NM 521

[datzenmike]

There are two BB (ball bearings) held in place with small springs that act like one way valves. One is directly under the accelerator plunger. When the plunger lifts to draw in fuel from the float chamber the BB is pulled off the opening by suction but will be gently pressed back by the spring to prevent fuel from being reversed back into the float chamber. There is actually a small designed leak so that soft pedaling of the throttle while driving does not discharge fuel into the primary when not needed and saves gas. More sudden or deliberate step down on the throttle delivers the correct amount of enrichment. The other BB is on the discharge side of the pump and allows fuel out into the primary when the accelerator pump plunger is pushed down but the spring pushes it back into place on the upswing or suction stroke preventing air from being drawn in. Something to be aware of.

 

The secondary is vacuum operated to prevent it opening too soon unlike the Weber which has to be driven carefully just below the tip in of the secondary to raise the gas mileage and to prevent that slight bog from too much carburetor all at once and very low speeds. There is an interlock on the primary that both helps push the secondary closed snugly after use and prevent it opening below about 60% throttle. You can floor the Hitachi and only the primary opens. Once RPMs and internal vacuum are sufficient the secondary begins to open.

 

 

The L16 Hitachi was a 30/34 compared to the 32/36 Weber.

 

2 hours ago, Charlie69 said:

Mike always love the wording you use to describe a Hitachi anchor!!!  LOL

 

The best words I can use in a sentence containing a Hitachi carburetors are expensive parts (providing you can find them) and frustration.

 

I like them when they work. lol.

[Oilspot]

1 hour ago, datzenmike said:

There are two BB (ball bearings) held in place with small springs that act like one way valves. One is directly under the accelerator plunger. When the plunger lifts to draw in fuel from the float chamber the BB is pulled off the opening by suction but will be gently pressed back by the spring to prevent fuel from being reversed back into the float chamber. There is actually a small designed leak so that soft pedaling of the throttle while driving does not discharge fuel into the primary when not needed and saves gas. More sudden or deliberate step down on the throttle delivers the correct amount of enrichment. The other BB is on the discharge side of the pump and allows fuel out into the primary when the accelerator pump plunger is pushed down but the spring pushes it back into place on the upswing or suction stroke preventing air from being drawn in. Something to be aware of.

 

The secondary is vacuum operated to prevent it opening too soon unlike the Weber which has to be driven carefully just below the tip in of the secondary to raise the gas mileage and to prevent that slight bog from too much carburetor all at once and very low speeds. There is an interlock on the primary that both helps push the secondary closed snugly after use and prevent it opening below about 60% throttle. You can floor the Hitachi and only the primary opens. Once RPMs and internal vacuum are sufficient the secondary begins to open.

 

 

The L16 Hitachi was a 30/34 compared to the 32/36 Weber.

 

 

I like them when they work. lol.

Gold!!!!! It's this kind of understanding that will help me to get the smoothest operation out of this carb as well as maintain it. I'm actually looking forward to tearing back into it now where as I was kind of dreading it earlier!

thank you so much for the explanation!!!!!!

[datzenmike]

The main jets can also accidentally be swapped. Primary are always smaller than secondary. Front mounting screw that comes up from the bottom is hollow. Rear one is not and are often mistakenly swapped.

[Charlie69]

Mike is good with the anchors.  I always swap to a Weber and forget about carb problems.  I installed a new Weber DGEV 32/36 from Pierce Manifolds when I bought my 86 720 king cab in 2011.  I am still driving this truck daily and I drive my trucks hard.  No light footing the pedal hear!!!  LOL

[mklotz70]

Haven't read all the comments......  The factory carbs are great if they're done right and aren't worn out.  The best running L-series engine I had at one point had a Hitachi on it.  More torque and off idle response than a weber....by a mile!  Typically, the Hitachi's are completely worn out at the throttle shaft bushings.  If you can feel any wiggle in it, it's bad.  You can spray carb cleaner or brake cleaner at the bushings while it's idling.....if the idle changes, they're bad.  

 

Biggest problem with the weber is they get tuned the same as the hitachi and that is NOT the correct way to do it.  I don't have time to explain it all and I've posted it before....somewhere......but the goal with the weber is to get the butterfly as closed as possible and still run....then adjust the air mix.....if it speeds up, adjust the butterfly more closed to where it barely runs....chugs like a tractor....do this until there no change with the air mix.  Close the air mix until the idle starts to drop.....open it back up a 1/4 turn?  I think the tuning instructions found online say how much.  If it's still chugging, you can now open the butterfly up a tiny amount.  The hole for the vac signal to the dizzy is just above the butterfly, so if it's open even just a hair too much, you will get constant vac on that hole(and dizzy) and your off idle wil suck.

 

[Oilspot]

The weekends here and I'm back to this carburetor, and I'm not liking what I'm seeing. Close inspection does reveal sloppyness in the throttle shaft.  I figure I can get the truck going and look for a better carb here in the next few weeks. So I start looking to check if the "hollow bolt" is in the right position. I'm hoping I'm looking in the wrong place. But there's three bolts holding the base of the carb to the body coming from the bottom, and one that comes from the top. Well..... none of them are hollow. I went into the morning already knowing that i was gonna need to go pick up a M6 helicoil kit because the front bolt that hold the top piece of the carb (the one that goes through the bracket that locks the fuel inlet). 

 

seeing as how my carb is missing correct parts, needing repair, and just plain worn out, I think I'm dead in the water this morning. Does anybody have a good carb they wanna sell me? I'm seeing remakes on ebay for a little less that $200 but I'm afraid I'd probably being buying substandard crap that I'll never be happy with. 

 

 

Edited September 18, 2021 by Oilspot

[mainer311]

I’ll ship you my old Hitachi if you want it. Truck ran great when I pulled it off, and had very minimal runtime after I rebuilt it.

[Oilspot]

1 minute ago, mainer311 said:

I’ll ship you my old Hitachi if you want it. Truck ran great when I pulled it off, and had very minimal runtime after I rebuilt it.

Let me know what you want for it and I'll PayPal or vinmo you. 

[mainer311]

Freebie. Same address?

[Oilspot]

Yep, same address.

Man this is to incredibly nice of you and you have no idea how much I appreciate it!!!!

 

I'm not trying to get all weird and emotional and shit, but I've gotta say the help/ support I've gotten on this forum overall has been badass. A lot of the car scene now days has been overwhelmed with asshats gatekeeping information and shit like that. 

I enjoy this crap, and it's nice to be in with a group of weirdos that truly enjoy it also 😂. 

[mainer311]

Cool, I’ll get it out this week. The main reason that I save stuff is because I know someone else will need it eventually.

[datzenmike]

2 hours ago, Oilspot said:

 Close inspection does reveal sloppyness in the throttle shaft. 

 

I figure  So I start looking to check if the "hollow bolt" is in the right position. I'm hoping I'm looking in the wrong place. But there's three bolts holding the base of the carb to the body coming from the bottom, and one that comes from the top. Well..... none of them are hollow

 

 

The Hitachi evolved as the engine displacement went up. Possibly only used on the L20B carb but all carbs have the power valve and need a manifold vacuum signal. Maybe there is just a hole up through the base on the earlier carburetors and with the L20B they combined hole and screw.

 

It's the front one under the float chamber. The plastic spacer under the carburetor has a gap in it to allow intake vacuum to the head of the hollow screw. The one directly to the rear is the same length and can accidentally be swapped.

 

 

Worn throttle shaft could leak some intake vacuum, but this would only affect idle mixture and speed when intake vacuum is highest. Driving or under load the intake vacuum is much lower and less air is sucked in and would have almost no effect diluting a revved up engine. If the leak was bad enough to affect running t would be much too big to let the engine idle. At idle mix would be made richer to make up for the extra air. Speed would go up from the extra gas and air. Another problem is the brass throttle plate being mis aligned when closing and catching on the walls of the barrels. I had one that wouldn't idle down unless you stabbed the throttle to shake it off.

[Oilspot]

24 minutes ago, datzenmike said:

 

The Hitachi evolved ad the engine displacement went up. Possibly only used on the L20B carb but all carbs have the power valve and need a manifold vacuum signal. Maybe there is just a hole up through the base on the earlier carburetors and with the L20B they combined hole and screw.

 

It's the front one under the float chamber. The plastic spacer under the carburetor has a gap in it to allow intake vacuum to the head of the hollow screw. The one directly to the rear is the same length and can accidentally be swapped.

 

 The three bolts that go through the underside of this carb are the same length, the fourth (the top one) is shorter. Figured I'd throw that out there in case somebody else runs into a similar dilemma. 

 

I moved on to put in the new rear wheel cylinders so I could at least get the brakes finished up. As I'm tightening down the unit, one of the studs strips. (3/8 ratchet, choked up, maybe 2ft lbs.). Yeah I guess I could replace the stud(s) but I really don't like fixing new parts.   

Anybody here have any experience with warranty/ faulty parts from rock auto? The wheel cylinders are centric. 

 

Decided to edit/ add to this post after looking at this picture. I'm wondering if the nut just ran outta threads, like the QC on this unit didn't catch that the studs weren't sunk in to spec. But then I couldnt help but notice that the whole unit fits into the backing plate way looser than the units I took out. The banjo bolts do fit/ have the correct sae threads. 

I've got the other wheel cylinder in place but didn't feel like tightening it down in fear this may happen to the other wheel cylinder. The thought of stacking another washer came to mind, but again, I really don't wanna be making shit work when it comes to new parts. 

Edited September 18, 2021 by Oilspot

[datzenmike]

If threads didn't match you wouldn't have got it on that far. This wheel cylinder only has to push through the backing plate thickness? That's like 1/16" Those studs look a bit long. That would take way more than 20 ft lbs to strip... maybe it came already stripped and not noticeable when mounted.

[Oilspot]

9 minutes ago, datzenmike said:

If threads didn't match you wouldn't have got it on that far. This wheel cylinder only has to push through the backing plate thickness? That's like 1/16" Those studs look a bit long. That would take way more than 20 ft lbs to strip... maybe it came already stripped and not noticeable when mounted.

It was the correct nut/ thread pitch etc. I was thinking the nut may have hit the shoulder before it could actually snug the wheel cylinder down. 

Just went through the return process with RA, all automated. A replacement will be shipped out priority. Well at least that was easy enough.   I went ahead and snugged the other one into place before processing the return with no issues. 

 

[mklotz70]

6 hours ago, datzenmike said:

If threads didn't match you wouldn't have got it on that far. This wheel cylinder only has to push through the backing plate thickness? That's like 1/16" Those studs look a bit long. That would take way more than 20 ft lbs to strip... maybe it came already stripped and not noticeable when mounted.

If I remember right, there's a reinforcement bracket/plate behind the backing plate that the studs also go through....plus any flat and or lock washers.

 

[Oilspot]

any tips/ tricks/ proper tool to get the top (heavy) spring  on the rear brake shoe assembly. 

I know i can sit out there and cuss and eventually get it. But I figure there may be an easy way to get it together.

 

The manual I have isn't clear, It just shows how to get everything apart and says reverse that. 

I guess most of the older drum stuff I've worked with I've been able to just assemble all the springs etc and pull them over the wheel cylinders and adjusters. The axle flange keeps me from doing that on the truck. 

 

 

 

 

[Oilspot]

Went and bought a pair of needle nose vice grips on suggestion from an old mechanic friend and got the rear brake shoes put together. 

 

I adjusted the rear brakes, got that all together and moved to the front. Figure no better time than while I'm in there to clean and lube the front adjusters and go ahead and repack the front wheel bearings while I'm in there. When I was pulling all the old grease from the void between the inner and outter bearings, a thin spacer ring (hopefully) came out. I look at the manual diagram and can't tell where this goes or if maybe it's the remnants of an old inner bearing seal. 

 

Hoping to identify this little thingus so that I can get it back together in the morning. I can probably figure it out by taking the other side apart but honestly I'm beat tired and don't feel like working on this truck any more today. 

 

 

Edited September 26, 2021 by Oilspot

[Charlie69]

Looks like parts of the inner wheel seal.  Compare for fit with the old seal.

[mainer311]

I think mine had those too. I want to say that it’s a spacer that goes between the inner bearing and inner seal, but I’m not certain.

[mklotz70]

It goes between the bearing and the wheel seal as a spacer.  It was used to make sure the seal wasn't seated in too far.  Most have been lost or removed over the years.  If you take note of where the seal is in relation to the end of the hubs before you remove it....then put the new seal in that same amount, you won't need the spacer.  As seal manufactures varied the width of the seals, I'm sure those were left out on purpose at times. It's item number 5 in the pic. 

 

 

[Oilspot]

I finally got to drive it!!!! 

 

 

Need to readjust the brakes (lr is wanting to lock up). Trying to get the timing and idle sorted. I've got an old style timing light and no tach so I'm having to set the idle by ear. I've taken it on two little drives and each time I come back the idle is a little higher than it was. 

 

Can't tank mainer enough for the carb and wheels!!!!! 

 

This little things so much fun to drive!!! At 6'2" I feel like I can almost hang my arms out of both windows  at the same time while driving

[banzai510(hainz)]

Oh DUDE!!!!!!!!!!!!! that is awesome  I drive it just like that.

 

O rileys or whatever part store you go to should have a wheel cleaner that keeps the white on the white wall brite as or time it fades white. spray it on then it then wash the wheel when you wash the truck and looks new again.

 

use the distributor and the mixture screw at the bas it get the idle right. One had to adjust over time and for lights and heat on if you run them alot.  then adjust the speed screw.  7 to about 12btdc is the timing using the Light. I would run little higher adv is you got better than 91 octane gas.

 

truck look great  Love the Patina

[Oilspot]

44 minutes ago, banzai510(hainz) said:

Oh DUDE!!!!!!!!!!!!! that is awesome  I drive it just like that.

 

O rileys or whatever part store you go to should have a wheel cleaner that keeps the white on the white wall brite as or time it fades white. spray it on then it then wash the wheel when you wash the truck and looks new again.

 

use the distributor and the mixture screw at the bas it get the idle right. One had to adjust over time and for lights and heat on if you run them alot.  then adjust the speed screw.  7 to about 12btdc is the timing using the Light. I would run little higher adv is you got better than 91 octane gas.

 

truck look great  Love the Patina

 

thank you!

The blue crap they put on these whitewalls it brutal. I'm having to scrub the hell out of them and they still have a blue tint.

 

as per adjusting brakes, the manual says to adjust till you feel drag and then back off 12 "ratchets". This seems a little excessive. I'm used to the old vw's where you feel drag and just back off till everything frees up. 

With that being said the brakes seem like they're not wanting to full release when i just took the truck around 5 miles to get some gas and a burrito. Damn brake lights stayed on when I got home to. (Looks like maybe I didn't/ don't know better than what the manual recommended!!!!)

 

I've got some issue with my filler tube also. Went to put it gas and I had a decent amount raining from under the truck. 

 

 

[banzai510(hainz)]

back off 12? shit back off 3 if that   

 

drive first drive and fwd and back ward to center the drums. and the lower adjuster tumbler

 

I spray some lithium grease behind the drums where it might rub on the backing plate. I usually dont put anything but have done this.

 

really I had a time when the bottom slider for the brake adjustment (tumbler the back side side spring or what ever you call if was not tight enough and the whole adjuster was moving causeing my brakes to cook and not release correctly. Hopefull this isnt it with you. just tighen it up first and feel the brakes if getting to hot.

 

like you said with the VW bugs tighten till slight drag and back off.  just remember when you slam on the brakes if the rear brakes is tight they will lock up ezer but doesntt mean not to push down harder to get the fronts to lock up. I would always not push as hard thinking my brakes were all locked up but they wasnt and still had more stopping power cause the front were not actaully locking up. there is no  equalizer valve or what ever they call it in the early trucks

Edited October 2, 2021 by banzai510(hainz)