1972 Datsun 240Z | SU carburetor cleanup/ rebuild

In this video, I take apart, clean and refurbish an SU "round top" carburetor.
Main video: • 1972 Datsun 240Z | Wil...

[@darrylleigh7514]

There's a little more to that. Setting the needle depth, putting the correct cc's and type of oil in the pistons and turning the mixture screw in until it touches and backing it out 2.5 turns to start. Adjust and or correcting the throttle linkage and then using a side draft sync tool to balance them.

[@atombawm]

Yep lol this is one of my first video attempts and a lot of info was cut out while editing as a rookie mistake. I didnt narrate or explain most of it and half the time i forgot i was recording. Thanks for the mentions :) I used the recommended oil in the carbs but switched to ATF which worked really well. (More on what i missed/ didnt include is in previous comments too)

[@denisewester9688]

Great job!

[@atombawm]

Thank you! Cheers!

[@rallycarsdinosaurs7623]

Great video, thanks man! Only wish you’d have kept talking some on the rebuild but I could follow along. Also you don’t mention how much to screw in the jet. From the info I’ve found it’s ‘screw it in until jet is flush with bottom of cylinder, usually all the way, then back it off 2 whole turns’ I’m hoping this is right. Gonna be a while until I actually turn my z over again :)

[@atombawm]

Im glad you liked it! I will work on my narration in future videos, it was very cold and i was in the zone while cleaning and just stopped talking lol. You are correct, screw it in till flush then back off two full turns is the base setting. The needle in the piston also needs to be set where the shelf on it is flush with the bottom of the piston using the edge of a feeler gauge as a stop. Ill post more videos for the z car in the future, if theres anything specific you want let me know and ill see what i can do! Love your username btw, made me laugh.

[@tthams73]

Try ATF in your Dashpots instead of that oil. I switched a couple years ago and it’s awesome! Super responsive. ATF is equivalent to SAE 15 viscosity.

[@atombawm]

I will try it out, thanks for the recommendation.

[@hoedemakerbart]

@@atombawm stock is sae30. 10w40 works fine to

[@guntherbbb]

When you put the needle on I saw you using a feeler gauge. I was wondering if you were just making sure it was completely straight up and down?

[@atombawm]

Theres a ledge around the circumference of the needle base, the feeler gauge was used as a straight edge to set base depth. I should've narrated it lol i put the needle in, tightened set screw until needle has very slight resistance sliding, placed feeler gauge flat against the piston (in groove) then pulled the needle out until the needle ledge came against the feeler gauge then tightened set screw. Needle depth base setting is complete.

[@guntherbbb]

@@atombawm Ahhhhh okay! Nice yeah that makes sense! Thank you for the quick response about to get my 620 back and then i got to rebuild my roundtops lol looks pretty straight forward just a few qwerking things def saved this and will be watching in the future for prep! Thanks again!

[@atombawm]

Glad to be some help!

[@TRUTH4U2NO]

You installed the jet needle wrong. The shoulder of needle should be flat with the pistons bottom not the venturi gap. But whateva Datsun Twin SUs all leak air at 50 years of age and frankly they never have provided a balanced tune mixture across the rpm spectrum. In other words they perform ok either at low end mid range or high end NEVER waste your money or time with these issues. Buy Mikunis triples or Triple Webers or FI ITs.

[@atombawm]

Thanks for the heads up, ill double check the reference material i was using and adjust accordingly.

[@BUCK4NIER]

Great video, where did you purchase those nifty hose clamps that you installed at the 16:09 mark?

[@atombawm]

Those "two wire hose clamps" are stock hardware.

[@lolman77]

I have the same rebuild kit. Aren't you left with a few washers after the rebuild? I have 3 left after replacing the plastic washer, the 2 gaskets, the neddle valve & its washer. I am wondering if I didn't miss something...

[@atombawm]

Yeah i went through the same process of questioning why theres extra orings. I assume that the “bonus parts” could be for different models of the carbs with different emissions mods but im uncertain.

[@lolman77]

@@atombawm thanks, that answer made me feel better! I also recommend ATF oil in the dashpots. If I remember well, even Ztherapy recommends it. It allows the piston to rise quicker

[@marcoluna1850]

I know this might sound dumb but would I have to get a rebuild kit

[@atombawm]

Marco, there's no such thing as a dumb questions, only dumb answers. It depends on what youre trying to do i guess. I do recommend getting gasket kits or some gasket material before taking things apart especially if youre working on something containing fuel thats directly over the exhaust manifold or another heat source. If youre on a tight budget, plan ahead for what youll be taking apart and get just those gaskets or a roll of gasket material if you feel confident in tracing out and making your own. You don't want to have any leaks.

[@jonathansarley1499]

Only if you need the new jet jet needle and gaskets then yes the jet lines are broken yes also this jet here is a fix a jet don't know we're to get them check out Joe Curto here on you tube also his website specializes in SU carburetors

[@sowedibrahim2540]

There are no experts in my country..my car is grounded Because of failure to tune the twin carbs

[@atombawm]

Maybe i can help, is it just not running or is it running badly? There is a lot of datsun groups on facebook that is a good source on information as well.

[@sowedibrahim2540]

@@atombawm thanks bro...its running but not smooth...needs a bit of tunning

[@sowedibrahim2540]

Needs to balance the carbs

[@atombawm]

I will try to get a base tuning video made to help, it will be a little while due to other projects not currently on the channel but ill make one on the dual SU carbs to get people close.

[@TRUTH4U2NO]

Weber it x3. SUs junk.

[@atombawm]

I have mikuni triples on the 73, the 72 i rebuilt these for is getting sold but if not i have a arizona 4bbl for it. Flat top su carbs are junk, i do like the round tops though lol might be an unpopular opinion.