whamo

I installed a 280zx distributor in our L24 a couple years ago and set the initial timing at 8 degrees advanced at idle. For the last few years I have noticed a buzzing at part throttle tip in that sounds like detonation. I also changed the exhaust at the same time and dismissed this as a resonance issue with the aftermarket exhaust and not detonation, dumb mistake in retrospect. I hooked up my innovate wideband o2 sensor to aid in tuning the carbs this last weekend and in the process checked the total advance with my dialback timing light. Holy crap, it showed 48 degrees of total advance in by about 4000 rpm that seems like way to much to me. I ended up backing my initial timing back to 2 retarded to get the total advance down to 39 degrees, the detonation is gone with a little richer mixture and the timing change. Does anyone know what the total advance was on the 280zx distributors? I believe ours came off a 1979 or 1980 car. Also noted that the mixture it really rich at idle (10:1) when the mixture under hard acceleration is in the right place 12.5-13.2:1. Does anyone else have experience looking at Air Fuel ratios with the SU carbs?

Update on our problem. We drove the car up to Seattle and back this weekend and the car ran fine the whole way with one exception. cruising back on the freeway we lost some engine power. I was cruising about 75 and suddenly it dropped power and I was only able to maintain about 60 for about 45 seconds or so, then the power cam back and it ran fine the rest of the way home. I just determined that the vacum advance was bad and not operating and was leaking vacum. I replaced the distributor with another I had in the shop. We will see if this cures the problem we were experiencing.

Dave, I installed the uprade park lamp and headlamp harnesses today. They fit and worked great. Thumbs up from us on these wonderful products. It was great to meet you this weekend at Golden Gardens, hope to see you again soon.

If you zoom in on my pin in deadhorse and switch to satellite view you will see that it is actually pinned on the shop where I live/work more than half the year.

It seems that the problem is occurring upon hot restart after the car has sat and heat soaked, therefore I believe it is a classic case of vapor lock. Any suggestions for alieving this problem? My thought is to insulate the fuel rail brackets from the cylinder head with a rubber or phenolic spacer/insulator. Any other ideas?

I think I would draw the line at rust holes in the roof panel. That means everything below that point is probably swiss cheese. Theres alot of stuff below the roof panel.

Did you check for spark before replacing the ignition parts?

I havent and Im out of town currently, but when I return Im installing my wideband o2 sensor on this car to monitor mixture when the problem occurs. That should tell me if its ignition or fuel.

The pump came off a carburated car.

The coolant flow through the intake has been bypassed on my car. I didn't think that restoring that flow would reduce intake heat issues but I suppose it might. Also, I was reminded by Gary (beandip) that we installed a 280zx coil on the car in place of the MSD blaster coil I had been using previously. I dont know the fuel pressure delivered by the RX7 pump but I'm sure its not more than 5. Of course mine is a used one so it might be weak.

I'll give it a try.

CSF is the only manufacturer producing a replacement 240z radiator on a large scale (Part number 110). There are specialty radiator manufacturers who will build any radiator to your dimensions. I suspect that MSA sells CSF radiators.

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.

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.

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

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 personally believe its the throttle not opening all the way. Foot pedal assy or throttle linkage bent, limited or maladjusted. Lift the slides, shine a flashlight down the barrel while someone has the pedal mashed and check the throttle plate open completely. Engine turned off of course.

I believe it was less than 3k total for the lift. Do a quick search and you will find some excellent deals, probably even cheaper now that the economy is tanking. The install was simple and I did it myself. Leveling the whole thing was the most time consuming part. Well Arne, you have touched on the one downside of that system in my opinion. the muffler has to be installed at a slant and the exhaust does reduce ground clearance a bit, especially after lowering the car. Its not objectionable in my opinion. I'll see if Toni can take a picture of the exhaust from the rear and post it.