I did some searching and couldn't find a solution to this problem. I have a 1971 240Z that I have recently restored. We have had an intermittent problem that has popped up occasionaly since we purchased the car 3 years ago and it continues to this day. It will intermitently run extreamely rough and virtually stall when hot. Its is like its dropping one carb. I dissassembled and cleaned the SU carbs per the Z therapy video (several years ago). The fuel tank has been cleaned and treated with POR. The fuel lines have been cleaned, flushed and all of the hoses replaced. I added an electric fuel pump from an RX7 in the back and replaced the mechanical fuel pump up front with a new MSA replacement pump. I recently replaced the fuel inlet valves and reset the float levels. The car has a 280zx distributor with new plug wires, cap and rotor and we have replaced the module once trying to resolve this issue when it completely quit one time. I am begining to think that one of the carb slides/pistons may be sticking when the engine gets hot. I don't remember this problem occuring right after I cleaned and adjusted the carbs. I'm looking for any suggestions.

I assume you have a heat shield installed?

I assume you have a heat shield installed?

I assume your talking about the shield between the exhaust and the carbs. Yes I do.

I see you are running a 280zx distributor. Do you have the matching 280zx or similar electronic coil? The coil could break down when hot. Have you bypassed the ballast resistor?

Edited March 6, 200916 yr by Nigel1943

I see you are running a 280zx distributor. Do you have the matching 280zx or similar electronic coil? The coil could break down when hot. Have you bypassed the ballast resistor?

Actually I am running the stock 240z coil. I previously had a Mallory or MSD coil (can't remeber which) but that was removed. I had the same type problem with that coil.

It will run with the stock coil but not properly. Have you bypassed the ballast resistor? You will need to do this even with the stock coil.

It will run with the stock coil but not properly. Have you bypassed the ballast resistor? You will need to do this even with the stock coil.

I did bypass/remove the ballast resistor. Are you telling me that I should use a 280zx coil instead of the original 240 coil? I haven't tried that.

Vapor Lock ? The car is famous for this....

Jay

Not just a Z - zdisease

Vapor Lock ? The car is famous for this....

Jay

Not just a Z - zdisease

Yeah, I know. I installed an electric pump in line with the mechanical, I believe that was nissans solution for the problem. Are there any other "solutions" to the vaporlock problem?

I did bypass/remove the ballast resistor. Are you telling me that I should use a 280zx coil instead of the original 240 coil? I haven't tried that.

Yes, definately.

Vapor Lock ? The car is famous for this....

Jay

Not just a Z - zdisease

Which is why I asked if he was running a heat shield, but as he is I wouldn,t think he has too much of a problem with under hood heat in Vancouver.

Yes, definately.

I'll give it a try.