SU Carb ID, Vapor Lock, Ignition Question

[z boy mn]

Hey everyone, I'm off to look at another Z this weekend that has a stock motor in it.

It's a 1973 240Z, and I want to make sure it has the "domed" SU Carbs and not the "flat-topped" SU Carbs, which seem to be more prone to vapor lock from what I've read. The problem is all the carbs online seem to look the same to me. They have a black screw on top and look reasonably "domed." See the one attached as an example. Does anyone have a photo of the flat-topped carbs so I can be sure to tell the difference?

Also, I understand that vapor lock was a common problem with these vehicles, and that there were things you could do (like insulate the fuel lines) to remedy it. Are there other "fixes" that are possible that I should look for?

Finally, the seller also suggested that the ignition has been replaced, but wasn't sure what was done or how. Is there an easy way to tell whether or not it has points still?

Thanks in advance!

Adam

[SteveJ]

Hey everyone, I'm off to look at another Z this weekend that has a stock motor in it.

It's a 1973 240Z, and I want to make sure it has the "domed" SU Carbs and not the "flat-topped" SU Carbs, which seem to be more prone to vapor lock from what I've read. The problem is all the carbs online seem to look the same to me. They have a black screw on top and look reasonably "domed." See the one attached as an example. Does anyone have a photo of the flat-topped carbs so I can be sure to tell the difference?

The carburetors in the picture are round top carburetors. As for pictures of flat top carburetors, you could always download the FSM for the 73 and look at the drawings & pictures in there.

Don't believe EVERYTHING you read on the internet, especially when it comes to flat top carburetors. I had no problems with vapor lock with the flat tops when I went Savannah for the national convention.

Also, I understand that vapor lock was a common problem with these vehicles, and that there were things you could do (like insulate the fuel lines) to remedy it. Are there other "fixes" that are possible that I should look for?

If the car in question is the one from the picture, the headers are wrapped, but it might not be a bad idea to source a heat shield to install between the carburetors and the headers.

Finally, the seller also suggested that the ignition has been replaced, but wasn't sure what was done or how. Is there an easy way to tell whether or not it has points still?

You can do one of two things:

1. Take along someone who knows about working on old cars.

2. Take off the distributor cap & rotor and look for the points.

[z boy mn]

The photo isn't one of the car in question...just another vehicle. I think I have a link for the FSM at home and will try downloading it for a photo/picture of the non-domed carbs. Good to know that the vapor lock may be less of an issue...it isn't that warm here in MN anyway, but the car does have AC, so I'm guessing it will get warmer under the hood when it's on.

As for the ignition...I have rounded up someone to go with me...that should help, too!

[Bruce Palmer]

A couple of thoughts relating to that picture that bear study.

Tube headers, like those, often interfere with the installation of a heat shield, which then requires wrapping the tubing headers with the heat wrap, which in turn can result in premature burn out of the headers. Pretty cool program just to be able to say "my car has headers" and all the problems that go with.

Just saying.......

[jackboxxx]

These pics should help clarify the difference between "round tops" and flat tops" for you.

ROUND TOP CARBS

FLAT TOP CARBS

See the difference?

should be easy to spot

Hey everyone, I'm off to look at another Z this weekend that has a stock motor in it.

It's a 1973 240Z, and I want to make sure it has the "domed" SU Carbs and not the "flat-topped" SU Carbs, which seem to be more prone to vapor lock from what I've read. The problem is all the carbs online seem to look the same to me. They have a black screw on top and look reasonably "domed." See the one attached as an example. Does anyone have a photo of the flat-topped carbs so I can be sure to tell the difference?

Also, I understand that vapor lock was a common problem with these vehicles, and that there were things you could do (like insulate the fuel lines) to remedy it. Are there other "fixes" that are possible that I should look for?

Finally, the seller also suggested that the ignition has been replaced, but wasn't sure what was done or how. Is there an easy way to tell whether or not it has points still?

Thanks in advance!

Adam

[Healey Z]

Zboy, I think you are doing this right and will be rewarded with a nice car in the end.; my old rule was to look on line at 1000 cars, call on 100, physically look at 10 and buy 1.

It takes a lot of work to find the right car and I think you are putting in the time and getting educated along the way.

To your original post, I think most of the "vapor lock" issues are due to people removing the original equipment, like the motor above or the car has worn parts that need replacing. A common and one of the best upgrades for these cars is to replace the points with electronic ignition. Pop the cap to see if it is a later Z,ZX unit or an aftermarket Pertronics item. Both are good upgrades....good luck, hopefully this is the one

[pbarcher]

I bought my car new in 73 and the vapor lock in the summer made the car almost un-drivable, even in upstate NY. There was a factory recall that included insulating the fuel lines under the hood and installing an electric fuel pump near the tank. Check to see if yours has that pump. There a lots of options for insulating the lines that are preferable to what Datsun installed.

The recall helped a bit, but things improved noticeably after I installed round tops.

[Walter Moore]

A couple of thoughts relating to that picture that bear study.

Tube headers, like those, often interfere with the installation of a heat shield, which then requires wrapping the tubing headers with the heat wrap, which in turn can result in premature burn out of the headers. Pretty cool program just to be able to say "my car has headers" and all the problems that go with.

Just saying.......

I have the factory heat shield installed, and I have a Motorsport 3-2-1 header. I may have had to "tweek" the heat shield slightly (I honestly don't remember), but it fits fine. Why anyone would remove the heat shield with stock SUs is beyond me...