Stanley

Spent a good bit of time over the last 48 hours reading posts on the topic, studying my Nissan 72 L20A & L24 series engine manual. Not feeling any smarter, though. Got '73 240Z with SU's, C211 head & cam, nearly new euro non-emission distributor. Had to retard the timing a little to stop ping when they put the new head a couple years ago. Maybe a little more compression. Recently read (no controversy) that initial advance is 17 degrees at 700 rpm for the automatic, also that it makes 15 deg. centrifugal. Not going to happen on CA gas. Putting all the numbers and technical stuff (like the esoteric diagrams on page EE-31) aside for a while, I figure there's two ways to go. Either keep the vac advance and set the initial as high as I can without ping (probably about 7 deg at 700 rpm, have to test), or else cap the vacuum and set initial at 17 degrees or so (17+15=32, maybe about right for 91 octane gas). Obviously I'll need to do some road tests but someone with experience might have some ideas? Car is a more or less stock daily driver but I'd like to run the quarter a few tenths of a second faster next time.

Took drove about 25 miles yesterday on the freeway and surface streets, no sputtering or backfires so I guess it's really fixed. Still not quite right though, pretty sure it's the mix/timing. Someone that doesn't drive like I do wouldn't know there was anything wrong with the car. Yes, the carbs are probably off, I haven't set mix since putting new needles and nozzles a couple weeks ago. Done so many 30 second adjustments I don't remember how many turns down they are. Also, the timing isn't advanced enough. The Innovate came today, didn't have time to do much but if I pushed the right buttons it's 10 deg advance at 1300 rpm, supposed to be 17 deg at 700 RPM (euro dist with automatic trans), so it's way off. Doubt if it will run at the stock setting with CA gas, but will get it as close as possible with no pinging on the hill. The Innovate light seems ok, BTW. Strobe is rock steady - with the other cheapie light the marks on the damper jumped around. Should be better, it cost 4 times as much. Will make it much easier to document settings, and record and graph the advance curve. Nice to check dwell, rpm, battery and alternator with just one gadget. The distributor is ok, it was new 6 years ago, only 6000 miles on it. I didn't dissemble the plate, just removed it with the 2 screws and put it back like it was. Everything looked new inside.

Enjoyed hearing Z car engineer/designer Yoshihiko Matsuo describing his unauthorized top speed run (200 kph=124 mph). Hadn't seen this before.

Well, everyone that said it was ignition was right on the money. Was going to set the mix today but had a load in the laundry so decided to do a 20 minute (I thought) job while it was drying. Had a new Nissan condenser for the distributor so started to install it. What a nightmare getting to old one off - the upper radiator hose and the thermostat housing are in the way, even the little stubby screwdriver was no good. Got the 90 degree screwdriver but it didn't work either, finally got it off with a screwdriver bit in the needle nose vicegrips. Same thing with the upper screw where the wire connects. Cleaned off the terminals, got the condenser in place, but couldn't tighten the upper screw. The square nut inside had fallen into the guts of the distributor. Next time I'll take off the cap and hold the square nut. Had to remove the vac advance and the plate under the points, was intimidated by the task but it was easy. Glad I didn't take the points out first. Found the nut, put everything back together, and installed the new condenser. Noticed the rotor end wasn't shiny and there was some corrosion on the contacts in the cap, brushed them with a small wire brush. The point, cap and rotor are only 6 months old, the condenser was probably 40 year old. The points looked a little played so I check the dwell next time. Took a drive, no more sputtering. So it was either the condenser, corrosion at the condenser's connection, and/or the corrosion on the cap and rotor. Wonder why it didn't affect mid-range and top end.

Don't have an answer, but the ZTherapy video covers this topic in detail.

Took 2 hours to adjust the front float, even with the sightglass. Make a tiny adjustment and it doesn't do anything, make another tiny adjustment and it floods out the vent. Finally about sundown had it slightly high. Would rather it be slightly low than high for safety, so I decided to do one more - if it was too low hell with it - but it came up perfect. Too late to set a mix. Took a drive, still sputtering at low RPM. Midrange and top end seem stronger than ever. Watching the tach it sputters up to about 2100, then it's like you flipped a switch and it instantly zips up to 2300 and starts winding nicely.

After setting carbs 1/4 turn richer yesterday with no improvement, set them 1/2 turn leaner today and drove to the store. Didn't make a noticeable difference. New timing light won't be here for a few more days so I checked the carbs, rear one was low on oil, and fuel level in the bowl was about 5 mm too low on the front one. I had them set correctly last winter. Don't know if it's part of the problem but it needs to be fixed anyway, so I'll check the valve and set the float tomorrow. Hope the float's ok. Read an article couple months ago in Hot Rod IIRC that ethanol is shredding the floats, even the new ones that are supposed to resist it.

Always used 3-in-one oil (20 wt). Put some in 2 weeks ago.

Tried lowering the nozzles about 1/4 turn - maybe try a real mix adjustment tomorrow. The idle dropped slightly so maybe it's too rich now. Seemed to do a little better but it backfired at about 2000 RPM when floored after a stop sign. Fuel pressure steady at 3.9 psi while driving, drops to 3.8 psi at idle. Seems about right. Very inconclusive. Thought I'd gotten past the beginner stage up to intermediate with my tuning but apparently not.

The miss happens only under load, worst at about 2000 rpm. Been driving the AT like a stick to keep the revs over 2600. Plugs are about 5 months old and show light brown/red/yellow color, no wet or dry black, no whitish, gaps all 33-35 thou. No smog stuff, BSPT plugs in all the balance tube holes. No vac leaks. The carbs are balanced with each other, maybe slightly lean but pulling choke lever after it's warmed up doesn't help. Float bowls set to spec with sight glass. The previous carb problems were sticky choke causing rich condition, and too lean condition caused by my tune-up, both fixed. It backfires through the carbs once in a while accelerating at low rpm when it's not fully warmed up, or on the freeway when I take my foot off the gas due to traffic ahead and then step on it again. Had it on the freeway Saturday but it didn't backfire, ran great until back on the surface streets. It ran ok before with the same head assembly. I'll set it a little richer today and see if it helps. Work is interfering with my "messing with the car" time.

Have a miss and occasional backfire through the carbs under about 2600 RPM. 73 240Z with 3-screw SU's and 6 year old euro distributor. Stock head and cam from C211. Runs strong mid-range and top end. Plugs look ok but I'm no expert at reading them. New needles and nozzles fixed top end miss and improved the idle. Not sure when it started since there other carb problems, too rich, then too lean. Thinking it's ignition. Feels like it's too lean but richening with the choke lever doesn't help. The chokes aren't sticking. New advance timing light on order - should be here next week. Will try retarding it a little but don't want to. Top end is good and no ping. Something else to check?

Nice translation tip. Been thinking how to cover the oil cooler for winter, had no idea the covers exist/existed. My MSA cooler has a bi-metal strip that supposedly cuts off the flow until the oil is hot, but the cooler still feels warm on cold days when the gauge shows the motor hasn't warmed up. Planned to wire some foil-backed insulator pad over it. Don't like how it would look but will do it anyway for winter.

Helps to drain out the gas and turn the lid 90 degrees. Don't need to use any muscle on it. The floats are fairly tough so when you get it out you can probably straighten it up enough to use. The float bowl valves have a rubber tip that should have a sharp conical point - if not they're shot. New ones are available from MSA and elsewhere. Lot's of information on this site. ZTherapy has a video. The flange on the side is no problem if you drain the gas.

That link is played - this one's better.

Checked my 72 engine manual - it says dual points were for emissions spec AT's only. AT's elsewhere used single point same as manual. Non-emissions AT's set timing at 17 deg at 700rpm in neutral, manual trans 17 deg at 650 rpm. Setting dual points clear as mud, for me anyway. So Nissan made the advance set of points come on when it's below 30F for easier starting. Guess if you want to start your emission-spec AT car when it's cold but more than 30F you're just out of luck. Speeding (and starting?) is bad, um'kay? So don't get rid of that dual point.

There's this:http://www.zcarsource.com/distributor-240z-70-73-manual-transmission-rebuilt-de_8_77854_54132.html

Wow good explanation, always wondered how that worked. Had the stock dual point on my 73 AT. Took forever to start. Put a 72 single point - works good.

My 73 came with an owner's manual, it says to use 96 octane. I remember a post about how 70's octane ratings are different from today. It didn't ping with 89 octane until I put a 81 JDM head on it, now it's set up for CA 91 octane, I think it likes Arizona 92 or 93 better though. Could be my imagination. I advance the timing slightly when I'm there. Wish I knew more about timing adjustments for various gasolines. Maybe a valve job? They'll put better valve seats, and performance should improve.

Yahoo! Lamborghini also did 250 in the mile, but slower ET.

Very nice - more photos, please. C211 series? Would like to see the engine bay, even if it's not shined up yet. Will you keep it all stock? The color's great.

Yeah, 140k, non-smoker and runs good but rings or hopefully bore and bottom end rebuild down the road. Just now figured out that if I tee the cam cover vent into the PVC hose, it would bypass the PCV valve (especially when it's closed at high or low vac) and make a closed loop from the crankcase vent tube to the cam cover, not what I had in mind. Still want to improve it though. Guess I'll do this, then: PCV hose with strainer, no tee, from the tube to the valve. Hose from cam cover vent with small strainer or filter at the end, between the two K&N's. Hate to turn it into a snake pit like the US emissions spec cars. Maybe a gunked-up PC valve has something to do with the junk in the cam cover filter.

My PCV hose is greasy inside and about shot, just ordered a new hose, have a new valve for it. The cam cover vent just has had a little chrome filter on it. Noticed the filter was gunked up, cleaned it, but seems like the setup could be improved. I guess some people drill a hole in the K&N backing plate and put a hose barb there, but don't want the gunk (fumes ok) going through the intake. I'm splicing a little strainer/filter in the PCV hose to keep some gunk out of the new PCV valve. How about teeing a hose from the cam cover vent into the PCV hose before the strainer ? Is there a reason not to do it that way? With the stock air cleaner setup the fumes from both places end up in the same place more or less, except only the crankcase vent goes through the PCV valve. It would be a "cleaner" setup with just one strainer.

It would be great to be in Tsukuba to watch this race. Got the DVD in a magazine. Wish my TV was hooked to a good sound system.

When I bought my Z a few years back the suspension was shot and I had it rebuilt with a polyurethane kit from MSA. They recommended that I replace a couple of those parts with rubber unless the car was just for racing, so I did, and like the results. Don't remember which parts, though.

Fuel level in the front bowl needs to be 2 mm lower than rear bowl. that's why the ears and valves are 2 mm longer (for the later 3-screw SU's) for the front carb. Then the fuel in both nozzles will be at the same level (the main thing). Wonder if the 4-screws also ran longer nozzles in the front? The 72 FSM doesn't mention this change - wonder if Nissan engineers were embarrassed that they got it wrong with the 4-screws. Maybe the factory race team noticed the fuel level difference when they pulled the domes and checked fuel level in the nozzles. Easy enough to fix with a couple of washers, so maybe they passed it along to the designers who incorporated the change for the 3-screws. ???