SU Carb advice

[Cxracer]

I have been doing some searching but not finding anything specific to my current situation.

I'm replacing the L2.4 engine in the '72 240 I bought last summer from my friend. He had installed a 4 barrel carb intake with a carb that was too large (600CFM) and it got stuck open and over reved the engine causing major internal damage.

So... I picked up a '75 280z engine with the fuel injection intake on it. I want to pull of the FI and install SU carbs (after reading opinions here on the site).

I now have 3 different pairs of SU carbs and intakes (don't ask). They all seem to have different intake headers and spacing and I'm sure they all will need a little TLC so I intend to get a rebuild kit from Z-Therapy but I only want to deal with rebuilding one set.

Can anyone tell me the best set of carbs out of the batch I have to rebuild and install on the 280z engine I have based on the pictures attached?

The intakes say E46, N33, N36 on them but as far as I can tell they are all "round top" style SUs.

I intend to strip off as much of the emissions stuff to simplify things since my car is CARB exempt and I live in CA so cold weather starts aren't too much of an issue.

[Arne]

OK, here's what I think you have.

The first pair (E46) appear to me to be a pair of 3-screw carbs from a '72. Not certain on the manifolds, but I think the E46s were also for the '72s.

The second pair (N33) are also 3-screws from a '72, but are on manifolds that I think are from a '73 with EGR.

The third pair (N36) are a pair of later 4-screws (w/float drains) from a later '70 or a '71. The N36 manifolds are (I think) from a '74 260Z with an earlier balance tube.

All of the carbs are pretty much interchangeable in pairs. The heat shield on the N36 manifolds is the early type, for cars that have no heat riser.

You could use any of the manifold pairs, but should use the balance tube from either the E46 or N36, not the one with the ERG stuff. Some people think the N36 manifolds flow better than the others, but I've never seen hard numbers to confirm that.

So all in all, it looks like the last picture has the best-looking carbs, has the heat shield, and are on (arguably) the better manifolds with an easily desmogged balance tube. Probably the package to use, IMO.

[Bruce Palmer]

I'm voting for bling!! Half your work is done and it wont matter a bit. The 4 screw carbs on the N33 manifold will work fine but grab a set of the thick insulators off the N46 manifold and change to the longer studs to go with the insulators. Take a look at our Smooth and Clean balance tube picture to see what can come off.

The brake booster tap coming off the top of the balance tube may need some fiddling if your hose is preformed for the end tap nipple on the balance tube.

[Zs-ondabrain]

And I'll take what ever you don't use. I'm trying to get a few together for my 240 and 260Z.

Let me know,

Dave

[JohnnyO]

.....grab a set of the thick insulators off the N46 manifold.

So, I just pulled my carbs off the manifold for cleaning and new jets. When I pulled them off some of the insulator "stuck" to both the manifold and the carbs. Not much, about as much as gets stuck when you peel a gasket off.

My question is this:

Are they reusable with a little sanding?

Can the exterior be cleaned a little to "lighten" the color up or should I leave the dark patina on them?

Sorry about the hijack.

John

[Bruce Palmer]

Sand the insulators to remove the gaskets. We sell 'em. Don't have any suggestions on what to do about the color of the insulators.

[blue 72]

I agree that it's probably the best combo to use either the N33 or N36 intakes and whichever set of SU's are in the best condition coupled with the thick insulators and bolts.

I've done just that. My car is currently running N36 manifolds from a '73 flat top equipped car coupled with thick insulators and their appropriately longer studs. While the intakes were off I took the opportunity to have the extra holes on top for emissions equipment welded shut. My overbored '72 three screw domed SU's are bolted on to them and I'm using an E88 balance tube.

Edited February 21, 2009 by blue 72

[Cxracer]

I'm voting for bling!! Half your work is done and it wont matter a bit. The 4 screw carbs on the N33 manifold will work fine but grab a set of the thick insulators off the N46 manifold and change to the longer studs to go with the insulators. Take a look at our Smooth and Clean balance tube picture to see what can come off.

The brake booster tap coming off the top of the balance tube may need some fiddling if your hose is preformed for the end tap nipple on the balance tube.

Hi Bruce,

So are the 4 screw carbs better than the 3 screw type? What rebuild kit would you suggest I get to make them reliable?

[Cxracer]

And I'll take what ever you don't use. I'm trying to get a few together for my 240 and 260Z.

Let me know,

Dave

Dave,

My project is coming along pretty slowly but I'll let you know what I have once I get the car running.

[Bruce Palmer]

Hi Bruce,

So are the 4 screw carbs better than the 3 screw type? What rebuild kit would you suggest I get to make them reliable?

Three screw vs 4 screw is a you pick'em deal. The only difference between the kits is the gaskets to the manifold. The 3 screw gaskets have the holes for water.

Reliability? That's in the hands of the builder. Our Reman Carb Service carries a 3 year warranty because we can control every step of the process.

Remeber too that worn out throttle shafts will not be addressed by the Tune-Up Kit.

[Zs-ondabrain]

Dave,

My project is coming along pretty slowly but I'll let you know what I have once I get the car running.

Awesome, just let me know.

Dave.

[Cxracer]

Three screw vs 4 screw is a you pick'em deal. The only difference between the kits is the gaskets to the manifold. The 3 screw gaskets have the holes for water.

Reliability? That's in the hands of the builder. Our Reman Carb Service carries a 3 year warranty because we can control every step of the process.

Remeber too that worn out throttle shafts will not be addressed by the Tune-Up Kit.

Bruce,

I'm on a bit of a budget right now and I'd like to learn more about carbs anyway so I figure rebuilding a set will be good for me. Should I change the needle size for the 2.8L engine or should I stay with the stock size in the carbs I have now?