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De smogging Flat top SU's ?'s


LeDevil

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The flat-top SUs were factory carburetors on non-US market L18SSS engines. This engine was found mainly in what we here in the States know as the 610 and 710. Because Datsun/Nissan never imported that motor to the States in any car, parts for these carbs are not available in the U.S. These carburetors made their way to the US bolted to L18SSS motors that were heavily imported in the mid '80's (among other decades) and sold through a variety of import-engine resellers. However, if you're about to pitch your newly acquired setup into the trash, hold on for a minute...

 

First paragraph of:

 

http://www.jetlink.net/~okayfine/su/tunacan.html

 

I thought they came on Roadsters too?

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I was told the SU's were from a 2000 Roadster, As for tossing them ain't gonna happen I'm really looking forward to figuring out how to set them up and run them on my truck or Wagon might go with the Wagon seeing as it has a JDM L-18 . Thanks for the help though guys :D

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The roadster Hitachi's are 38mm for the 1600 and 42mm for the 2000 and they should be round tops. If you have the roadster Hitachi's there should be no smog devices on them and they shouldn't be flat tops. If they're in the 42-44mm range and they are flat tops they would be the 240z, 260z flat tops and they should be avoided. Also, to note the Roadster Hitachi's are not "handed" into left and right carburettors as are the 510 ones, you will be forced to use a throttle cable to use them. Come to think of it, tha's not such a big downside as the stock throttle assembly on the 510 is at a pretty nasty angle....

 

Here's a picture of the later model desmogged 510SSS 38mm Hitachi/SU's on a L20b in my wagon. You can just see the block off plates for the emissions stuff.

 

IMAGE_157.jpg

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Why should a person avoid the ones from the Z cars? Just too big?

 

For the most part, yes. They work good on a cammed L20B or L22, though.

 

There's alot of "conventional wisdom" about which are good and which are bad, mostly handed down by people who've used neither. They both work well for their intended application.

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I gave a set of Flatop SUs away FREE

 

Mike Offlson pulled his SUs off and went with a DGV later and nobody would buy his when they were separated and in a pile. Rays Datsun BBQ one year.

 

I would buy a pair off a running car knowing that it was good for maybe 100-200$

 

If a hand me down set or has been passed on the internet a few times AVOID>

I just get Mikunis from someone that is huring for cash (most have less wear and tear on them)

 

My 40mm Mikunis I paid 250$ rebuilt and has been on the car for about 7 years.

 

But if it makes you feel better to buy them then get them

Let us know when they are running.

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No experience with either, but this is from ZTherapy's website:

 

This is not a carb-It is a boat anchor!

June 1972 240Z to all 260Z's (US) Flattop "Hitachi"

Flattops.jpg

Evil things, these square mouthed carbs.

If you have these carbs on your 240Z-trash them and get ZTherapy SU's. You will experience a huge increase of power, mileage, and less breakdowns!

These are commonly referred to as "Hitachi's" or "Flattops". The dome shoulder is square, and the float bowl is on the bottom.

These carbs are not acceptable as cores. Please pay the core charge instead of sending these in.

 

That said, another site explains that the flat tops were a major redesign in response to the US smog laws. Amongst other differences, they incorporate a power valve. The site says the flat tops can be made to run properly. More info:

 

http://www.zparts.com/zptech/tech_tips/izccposts/su_differences.htm

 

Just Google on "flat top SU carb" and you'll find what I found. I love the internet. Thank you Al Gore!

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Measure the throttle bore at the manifold end. The number of 1/8 inches over 1" determines the model. 1 1/4" is an HS2. 1 1/2" is an HS4. 1 3/4" is HS6. If your carbs have a central float bowl built in then the are HIF series carbs as opposed to HS series carbs. I have never seen an HIF on a Datsun so you probably don't have to worry about those.

 

If you multiply your inches measurements by 25.4 you'll get the answer in mm. For example, if you measure 1 1/4" this works out to 38mm, a 1 3/4" is 44mm and so on.

mike

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