Re: 240 z motor

All 240's had Hitachi SU carbs, not just the 73. But the 73 had the flat top SU's (HMB46W's) compared to the early and great dome topped (HJG46W) carbs.

Then they weren't genuine SUs, they were Hitachis made on license or something? Anyway, the ones on the '73 had a choke; I had never heard of a choke plate on an SU until then.

I still have my Unisyn carburettor synchronizer. Any buyers out there?

I see they share my opinion of the Hitachi SUs in the'73 Z.

My only other experience with SUs was with an MGB and with friends' MGA and Austin-Healey. Those SUs have *throttles* of course, but no *chokes*. For cold start, the mixture is enriched by pulling down the nozzle at the bottom of the carburettor so that more fuel passes around the needle, which is attached to the dashpot. The mixture control being at the bottom, the float chamber is at the side, with the float readily accessible for adjustment.

As I said, the Hitachi-SU has a choke, making it possible for them to cleverly move the float chamber to the bottom where it is inaccessible.

The beauty of the real SU is its simplicity and ease of cleaning and adjustment.

The mixture assembly of a genuine SU is pointed out in the photos on the ZTherapty.com page for the Datsun 1500 roadster. The photo on the Z page that shows three Z carbs (the photo with arrows pointing to tabs) appears to show this same assembly on all three carbs.

If the carbs you worked with have the float chamber at the side and fuel feeding from the float chamber to the venturi from the bottom, then I do not believe they have chokes.

Where did you attach the "choke" cable? If it was in such a way as to pull down a gizmo at the bottom of the carburettor, then what you have is genuine SUs, although perhaps they were manufactured by Hitachi--I wouldn't know about that.

I have only spoken to one mechanic that liked the flat top SU's, but it seems both 260s at his shop had been converted to dome top. Maybe he isn't as good with them as he thought.

the Hitachi model HJG46W (found on early 240's) SU type carb has an adjustment for a reassembled carb: "When the carburettor has been completely reassembled, check the starting interlock system. With the choke control pulled fully out, the clearance between the edge of the throttle burrerfly valve and the carburettor body should be between 0.0232 and 0.0272 inches."

One of the first instructions in any repair manual for these carbs says "disconnect choke cable". The handle inside the car has "choke" printed on it. The light on the dash flashs "choke".

The choke cables are attached on these early 240 carbs in the same place they were (from what i remember from the conversion) on the 260 carbs, a small arm between the throttle linkage and the air cleaner box. That arms is attached by rod to the bottom of the jet assembly (under the carb). As for a genuine SU...SU is a type of carburettor, not a brand name. It stands for "Skinners Union", the name give by 3 brothers that invented that style of carb. Hitachi is just one of several companies that have made this style of carb. Early and late 240z's and 260z's came with twin Hitachi SU type carbs. If you look on the top of the float chamber on a 240z you will see the Hitachi logo between the fuel inlet pipe and the carb body (dashpot). It looks like a circle inside a circle, with points on the outer band.

When I said "choke" I meant a choke plate. The Hitachi SU's in the '73 Z have a choke plate. That's like no other SU I ever heard of.

Anyway, if you were referring to what I call a mixture control when you said "choke" then I apologize for the confusion. In any case I'm confident that the mixture enrichment device, whatever we call it, is different on the '73 Z from that on earlier Zs.

According to

I haven't owned the 240Z since 1975, so don't have one to go look at, but either: Hitachi built them under license from BMC or the patents had expired so they could build them without a license.

I could not find that part on their page. Was it on page 1 or 2? I looked mainly in the "cold start enrichment" section, but just skimmed over the rest looking for choke plates.

In the beginning, true. Now it is simply a style.. Much like Band-Aid and Post-It are names of only one maker, but now anything of the same style is called the same name.

What happened to your Z in '75? sold/wrecked/stolen? never wanted another one?

Page 1. The page is quite long, and about a third of the way down are drawings of carburetors with choke plates. This is followed by a section titled "The Constant Vacuum carburettor" with drawings of SU carburetors, one of which is animated. None of the SUs has a choke plate.

The drawings are all on the right side of the page; maybe you need to widen your viewer window.

That can be so only if the patents and trade mark registration have expired, which may have already been the case in the 1970s. How long do patents last in the UK?

One of the sidebars at

It was 12 years old and rust was eating through the rocker panels and the wheel wells. I had already had to patch a one foot diameter rust-through hole in the driver's side floor board. (240Zs were terrible for rusting.) Also, they were tightening up on emissions limits in the Virginia suburbs of Washington, DC, and I didn't think my Holley carburetor substitution was going to pass the semi-annual emissions inspection. So it was time for it to go. I sold it to a man from Maryland, where they inspect cars only at time of purchase. I told him about the carburetor substitution and insisted that he take the Hitachi SU carbs and manifold, which he didn't want, in case he had to put them back on before he could get the car registered in Maryland. I never heard back from him so I guess he did OK. He was kind of blase about inspection, so I suspected he had a buddy who worked at an inspection station. I replaced the Z with a Honda Prelude 2.0 Si. I think I had the first one in the DC area. A few months ago I bought an Infiniti G35 and have been lurking here in case someone says something about the 350Z that applies to my car.

That should be "biennial" inspection--every two years, not twice a year.

Oops. That should have been '85. I sold the car in 1985. When you get to be my age it's usual to err in dates by a decade or two.

"E. Meyer" snipped-for-privacy@ieee.org wrote in news:BB66D33D.C489% snipped-for-privacy@ieee.org:

I understand that. My comment comes from the guy at the Z store in the local Nissan dealership. I was asking about ways to goose up the S13 240sx and he told me the Z engine will drop right into it.

The car or the engine? The car yes but the engine... for the most part... not really. Anyone that owns a 240 with an L24 engine dreams of dropping in an L28. Not too many people will take in an L24 as a core anymore. Sorry.