710 Carburetor Options

[Randalla]

Finally getting around to working on my 76 Datsun 710 wagon with L20B. My original Hitachi carb is toast and I've no interest in rebuilding it. Wondering what some of you with 610 or 710s are running on your motors. As I see it, my options are fairly limited if using the stock intake (Hitachi clone, used Hitachi OEM, clone Weber 32/36 or genuine Weber 32/36). I'm interested in any real world performance and reliability information you're willing to share, as well as any mods you had to do to mate it with the stock manifold. Thanks!

 

[datzenmike]

The best over all is the stock carburetor but you don't want that so second best is an L20B carburetor from another Datsun but to be fair you really should rebuild it and set to stock adjustments, so might as well do yours. A clone of anything is a bad idea as they really are a 'cheap' knockoff and while it probably will work, what do you expect for $50? The stock carburetor was likely $500-600 from the dealer back in the day. So this leaves an original Weber 32/36. It's very basic, less to go wrong, not overly complicated and for about $300 comes in a kit with adapter plate and installation hardware. Beware, there are lots out there on e-Bay that are the dreaded clones from China. Redline sells the original ones so make sure to contact them directly. I would advise that you not buy a used one even if original. You're just buying someone else's problems.

 

Use a thread sealer on the adapter bolts as they tend to vibrate loose. There is provision for placement of a plastic elbow on the bottom of the air filter for the valve cover vent hose. Use it. Be sure to get the electric choke and the electric idle cut solenoid. Life is so much easier with these two items.

[Randalla]

Mike, when you say the best is the stock carb, what specifically makes it a better choice than a 32/36 Weber? Of course the OEM carb was engineered for the engine, but from a real world performance standpoint what makes it better? I've just been through this exercise with my L18 equipped 620 that I installed a new 32/36 Weber carb on.  

[datzenmike]

The Hitachi combines excellent mileage, performance, easy hot and cold starting in all weather, good emissions, provisions for EGR, and ATC (automatic temperature control) of the inlet air, and what I call drive ability, or smooth ease of operation with a vacuum secondary which automatically engages depending on engine need. For what it's worth the Hitachi has a glass window that at a glance shows the fuel level. Invaluable for trouble shooting. The 32/36 is way less complicated with fewer parts though and it is larger that the Hitachi which is a 30/34, so it performs better but not as good mileage. The Weber has a tiny expensive air filter that does nothing to silence the intake sound. The air filter does not control the intake air temperature where the Hitachi's ATC uses exhaust manifold heat to warm cold ambient air at around 100F so in effect the engine operates like it's July all year. The warmed air will never cause carburetor icing from charge cooling effect in near freezing humid conditions. Another feature of the Hitachi air filter housing is that it has a sensor that corrects for extreme under hood air temperatures that cause an over rich idle by providing an air bleed to the intake to lean it out.  Some have cut the bottom out of the Hitachi's air filter to fit the Weber and run it. The 32/36 has a progressive secondary which begins to open at around 60% throttle. In this case you have to actively drive it just below this for best mileage and it's too easy to run into the secondary when not really needed. If the Weber had a vacuum secondary it would almost be the perfect carburetor. Hitachi vs. Weber 32/36 is like the choice between Ginger and Mary Anne ... you can't lose.

[Randalla]

Thank you for the education Mike. I can definitely vouch for the induction noise of the Weber on my 620, as well as what seems like inferior mileage to the stock carb. I'm stripping most of the emission hardware off the 710, so those related benefits are less important to me here in AZ. Leaning towards Mary Anne at this point😁. Thanks again for the thorough explanation.