escapedan

Curtis - thanks for the reply. Makes sense, but it doesn't really feel like the engine is stalling due the brakes being applied, but rather due to the vacuum line being "plugged up" when the line collapses. I have not changed the master cylinder yet, but was planning on ordering one. Do you suggest sticking with the 240 one or going with the 280 version?

UPDATE - My 73 is still having the "Stalling at Speed" issue, but I believe I've found the cause. For some reason it is pulling massive vacuum between the brake master cylinder and check valve - so much so that it causes the vacuum hose between the brake master cylinder and check valve to literally collapse. Important note - this began shortly after installing rear disc brakes, but not immediately after. Once it gets to the point where there is no free flowing vacuum, the car dies while driving. It will rev (sometimes) with the clutch in, but will not accelerate at all with the clutch out. I performed a "tracheotomy" on the road by puncturing a hole in the vacuum line and inserting a relief valve, which got me home, but is clearly not a permanent fix. So, question is has any experienced similar vacuum issues? If so, was it a faulty brake master cylinder? Booster? Any help would be appreciated!

Wish I could help, but I too am having the same problem now.

That's great news. I was thinking I would have to end up pulling the fuel pump or upgrading the ignition, but just wasn't sure where to start. Ideally, I should ditch those points anyway...

Great suggestion - I'll definitely start simple and check the fuel filter. It does run fine with the clutch in. In fact, once I pull off the freeway and/or slow down a bit, I can rev it to redline with the clutch in. On a side note, while I'm in there working on things, what do you think about getting rid of the points with a petronix or Crane or something?

My 1973 240z (2.6L engine; no smog equip) initially starts and runs normally. It runs fine for 5-10 minutes then, for lack of a better description, the engine starts cutting out at about 65 mph (any gear). I can hear the carbs "sucking air", but it seems to be starving for fuel and/or spark. With the clutch depressed, it will rev to ~4,000 rpm and again cuts out. It gets progressively worse until pull off the freeway. Once I get off the freeway and drive on the side streets, it seems to work fine again so long as I dont get above ~45mph. Also, it then rev's all the way to redline as if nothing was wrong. I'd sure appreciate any suggestions before I go buying fuel pumps, ignitions, etc.... Here are some basics: - 240z chassis, 2.6L engine (emissions equip removed), SU carbs, standard 240z distributor with points (ok, stop laughing), upgraded coil, 5-speed trans, headers, etc.

Anyone autocross? What about a Thunderhill day? I live in San Jose, but am willing to drive "where - ever" to hang out with other z guys. Daniel

Thanks a million! I've adapted the ST bushings and fab'd the metal plates. Worked like a charm! Take care, Dan

Hey guys, I'm in the process of mounting an MSA rear sway bar on my 73 240. The car did not have an existing rear bar, however it appears that there are factory mounting brackets welded to the frame. I have secured the swaybar to the a-arms with the appropriate linkage, and interestingly the sway bar fits right into those welded "mounts" on the frame. The instructions that came with the MSA bar don't mention this mounting place and suggest drilling holes through the frame (via removing the carpet behind the seats). Can I just use the existing "mounts" or do you suggest using the MSA method??? Thanks! Daniel Stampf

I’m trying to understand what the pistons inside the carbs “do”. The reason I ask is that after taking all the smog equipment off my 1973 L24 engine and capping all the left-over ports, my engine is idling at 2400+ RPM at 7degrees advanced. (even after warming up for 3+ minutes in already warm California) The only thing that seems to drop the RPM is when I manually lift the pistons inside the carbs leading me to believe they should automatically lift when the engine is idling. When the pistons are fully down, the high RPM’s return. Additionally, the car “diesel’s” (continues to run, chugging and spitting raw fuel out of the rear carb) when I shut it off. The air/fuel screws are 2 ½ turns open and the idle screw is full up (not pressing down on the throttle at all). I have removed the choke cables from the car entirely (as it will be an autocross car) but I’m not sure how to determine if the car is in “open choke” position. This could certainly be a cause for the high rpms…?? Finally, would a vacuum leak cause the high RPM’s? I have everything well sealed, but its very hard to be 100% positive all the seals are fully seated. Thanks in advance for any advice; I am eager to get the car running properly. Dan

WOW!!! THAT IS QUITE POSSIBLY THE BEST RESPONSE I COULD EVER HAVE ASKED FOR!!! I'm printing out your advice as we speak and I'm going to follow it to the letter as soon as I get off work tomorrow. I should have mentioned in my orig post, but the choke cables were removed from the car. I can see where the linkage hooked up, but the cables are not installed....or even there at all. I dont think this will hurt anything as I wont be driving the car in cold weather....furthermore, I live in California and out here 60 degress is considered cold! =) Do I need to secure the choke linkage somehow, or can it be left alone? I recall seeing the idle screws, but i will make sure I'm looking in the right place. Thats great news about the pistons sounding like they are working correctly, I was really thinking that they were the problem. So the idle screws should only be adjusted when the car is running right? Also, my mixture screw is currently only 1/2 turn open from the fully closed position, I will open this up as you suggest and start from there. Thanks again for the awesome reply, I'm determined to learn enough about these cars to be able to reply on this board instead of always posting questions to it!!!! =) Dan

Ok, I finally got the beast started...definately a home run for the night, but now I have a different situation. When I start the car, the engine revs very high and stays that way. I have twin SU's on a 1973. This is the first time starting since removing all the smog equipment. I have never worked on an SU carb before but I can tell you that the piston inside the carb is all the way "down". If I manually move the piston up, the engine revs slow considerably and then the engine dies. What am I missing?? I have filled the carbs with SAE20 wt oil and inserted the dampner rods as described in the haynes (useless) book. When the dampner rods are screwed in, it is pretty hard to move the piston up. As always, thanks in advance. The advice is always sincerely appreciated. Dan

Thanks for the excellent tips!! I would be totally lost without this site! I'll be heading straight to the garage when I get home and will post the results! Hopefully good news!

Thank you very much! I will recheck all this first thing tomorrow...dont want to p.o. the neighbors tonight!

This is my first attempt with SU's. I've just reinstalled my twin SU's after replacing all the hoses and removing the smog equipment and now I cant seem to get the car started. Should I remove the float bowl covers and fill them with gas?? At the recommendation of a local mechanic I tried spraying starting fluid into the carbs while turning the car over, but no luck. Just lots of popping and smoke coming out of the carb!! Any suggestions?