Help needed ASAP

[Jeff G 78]

I want to thank everybody for your help and support. The Z is on its way to the race and I am just awaiting another teammate with the camper to arrive at my house. We should roll into Nelson Ledges around 11pm tonight and we'll know tomorrow if it runs right.

I won't likely have any internet signal, but if I do, I'll let everyone know how it goes tomorrow. The race starts at 10am Saturday and finishes at 12:30pm on Sunday. Other than an hour safety break to rotate corner workers, we go straight through for a total race time of 25:25:25. Fingers crossed...

[beermanpete]

Good luck and have fun.

[Captain Obvious]

Excellent. I hope you have those issues licked and have all the horses you're supposed to have. No rolling chicane for you!!

Good luck!

[Jeff G 78]

I'm WAY too tired to go into the details, but the car ran terrible at times and great at times. In 25 hours, 25 minutes and 25 seconds (25:25:25), we completed 698 laps for a total of just under 1400 miles! We finished 30th out of 75 entries and had a great time. The handling was amazing and the motor ran great at night when it was cold. We had terrible vapor lock and other heat related fuel issues in the heat of the day.

Thanks to all who helped and I promise to give a full race report with the symptoms and fixes once I get a shower and some sleep. I haven't done either since Thursday.

BTW, we won the Mr. Clean award for the cleanest driving. The Datsun only has one scuff in the fender and a chunk out of the front bumper. Both were caused by other drivers sliding into us in the middle of the night.

[240260280z]

Congrats! Sounds like a great time was had.

[Captain Obvious]

Sounds fantastic. Well, other than the vapor lock stuff of course.

Looking forward to the full report!!

[kjones]

Hey - What's your Chump Car team name?

I run with SkoolBoyZ Razing down here in Florida in an old ratty 280z.

Just noticed your post...

One thing that I've seen in 3 separate Z's

I bought a pristine 260z from California from the original owner many years ago. He complained about all the things you have experienced and said Nissan couldn't figure it out for over 10 years.

When I got the car I eventually found the problem...

When we opened the fuel tank (and I've seen the same problem 3 times since) there was a slight "kink" in the pickup tube inside the tank. If any sort of debris was sucked up, it could not make it past the kink... let the car sit and it the debris would sometimes fall back to the bottom of the tank... so it presents itself like an intermittent problem... or sometimes just a fuel starvation problem with restricted flow.

I used a 2 gallon fuel cell and hooked up my pump to it, bypassing the stock tank and tested it that way...

Also, when I blew compressed air from the line on the suction side (fuel rail) back into the tank, I suspected a restriction because once I blew out the debris it would go away temporarily...

Draining the tank and inspecting with a scope always looked like the tank was perfect inside - wasn't until we cut it open that we found it...

Also, I suspect your float settings as a secondary problem...

Good luck and keep us posted

Would be good to know what your AFRs look like

Another item to suspect is your distributor/ignition box/ignitor -

Ken

[Jeff G 78]

OK, be prepared for a long post...

We went out on the track Friday morning for practice and the car immediately exhibited the same issues as before. We pinched off the return line with no improvement and kept trying different things to no avail. At one point, we went to restart the car and the battery was dead. We checked voltage and it appeared the alternator was not working. We had a new one with us, so we installed it with no improvement. We then swapped the voltage regulator with no luck before we started tracing back every wire in the car. The problem turned out to be a missing wire that was removed during wiring cleanup. A teammate had inadvertently removed the wire that powers the alternator! With the wire back in place, we were once again charging and we figured that our high RPM issue might have been caused by low voltage to the coil. It was now 4pm and we still had to go through tech, so daytime practice was over and we had very little track time. We got through tech and prepared the car for night practice which started at 7:30pm. The car ran way better and we thought we had been chasing fuel issues when it was really low voltage this time. We swapped tires and did the final checks Friday night before we hit the sack.

Saturday morning came and we took the green flag at 10am. The weather was beautiful, and the air was still cool. There is a 2 hour driver stint limit and with our new tank, we should be able to run that long, but after 1.5 hours, the driver radioed in saying he needed fuel. The car took only 10 gallons to fill and we were back on the track. He said that the car ran well and made power to 6500 RPM, but it stumbled off turn 13, the tight right-hander leading to the front straight. The second driver again went 1.5 hours and used 10 gallons of fuel before the car began to backfire on decel and sputter out of the turns. By now, it was a little after 1pm and the temperature was up into the high 70's with bright sun. The car began running worse and worse on the straights going back to its old habits of not revving past 5000 RPM. This time, when the driver came into the pits for fuel and stopped at the beginning of pit road to get his timer, the car died(they put a magnetic timer on the roof of every car entering the pits to make sure you spend a full 5 minutes in the pits for fuel stops). We pushed the car to our pit stall and fueled it up. When he tried to restart, it had all the signs of vapor lock. The car tried and tried to start, but wouldn't keep running. We lost almost 15 minutes before we finally got it going. We cycled through the drivers and it kept running worse and worse through the day. At every fuel stop, it would refuse to restart hot and we kept losing time. Our fuel pump was struggling to prime and fuel pressure was sometimes good and other times not during engine restarts. We tried every combination of return open and closed. We then decided to go back to the paddock and install the mechanical pump in series with the electric pump. We lost a lot of time and when we finished, it made the problem worse, not better. At was now 5pm and the race was checkered for a 1 hour safety break to rotate corner workers. After a 15 minute drivers meeting, we got busy making changes. We removed the electric fuel pump and made a bracket to drop it down a foot lower to be right at the height of the bottom of the fuel tank. We were sure that the pump couldn't lift the fuel to prime once we got low on fuel and sucked some air. We also removed the mechanical pump again and we were ready for the 6pm restart.

I finally got my turn at the wheel after the restart and the car ran great other than the stumble down the front straight and back straight after right hand turns. All was fine for 20 laps of so until a full course caution and the safety truck came out. The truck was going very slowly and we came to a full stop as we waited for a tow truck to extract a car from the mud. As soon as we stopped, the car died on me and wouldn't restart. I was dead in the center of the track with classic vapor lock symptoms. I tried for several minutes to refire it on the track, but it wouldn't catch and I had to be towed back in. After we iced the carbs and it cooled a bit, it fired back up and I was back on the track. It ran great other than the two stumble spots. As my stint finished, it was just getting dark out.

It is now 7:40pm and it's dark out. We are in 50th position out of 75 teams. The temps began to drop right away and the car ran better and better. We never missed a beat over night and by sunrise we had climbed to 39th place. The stumbles went away completely by the time I got my next stint at 3am and the car was running perfectly. It made power to 6500 and was able to keep up with most of the other cars. One thing that showed up in the night was that when we came into the pits and popped the hood, the exhaust manifold was always glowing BRIGHT red. I assume this was happening all race and we could only see it at night, but I can't say for sure. Now that we lowered the pump, we never had any priming issues and we could use more of the tanks capacity.

Sunrise over Northeast Ohio and the race was stopped for a quick drivers meeting. Overnight was some of the worst driving I have ever witnessed on a racetrack. There were cars going off everywhere and in the first 17 hours of the race, we had 6 rollovers!!! All teams got a stern warning to stop driving like asshats and we were back to racing. We kept gaining spots and we were in 37th place at 8:45am. The next to last driver got in the car and ran his 1:45 stint. He came in at 9:25 and said that it was starting to stumble more and not rev all the way. He also said that the tires were really losing grip and that I'd have to go longer on gas than anyone else was able to do and just bring it home with what I had to work with. I got in the car to finish the final 2 hours of the race at 10:30am. The car was running even better than it did overnight and unlike overnight, I had a lot of clear track to work with. It was the best 30 minutes I have ever had on a race track. I had several close calls though. After only a few laps on the track, I entered Oak Tree, a banked left hander, in the outside lane and I there was a very fast V8 inside of me. I heard his tires howling and I knew he wasn't going to hold his line. He slid across the track and I was prepared to get hit. He nailed me in the rear bumper and I quickly corrected and saved it. He got the black flag the next time by the start finish line. After another few laps, three other cars spun right in front of me and I was always able to avoid them as they blocked my path. Unfortunately, I lost communication with my crew only a few minutes into my stint, so I had no idea how long I had been in the car or how much time was left in the race.

Not knowing how long I had been in the car, it started backfiring on decal and really stumbling coming out of corners. This is exactly what it does when getting low on fuel. With no pit communication, I ducked into the pits to get fuel. This was the wrong thing to do! As soon as I cam to a stop at our stall, the car died. I asked how long I had been out and the answer was only 45 minutes! Oops! There is no way I was low on fuel, so the problem was simply that the car running poorly due to the hot weather and ongoing fuel issues. The car refused to restart for several minutes. I got back on the track with my communication working again and I just drove what I had and worked around the poor running. With my poor decision to stop, I lost 2 positions. I ran the car as hard as I could and took the checkers after 25:25:25.

We finished in 30th place and logged 698 laps and close to 1400 miles. In the awards ceremony, they again scolded the field for terrible driving and said that nearly every car in the race was damaged. The ChumpCar staff had talked it over after the race and asked the corner workers if there were any cars that didn't have any damage and were never called out for going off track or running into anybody else. They concluded that only one car ran a truly clean race and they announced the #46 Broke Racing Effluence Datsun as the "Mr. Clean" award winner. It was really cool getting another award. Last year, we won an award for the best looking car.

After the race, we spoke with many teams who told us how pleased they were with our driving. We took the oldest car in the field by a decade and completed the longest endurance race ever. We were never fast on the straights, but I'd say we have the handling dialed in near perfect. We started the race on used 195/60R14 Falken tires that ran our first 24 hour race two years ago. They ran 185 laps in that race and 698 laps in this race and they are still not to the wear bars and they have worn perfectly evenly across the tread. The Porterfield R4-E brake pads have now run 14+ hours at GingerMan, two track days, and 25+ hours at Nelson Ledges. We never even replaced the brake rotors that were on the car when we bought it two years ago.

We were ecstatic with our race overall and we will figure out and fix the issues before next season.

Thanks to all who helped us!

[Jeff G 78]

I forgot to discuss a few more details about the running issues.

One thing we noticed is that during normal operation, our temp gauge reads about 180F, but at track speeds, it reads only about 130F. This is with a brand new 180F thermostat. The engine is clearly getting plenty warm if the exhaust manifold is glowing red, but why is the water temp so low?

To try to help the vapor lock issues, I made a heat shield that protects the fuel bowls from the exhaust heat, but it didn't help at all.

When we had our high RPM issues, I replaced the bowl to nozzle hoses with stiffer clear Tygon hose with no improvement.

At about 5am, I had a nice discussion with a fellow racer who knows old Japanese carb cars very well. He said that our stumble exiting corners is due to "spill over", a condition where the floats are set too high and the fuel is forced up the nozzles in long corners. The car goes rich in the corner and the plugs get wet. It takes several seconds for the plugs to dry and fire properly again causing the acceleration stumble after a hard corner. He went on to say that to lower the floats, I need to drill the jets bigger to allow fuel to flow into the bowls faster to avoid the high RPM starvation. Raising the floats like I did fixes one problem, but causes another. It was a good trade-off, but drilling the jets out and lowering the floats a bit should let it rev as well as fix the stumble.

We will make a more permanent bracket for the fuel pump (the current one is really chumpy as it was made in 10 minutes from 22 gauge sheet metal), but we still haven't figured out how to fix the fuel temp issues. The return system doesn't help the fuel that's sitting in the bowls.

Why is the exhaust manifold so hot? Is that normal? Hot normally means lean, but we already have SM needles and have fattened it up by raising the floats.

Even when running perfectly, we really need more power, so we might have to look at a L28 or even a turbo L28. We just have to do it on a shoestring budget to stay legal.

[LeonV]

Glowing exhaust means it's rich. If you're burning fuel inside your manifold, it will literally get red hot! As far as the vapor lock issues, try to insulate all fuel lines, and don't mount the fuel lines to anything attached to the engine. The original fuel rail will conduct heat from the engine to your fuel lines if you're still using it.

[LeonV]

And congratualtions on the finish and award. Sounds like hell, errr fun!

[Jeff G 78]

Rich? Hmmm, I always thought that hot exhaust meant lean. Makes sense, I guess. And yes, we are still using the stock rail. I guess it's time to ditch that too. It's still bolted to the head in the stock four locations.