just might knock some crap out of your idle circuit and fix it (unlikely though) but for a 5 spot its worth a try. I will read the section on your carb and see if I can shed some light on your issue. For now though you really need to make sure all the basics are right. Check plugs and filters and so on. Really the best thing to do is just do a complete tune up plugs and wires, filters, and oil that way you know what's right and its easier to figure out what's wrong. Good luck I'll see if there is anything else I can come up with.

 

Oh and it looks like all the vacuum hoses are gone. I know my 77 has a whole lot more and I'm pretty sure I should be able to see some on yours.... But then that's a whole other can of worms. Start with the tune up first

 

I like the name of that book and I agree with what you said about learning the basics first.

Looks like amazon.com has some used books:

http://www.amazon.co...e/dp/0912528656

 

Vacuum hoses missing? uh-oh lol you have a pic of your 77 engine bay? Ill probably get the maintenance book for 620 too just to check for stuff like this. the truck will idle extremely slow if i let it, it goes put put put.and if i just tap the gas it puts even worse or just dies, but if i give it ALOT of gas, it will rev up nicely until i take my foot off the petal. once its at full running temp it will idle normal.

 

 

 

 

personally when i bolted my weber 32/36 down, it ran a little rich... ill call my buddy up in the morning, he has a l18 with the same carb... i dont think it was anything extreme, just leaned out the mixture abit...... also found this... mabey it can help a bit... ive seen it pop up from time to time in here about webers vs hitatchi carbs... and also about l18's and webers

http://dimequarterly...ning_guide.html

 

 

I ran into that article too. I havnt read through all of it yet though, my brain is bleeding datsun right now so Ill probly look over it later but Im interested in what your friend says. let me know and thanks for the help

[mysterymojo]

I also found links to these 3 books which may be of some use down the road. Have any of you seen or heard of these?

 

http://www.paperbackswap.com/Haynes-Repair-Manual-John-Haynes/book/0856966436/

http://www.paperbackswap.com/Weber-Carburetors-Pat-Braden/book/0895863774/

http://www.paperbackswap.com/How-Rebuilt-Nissan-Tom-Monroe/book/1931128030/

[Rob W.]

I'll see if I can get a pick of my bay its a lot busier on the drivers side than yours. I have the book I mentioned above and 2 others I like the one I mentioned best. Is there a hose on yours from the exhaust manifold to the bottom of the air cleaner intake? Mine was missing and adding help with the cold idle a bit.

 

I have the first one and its as good as any other Haynes manual the other 2 I Haven't seen

[Rob W.]

Here's a pic of my engine bay it should be similar to yours but not the same

 

 

 

[mysterymojo]

Here's a pic of my engine bay it should be similar to yours but not the same

 

interesting, i wonder if they added those hoses to the 77. ill have to check see if mine is supposed to be like that

thanks

[justin 620]

thanks will do. just started going through the brakes section.

For that weber you mean that out of the box they are set perfect for the L20b's? just so long as it is tunable for the L18. From what I gathered it seems like those 32/36 webers are a direct bolt on to the L18 engine with some tuning required. from your experience is it a direct bolt on true? or are there any other modifications you have to make before slapping it on? or after?

 

The only problem I ran into was the fuel line being a lil cock-eyed, but that was just a matter of using a long section of soft rubber hose. And getting the studs out took some heft to get out, and the throttle linkage was confusing, but that was my stupidity, ha<_< And I had to lean mine down for my l20, so it must all depend on the truck and carb... make sure you tune it while it's warm.

[mysterymojo]

thanks for the advice

[mike]

On those books you listed, skip the haynes... If you read the FAQ (frequently asked questions) thread under general discussion, you will find info on brake swaps and some other 620 tech. There is also a link to olddatsunpickups.com that has copies of the factory service manual for a 74 620... Its free and its a far better repair/maintenance guide than a haynes or chiltons manual. Theres also a bunch of basic datsun tech there.

 

http://www.paperbackswap.com/How-Modify-NissanDatsun-Frank-Honsowetz/book/1931128049/

Id buy this book before I bought the others... Seeing as how youre talking about swapping carbs already... If youre like damn near everybody else on here, it will be ignition next, and then a closed chamber head, and then youll want an L20, then youll want to build an LZ22 and so on and so forth... :rolleyes:

 

For your idle problem, make sure your carb is clean and that ALL your vacuum lines are hooked up correctly and in good shape (not dryrotted or cracked). This solved a good portion of the problems with mine after sitting for about 15 years. If youve still got all the stock accessory stuff on the engine (looks like you do) and your throttle shaft doesnt have much if any play in it on your carb, Id vote to keep the stock hitachi over a weber and just get everything in good working order.

 

One other thing I did was cleaned out the EGR thing bolted to the side of the manifold and everything else associated with the EGR system... I just followed the directions from the factory service manual... Its all bone stock and runs like a top, it all ended up costing about the same as a weber swap but its got better and smoother power (better low end torque) than the identical set up in my other truck (L18/A87) with except it had a weber. Its a hell of a lot quieter too.

[herculesinwyoming]

On your brake issues!!!!!

Thats not a 74 620 brake master cylender, looks like on for disk brakes your brakes are probably getting more pressure than needed. your braqke master should have two small round resivors not big square ones.

 

also by the look of how far out your parking brake pulls out, your rear brakes are either worn out or really need adjusted.

 

 

oh and that little truck is a nice find

[mysterymojo]

Since ive been on here I found out only 2 of my cylinders are firing. So Ive tuned my valves, got new spark plugs, spark plug wires, coil, distributor cap and rotor, oil change, oil filter, air filter.

when i turn the car over it sounds great but it still wont run for more than a few seconds.

I can still warm up the car if i baby the gas petal in an awkward way. once its warm it will rough idle since only 2 of the plugs work.

 

I also purchased this book to tune my valves and for any other problems i may run intohttp://www.amazon.com/Keep-Your-Datsun-Nissan-Alive/dp/0912528656

and its very helpful.

 

However, i accidentally found out my problem when I was checking to see if my spark plug wires were connected correctly. It seems it is the distributor. I warmed up the car and let it rough idle and I pressed down on one side of the distributor cap. As i pushed down the cap i noticed it wiggled just a little bit and as i held it down the car started running perfectly normal. wtf. so i then checked to see if there was anything on the surface where the distributor cap fits on and it seems that not only is the cap not on a flat surface but the top of the distributor wiggles just a little causing the miss fire on the two cylinders.

 

I guess I should replace the distributor? or maybe only part of it needs replacing? i already replaced the cap and rotor, those are fine, but maybe the shaft that goes down is off or something else in there is loose. not sure, but it seems it might just be a good idea to replace the whole thing. not sure yet.

 

any suggestions??

[mysterymojo]

On your brake issues!!!!!

Thats not a 74 620 brake master cylender, looks like on for disk brakes your brakes are probably getting more pressure than needed. your braqke master should have two small round resivors not big square ones.

 

also by the look of how far out your parking brake pulls out, your rear brakes are either worn out or really need adjusted.

 

 

oh and that little truck is a nice find

 

 

u have a pic of a stock 74 620 master cylinder? ill search and see if i can find one to compare but if you have one of the exact part or a link to one, send it my way please. and thanks for the tip. im sure these brakes are worn. that brake comes out pretty far.