15 Mar 2008: Project Hakosuka: Now Going.
After a quite a long period of firstly waiting for the car to arrive from Japan, and then a seemingly-even-longer period of fixing the various issues that the car came with, it was with a certain trepidation that I fired her up and gingerly backed her out of the garage under her own power for the first time.
Now that all the various mechanical issues were sorted, and the electrics were all working again, I put everything back together again in the engine bay:
And the interior was converted from a mess of hanging wires back into something resembling a normal dashboard:
Those readers who've been following the buildup over the past mth or so will know that I've had quite a few attempts at tuning the Webers without actually getting it right! But now that the car was ready for the road, it was time to have a last go and this was the result:
Although I think it still isn't perfect (and the driving impressions below suggest that there is some room for improvement) I think this is the least-worst result I've got so far
It idles steadily at 1200rpm, starts easily, gets off idle quite cleanly and doesn't diesel-on like it did before. Good enough as a starting point I think.
But one last job I did before rolling her back out of the garage was a little mod I was saving for later. Now, the engine was upgraded to a 280ZX electronic distributor in Japan, which isn't compatible with the stock GC10 tachometer. The stock tach relies on an inductive loop principle, which assumes that you have a flow of current through a set of old fashioned points in the distributor. The later electronic distributor doesn't have this so the stock tacho is dead.
So I did a mod which has proven to be surprisingly divisive. Most modified Hakosukas you see in Japanese magazines are fitted with Autometer tachs, and of course Autometers have been popular with the 240Z guys in Japan and everywhere for a very long time. So I removed the stock tach and fitted an Autometer 3'3/4 tach in its place.
The Autometer slotted snugly in place, and to my eyes, looks subtle and very appropriate. The font and colours etc are more oldschool than say a modern Defi gauge, and I like the fact that it sits deep in the instrument cowl, and you don't really notice it unless you're sitting in the hot seat.
But like I said, it's been quite a divisive little mod in that some people are so upset about it that you'd think that I've just ruined the whole car
Of course it's 100% reversible should I want to return it to stock in the future, but I guess some were disappointed that I didn't go for a JDM brand instead. But if it's good for Hakosuka guys in Japan then it's certainly good enough for me and I think to drive the car without a working tacho would have been a disappointment. After all this work I wanted the car to be as "finished" as possible when I hit the road for the first time.
And with that....I fired her up and drove her out of the garage for a quick wash!
The next day....I had an appointment at an inspection station to get the car certified for road use, and so it was hugely nerve wracking to take the Hakosuka out onto morning rush hour traffic, a car that was pretty green and unproven when I first got it a mth earlier, and a a car that I had only ever driven up and down my driveway.
But I need not have worried. The car sat happily in peak hour gridlock with the water temps holding steady between 70 and 80 degrees, and she didn't stall, smoke or eat her plugs or get sucked into a wormhole or anything like that. To my relief, it's a very solid, tight car with no rattles or squeaks and I have no doubts about being able to drive it anywhere now. The downsides at this point are that the suspension and brakes are simply awful.
The suspension is soft and way too low (more of this anon) and in fact is resting on the bumpstops at the front, so is very bouncy and pogo-ey as we negotiate Sydney's bumpy roads. Not confidence inspiring at all, and the shocks also seem to be quite worn. But even less confidence inspiring are the brakes. The pedal goes a long way to the floor before anything really happens, and then in that last centimeter of travel, it's a fine line between stopping safely and locking up the front wheels. This is usually the symptom of a worn mastercyl, so I suspect that the rebuilt master cylinder may be the culprit, so I'll give the brake shop who did the job a call. Old cars are reknown for poor brakes, but my old 63 Beetle had much better brakes than this, so I think something is definitely amiss.
On the good side, the engine has plenty of power even though it's not quite 100%. Nothing smokes or rattles and oil pressure is a steady 1.2bar at idle, and the sound from the Webers under full song is simply unbelievable. Give it more than 1/2 throttle and you get the Italian National Anthem being played at deafening volume out of the Weber carbs and it's a wonderful thing!
The response at low rpm is quite fluffy however, and the powerband hits a real brick wall at about 5000rpm so the powerband is a thick slice of torque between 3000 and 5000rpm. The low rev response is due to the 280ZX not having enough static advance. Big carbs and big cams need to have about 18~20 degrees of advance at idle, but the 280ZX distributor has 18 degrees of (rpm based) mechanical advance built into it, so if I set it up with 20 at idle, then I would end up with 38 degrees of advance at high rpm which I think would be too much. So the current setup is 14 degrees at idle, which translates to 32 degrees at redline, which is not optimal for low rpm running but is safe and won't hurt the engine at high revs.
I have some parts coming from Japan however that should address this issue so watch this space. As for the power tailing off abruptly up high, I think that is something that I won't be able to diagnose properly until I get the car on a dyno. At the moment the car is stable and driveable but feels a little out of sorts and you get the feeling that there are just a few tweaks that are holding it back at the moment, and once those are sorted the engine will really be unleashed.
As for the registration inspection, well we didn't pass. But there are only 5 items that I need to address and we'll be legit. All of the electrics checked out, and rather surprisingly the hot, big cammed and multiple carbed motor actually PASSED the pollution test (maybe that tune isn't so bad after all)! But the issues I have to fix are:
1. The car is too low and needs to be raised 25mm at the front. The sump is only 7cm off the ground, and given the poor driving characteristics of the current setup, this is a problem that I am looking forward to fixing. I think I'll remove the front struts, and convert them to coilover so that I have height adjustment, and also put in a Koni insert while I'm at it. Changing the rear shocks should be a quick job though.
2. The car is slightly too noisy. The legal limit for a car of this age is 96dB and the Hako tested at 95.7dB. While it's under the limit, it's borderline and technically I have to pay for a second, drive-by noise test to reconfirm that the noise level is legal. However the engineer at the inspection station suggested that if I put the K&N air filters on the car the next time I have it tested, it would probably take the edge off the noise level enough to pass without a drive-by test.
3. Inoperative horn. Believe it or not, one electrical item I didn't check was the horn! But I guess since I mainly work on the car at night maybe I subconsiously didn't want to wake up my neighbours!
4. Fit rear seat belts. I fitted front seat belts but rear ones are required for a car of this age too. I believe that the holes and mounting points are already in the chassis, so this might be an easy mod.
5. Fit a stalk buckle to the front seat belts. The mounting point for the lap part of the front belts is very far behind the front seat on the trans tunnel. And the longest buckle on a stalk I could find from an Australian supplier was 450mm, which is about 100mm too short. But the rules say that the buckle can't be on fabric webbing, since the movement of the seat may abrade the fabric over time. So the answer is probably to bite the bullet and redrill new mounting holes further forward on the trans tunnel so that I can use the approved stalk mounted buckles. Motorsport shops sell FIA-approved harness plates with a seatbelt sized nut welded to a thick steel plate, and I can rivet one of these to the inside of the trans tunnel as the new mounting point, so that shouldn't be too much of a headache.
And that's it! All I have to do is address these 5 things and I will get that precious piece of paper that will allow number plates to be issued to me. For an old modified car I think I got off very lightly and I think that anyone will agree that the modifications they want made are quite reasonable. After having driven the car properly for the first I'm more relieved than excited I think. The car still needs a lot of work before I can really enjoy it and I think the excitement will come later when the car is in a more refined, finished state.
The build continues...but hey...it runs!
20 Mar 2008: Project Hakosuka: We have BRAKES!
You might recall that, in the last (and only!) time I drove the car, the brakes were awful. With the pedal going most of the way towards the floor with little feel or resistance, and not actually doing any braking until just before the pedal hits the carpet. Quite terrifying, actually, and the more I thought about it, the more I was convinced that there was something wrong, rather than any inherent weakness with the Hako braking system.
I did a bit of searching around the vintage Z forums and there were an awful lot of posts complaining of the exact same symptoms. After replacing or repairing the brake master cylinder the pedal goes all soft and long and the brakes hardly have any retardation at all. In most cases, it was blamed on something called a Reaction Disc, which is this striped, #18 thing in this diagram below:
This is a diagram of a 240Z brake booster (a Hakosuka one is similar in design but smaller), and the Reaction Disc is a 6mm rubber spacer that sits between the master cylinder activation pushrod and the internal plunger inside the brake booster. If you remove the brake mastercyl and dislodge the pushrod, then it's possible for the little rubber disc to fall out, and into the depths of the brake booster. When that happens, you have 6mm of freeplay inside the mechanism, and so the first half of the brake pedal travel does nothing except bridge this new gap.
It sounded plausible to me, so I took off the master cylinder and measured the depth of its internal piston. Then I measured the depth of the pushrod inside the booster...and well what do ya know? 6mm gap! So I reached inside the booster with my finger, and yes, down at the bottom was something round and rubberlike. But after 20mins of trying to dig it out with my finger (you can only get one finger in there!) I bit the bullet and removed the brake booster.
Here it is, with the pushrod removed (the rubber disc goes behind the piston end of the pushrod). And after jiggling the booster around for a while, the little rubber disc flopped into position, and you can see it at the bottom of this "well" inside the booster:
Carefully put pushrod back in place before the little %$$@^ rubber disc falls out again...
And bolt the master cylinder back, all the while keeping an eagle-eye on the pushrod!
Reconnect the pedal, bleed the fluid, and....PHEW. The pedal feels normal. With the engine off, the pedal goes firm within an inch or so of travel....basically like a normal car in other words! I haven't driven it yet but the pedal feels good, and I am sure this will restore normal braking power to the Hakosuka....so now I can floor the accelerator pedal in safety!
When I removed the brake mastercyl, I was quite careful not to touch the pushrod (I was scared that there might be a clip or something holding it in). But you might remember that when I sent away the mastercyl for rebuilding, it took quite a few days before it came back, and during that time I was working on getting the accelerator pedal adjusted correctly. I think what I did was accidentally brush against the brake pedal when I was mucking around adjusting the accelerator pedal mounting. So the pushrod got nudged out a bit and the little rubber fell out.
We get a 4 day long weekend over Easter this weekend, and all of the necessary parts to install the rear seat belts have arrived. So I'll do that, and remove the front struts for coilover conversion this Saturday or Sunday.
...and yes, now that I look at the pictures above, it's really bugging me that I didn't repaint the booster before putting it back!