New carb advice for novice mechanic

[Ricky Harline]

Girlfriend and I are climbing dirtbags, which if you don't know anything about climbing that means we have no money. Girlfriend bought a Chinook RV which is built on a '78 Datsun 620. Thing has been all kinds of trouble. Huge shout out to these forums and Datzenmike which have helped us solve many problems. We're having significant carburetor problems and are looking at rebuilding the carb. 

 

Doing a quick search I noticed that Datsun 620 carbs are surprisingly cheap, so we're considering just buying a new one and then rebuilding the old one to have on hand if needed. The engine is the L20B and I've been having a hard time finding carbs for that model, most of what I can find are for the smaller engines. I see that other carbs are popular to retrofit rather than running and maintaining the original. I like that those seem to have a better reputation but they seem to cost a lot more. If we go that route is this the right product? 

 

https://www.californiadatsun.com/carburetor-parts/weber-32-36-dgev-electric-choke-carburetor-conversion.html

 

If we wanted to go with a new OEM carb for the L20B any tips on finding the right one? Maybe my Google-fu isn't up to par but I can't find the danged thing. 

 

Presumably some day we'll get this thing running well and in such a case we would be driving it a lot. Would the Weber pay for itself in fuel savings? Maybe worth the extra cost just for an easier to maintain carb? Or would it make the most sense to go the true dirtbag route and just rebuild the carb? Would really love to get y'all's input. Will begrudgingly work for the man a few more days if it means getting a much better carb.

 

I was an airplane mechanic in a previous life in the Air Force so I can turn a wrench OK, but L20s are very different from turbines so heads up that I don't know my jets from my floats and am figuring this all out as I go. 

[datzenmike]

First, do you need to pass emission testing because only a stock carburetor will pass. If you do then rebuilding is really the only option.

 

Don't care much for California Datsun but... You can get a brand new genuine (not a counterfeit knock off) Weber 32/36, adapter and all hardware needed for the swap from Pierce Manifolds for just under $300. There are also really cheap Chinese replacement carburetors for $80??? You get what you pay for.

 

 

[Ricky Harline]

Dang you're fast. Thanks for the reply. 

 

Yes, it will have to pass emissions, at least for now. GF is based in the SF Bay Area for now, where I live in the boonies it only has to pass smog once and never again, so sounds like when she moves out here we might be able to upgrade. Real bummer that the Weber won't pass smog. 

 

Anyone have any experience with these cheap Chinese carbs? I'm not crazy about the idea but if someone has had some good experiences we might consider it. 

 

Sounds like I'm probably about to learn a whole lot about carburetors. Again, appreciate you a whole lot man, you've been a life saver, dude. 

[datzenmike]

[Stoffregen Motorsports]

Cheap Chinese carbs are know to fail. But, if you need parts for your carb, a cheapo carb may be the best way to get all of it.

 

Where in the foothills are you? Some counties don't require smog tests.

[Ricky Harline]

Yeah hopefully the carb just needs a good cleaning! We'll see.

 

I'm in Calaveras County. No biannual smog which is nice, but looks like we need the rig to pass smog once to register it in my GF's name. all the emissions shit has been removed, so it looks like I'm going to be learning about all that here soon, too. Thing is a '78, wish it was just a couple years older and we wouldn't be dealing with any of this! Good ol bureaucracy, eh?

[Stoffregen Motorsports]

Maybe you can find a shop to give it a pass.

 

I'm in El Dorado county, and we need to pass here. It's good and bad. Make me careful of what vehicles I put in my lineup.

[bilzbobaggins]

https://nationalcarburetors.com/Datsun-620-720-1978-1979-159517701952-CC-L-20B-engine-California-Emissions_p_270.html

 

I used these folks when I first got my 521 and bombed my first rebuild on my carb.  I had good results.  It does say this is a r&r service on this particular carb.  Id be shocked if someone close to you did not have a complete carb they would give you to send to National to get it rebuilt.    

 

Just an idea.

[Ricky Harline]

@Stoffregen Motorsports

I'm not the best at reading subtleties in communication so I'm not sure if you mean like nudge nudge wink wink a shop could pass the rig, or if you mean I might be able to find a shop that will actually get it up to spec. Honestly it's been hard finding anyone that wants to work on the rig, not that we're much keen on paying for work anyway though until we give it a try ourselves first. 

 

People often express envy at how much time I have for climbing, and this here is the flip side... Lots of work I gotta do in order to not spend the monies. To quote my favorite mixed aphorism, I opened this can of worms, now it's time for me to lie in it =p 

 

@bilzbobaggins duuuuude thank you! We'll give the carb rebuild ourselves a go but it's super helpful to know that exists! Tbh I'm considering sending it in just so I know the carb is done to a high standard; I'd probably feel better while driving the rig in the middle of nowhere that way. Thanks for taking the time to find the specific link for our engine! Appreciate you. 

 

 

 

[Stoffregen Motorsports]

1 hour ago, Ricky Harline said:

@Stoffregen Motorsports

I'm not the best at reading subtleties in communication so I'm not sure if you mean like nudge nudge wink wink a shop could pass the rig, or if you mean I might be able to find a shop that will actually get it up to spec. Honestly it's been hard finding anyone that wants to work on the rig, not that we're much keen on paying for work anyway though until we give it a try ourselves first. 

 

People often express envy at how much time I have for climbing, and this here is the flip side... Lots of work I gotta do in order to not spend the monies. To quote my favorite mixed aphorism, I opened this can of worms, now it's time for me to lie in it =p 

 

@bilzbobaggins duuuuude thank you! We'll give the carb rebuild ourselves a go but it's super helpful to know that exists! Tbh I'm considering sending it in just so I know the carb is done to a high standard; I'd probably feel better while driving the rig in the middle of nowhere that way. Thanks for taking the time to find the specific link for our engine! Appreciate you. 

 

 

 

Wink wink, case of beer and some chocolate chip cookies.

[datzenmike]

No one wants to work on it because you can't plug it into a diagnostic console and let it do all the thinking. It's 45 years old and before EFI which is all they know or need to know today. What does a mechanic charge? $80-$100 an hour? I really don't know.  I've have never had my '78 truck of '76 710 to a shop, I do all my own work. Yes partly I'm a typical Datsun owner and cheap, but also why pay some idiot to learn how to rebuild a carburetor when to start you know as much as he does? Makes no sense to pay him to learn and he gets to keep that knowledge, (you learn nothing) why not keep the knowledge and the money for a win win? There is almost nothing that an owner can't do on an old 620, unlike vehicles today that you can't even check the oil on.

[Stoffregen Motorsports]

True, the owner can fix anything on an old truck. But some times the learning curve is steep. Figuring out what all the devices do and how they work can be really challenging. Since the info is not out there anymore.

 

An experienced old-time mechanic can look at the engine bay sticker and the smog devices and figure it out pretty quick, but as you said, nobody wants to do that anymore.

[720_Jeff]

On 6/5/2023 at 11:28 AM, datzenmike said:

No one wants to work on it because you can't plug it into a diagnostic console and let it do all the thinking. It's 45 years old and before EFI which is all they know or need to know today. What does a mechanic charge? $80-$100 an hour? I really don't know.  I've have never had my '78 truck of '76 710 to a shop, I do all my own work. Yes partly I'm a typical Datsun owner and cheap, but also why pay some idiot to learn how to rebuild a carburetor when to start you know as much as he does? Makes no sense to pay him to learn and he gets to keep that knowledge, (you learn nothing) why not keep the knowledge and the money for a win win? There is almost nothing that an owner can't do on an old 620, unlike vehicles today that you can't even check the oil on.

I wish mechanics were that cheap.  Son called the Subaru dealer, just to get a baseline estimate for a clutch job.  Their labor rate was 185/hr.  A Subaru specialty shop, think they were closer to $225/hr.

 

Most mechanics were born in the 80's or 90's.  Probably have never owned or worked on a vehicle with a carburetor, or anything like your '78 620.  Like Mike says, no reason to pay them to learn.  No matter what they learn, they'll likely never seen another one of these, so learned and lost.

 

 

[EDM620]

Find an old mechanic - check into local barber shops, parts stores etc and ask around. Network a bit. Any dealership won't be able to fix without learning it themselves first, and you'd be paying for thier education.

 

and BTW, Mike isn't kidding about new vehicles and not being able to check the oil - Thank you Mercedes.

[datzenmike]

Me in a panic during long trip: Have you checked the oil!!!! ??? Wife: It tells you when it's low or needs changing. Me: oh

[Stoffregen Motorsports]

13 hours ago, EDM620 said:

Find an old mechanic - check into local barber shops, parts stores etc and ask around. Network a bit. Any dealership won't be able to fix without learning it themselves first, and you'd be paying for thier education.

 

and BTW, Mike isn't kidding about new vehicles and not being able to check the oil - Thank you Mercedes.

Every small town has one small auto repair shop. Most of those shops cater to owners of older vehicles. Ironically, the small shop in my small town only works on older cars.

[Charlie69]

On 5/31/2023 at 2:25 PM, Ricky Harline said:

Girlfriend and I are climbing dirtbags, which if you don't know anything about climbing that means we have no money. Girlfriend bought a Chinook RV which is built on a '78 Datsun 620. Thing has been all kinds of trouble. Huge shout out to these forums and Datzenmike which have helped us solve many problems. We're having significant carburetor problems and are looking at rebuilding the carb. 

 

Doing a quick search I noticed that Datsun 620 carbs are surprisingly cheap, so we're considering just buying a new one and then rebuilding the old one to have on hand if needed. The engine is the L20B and I've been having a hard time finding carbs for that model, most of what I can find are for the smaller engines. I see that other carbs are popular to retrofit rather than running and maintaining the original. I like that those seem to have a better reputation but they seem to cost a lot more. If we go that route is this the right product? 

 

https://www.californiadatsun.com/carburetor-parts/weber-32-36-dgev-electric-choke-carburetor-conversion.html

 

If we wanted to go with a new OEM carb for the L20B any tips on finding the right one? Maybe my Google-fu isn't up to par but I can't find the danged thing. 

 

Presumably some day we'll get this thing running well and in such a case we would be driving it a lot. Would the Weber pay for itself in fuel savings? Maybe worth the extra cost just for an easier to maintain carb? Or would it make the most sense to go the true dirtbag route and just rebuild the carb? Would really love to get y'all's input. Will begrudgingly work for the man a few more days if it means getting a much better carb.

 

I was an airplane mechanic in a previous life in the Air Force so I can turn a wrench OK, but L20s are very different from turbines so heads up that I don't know my jets from my floats and am figuring this all out as I go. 

If you are serious about the Weber 32/36 buy it from Pierce Manifolds https://www.piercemanifolds.com/product_p/k660.htm.  This is the kit that will work for your L20B. 

I have been buying Weber's and Weber Parts from Pierce Manifolds since the 1970s.  Good people and excellent Datsun knowledge.my last new Weber 32/36 is on my 1986 720 with a Z24 5 speed, installed in Battle Mountain Nevada in 2011 and it is still running great to day in Tolleson Arizona.

Weber's are simple carbs, I have a stack of of used Weber's I use for parts.  Weber's need to be re jetted for high altitude.  If you call Pierce Manifolds talk to them about the re jetting for your altitude if it is necessary they will advise you also ask if they can sell you the jets you need if your altitude requires re jetting. 

Battle Mountain Nevada has an altitude of 4,500 feet and Tolleson Arizona has an altitude of 1,000 feet.  I did not re jet for this altitude change when I moved back home to Tolleson. Stock jets that shipped in the new Weber are still in it today.

I hope this helps.

 

[Charlie69]

One thing I forgot to mention is buy a real Weber, Not the cheaper Chinese nock off.  The Chinese nock off has a 50 percent failure rate right out of the box new.  This means that the buyer has a 50% chance of the Chinese nock off working out of the box.  Simpler terms is 1 out of 2 Chinese Knock offs will work out of the box.  I think your odds of winning are better a the Nevada Casino's!  LOL

Edited June 11, 2023 by Charlie69

[Ricky Harline]

I can't thank y'all enough for all the help and input. We've been busy with other stuff but will be rebuilding the carb soon, and if we fail (not unlikely) then we might be looking for professional help and utilizing many of the suggestions from y'all.

 

Does the stock Datsun carb handle elevation changes better than the Weber? I know significant elevation changes are hard on carbs but don't really know much more than that. We will be wanting to routinely take the rig up to 6,000-8,000' feet and sometimes as high as 10,000' as that's where much of the good climbing is and us climbers escape to high elevation in the summer. Or Canada, but we're currently too broke for that option =p

 

Would the stock carb be better for such significant elevation changes or would the Weber handle that fine? Any tips on getting either the stock carb or the Weber to handle driving at high elevation while still having it operate fine while we're at home at low elevation?

[datzenmike]

All carburetors go over rich with increased altitude. The air is less dense so very roughly decrease one jet size per 2,000 feet rise. So if you are at 4,000 feet and jet for that you should be fine 2,000 feet above and below that.

 

My 710 is from Nevada (average altitude 5,000 feet) and had 99 jets in it. I'm literally at sea level, and I noticed that I got better mileage inland in the mountains. I was actually running too lean at home. I increased to a 112 jet (denser air needs more fuel) and my sea level performance and mileage increased!!!!

[Ricky Harline]

Rad, very helpful as always, thanks man. 

 

Looking for Hitachi DCH 340 jets and not finding anything-- any tips on pinning these bad boys down? Having the standard jets now (which I assume are for sea level) and some for 4,000' would actually make a lot of sense. Just need to find the buggers. 

[datzenmike]

The '78 620 L20B uses a # 103 primary and a # 101 if in California. To really see how close the air fuel mix is you really need a wide band gauge. Couple of hundred dollars though. A #101 jet is 1.01mm or 0.040" drill. If too rich you'll want to try something smaller. Here's a JEGS 90 -100 jet kit... https://www.jegs.com/i/JEGS/555/15022/10002/-1#

 

 

 

 

Amazon...

 

Try Amazon for motorcycle carburetor tuning jets. They're cheap. Then buy a twist drill the size of the jet you want to try and drill it out. Start small and work your way up till you get it perfect.

 

This is what I did on my Yamaha R-1 carburetors. Worked my way up to around 0.025" per cylinder. Idles at 14.3 cruises at 14.7 at 50 MPH. Full throttle drops to high 12s low 13s.

 

 

[EDM620]

On 6/8/2023 at 7:40 PM, datzenmike said:

Wife: It tells you when it's low or needs changing.

That's the rattling sound... 🤣