Sprocket

G'day. It's been a while since I looked in here, and I found this old thread I started a few years ago and thought an update might be of interest to members. Long story short - I bought new valve springs and fitted them without removing the head. To hold the valves on their seats while removing the springs, I fed a length of soft 1/4" rope down the spark plug hole and turned the crank until the piston jammed the rope against the top of the combustion chamber. However, the new valve springs made absolutely no difference to the engine's performance. The "expert" engine tuner I took it to had made a wrong diagnosis. Now at a loss as to what the problem could be, I figured I'd leave it as a job for another day. That was a couple of years ago. In the meantime, the car was still driveable, just not to its full potential. Short story long - April 2020. It's the middle of the Coronavirus lockdown, so I’m looking for stuff to do. The “job for another day” became the job for today. Time to do a bit more head scratching. The head scratching goes like this: It can only be a couple of things - fuel mixture leaning out (not getting enough fuel) or a breakdown of the spark at high revs. Fuel starvation could be poor pump capacity, but it has a mechanical pump as well as an electrical one. The car belonged to my late brother Bob. Reading through his notes, he was under the impression that the electrical pump was a bit under-rated, so he fitted a mechanical pump as well. With both pumps operating, it seems unlikely to be a starvation issue. Sure enough, with the fuel line disconnected, it seems to gush petrol at a prodigious rate. I also took the carbs apart, cleaned, checked, re-balanced. All good there. Fitted new air filters. None of which made any difference. Cross fuel starvation off the list. So, looking at the ignition system, it has an aftermarket electronic doohickey in the distributor that replaces the original points system. That’s a good thing I guess, and it seems to work because the car runs and the auto advance works (I checked it with a strobe). Plugs are all new so no problem there either. Coil looks new, so I guess someone has added it at some stage. I checked the coil's primary resistance and it reads 3Ω on the meter. That seems about average for a motorcycle (I'm a motorcycle fettler, not a car guy). Typically a motorcycle coil only fires once per revolution (usual bike setup is an ignition trigger on the crank), but what about a 6 cylinder car where it's firing 3 times as often? Checking the workshop manual specs, it says 0.5Ω. Aha, we could be onto something. I need to try a coil with the correct resistance, so I bought a 0.5Ω coil and installed it. The car would start but not run. Hmm ... more head scratching. It would continue to run if I connected a jumper wire from the battery to the coil positive. That got me thinking about the voltage getting to the coil via the ballast resistor. The ballast resistor measured 1.5Ω. That’s abought right for the 3Ω coil because the coil gets about 8V. (Ohm's Law for series resistances - system voltage = 12V, of which 4V is lost through the resistor and 8V through the coil). But putting a 0.5Ω coil in with the same 1.5Ω ballast resistor meant that most of the voltage drop was across the resistor rather than the coil. The coil was getting heaps of current due to the low overall resistance, but the voltage drop now becomes 9V across the resistor and only 3V across the coil, which is nowhere near enough to allow it to make a spark. It would start OK because the coil gets full battery voltage when the starter is cranking. As soon as the key turns back to the run position after starting, the ballast resistor comes into circuit, effectively shutting the coil down. That's when the light bulb moment happened. The car originally had points/condenser setup and the electronic trigger is an aftermarket fitment, so the original coil and resistor spec may now be irrelevant. I rummaged through Bob’s paperwork and found a receipt dated 3/2/2015 from Performance Ignition Services in Nunawading for the supply and installation of a Pertronix ignitor kit. A bit of internet googling on Pertronix ignitors found the installation instructions for that unit. It revealed that the 3Ω coil is in fact correct, but it said the ballast resistor should be removed or bypassed. Pennies are starting to drop. Even with the 3Ω coil, it appears that 8V it was getting via the ballast resistor was insufficient to allow the coil to reach saturation when it was trying to cycle faster than 15,000Hz (3 cycles per revolution @ 5,000 rpm). The ballast resistor could be all that’s standing in the way of full ignition performance. So I bypassed the resistor with a short piece of wire. I took the car for a test drive and it revs right through to the red line. Problem solved … finally! All that farting around changing the bloody valve springs, and all it needed was a little bit of wire to short out the ballast resistor! You’d think a company called Performance Ignition Services would have got an ignition installation right, especially when the correct installation procedure was in the instructions that came with the Pertronix unit. According to their invoice, along with the Pertronix unit and the new coil, they also supplied and fitted the problem ballast resistor (presumably to replace the original lower value resistor?). They also supplied and fitted a new condenser - another item that's not required with an electronic trigger. The take home lesson is never trust self-proclaimed experts. The professional ignition installer got it wrong. Then the engine tuner I took it to mis-diagnosed the problem that was created by the first guy, and led me up the garden path in the direction of valve springs.

Not keen on buying used valve springs. I've already got a set of those in the engine! I don't have a lot of experience with cars, but I do heaps of work on motorcycles. I'm aware that some aftermarket motorcycle valve springs are rubbish and perform like they're made from coat-hanger wire. I just wanted to avoid the same trap with car part suppliers. Free length is one indicator. Others are seat pressure, pressure at full lift, installed height, coil bind clearance, etc. I haven't lifted the cam cover yet so I dunno how my springs measure up to any of these specs. I was hoping to source a set of good springs before I start spannering. That way I can take the old springs out and fit the new ones straight away, so the car isn't out of action for too long (planning to do it with the head in place). The car is a bit of a problem when it doesn't go because it blocks access to my bikes in the garage.

G'day folks My poor old 260Z isn't going very well. Actually, it's never gone very well since I inherited it. It's basically a stock L26 engine. It starts and runs OK in rev ranges below about 5000 rpm, but then it hits a wall. It doesn't even get to where the peak power should be. I took it in to Andrew at Pro Automotive in Moonah (Tasmania) for a dyno tune. His diagnosis is weak valve springs. The SU carbies are a bit out of whack but there's not much point going any further with carb tuning while the valve springs are knackered. At least the ignition timing is spot on! So, I need to buy and fit a set of springs. There are plenty available on the interweb, from people such as Zcarsource, Zcardepot, Andy's Autosport, TheZstore, etc. but they're all in USA. I couldn't find any in Australia. Are there any local suppliers for Z valve springs, and any suppliers or makes of spring to avoid? Cheers, Cam Tasmania

I'm looking for a replacement a similar wheel cap (40343-N3200), one of which went AWOL from my Z a while back. Alternatively, if anyone has a full set of the 280ZX caps with metal fixings, I'd be happy to buy those and fit them. That would make my 3 existing caps surplus to requirements. In that case I'd be happy to offer them for sale to folks who (like me) are missing one. Can someone post the part number of the 280ZX caps? Cheers, Cam (Tasmania)

G'day Joel, and welcome. I'm in the Hobart area too, and have also recently become a 260Z owner. Your comments about the fuel pump interest me because I suspect the mechanical pump on my Z isn't quite up to par either. The car falters when the pedal is floored for more than a few seconds (going up a long hill for instance). The car originally came with an electric pump. The mechanical pump was installed by the previous owner (my late brother) because the electric pump was a bit old and tired. The original electric pump is still in place and I can turn it on with the flick of a switch. With both pumps running, the fuel starvation problem disappears. One of these days I'll have a look at the mechanical pump to see if it can be improved. Maybe it has a dodgy valve like yours. Cheers, Cam

G'day Just popped in here to add my car to the Tasmanian group. I'm in Bellerive and have recently acquired this 1976 260Z. It's pretty much bog standard with its original L26 engine, SU carbs, etc. It has aircon which I think may be an aftermarket fit. Also has electronic ignition which might be a modification (workshop manual reckons it should be points). I drove it home from my brother's place in Wangaratta earlier this month. Discovered en route that the head gasket was leaking coolant into cylinder #1, so that was the first job when I got home. That's now done and it seems to be running nicely and no longer losing coolant. It passed its roadworthy test yesterday without any issues and is now on Tassie SI plates. The steering is heavier than I was expecting for a car of this size and weight, but maybe I've become a wimp in the last 2 decades of driving cars with power steering. I'll try a bit more pressure in the tyres and see if that makes a difference (currently running 28 psi). If not, I may be in the market for a power steering conversion. I see from browsing the forum that Justin has a neat electric steering assist on his car. Cheers, Cam

Well, the head is back on. Car was very reluctant to start. Took a lot of cranking, but I suspect I may have flooded it in my enthusiasm to get it going. Anyway, it eventually coughed and spluttered into life on what seemed like one cylinder at a time until all 6 were working. It then smoothed out and sounded OK. Took it for a short test drive to get it up to operating temperature and everything seems to be working normally. Temp didn't go over about 80 deg C (measured at the top radiator tank with an infra-red thermometer). I'll let it cool down and re-torque the head bolts. I'll also drain the coolant (only water at this stage after a cooling system flush) and replace with proper corrosion inhibited green stuff. Will check torque again after a few more heat cycles. Hopefully I won't be looking at the pistons again for quite a while! Thanks for the advice. Cam

Thanks Dave. Yes, I did a bit of homework before disassembly, so was aware of that little trap. I jammed a wooden wedge down there. I must remember to take it out again! Actually, it's the first time I've worked on an engine with a hydraulic tensioner. As I mentioned earlier, most of my engine work has been on motorcycles, all of which use spring-loaded tensioners that can be backed off. When I first took the rocker cover off the Datsun I thought the chain was a bit slack. That was before I sussed that it's a hydraulic tensioner. Presumably the slack disappears when the oil pressure gets up a bit. @ Gareth - Sorry, I didn't respond to your suggestion to pull the engine to check rings and bearings. I'd rather not yank out the engine at this stage for a couple of reasons. Firstly, I have no reason to suspect there's any issues in there - oil pressure is good, as is compression, and apart from losing coolant, the engine was running well. I've checked the gasket face on the block with a straight-edge and feeler gauges, and can't detect any non-flatness. Secondly, my workshop isn't set up for working on cars so I don't have an engine hoist. I do have a 1 ton chain block, but where the car is parked, there's only light tin roof purlins above it to hang the hoist from. I reckon the roof would cave in if I were to hang that lump of Datsun cast iron from it! One of he things on the wish list is to install an overhead beam the length of the workshop on which I can run a trolley car to hang the chain block from. Thirdly, with a whole stack of motorcycles, storage shelves, tool cabinets, benches, lathe and various other crap in there, there's not a lot of room to work. I need a bigger workshop! Cam

Thanks for those contacts. I've heard of Mick Williams but have never met him. I've had work done by Phil Young in the past. He did the head on my Volvo Penta Diesel boat engine and a couple of motorcycle engines. Seems to do a good job. Only reason I go to Reggie now is that he was recommended to me by Rob Warren (Red) at Red's Motorcycles next door. Also, Reggie is closer when I'm coming from Bellerive, and I used to work in Moonah myself.

Head is now off and with Reggie (the cylinder head man) in Moonah. He'll give it condition check, replace anything that needs replacing (hopefully only valve guide seals) and shave as necessary to flatten it. He also said he'd source the gasket kit (incl manifold, thermostat and fuel pump gaskets) for me at trade price - probably from Repco, around the corner from his shop. I've had heads done by Reggie before and he does a good job. As I walked into his workshop carrying the head, he said "That looks like a bit of ancient history - an L26". The fact that he could recognise it at a glance gives me some confidence that he knows his stuff. Cylinder block face is already cleaned up and waiting for the reconditioned head. I was careful to avoid cap getting in any of the oil galleries, and I gave all the holes a suck out afterwards with my compressed air suction doohickey, just to be sure. As for head bolts, I've found out that they're not torque to yield type, so are OK to re-use. PS: Hey Clockwork (Joel?) I think we may have met. Are you a mate of Alex R, the bloke with the Alfa GTV?

I just had a close look at the original mirror on my 260Z's drivers door (right side). The base is not perpendicular to the stem, so if it were placed on the left door, it would sit at a different angle (lower). So these mirrors are definitely left/right handed, but other than the base angle, I can't see any other differences. Having said that, a right mirror could be made to sit at the correct angle of dangle on the left by grinding the base to produce a left inclination, but the base would then be a few mm thinner, so may not look quite right to a rivet-counting originality nut. Shh - don't mention OCD. In previous posts, there was some discussion about making reproduction mirrors. As far as casting new stems is concerned, the original items appear to be die cast (made with a re-usable steel mould) and making a die is not a simple thing - trust me, I'm a engineer . Low volume casting would generally employ a sand-cast process, where the mould is destroyed during removal of the cast item. Another sand mould would then have to be made for the next one, and so on. So it's a bit labour intensive and therefore not particularly cheap to have done in any kind of numbers greater than you can count on one hand. Also, the quality would be a bit on the rough side, with porosity a definite possibility. The simplest, most effective as far as quality is concerned, and probably cheapest alternative for low volume reproduction would be CNC machining from billet. I'd suggest aluminium because it's easily machined and plenty strong enough for this application (at least as strong as die cast metal which is usually a zinc-aluminium alloy). If someone were interested in setting up a CNC program, the way to do I would be to make it with a base of sufficient depth to cut the left/right slant either way. The stem would need to be polished and chromed after machining.to make it look like an original. Trapezoidal mirror heads are available from motorcycle accessory outlets. Cheers, Cam

Thanks for the welcome, and the condolences. Much appreciated. Here are a couple of photos. One taken while waiting to board the boat to Tassie, and one when it arrived in my now crowded garage. Bonnet is cracked open in the second pic because the battery float charger is connected. Cheers, Cam

G'day I'm a new owner of a 260Z, having only picked it up yesterday. On the run home (some 500km) the car ran beautifully right up until the last few km, when it blew a head gasket. We were able to limp those last few km home OK without the temperature gauge going too berserk. Once home, I did a compression test while the engine was still warm and got 160 psi on all cylinders except #1, which was well over 200 psi. Cylinder 1 also had coolant spurting out of the plug hole when I cranked the engine, so I figured the high compression reading was because the cylinder is partially filled with coolant. Anyway, it's obvious that coolant is leaking into cylinder 1, and possibly oil as well (bowing smoke). So the head has to come off to check it for flatness, shave it if necessary, and fit a new gasket. I have a Datsun Service Manual for S30 models and I'm OK working on engines in general, including OHC. But being a new Z owner and not familiar with these engines in particular, I'm on a steep learning curve, so I have a bunch of questions before I get the spanners out ... 1 Are the gaskets the same for 240Z, 260Z, etc.? 2. Is there a recommended brand of head gasket to use? (basically stock engine - not high compression) 3. Who/where is the best source of parts for these old engines in Australia? (with particular reference to head and manifold gaskets) 4. Are the head bolts re-useable (ie. not the stretch to yield type)? 5. The engine looks pretty basic SOHC, but are there any esoteric traps for a newbie doing a head-off job? Sorry about the dub questions. I'm sure won't be asking so many when I get to know the car better. Cheers, Cam (Tasmania)

G'day folks I've just taken possession of a 1976 260Z and driven it from Wangaratta back home to Hobart. It was my brother's car, but unfortunately he passed away a few weeks ago. I decided to take on the car myself because a) it's a nice car, and b) to continue it's restoration as a tribute to my late brother. He was a pretty handy mechanic so the car is well sorted mechanically. What's left to do is mostly cosmetic. The car ran well for 99.9% of the 500 odd km trip from Wang to Hobart, but in the last few km the temperature gauge started to go up. We got home OK with the temperature needle just short of the red zone on the gauge. Coolant level was found to be well down. After a short diagnostic session, it was obvious that the head gasket had sprung a leak (coolant getting into Cylinder #1) which explains the loss of coolant. So that's the first job on the "to do" list! I'm reasonably handy on the tools myself so not anticipating too many problems. I have a lot of experience with motorcycle engines (including 6-cylinder ones!) and the general principles are the same. However, I'm not particularly knowledgeable about these Z cars, so will probably be asking dumb questions from time to time. I'll be posting my first technical question (on head gaskets) in the "Engine" section as soon as I've posted this intro. Cheers, Cam