Ok, I've just spent the last 4 hours trying to tune my 1971 240Z. I thought I would be through in 30-45 minutes at the most. This is the first time I've tried to tune it since I bought it.

Anyway, before I set the dwell and timing I checked them both. The dwell was at 28 degrees and the timing was actually running slightly before the first mark on the pulley so it was running after TDC (right?). So, I set the dwell at 38 degrees and the timing at 5 degrees BTDC (the second mark). The engine actually ran worse. No pickup and back-fired through the first carb. So, I took the domes off the carbs, cleaned the dampers, put new oil in them, etc and kept trying. Still, ran poorly. By the black junk on the carb pistons, I figured it was running rich, so I cranked down on the mixture nuts. I must have gotten at least 4 turns out of each one. So, I bottomed them out (carefully) and backed out 1 1/2 turns. Still ran like crud.

Oh, and the engine began to run much hotter. I must have set and reset 20 times. All I know is that if I set everything to the factory settings, it ran worse than before and got hotter, so I finally set the timing back to before the first mark, the dwell at 28 degrees and the mixture nuts 3 turns out. Guess what, it runs fine.

My wife says I should just furgetaboutit and be happy its runnning well, but I'm worried that these settings will cause engine damage. Your thoughts on what's going on and whether I should leave well enough alone are most welcome.

One last thing, while changing the antifreeze, dumb me, only put a gallon back in the radiator (it was full). Well, it must not have gone into the engine (cold engine) because the themostat was shut. So, I cranked it up and kept waiting for the temp gauge to go up. Finally, steam started coming out of the radiator and the gauge went up really quickly. I shut her down and let it cool for awhile and then filled it up the rest of the way. I've pressure checked the system hot and cold now and it holds 13 lbs of pressure for two minutes with no loss. Anything else I need to think about here? Water pump?

I thought this was supposed to be fun!!!!

BTW, I already know I win the stupid award for the radiator thing, so extra comments on my stupidity won't help!!! I'm also now sure I like my 1970 much more than my 71. It read the maintenance book and runs great using the factory settings. Sorry for the long post, it's been a long day....

Bob

Bob, I suggest that you give a call to Steve or Bruce tomorrow. They area at Ztherapy here in Salem and might be able to work with you on this. It sounds to me that you might have a needle issue. Replacing the SU needles and seats should help out. I am suspicious of the needle because it took you 4 turns to get it to work right. Anyway, their website is: http://www.ztherapy.com .

You might try this link instead:

http://www.ztherapy.com/

Although based on your post is sounds like both might be useful :knockedou

Anyway, before I set the dwell and timing I checked them both. The dwell was at 28 degrees and the timing was actually running slightly before the first mark on the pulley so it was running after TDC (right?). So, I set the dwell at 38 degrees and the timing at 5 degrees BTDC (the second mark). The engine actually ran worse. No pickup and back-fired through the first carb. So, I took the domes off the carbs, cleaned the dampers, put new oil in them, etc and kept trying. Still, ran poorly. By the black junk on the carb pistons, I figured it was running rich, so I cranked down on the mixture nuts. I must have gotten at least 4 turns out of each one. So, I bottomed them out (carefully) and backed out 1 1/2 turns. Still ran like crud.

Oh, and the engine began to run much hotter. I must have set and reset 20 times. All I know is that if I set everything to the factory settings, it ran worse than before and got hotter, so I finally set the timing back to before the first mark, the dwell at 28 degrees and the mixture nuts 3 turns out. Guess what, it runs fine.

First question - if the engine was running good before, what was the reason for changing it? In my experience, attempting to "tune" an engine that doesn't need it right now is a great recipe for messing up a car. Thank goodness you had the foresight to note the 'before' settings so that you could restore them.

But now for thoughts on what happened. Due to your description of the symptoms, especially the running hotter part, I'm wondering if your timing marks are correct. Has the timing cover ever been off to your knowledge? Are the timing cover and front pulley both either original, or from the same engine? I think my first recommendation would be to manually set the engine at TDC (looking at the piston through the spark plug hole, or the cam lobes, not the timing mark) and compare that to the timing marks to verify they are correct.

I think my first recommendation would be to manually set the engine at TDC (looking at the piston through the spark plug hole, or the cam lobes, not the timing mark) and compare that to the timing marks to verify they are correct.

Agreed, the stock crank pulleys have been known to break the rubber dampner and shift the pulley around causing the timing marks to line up incorrect.

Thanks, I was thinking the same thing about checking tdc against the timing mark. Just ran out of patience yesterday!

learned the hard way that the first step of a 'normal' tuneup is to adjust the valves.

has this been done?

had similar issues with the car running like crap and started to screw with the mixtures. made things worse. after adjusting the valve lash, suddenly the weird things i had attributed to mixture or ignition went away!!

your overheating suggests a timing issue, but start with a fresh slate at Step#1 and try adjusting valves first.

Ok, I checked the harmonic balancer (crankshaft pulley) against the position of the number one piston and they are dead on. When the pointer lines up with the first notch on the balancer (far left when facing the car), the number one piston is at the top of it's stroke.

I haven't checked the valves, but I'm just thinking about taking it to Pierre Z and saying "go for it!" Sure, never had this problem with my 70!

Bob

Bob, somebody mentioned setting the valve lash to specs - do that first

Overheating / hot running engine = over advanced timing (hence all of the pinging), lean fuel mixture - low coolant not withstanding

Does the dist still have points? If so, I would really recommend the Crane XR-700 or 3000 electronic ign setup. Vs. the pertronix. You can set the dwell angle to whatever you like with the Crane product.

I used to use the Allison elect ign (now Crane) on my 71'. I set the dwell to 48 degrees, and simply set the timing using the "retard until it just start to ping, and then back it off a hair" method. My 71 with an L28, w/stock SU's would scream all the way up to 7600RPM.

There are allot mechanical variables to consider when setting the timing, i.e. camshaft gear position, compression of engine, valve lash etc. So using an inductive timing light is accurate, but I usually found it necessary to either advance or retard an engine after make a test run or two.

Happy motoring!!

Did you remember to disconnect and plug the vacuum line to the dizzy before checking the timing at idle speed?