Zooter71

So, you guys are so helpful!!!! Thank you so much for the great advice and possible tactics. I'll definitely try some of that stuff (next fill up) I promise! This is very helpful!!! Here is a shot of the engine. I took off the K&N filters for now, and just have short horns on it. But man when it's running right, it's a blast to drive!

The car: 1971 Datsun 240Z. Original motor, fresh rebuild (less than 2500 miles.) Original SU carbs freshly tuned, New spark plugs. MSD Hall Effect electronic ignition, Pertronics coil. Electric fans. Schneider Stage II cam and new springs. 6-2-1 headers with carb heat shields. 4 speed manual transmission. All smog components deleted. So, pardon the lengthy intro. Bought the car Jan of 2023. Fresh rebuild on the motor. Always smelled gas in the car, so after researching the forums, it seemed like fuel hoses were the place to start. Also I saw fuel dripping at the rear of the car. So I removed the fuel tank and all hoses and replaced said hoses because I found 52 year old hoses.... While I had the tank out, I checked the tank with a borescope, looks clean. PO must have done some work on the inside of the tank. This car came with a mechanical fuel pump AND an electric mounted to the mustache bar. I removed the mechanical and run on the electric full time. I have changed the electric pump filter and the right angle one under the hood. I have checked the screens at the carbs. They're clean. I have tuned the carbs and checked them, they are good to go. The oil in the dampers is the correct oil and at the correct level. On a longer trip recently, I found that I had left the filler neck screws in but not tight so I tightened and monitored that for leaks---fixed. Here's my problem...After I fill the car up completely at the gas pump and go to drive it, when sitting still at a light the engine stumbles...but I can't tell what's causing it. If I press on the gas pedal to rev the engine, or hold it at a higher RPM (say 1000+), then it seems better, but not 100% right until...after a gallon or less of fuel is burned, then this symptom clears up. So, only when the gas tank is at its fullest, that's the only time it does it, so I feel it's fuel delivery or return related. Any ideas? Of has someone else experienced this phenomenon? To be clear, I will be buying a fuel pressure gauge that can sit under the hood permanently and monitor the pressure that way. TIA!!!

Well, I actually had not thought it through, which after reading your reply....I guess I'll stick with the SU's on the vehicle. I tuned them via the factory service manual just yesterday, and they work really well. Thanks for taking the time to explain the pitfalls! If anyone else is reading this, just ask and I'll scan the SU section of the factory manual for the round tops and post the files here. I know it's all over the internets, but it never hurts to have it more places.

Hi DuffyMahoney. I'd be interested to know if you put together a "Guide To Injection" type of document for the conversion you did to your Z. I just recently acquired a 7/71 DOM 240Z with the original 240 L24 motor (with a few upgrades) and would like to convert to injection. But, I haven't really found a good tutorial that has a parts list and step by step guide....I don't really know all that much about fuel injection other than how it works. But for this motor and these cars, I know a lot of people have accomplished it. Anyway, nice work on your Z. It's really incredible! Here's the Bring A Trailer link to the one I bought. https://bringatrailer.com/listing/1971-datsun-240z-244/ It didn't sell at auction, but I tracked down the owner and bought it. So now it's going to get some (more) loving attention. Thank you in advance sir!