Anyone run SU carbs?

[distributorguy]

I have two sets of perfect SU carbs on the shelf, 1 1/2" and 1 3/4".  HS4s and HS6s.  Does anyone run them on an L18 or L20 and if so, what needles do you go with?  They're SO much better than Weber DGVs for throttle response, drivability, and economy.  With a little guidance I may put a set on my spare motor rather than dump a Chevy 327 into the spare truck.  Sure would be easier.  

 

All I'd have to do is pick up one of the many intake manifolds on Ebay and make longer linkage rods to fit them.  

[G-Duax]

I always held SUs about to be about the same level as I do John Lucas Electronics..........You know, the prince of darkness.

 

Always having to dick with them, check the oil dampener level, break out the carb synchronizer, etc..

Had a close friend years ago that was into the Queen's own sports cars.

I would get the thing running nice & crisp, with good throttle response, and within 2 months he would be back asking me to dick with them again.

 

I just know the hate is coming now....

[wayno]

I have 1 1/2" SUs on all my gas L blocks, but I just use the stock needles what ever they are.

I like SUs, but you have to understand them and they need to be serviceable units, wore out ones are impossible to adjust properly.

I have never tried to use British SUs on a Datsun L block manifold, linkage might be an issue.

[red13]

Hs4s i am running i also made a cold air ontake set up for them

[Dolomite]

Hitachis are damn good in my opinion. Pretty much set and forget. I think I've replaced the dashpot oil probably three times in about twelve years. Mine are on stock needles for an sss l18 and they're near perfect on my l20b. It runs a bit fat at idle but pretty spot on everywhere else.

[john510]

I had Hitachi SU's on my L-18.Loved them,great throttle response,power and even good gas mileage.They seldom needed adjustment once dialed in which is pretty simple.Put some velocity stacks on em and they sound cool to.

[distributorguy]

Duax, you were over-filling the dampers.  That causes a vacuum in the dashpot that sucks oil out of the chamber and it gets all over the piston.  Then the piston collects dust and they hang up, come out of balance.  Its a common scenario.  Set them up right and they go years without service, and are as likely to plug up with crap like the emulsion tubes in a Weber.  And the float needles aren't as temperamental as those in a Weber.  And they are load (vacuum) sensing, so fuel mixture is generally more accurate.  Weber float tangs also bend easier, so the floats tend to need readjustment every 2-3 years if you don't have great, smooth roads.  

 

If you mount the carbs, remove the dashpots, fill them with oil, insert the plunger until it bottoms out, remove it, wipe off excess oil, and THEN install the dashpot and chamber individually, it will run great and stay balanced for years.  

 

If you are running rich at idle, your needles are too lean.  Go to the next richer needle set (from JoeCurto.com) and set the jets lower to lean out the entire curve.  You can compare needles here:

http://www.mintylamb.co.uk/suneedle/

 

I figure the British SUs will fit in place of the Hitachis, just make longer linkage rods.  Its just 5/16" rod if I recall - nothing exotic.  

[G-Duax]

Nope......

[distributorguy]

That's what everyone says...

[red13]

https://www.facebook.com/Hackers-Hack-Up-1973-Datsun-620-Rebuild-1854433418114441/heres a page with some pics of my set up i am working on

[G-Duax]

I was only referring to the over-fill thing.

[distributorguy]

Its imperative that the pistons remain dry in the dashpots.  When they seal with oil is when they create a vacuum and start sucking oil out of its chamber.  Otherwise there should be no oil working its way out.  Get oil on the pistons and balance changes.  Underfill the heck out of them and keep them that way.   :thumbup:   It really is the simplest carb on the planet.  

[wayno]

Well I guess I have over filled my SUs since I bought them new from Nissan in 1995, and I have never had an issue with them hanging up or anything else for that matter until recently, they are getting worn out from over 20 years of daily driving, the rear carb runs rich now and I cannot fine tune it anymore by spark plug color, it needs rebuilt, but runs good so I just keep driving it.

I always believed that they were self leveling as they don't stay over full.

Every gas engine car/truck I own except for the Datsun 320s have dual SUs except for the Mini, it has one SU, I do have dual SU packages for the E1 engines, and one side draft Mikuni also, but I have never installed any of them on an E1 engine as they all have rebuilt stock carbs except for the Weber clone on the NL320 that Mike installed on it before delivering it to me.