DCH340 FYI - All 3 of my Choke Pulloffs are Bad (& other problems)

[Cardinal Grammeter]

The one on my truck and my 2 parts carbs are now all bad.

 

The one I put on my truck 10 years ago was good when I thoroughly checked every jet, bleed, and emulsion tube and assembled my basket case DCH carb.  I just checked it today and it was dead, then my 2 parts carbs and they were dead too.

 

I'm betting a lot of OE ones are dead by now - so if your choke isn't working quite right...

Edited April 15, 2022 by Cardinal Grammeter

[Pacific coast Datsun]

www.piercemanifolds.com

Deep 6 your Hitachi...

Your welcome...

 

[Cardinal Grammeter]

What are you thinking, the $500 Weber conversion?

[Pacific coast Datsun]

I paid $220 shipped for a 32-36 dgav.. Included everything needed to install..

[Cardinal Grammeter]

Was that a direct replacement:  electric choke, fuel line, throttle cable linkage, etc. can swap out with the OE carb?

 

I believe the adapter for the OE air cleaner is like $50 - I'm guessing that was not included.

 

I was looking around and on Redline and all the pieces were around $500 shipped and I still wasn't sure if any mods would be required to install.  

 

Would the air cleaner V bracket still match up (Weber w/adapter same height as Hitachi?)

And then there is jetting - do they have ones jetted for the 3 engines?

[Pacific coast Datsun]

DGAV manual choke..

Made a cable bracket..

I ran the aftermarket air cleaner..

They sell different sizes jets..

[Cardinal Grammeter]

Thanks for letting me know what you did. 

 

If I go Weber, it has to have electric choke, cable linkage arm on throttle shaft, fuel fitting in right place, and the adapter to run the OE air cleaner.  While my truck is a "work truck", my objective has been to remove all mods and hack jobs that were done to this truck.  A rusted out 620 that looks like it was never molested is still an impressive sight.

 

I've even been eyeing up those DCH340 Chinese knock off carbs since they look close to the original.  It shouldn't be that hard to copy a carb - all you have to do is get the hole sizes correct.

 

But I still haven't given up hope on the Hitachi.  I do have a new pulloff. 

 

I've worked with carbs since 1965 and I've never seen one that has the problem I'm having.  I know how the DCH340 works and I'm concerned that it's possible to put a new carb on the truck and still have the problem:  "popping lean" primary.  Current theories:  debris in power valve, intake manifold gasket chunk blown out from lots of popping (but plugs don't show a lean cylinder.)  Do these engines ever jump a tooth on the timing chain?

 

[bilzbobaggins]

On 3/20/2022 at 2:19 PM, Cardinal Grammeter said:

Thanks for letting me know what you did. 

 

If I go Weber, it has to have electric choke, cable linkage arm on throttle shaft, fuel fitting in right place, and the adapter to run the OE air cleaner.  While my truck is a "work truck", my objective has been to remove all mods and hack jobs that were done to this truck.  A rusted out 620 that looks like it was never molested is still an impressive sight.

 

I've even been eyeing up those DCH340 Chinese knock off carbs since they look close to the original.  It shouldn't be that hard to copy a carb - all you have to do is get the hole sizes correct.

 

But I still haven't given up hope on the Hitachi.  I do have a new pulloff. 

 

I've worked with carbs since 1965 and I've never seen one that has the problem I'm having.  I know how the DCH340 works and I'm concerned that it's possible to put a new carb on the truck and still have the problem:  "popping lean" primary.  Current theories:  debris in power valve, intake manifold gasket chunk blown out from lots of popping (but plugs don't show a lean cylinder.)  Do these engines ever jump a tooth on the timing chain?

 

 

You have more faith in china than I do.  Nothing like getting a very simple part like a motor mount and having to redrill one hole and ream the other 3.

[Cardinal Grammeter]

I wonder if anyone here has tried one of those "hundred dollar carbs" on L-series engines.

Actually I'd be a little less confident with a motor mount:  did they get the rubber to steel bonding right?  But China is the world leader in high speed rail in all aspects so they definitely know how to do things.  Our rail system is humiliating.  They're also world leader with 1100KV  UHVDC power transmission over 3000 km into the western provinces which are basically desolate areas.  (this corridor is what was the Silk Road route.)  Shanghai looks like a city from the future.

[Pacific coast Datsun]

On 3/20/2022 at 11:19 AM, Cardinal Grammeter said:

Thanks for letting me know what you did. 

 

If I go Weber, it has to have electric choke, cable linkage arm on throttle shaft, fuel fitting in right place, and the adapter to run the OE air cleaner.  While my truck is a "work truck", my objective has been to remove all mods and hack jobs that were done to this truck.  A rusted out 620 that looks like it was never molested is still an impressive sight.

 

I've even been eyeing up those DCH340 Chinese knock off carbs since they look close to the original.  It shouldn't be that hard to copy a carb - all you have to do is get the hole sizes correct.

 

But I still haven't given up hope on the Hitachi.  I do have a new pulloff. 

 

I've worked with carbs since 1965 and I've never seen one that has the problem I'm having.  I know how the DCH340 works and I'm concerned that it's possible to put a new carb on the truck and still have the problem:  "popping lean" primary.  Current theories:  debris in power valve, intake manifold gasket chunk blown out from lots of popping (but plugs don't show a lean cylinder.)  Do these engines ever jump a tooth on the timing chain?

 

Good luck..I tossed my Hitachi in the bin.. Bolted on a Weber & drove the truck...

[Stoffregen Motorsports]

I also firmly believe in the Weber conversion. Much easier to tune than the stock carb because of the easily obtainable selection of jets and emulsion tubes. Get one with an anti dieseling solenoid (fuel shut-off solenoid).

 

Also, if you get a two piece adapter, use loctite on all threads. They have a tendency to become loose over time.

[Cardinal Grammeter]

I'm not ready to give up on the DCH - it's worked flawlessly except for twice I had to tear it down to remove huge "toothpics" of debris out of the primary main jet.  Yes, it has an inline fuel filter with clear bowl and the fine screen in the fuel line fitting.  The debris I removed had to come from inside the carburetor - a real mystery.

 

This time seemed to have a similar problem but not as bad.  Lean primary, popping if given quick throttle, and idle was too high.  Tore down didn't find anything obvious.  Put back.  Idle back where it should have been, not as lean, but still lean. 

 

NOTE:  I DID NOT check the power valve for debris - this was a BIG oversight.

 

If I could find a used Weber, I might buy it, but popping $500 for a carb modification that might not solve the problem, I'm not that eager.  (I don't come from the school of automechanics that just starts substituting parts w/o a proper diagnosis.)

 

WEBER QUESTION:  Is it designed for lead free gas?  Resistant to throttle shaft and throttle plate wear?

 

I have to verify that all the popping didn't blow out a chunk of intake manifold gasket. 

 

And while I've thought the timing chain was bullet proof and infinite life, I'm not ruling out an issue there.

[Stoffregen Motorsports]

Designed for unleaded fuel? I think most carbs use a hardened steel throttle shaft that rides in the housing of the carb body, with or without bushings. Some carbs have actual bearings, but this is rare.

 

If you're asking if the throttle shafts would wear out from unleaded fuel, the answer is no.

 

The throttle plates are brass.

 

I have a few used DGVs laying around. You can pick one up for $100, but it may need some love. And I wouldn't call it cheating. It's an improvement. Like an electronic ignition. That's not cheating either.

[datzenmike]

It's not $500 for a Weber. Less than $300 for EVERYTHING needed to convert.

 

The choke pull off only pulls the choke off if it is on and you floor it for performance. Can't see much going wrong with it. Suck on the hose and the linkage will pull the choke open.

[Cardinal Grammeter]

First, I lost the HDD in my main PC, so I'm in a shitty mood.  All my pics were on it.  I'm going to give 300dollardatarecover.com a shot.  Yes, there is pron on the drive but I don't give AF.

 

The pulloff sets the choke opening where it needs to be upon starting independent of choke adjustment.  Adjusting the choke sets the rate at which the choke opens as engine warms up.  In warm weather the pulloff becomes irrelevant since the choke is already starting to open from ambient temp.

 

I'd like to see where I can get everything for $300 - would seriously be tempted to try it.

The OE air cleaner adapter is $50

The cable throttle arm kit is $42

Redline K660 Electric Choke kit is $369 (there are unbranded "K602" carbs on eBay for $200, do they need the plate adapter?)

Total price $461 + 6% sales tax.

 

The box stores still show a Tomco Hitachi for $329 and a United for $269.

 

I do like the diaphragm accelerator pump of the Weber.  New Hitachi accel pump rubber pistons not sliding in the pump bore are a real issue.

Is no anti-dieseling solenoid a concern?  I never had an issue with 4-bbl vintage iron.  

 

Regarding carb wear:

All throttle shaft wear I've ever seen has been in the body.  Bushing kits are popular for the repair.

The throttle plate wear is a result of the Hitachi throttle return spring mechanism design putting a thrust load on the throttle shaft.  The plate is brass but it actually wears away on the aluminum body bores.  I posted a pic of what this wear looks like years ago.   The pic showed the small unworn area of the plate at the throttle shaft since the shaft bore is an area which does not contact the plate.

[Stoffregen Motorsports]

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

 

Ok, so CA Datsun may not have the best reputation, but Redline does - https://www.ebay.com/itm/373501396819

 

The only thing missing from those kits is a stock air cleaner adapter. But need/vs want= you don't need it. Buy it later if you must.

[Cardinal Grammeter]

Some Weber 32/36 questions:

 

1)  Does it have a choke pulloff? - looks like there is one near the choke, looks like the diaphragm is replaceable.

2)  No vacuum secondaries?  - how do they manage secondary throttle plate when flooring carb @ low rpm? 

Carter managed this problem in their AFB 4bbls with a weighted "flapper" above the secondary throttle plates.  If opened at low rpm, the flapper did not open - it opened progressively as rpm increased.  Vacuum secondaries are the best choice for fuel economy (and no bogging @ WOT & low rpm.

3)  Anti-dieseling solenoid available for DGEV (not DGV) - is this correct?  they say it replaces the primary jet?  (???)

4)  Is the adapter plate necessary? - looks like the studs are close, why not drill out the Weber base and eliminate?

5)  There appears to be a choke shaft through both bores and choke plates on both bores - why is there a choke plate on the secondary?

 

I'm thinking all I need is the carb, anti dieseling solenoid and OE air cleaner adapter.  NO base plate, NO linkage kit, NO kit air cleaner.

Cost $269 + $20 + $40 =  $329

 

NOTE:  I will not cut the crimped end off the throttle cable.   

[datzenmike]

2/ secondary too soon can bog. It has to be learned when to step into it. You actually have to drive it. The 32/36 would be near perfect with a vacuum secondary.

 

4/ you need the adapter plate. It comes with the kit.

 

You will have to cut the bottom out of the OE air filter, make a round pie plate with the top of the Weber cut out in it and weld to the bottom of the OE air filter housing. The OE is far superior to the dinky and expensive to replace Weber air filter. In addition with the OE you get to keep the ATC functional.

[Cardinal Grammeter]

That adapter is micky mouse.  I think I can mount it directly with a combination of offset studs and elongating the carb base plate holes.  I need to get dimensions or buy a Weber gasket to prove concept.

 

I'll bet the Weber doesn't even have a secondary lockout until the choke is wide open.  What a rudimentary design from an outfit know for its "tunability".

 

Here is the Datsun OE air filter adapter:  This one is $39 from Carbs Unlimited  (I think this is the right one.)

http://www.carburetion.com/Images/weber/99010.301.jpg

 

It looks like the Weber mounting nuts are easier to R&R than the Hitachi which is near impossible if you don't remove the BCDD.  But that is a moot point because the W is supposed to be "trouble free."

 

I'm not ready to drink the W Kool-Aid - the Hitachi is clearly the superior carb and probably why so many OE's chose it.  But I am more inclined to buy one of those $100 Weber knockoffs.  

 

OT:  Big Day today - I just sold my 32" throat metal cutting bandsaw (has 32" diameter wheels.)  Lots of room in garage now - a bottleneck has been eliminated.

Edited March 24, 2022 by Cardinal Grammeter

[Stoffregen Motorsports]

I feel like you're trying to poke holes in the Weber philosophy so you can talk yourself out of buying one. They really are a nicer carburetor. Easier to work on. Easier to tune. Easier to get parts for.

 

The adapter is not junk. It actually is the best adapter for the Datsun conversion. Other adapters have been made out of a single piece, but they are so tall that you'd never fit an air cleaner on without hitting the hood. Use loctite on the threads, and if it makes you feel better, use Threebond 1211 on the gaskets.

 

To use a stock air cleaner, cut out the base of the lower portion and weld in a plate cut to fit the Weber. You can make this any height you want, so if you want to use the stock Y-shaped bracket to hold the air cleaner housing, you can. I'll post a pic of the mod I made to my 320 air cleaner housing to fit the Weber.

 

[Stoffregen Motorsports]

Oh, and you can also remove the secondary choke plate. The reason Weber has one there is because the same carb body is used for the synchronous DGAS 38/38, which opens both throttle plates at the same time.

[Cardinal Grammeter]

I don't like the Weber and I don't like the Hitachi - they both have their PROs and CONs.

 

The $100 Chinese knockoffs are gaining appeal and they come in two flavors:  DCH and DGEV (!)

 

I was thinking about the air cleaner height too.  That 2-pc adapter raises the carb as does the air cleaner adapter - that's a double raise.  I'm not going to chop up my only 1974 air cleaner - too hard to come by.  I still think I can mount the DGEV w/o an adapter.

 

But I like to fix broken things, and this lean popping thing may not be the carb. 

 

Given the choice, I would clearly rather have a properly functioning DCH 

 

NOTE:  I'm also looking for alternatives to the DCH and DGEV.

 

 

 

 

 

[Pacific coast Datsun]

Your overthinking this process..stop asking so many questions.. You'll causing unneeded delays.. Once again..toss the Hitachi in the bin.. buy a Weber complete kit.. Run the chrome air cleaner assembly..set it & forget it !

www Pierce manifolds.com

will take care of you...out !!

[Cardinal Grammeter]

I'm not 100% sure my problem now is the Hitachi - so I have to diagnose that before I do anything else.  

 

IF I go Weber:

 

I have gone to great lengths to remove all mods from my 74 620.  When I open the hood, I want to see that iconic Datsun blue air cleaner complete with "V" bracket .  (I would have thought someone would have posted how they installed a Weber and kept the OE air cleaner.)  

 

 

NOTE:  I'm showing my age.  That Datsun Iconic Blue only means something to someone who ran beloved Datsuns in the 60's and 70's - young kids don't have that nostalgia.

 

 

 

 

 

 

[Stoffregen Motorsports]

I didn't drive until 1990, but I also love the stock blue Datsun air cleaners.

I agree that you're overthinking this. Cut the air cleaner, modify it, Install the Weber. Done!!! You'll never need to worry about having a cut up air cleaner because you'll never need to reinstall the stock carb again. As a matter of fact, those are the kind of mods that make the difference between a rookie job and a polished, well detailed approach.

Edited March 27, 2022 by Stoffregen Motorsports