gmr714

Thanks for the info. I live in Walnutport, PA 10 mi. NW of Allentown. I store the car at a friends and will try to use your info over the holiday to get a handle on what I am dealing with. I bought the car from a friend who redid the interior and exterior but not much to the engine after a fire. I will definitely look into the desmogging procedure. Thanks, Mark

Thanks, I do have the flat top hitachis, I was confusing "flat top" with the webers. Can I leave all of the things I described disabled and still get it to run decent? How do I adjust the idle mixture? Thanks, Mark:sick:

Sorry I wasnt clear. I have the round carbs with the oil dipstick on top. Is there anyting I can do with these ?

:disappoinI recently bought a 74 260z with Hitachi Carbs.I did a complete tuneup ++ and then had the carbs adjusted for $$$. It seemed oK at first. Now I have a problem with the way it runs if I start it while it is still hot. It runs pretty good for 50 miles but if I stop for gas or a soda then I start it back up it will stutter and run very weak. The engine temp stays low. I have to pull the hand choke all the way back to get power under load. It does not stall out. I have been through the vapor lock theory, and it is not the problem I think. I ran new fuel lines and insulated them , the pumps are new with good pressure. When I have this problem I can drive it for miles and it won’t smooth out, shouldn’t vapor be forced thru? I need to shut the car off for 15 minutes and it runs fine again. I found that the temp sensor on the air cleaner is missing and the air control valve on the intake does not function, should I close it so it only draws fresh air all the time? also the vacuum control valve is inoperative as the wire is torn off. The EGR has also been disabled since the diaphram was leaking and the VAC line is capped. When I pull back the choke am I cutting air or adding fuel or both? The vapor canister is also disabled.I have been attempting to figure out a way to adjust the idle speed and mixture also but all I have is an untrained ear and a screwdriver. I am a new Z fan and would appreciate any and all input on how to troubleshoot and get this car running smooth without replacing all of the above parts.I have antique plates ( no inspection or emissions) It is a driver not a show car. Thank you for your suggestions Mark in PA

I recently bought a 74 260z with Hitachi Carbs.I did a complete tuneup ++ and then had the carbs adjusted for $$$. It seemed oK at first. Now I have a problem with the way it runs if I start it while it is still hot. It runs pretty good for 50 miles but if I stop for gas or a soda then I start it back up it will stutter and run very weak. The engine temp stays low. I have to pull the hand choke all the way back to get power under load. It does not stall out. I have been through the vapor lock theory, and it is not the problem I think. I ran new fuel lines and insulated them , the pumps are new with good pressure. When I have this problem I can drive it for miles and it won’t smooth out, shouldn’t vapor be forced thru? I need to shut the car off for 15 minutes and it runs fine again. I found that the temp sensor on the air cleaner is missing and the air control valve on the intake does not function, should I close it so it only draws fresh air all the time? also the vacuum control valve is inoperative as the wire is torn off. The EGR has also been disabled since the diaphram was leaking and the VAC line is capped. When I pull back the choke am I cutting air or adding fuel or both? The vapor canister is also disabled.I have been attempting to figure out a way to adjust the idle speed and mixture also but all I have is an untrained ear and a screwdriver. I am a new Z fan and would appreciate any and all input on how to troubleshoot and get this car running smooth without replacing all of the above parts.I have antique plates ( no inspection or emissions) It is a driver not a show car. Thank you for your suggestions Mark in PA

I have a 74 260z and it runs great until I stop for gas or a quick bite to eat. If I start it while hot it will run very weak and I have to choke it to get some power this problem continues for miles. If I let it cool down for 15 minutes it runs great again. I thought it was vapor in the lines but I insulated the best I could with raybestos tubing and header wrap where I could. Both fuel pumps are new and good, new fuel lines, filters, good gas, and carbs are adjusted correctly. It's annoying more than anything since it is good after I wait 15 minutes. I need some Ideas on what to try, please. Thanks, Mark ( new old Z owner):cross-eye

Thanks for the info. I changed the electric fuel pump, strainer filter, fuel lines and added an inline filter before the mechanical pump over the winter before I had the carbs tuned. I 'll try wrapping the lines and shielding them from the heat. thanks

I have a similiar problem with my 260 that has Hitachi carbs. It runs great but when I shut it off and try to restart it while hot it either turns over and wont start or it starts but runs very weak like it is starved for gas. It is an intermittent problem and I was thinking it was vapor locked but I am unsure of how to proceed. Fuel pump pressure is around 3psi hot. Perhaps we have the same problem. I was ready to change the mechanical fuel pump.

I have a 74 260z. it runs great but sometimes when I shut it off I have a hard time getting it restarted (For instance when I get gas) it might start but it runs really weak, sometimes it wont start at all for 15 minutes then it runs fine. Is it vapor locked? any suggestions?? Thanks, Mark

I have a 74 260Z with twin hitachi carbs. It will not start after it sits for a few days no matter the temperature. I pump the gas and it turns over but refuses to start unless I spray it with starting fluid. Once it starts it is good for a day or so. I just got it and it will sit for the winter but I want to get it ready for spring. I am not a mechanic but the fuel pumps are good, no leaks. I just cant get ignition when cold without ether. The guy I bought it from said it has always had this problem. Any suggestions would be appreciated. I bought the original 74 service manual by nissan but need a push in the right direction. don't know anyone familiar with these carbuerators. Thanks, MARK

I recently bought a 74 260Z from a friend and it has a few mechanical problems but nothing major. Until I saw your post I was puzzled by the action of the tach. It pegs, floats or is dead at any given time. can you elaborate on cleaning the optical sensor. I havent gotten a good manual yet. The chilton I have doesn't mention it Thanks. Mark p.s. 1st post