I recently bought some round top SUs for my 260Z. I got them home and was having a browse through here and found out they are off a L4 motor. 2 holes to secure to the manifold and a angled float bowl.

The people i got them off(along with a L6 manifold) said they were used on a Z and was running fine. These people are in now way dodgy etc

They are still 1.5". So what im asking is will i find any downfalls if i use these insed of my old flat tops compared to Z round tops?

Cheers!

In the US the 510 carbs were smaller. 46mm for the Z carbs vs 38mm for the 510 carbs. I know a couple guys who run the Z carbs on L20b's, but I wouldn't even consider running the 510 carbs on an L24. The stock size SU's are enough of a restriction.

They might be 38mm carbs from an L20, but I don't know about the angled float bowls. I think mine are straight. I wouldn't use them on anything bigger than an L20.

Does the manifold only have two studs per carb? Any pictures?

You might have the original carbs off a U20 which are big enough to take care os an L series 6! Any identifying marks-or as suggested above, pictures?

Will

Well they are 38mm across the 'choke' hole. Which is just under 1.5". My book says the original 260Z carbs are 1.6"(40mm). 46mm is 1.8" and i cannot find that measurement anywhere in the book. The only markings on them is 'ISO' on both the body and fuel bowl.

2 studs have been removed from each side of the manifold(N36).

Pics:

I'd say your first guess was correct - 510 carbs on a Z manifold. My 38mm Hitachis have straight float bowls and mate to a E41 manifold. The E41 manifold is drilled and tapped for 4 studs, but only has 2 installed. Your seller didn't even bother to put the insulator blocks between the carbs and manifold . . . .

I know it needs isolator blocks, the carbs arnt even bolted down. All part of the deal! Ill be using my inlet manifold anyway because it has the eariler(75) balance tube, which looks much better:classic:

And i found out the fuel bowls are easily movable to any angle!

Ill clean them up at work tomorro and have them on the Z by this weekend! If I do notice a severe drop in power ill hunt down some Z round tops... or bigger SU's and put these to the Datsun 1000 project that is in the pipeline!

My guess is that you will run fine until you decide to put your foot into it and run the revs up. After 5500 or so, you'll start to starve for fuel and you'll stumble, have trouble continuing up the powerband. You'll need to shift. Should be okay for most driving conditions, IMO. Its when you are feeling spirited that you'll wish you had Z carbs.

Good luck!