30 April 2008
Ok, so I don't have number plates today

It turns out that in addition to the engineer's certificate, I also need a "blue slip" which you get from another type of authorised inspection station.

No worries, I'll get it sorted next week, and so I got bored tonight and decided to take out my jets

I didn't realise before how easy it was to take them out, so when I got the carbs rebuilt I asked the mech to write down the jet sizes for me, and they were: 145mains, 220 air corrector, F11 emulsion tubes, 32mm chokes. Now this may seem to be mumbojumbo but its actually not that hard to understand.

The way I understand it is that the chokes are what determines the airflow into the carb. The chokes are that grey "insert" you see inside the mouth of the carb, and you can see that it's smaller in diameter than the body of the carb.


This is deliberate, since the choke is a restriction in the carb, which causes the airflow to speed up, hence drawing/sucking fuel out of the jets (fuel comes out of that little tube in the middle). So my 40DCOE Webers aren't really the same as 40mm throttle bodies, they are really 32mm throttle bodies.

The choke is an airflow restriction and so the rich/lean fuelling is determined by the ratio of the choke size to mainjet size. The bigger the jets, the more fuel will be sucked out of them. In theory, once you get the jetting right, you shouldn't need to rejet the carbs for extra mods since the extra mods might suck more air into the engine but the ratio of fuel to air is controlled by the main jet to choke size ratio and so the AFR should remain the same.

Weber recommend that a jet size 4x the choke size is a good starting point when tuning. So for my 32mm chokes I would need 128 jets (but they come in steps of 5, so either 125 or 130 would do). I had 145 mains (or so the carb guy said) which sounded too rich...and given that the car fouls plugs black like it's going out of style that made sense.

Taking out the jets is pretty easy...remove the round jet inspection cap and just unscrew this long thing (there's 2 per carb).


The jet stack then just pulls apart into its component bits (from left to right): main jet, emulsion tube, air corrector and the threaded bit is just a holder for the whole shebang. So it's pretty easy to swap jets etc, and I guess you have to remember that back in the day before dynos, you would set the jets by swapping sizes, going for a blat in the car and determining if you were rich or lean by pulling a plug and reading the colour. So I suppose Webers were made so that swapping jets is more or less a 5min job you could do by the side of the road.


Now here's the funny thing...on closer inspection...I have a 125 main jet after all....which should be more or less on the money.


The air correctors are definitely 220 though.


Now as for the correctors. The main jets control fuelling from the midrange upwards, but the corrector adds some air into the fuel to lean things off at the top end. I guess any engine is going to be more efficient at high rpm, so if the fuelling is perfect in the midrange, at the top end it would have so much more airflow/suck that it would pull a proportionately higher amount of fuel thru the jets and hence run rich.

So the corrector adds some air to counteract that...Weber says that for a slogger engine, you would have a corrector size +50 above your mainjet size, and for a screamer race engine you would need more fuel and so it may only be +10. So for my L-series which might have peak power before 6000rpm something like a +50 corrector would be the go, while for say a really worked 9500rpm 4AGE it would be more like +10.

Put this all together and the ideal (or close to it) starting point for my engine should be 125 mains and 175 correctors.

Hence my 220 corrector is very weird and should make the engine fall flat at high rpm (which it does) from extreme lean-ness. But the midrange should be pretty close since it's the theoretically ideal 125. And at the moment the midrange power is crap.

I wonder why it's running so rich then...maybe the 125s were redrilled in Japan to a 145 size, which is possible........or maybe the ideal jet size is something like 115. Weber also says that when you have a big engine and small chokes, you often need smaller jets than the ideal because the big donk will get such a great suck thru the carbs that the main jet will work too well and overfuel, so it's very possible that the theoretical ideal 125 should be downsized to a 115.

I'll go see the carb guy and report back.

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Ok, the update is that the carb guy goofed when he wrote that the jets were 145 on the invoice He checked them today and they are actually 125, which means that the carb jetting for the midrange and low end anyway should be close to ideal.

After a bit of a chat he suggested two possible things.

One was to use hotter range plugs. I am using BP6ES plugs, and the "6" signifies the heat range and is the "normal" heat range for any modern car you care to name. But he said that old school cars running big carbs often need hotter range plugs for city driving and so maybe I could try 4s or 5s. So I bought a sextet of BP5ES to see if it makes any difference. Hotter plugs mean literally that...the plug surface will have more insulating ceramic to retain more heat and so be hotter...which would burn off excess deposits better. So possibly my carbs aren't rich, but the plugs were too cold to get rid of excess deposits from fouling.

Suggestion #2 was to reduce the fuel pressure. I have a 4psi fuel pump and the ideal pressure for Webers are 2.5psi. 4psi should be ok, but it's possible that the pump is overpowering the float needle mechanism in the carbs and causing some minor fuel flooding (which is the same as running mega rich). So I got an adjustable fuel pressure regulator I can try, see if it runs better with less fuel pressure.

2 May 2008

The fuel pressure regulator was a pretty easy install, I just put it inline in the short run between the fuel pump and the hard fuel line that goes around the front of the engine to the carbs.



Weber recommends 2.5psi...so 2.5psi it is.


Doesn't seem to idle much differently, although I did give it a 1/4 turn more lean on the idle screws and it seemed to like it.

The only changes are the richer 175 air correctors and the lower fuel press. The air correctors should only have any effect at the very top end of the revrange, so if it drives better at low rpm then excessive fuel pressure would have been the culprit all along.

I guess we'll see if it's any different when I get to drive it next.

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welcome babalouie

Get rid of that push dial regulator. They are notorious for going south quickly. I had two do it two me. Get yourself something like a holley adjustable FPR with set screw, and you will NEVER have to worry about it. The holleys can also be rebuilt so you have diff ratios and they are not that expensive either.

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1974 Celica ST 18RG "Eduardo"

kev, you might wanna use thumbs to ease loading & browsing

Great write up and great car. I just learned some new things about carb set up(at least webbers), and that is always good!

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Brad D.

'83 Sapporo Technica; '84 Starion ES; '87 Conquest TSi;
'91 RX7 convertible; '68 Camaro SS 350 convertible; '71 NSU 1200c

kev

lets see some before and after pics of the ride height.

I'll take some pics. At the moment it's definitely in Paris-Dakar Mode but it's also 2ins above the acceptable limit, so there's scope to make it sexy again without being illegal.

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amazing, great to read a build like that without interruptions, can't wait to see more, best of luck with it

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1980 KE70, 1986 AE86, 1998 SXE10

Thanks for the tip. I bought the dial regulator cos it was cheap and I wasn't sure if it was part of the problem or not, but now we know that it was.

Thanks for the tip on the Holley FPR too, I'm tempted to re-jig the fuel system, maybe move the fuel pump to the boot to clean up the engine bay visuals, and it would make sense to bolt up something like a Holley FPR back there.

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Fantastic thread. I think I just spent over an hour reading this. I really want one.

Your determination inspires me to go work on my stuff!

RORO is good. This, not so much....

Now that's a "Failboat" pic if I ever saw one

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I hope this project thread NEVER ends.

period.

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2 May 2008

Ok, I got to drive the car this morning to drop it off for the blue slip, and with the lower fuel pressure it definitely does drive better. Plug colour is better too. This pic is after holding it at 4000rpm for a bit, so maybe it might want even more fuel up top than the 175 correctors

(Before vs after)


It's still a little "funny" and fluffy but the richer jetting has opened up the top end quite a bit...the plug on the right is still a bit whitish which is a sign of high combustion chamber heat so maybe it might need to be a touch richer...

But even if you say hold it at 4000rpm and then crack the throttle open a bit it responds cleanly for an eyeblink then goes "brrrr" and you can feel it fighting itself a bit. But it is faster...not torquey and easy like you would expect a near 3L engine in a car that weighs 40kg more than an MX5, so still there is something wrong.

I did verify that the stock timing marks lined up but maybe the cam needs to be properly degreed or maybe it is just a piece of crap cam.

Bad news about the blue slip tho. There were a few little things like indicator and number plate lightbulbs that mysteriously died since the last time I checked them, and the left rear drumbrake was binding a bit (might have to change that wheel cylinder after all) but two things are a bit more serious.

One is that the heater matrix must have been leaking at one point, because the pass side floorpan has a few pinholes of rust (say the size of a pea). The floor itself seems to be still thick, so I was going to put in a POR15 floor kit or something to fix it later but that has to be plated now. Not a difficult job but it will be a hassle to organise it with someone who has a welder.

The other thing are the coilovers. The new height made the engo happy but the blue slip guy says he needs that coilovers to be separately engineered since they are cut and welded from the stock parts. I'll be giving the engo a call and see what he says.

Aaaaaargh *throws spanner at car*

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6 May 2008

Update! Some bad news actually.

I looked deeper into the floorpan rust issue that got me rejected from the blue slip inspection.

From below, it doesn't look so bad...to give you a sense of scale, the circular drain hole is about the size of a 20c piece. So the section peppered with little holes is about 12in long.




From the top, the JDM guys that restored the car a few yrs ago chipped away the stock sound deadener and then laid down some new sound deadening mat, which as you can see didn't stick down very well and whole sections of it peeled off quite easily.


...which meant that the mat acted as a water trap for any water leaking from inside the car, or from under the car (since they didn't put back all of the floor plugs)


And since they didn't paint or rustproof the floor (denuded raw unpainted steel now that the stock tar mat was gone) before putting on the new mat...it acted as a rust trap. The steel to the left of that big fat ridge running down the middle of the pic is pretty pitted and thinned. But to the right of the ridge the surface of the steel is intact and it's just got a dusting of surface rust.


It just boggles the hell out of me how someone in Japan could spend hours and hours chipping away at the stock deadener mat (very thorough job) and yet not be arsed to spend 30mins to paint/rustproof the resulting bare metal before putting down the new mat.

As I chipped off all of the mat, and then scraped the hell out of the floor with a wire brush, the holes got bigger...but again remember that the round hole is a 20c piece, so we're talking about a 12in x 3in section of the floor. Not that bad...but not that good either.


The driver's side is pretty ok, just these pinholes in this little localised area, and as you can see the surface of the metal is intact and it hasn't been eaten away and thinned like the outer sections on the other side.


Options at this stage are....fix it myself. Buy a good MIG welder and all the gear, take my time and practice a lot on scrap steel before having a go, cut out the cancerous steel and weld in a fresh new patch.



As someone said to me the other day, I've done all the work on the car myself so it's a shame to outsource it now, and it's a skill that I'll build on for the rest of my life. Give a man a fish and you feed him for one meal, teach a man to weld and he'll be building hot rods from scratch next yr etc etc.

But the Hako is also a pretty rare and special car, and it would be a hella huge shame if I borked it up. Anyone who's tried will know that normal panelbeaters won't touch this sort of thing, but my chance I managed to find a small outfit near my house who's quoted about $750-1000 to sort this all out. They'll flute the patch panel to try to match the floorpan pattern so that it's as seamless as possible.

Hmm....choices, choices. And while I love the idea of leaning how to weld, I think the Hako is a bit too special for me to be experimenting on. And I guess I have saved a bit of money so far by doing it all myself, and a grand is not a high price to pay to get it done once and done right.

So at this stage, Plan B is looking good and the Hako will be dropped off at the panel shop next week when I'm in Japan.

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7 May 2008

Tonight I thought I'd sort out the rear brakes. One of the blue slip failure points was that one of the rear brakes was binding quite a lot. Now, when I've driven the car, I've said before that something feels "wrong", like maybe the handbrake is on...well in a sense it was!

So up goes the rear of the car, and yes, even with the handbrake off the driver's side wheel is very, very stiff to turn by hand.

Now the Hako has very 60's style drum brakes back there, which are manual-adjusting. What you do is that periodically you have to adjust this bolt at the back of the drum. Newer cars have a ratchet mechanism which advances the shoes as they wear automatically.


What it does is as you tighten it, it drives a wedge between the brake shoes, which moves them closer to the drum surface. The ideal is that the drum shoes should be lightly touching/scraping the inside of the drum in their resting position, but not so tight that the drum can't move freely. So what you do is tighten the bolt until the drum locks, then back it off one click. There is a cam on the bolt inside, so it helpfully turns with a definite click, which makes it easy to adjust.

So I back off the adjuster one click, and the drum is still tight. Another click and another click and finally the drum frees up. But when I nipped the handbrake up and down, the drum was frozen again. As I turned the wheel (which was very stiff) you could feel that the wheel would free up, then get tight as you turned it.

Dang. Time for some maintenance....the best diagnostic tool for drum brakes are your ears. As you turn the wheel you should hear the brake shoes make a light scraping noise. If the wheel can move freely, then that means that the drums are well adjusted. An uneven scraping noise means that the inside of the drum is no longer round and has gone oval.

So the first thing to do is to get the drums machined round again at a brake shop.


Now the exposed drum. The wheel cylinder is at the bottom, and as you press the brake pedal, a piston pushes the brake shoes apart, to contact the drum. Very strong springs pull the shoes back to a resting position when you release the brake.


First you remove the steady springs. Pretty easy to do, just push them in with your fingers, then turn to allow the spade head to go thru the hole.


Then pull one of the shoes off its locating slot, and that slackens the spring enough to remove it.


Now remove the shoes.


For the shoes to move back and forth easily, you need to put brake grease on these oval contact patches. Not just any grease (which can melt with heat and go all over the shoes) but brake grease which is super-super hi temp



Here's how the handbrake works...see that little bar sticking out? That bar sits in a slot in one of the brake shoes. Pull the handbrake and that moves fwd against the drum.


Put it back together...


Then refit the drum and adjust. Tighten until the drum locks, then back off one click....and both drums now move freely! I think what might have happened was that the drums were very ovalised before, and was poorly adjusted in Japan to be too tight. Maybe not so noticeable when the car is cold because the ovalised drum probably made the wheel feel like it rotated freely enough. But once you start driving, the brake will bind a bit, then heat up some more, and then everything expands with heat and it binds even more.

It's a vicious cycle which ends up with the brakes dragging and holding you back as you drive. But it's fixed now

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Quite the trials with this one! I am so glad that our laws regarding registering cars are much less strict!

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Brad D.

'83 Sapporo Technica; '84 Starion ES; '87 Conquest TSi;
'91 RX7 convertible; '68 Camaro SS 350 convertible; '71 NSU 1200c

x2.

All they do here is check that all the lights and brakes work, then send me on my way...

Haha, in Michigan they just check if you have the money to register the car. There's no inspection at all. You should see the stuff that rolls around here (for that matter, you should see the state my Chrysler is in. )

Love the thread, still reading through it. I always learn something new!