6 carbs???

[Ricklandia]

The internet is a wonderful thing...

http://www.prirace.com/induction.htm

These are complete setups for the Spitfire/GT6 (very similar in size/power to the L24) but I'm sure that they could be easily adapted to the Z. Price is pretty steep, but these guys look as if they've been doing this for quite some time and could be a valuable resource.

[jcraig]

The DCOE/PHH type are really 2 carbs, sharing a common float bowl They work independent from each other, and are completely individually tunable. They work precisely as if you had installed six separate carbs.

That's good to know as I did not know this. Again, my experience with carburetors is pretty limited. I've mostly been working with FI cars.

As for 44mm being too big, well, it is, for a stock engine. Nissan race prepared engines used 50mm Mikunis. Trust me, the engineers at Nissan would not have used them if they were inefficient.

That's also good to know. I would like to check out some Nissan race motors to see what they are running. Although information is pretty limited from what I can find.

Despite the 'numbers' the calculator shows, it looks like any given motor is running around 40mm per 500cc; Motorcyles and cars alike. Harley's are a good example as well as some Suzuki's and Older V-Twins. So, for a slightly hotter L28, 38mm or 40mm Mik's would suffice. With a cam, head work, and header, 40's or 44mm indi's would work.

I would think that miniature SUs (6 of them) would be best...since they only allow into the motor what the motor needs

Can anyone point me to some info on the differences between SU's and DCOE's and how they work? I'm still not entirely knowlegable of the differences in round slide, flat slide, su, dcoe, tmx, etc., etc... I'm getting more and more interested in this old-school tunning approach.

- John Craig

[jcraig]

http://www.prirace.com/induction.htm

Wow great link! Thanks a bunch!

[dogma420]

Jcraig,

SUs, stand for Skinner's Union which made at one point the original SUs found on MGS, etc....Datsun had Tihatchi license the SU design, they are essentially the same carb, but made by Japanese. (might be wrong on the licensing part but close anyways).

DCOEs are downdraft, and like any other downdraft, the fuel / air mixture has to travel in a down, turn towards motor, and then go (and that point is where the SUs would be shooting their air / fuel mixture to begin with)...a shorter, straighter path is more desirable for air/ fuel...so SUs or any other sidedraft for that matter are just better carbs.

SUs are designed to only give the motor what air/fuel mixture it wants, depending upon vacuum. The gas pedal only controls the butterfly in between the piston/needle and the motor...allowing more or less vacuum. The piston in the SU is free floating, and moves on its own...hence why these are great carbs if properly synched and if they're in good mechanical condition, they aren't hard to synch...I can do it!!!

[HS30-H]

....Datsun had Tihatchi license the SU design.......

Hitachi licensed the designs from SU, and Nissan bought them from Hitachi.

DCOEs are downdraft, and like any other downdraft, the fuel / air mixture has to travel in a down, turn towards motor, and then go....

No, DCOEs are sidedraught.

DC = "Doppio Corpo" ( 'Double Body' in English )

O = "Orizzontale" ( 'Horizontal' in English )

...so SUs or any other sidedraft for that matter are just better carbs.

Depends what you mean by "better". Better for what? If you mean for a street driven car then any Variable Venturi design like the SU is probably going to be preferable, but for ultimate power and tuneability in sports and racing applications you need one venturi per cylinder and full adjustability.

[Ricklandia]

Early 240's are said to have the "SU" carbs, and the '73-74's (early) had the "flat-top or square" Hitachi's, correct? So... were the '70-'72 carb true SU's or were they in reality Hitachi '"clones" of the original SU design?

[dogma420]

70-74 all had SUs....the 70-72 had 'round tops' and the later ones are called 'flat tops'.....the domes are flat vs. older ones (good ones) being round.

Plenty of pictures on here of the round ones.

[dogma420]

the hitachis are almost exact clones of the british SUs...some of the parts are interchangeable. See Ztherapy for more info. Get their SU carb tuning video, well worth the money.

[Victor Laury]

Early 240's are said to have the "SU" carbs, and the '73-74's (early) had the "flat-top or square" Hitachi's, correct? So... were the '70-'72 carb true SU's or were they in reality Hitachi '"clones" of the original SU design?

Right. Hitachi had been making "Almost" direct copies of SU's, under license for Nissan since 1962. The last, true Brit SU fitted by Nissan U.S. to a 1960 SP212 Fairlady, being prepared for racing.

The first Hitachi SU copies were fitted to the SPL310 in late 62. The frist few cars had only 1 SU, changed to 2, mid year 1963. During the period 1959 ~1965, Hitachi was Nissan's largest contracted manufacturer. Disassembling an early Nissan, you get the impression that it really should have been fitted with the Hitachi sun, instead of the Nissan/Datsun logo!

They were suberb carbs, many retain the belief (myself included) that they are superior in Quality to the Brittish patent (that should get me in trouble).

The infamous "Tuna Cans" fitted to the US 1973 240 and later 260's, were such a departure in design that we just refer to them as Hitachi's.

[240ZX]

Early 240's are said to have the "SU" carbs, and the '73-74's (early) had the "flat-top or square" Hitachi's, correct? So... were the '70-'72 carb true SU's or were they in reality Hitachi '"clones" of the original SU design?

You are correct!

[Ricklandia]

Understood. Would I assume correctly that the "Tuna-can" units were developed to comply with new(er) US emmision standards? I guess the logic of all this is that were I to have a need to work on these carbs, I would in fact be looking at Hitachi carbs and not true (British) SU carbs.

[dogma420]

Yes, the US Emissions were the reason.