Quidam Posted November 25, 2009 Share Posted November 25, 2009 ha, idle jet. I need to sleep:) Quote Link to comment Share on other sites More sharing options...
moosens Posted November 25, 2009 Share Posted November 25, 2009 Great thread. Keep it going,please. I've trimmed a couple of posts so we have a cleaner thread for future reference. I'm going to make this a Sticky so enjoy the limelight. Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 25, 2009 Share Posted November 25, 2009 (edited) Hey Moosens, I didn't know that colour was called limelite. Here's a 28/32 Hitachi. That power valve is stuck shut, so it wasn't working at all. See the power piston below? It has three stakes holding it in. It binds up and sticks the way it is now. Cut the stakes and remove it. BTW, nothing less than a carb chem dip would get this all clean enough to but back together. You'll want to clean the brass piston and bore. Don't remove any material. Put it back together with moly lube or something and restake. I can measure the activation point with a vacume pump, fittings, and tape. That tells you when the power valve opens. If it's 8"vac it opens sooner than one that opens at 6. It's an area that can be tweaked. The vacuum signal. You need good fresh gaskets and I deburr and flatten mating surfaces of the bodys. Just lightly. Hook up a vacume gague. On this carb I plug the gague into the vacuum fitting right above the idle speed screw. It goes to the power piston and ports above and below the primary throttle shaft. Then through the center big screw right to manifold vacuum. If your engine doesn't have a good crisp signal here, it's very bad. Worn rings, cylinder wall, valves,loose clearance between the compression ring and the ring land...The carb depends on that vacume signal to work right. With a lumpy cam and a carb, low speed suffers because of that weak signal. That's where fuel injection shines. Doug Edited November 25, 2009 by Quidam Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 25, 2009 Author Share Posted November 25, 2009 (edited) The story so far as I understand it. Circuits: Idle circuit Primary and secondary main circuits Power valve circuit Accelerator pump circuit Idle circuit. The idle circuit by passes the barrels and feeds directly into the intake manifold. This circuit can be fine tuned at idle with the idle mixture screw. This circuit works best at idle but is always active. Primary and secondary main cuircuits are only active when their respective throttle valves are open. The more the open the more fuel and air is drawn in. The power valve is only active when there is low vacum in the MANIFOLD. Not to be confused with the vacum advance which gets its high vacum from inside the primary barrel. The least amount of vacum at this point is when both throttle valves are fully open. This valve bypasses the primary main jet and feeds to the primary main nozzle. As far as I can see it does not feed to the secondary nozzle. The accelerator pump is mechanically operated. It works best when the pedal is quickly pushed to the floor as it adds an extra squirt of fuel into the primary barrel to compensate for the sudden rush of air. Edited November 25, 2009 by Dirk Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 26, 2009 Author Share Posted November 26, 2009 Update. Current setup is as follows. #60 idle jet #98 primary main jet #147 Secondary main jet #45 Power valve Have set idle mixture to best running. Throttle screw has half a turn on it to achieve correct idle rpm (a little under 900) Engine idles sweetly. No hunting. General throttle responce is smooth through all the range. Power curve is diffinately more towards the top of the rpm but I feel I still have plenty of torque at the bottom end. She will happily pull a well loaded small trailler about. I'm actually very happy with the setup as it is but in the interest of science and generally mucking about I have drilled out a number 45 power valve and installed it. The smallest drill bit I have is 1mm which is massive compared to the orgional hole. Will let you know soon what happens. Cheers. Dirk. Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 26, 2009 Author Share Posted November 26, 2009 What is the purpose of the Air bleed jets and what happens if I change those sizes? Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 26, 2009 Author Share Posted November 26, 2009 I have far too much time on my hands! Any way I was thinking about the idle circuit. The idle mixture screw controls the quantity of fuel delivery at idle. So in theory it doesn't actually need a jet? Is it just a convenient regulator that is fine tuned by the screw? Also I still can't figure out why I would need and Idle jet for the secondary barrel. Its a wierd looking circuit. Looks like the fuel exits from the very top of the carb above the main body. Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 26, 2009 Author Share Posted November 26, 2009 Just got back from a wee drive and I'm stoked at how the engine is performing. My tweaked power valve has given heaps more power to the primary circuit. The throttle is smooth and responsive and when I open up both barrels it just keeps on giving. I'm not saying that I've turned it into a race machine, it just feels like the engine has bigger balls now. Oddly enough the whole engine sounds smoother now. The bigger idle jet has helped with smooth idling and also I don't have to give it as much choke as before and for less time. Amazingly my spark plugs are squeeky clean still so I guess all the fuel is being used. The only question now is what have I done to the fuel economy. I think I may be pleasantly surprised though because I have more power with the primary circuit. I may not have my foot on the floor as much as before. Time will tell. Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 26, 2009 Share Posted November 26, 2009 Hey Dirk, Good to hear. Before the other stock jets, air bleeds, emulsion tubes and such come into play with me, I need to have everything else worked out. You only went 3 jet sizes over on the one you changed. Not enough to have the air bleed come into play. What I'd do is plug a vacume gague into the port above the idle screw. Run the hose through drivers window, or something. See what's going on with that. This: Is a screw adjustable vacuum secondary cannister that easily adapts to the Hitachi. Others available where you change the spring. The Hitachi can is sealed and non adjustable. Unless you change the spring rate from the outside, or cut it open, change spring and put it back together. All work. You're optimizing the secondary opening rate for the car. Screw Adjustable preferred here. Doug Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 26, 2009 Share Posted November 26, 2009 " I have drilled out a number 45 power valve and installed it. The smallest drill bit I have is 1mm which is massive compared to the orgional hole. Will let you know soon what happens." Hey, I'm wondering if that power valve is rated at 4.5, would open at 4.5? None of mine are marked that I can tell. Mabie I ought to take a closer look. Changing it to 6 or 8 would be good I think. .039 or so huh. Next one I drill I'll try a 4 door. Four factory sized holes spaced evenly around the PV. Doug Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 26, 2009 Author Share Posted November 26, 2009 (edited) Hey Doug, My secondary is mechanicaly linked to my primary. I just have to bend the bar to adjust it. I haven't really fiddled with this beyond checking that it is set at manual specs. Would I prefer it to open earlier or later? I had another look at my spare power valves. One says 40 and the other 45. I suppose it could mean 4.5 but I deffinately do not see a point on either. A vacum gauge and a cylinder pressure tester are on my wish list but they seem to vary some what in cost. Can't really afford expensive ones but I can't stand buying cheap stuff that doesn't work properly in the first place. I think for the time being I will have to continue the trial by error method. What I plan to do next is run the engine at various conditions and monitor the results via the spark plugs. I start tomorrow by letting it idle on the driveway for a bit. By the way, did you see my post about the idle jets? What do you think? And no, the secondary idle is not adjustable. Cheers Dirk Edited November 26, 2009 by Dirk Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 26, 2009 Share Posted November 26, 2009 Hey Doug, My secondary is mechanicaly linked to my primary. I just have to bend the bar to adjust it. I haven't really fiddled with this beyond checking that it is set at manual specs. Would I prefer it to open earlier or later? I had another look at my spare power valves. One says 40 and the other 45. I suppose it could mean 4.5 but I deffinately do not see a point on either. A vacum gauge By the way, did you see my post about the idle jets? What do you think? And no, the secondary idle is not adjustable. Cheers Dirk I can see the linkage, didn't know a 26/30 was set up like that. Yea, try activating sooner. When you get to the limits, it will bog down. Back off from there and it can be a seamless transition with more power earlier. The temporary cockpit vacume gage is an esential for doing this work. They're about $20.00. Idle jet. Are we talking about the Primary slow jet and the Secondary slow jet? They mix air with the slug of fuel comming from the float bowl before discharge. Doug Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 26, 2009 Share Posted November 26, 2009 Something else to consider while covering the basics. Put the vacuum gage on it. Period. I have 4 28/32 carbs. Two of those have inoperable vacuum secondary cans. They were being driven and leaking air. Test it with vacuum. I take a measurement with a dial indicator of the throttle shaft to bore clearance. The best one I have has .006 on the primary, .005 on the secondary. I have one with .025...quite a difference. If you pour fuel in the primary bore and it leaks out the throttle shafts, that tells you it's worn. How much clearance is too much here? I'm not sure with these carbs, but that's where the vacuum gage comes into play again. If it's too loose, the motor won't pull as much vacuum. BTW, with a blow through turbo carb, this shaft to bore clearance needs to be small and tightly controlled. Doug Quote Link to comment Share on other sites More sharing options...
DR DLEX Posted November 26, 2009 Share Posted November 26, 2009 hello dirk, I now know that your jets are to small.here are some specs.from my Haynes manual. To tweek when the secondary throttle opens--use a small bolt/nut this saves alot of time bending the linkage.Does the carb your running have the countrweight on the secondaries(the pics don't). Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 26, 2009 Share Posted November 26, 2009 Here's another data point on the throttle shafts and bores. I just measured a carb a friend gave me, it had sat and was frozen up. I freed it up and took it apart. I get .005 movement on the secondary shaft, passenger side. I get .007 movement on the drivers side primary shaft/bore. I get .011 movement on the passenger side primary shaft/bore. This carb looks good and has most of the plating/finish intact. I'd think, it would be good enough to run as is. It is a little loose, but again, I'm not sure how loose is too loose at this point. Doug Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 26, 2009 Share Posted November 26, 2009 I just noticed from the thumbnail picture. This carb has a three position accelerator pump arm. Easy tune there, if you go larger on the exhaust probably max it out. Doug Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 26, 2009 Author Share Posted November 26, 2009 (edited) Hello Doug and Dr Dlex. I have the Haynes manual but I can't make sense of the carb specs because the serial numbers do not match either of the 3 carbs I have. This is actually what got me started on this thread. Also I can't understand how there could be so many stock variations of a carb for the same engine.....? I have discovered a limitation with the valve linkages. If I deduce the opening time of the secondary plate it will not open it fully at full throttle and conversely, if I try to advance the opening time too much it rotaes the seconadry plate beyond vertical while the primary does not open fully. Therefore I have set it so that the plates are fully open at full throttle. There is a counter weighted plate on the secondary barrel. Looking at it, it is quite a bulky and restrictive looking part (as shown below). I guess it is there for a reason but I wonder what would happen if I were too remove it? The valve body I am using on the car is the better of the three that I have but there is no doubt that it is worn. Unfortuanately I do not own any instrument capable of measuring the wear on the shafts. By feel I would say that it is within acceptable limits and I did grease up the shafts when rebuilding. Hopefully this will reduce any leakage. Edit, I missed the part about pouring fuel into the barrels. Ill give it a go as soon as. Cheers. Edited November 27, 2009 by Dirk Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 27, 2009 Author Share Posted November 27, 2009 Been in the garage butchering a donor carb. zzz Have removed the wieghted plate and shaft and have tried to reshape the lower part of the barrel so that it is round. Does this look like a good idea? I'm sure I can make a smarter job of the real thing if it is a good idea. And yes I will plug the holes. Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 27, 2009 Author Share Posted November 27, 2009 Well I hope it is a good idea because it is done! And not a bad job either if I say so myself but is best you don't ask how I did it. Any way, the plate is removed, the barrel is now perfectly round and the shaft holes have been filled. Been out for a test drive and enigine is still running well. Have not been able to test high speed yet. Best of all my spark plugs finally have a little colour! Must be getting close to optimum performance. Things I learned on the way: 1. My throttle body is quite worn. Secondary shaft wear is nominal but the primary by comparison is quite sloppy (still no tools to accurately measure). Have liberally smeared liquid gasket around the shaft holes in hope that it may stem some air flow. 2. Cover the manifold intake AT ALL TIMES when the carb is off. I nearly lost a nut down there and was very lucky to fish it out. It makes me cringe thinking about it. 3. Do not over tighten manifold bolts! I snapped one when re-installing the carb. Not the end of the world, and luckily the remainder came out without a fight but its not always that easy and it certainly wasn't welcome at 2am this morning. I have a spare 10mm spanner that I may cut down a bit to stop me from doing this again. Speaking of which, I should also grind the jaw down a bit too. Access to these bolts is a royal pain in the wosname. 4. Go easy on the liquid gasket! when removing the throttle body I noticed the vacum port was partially obstructed with some. Less is more. 5. Take your time, be clean and methodical. Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 27, 2009 Share Posted November 27, 2009 Hey, Looking good:) Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 28, 2009 Share Posted November 28, 2009 28 32 Hitachi on the left. 26 30 right, carb base gasket. Let me know if I don't have this straight. The EA-82 manifold and carb bolt on to EA-81? But not the EA-71...to use the 28 32 on your motor, you'd need an adaptor plate? Doug Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 29, 2009 Author Share Posted November 29, 2009 Yes. Thats my gasket on the right. I think if I were to go down this route I would fill the holes with brass and re-drill the manifold. Before I do this I need convincing that it is a good idea. What are the pro's and con's? Things that I would like to do in the near future are: 1. Upgrade the carb. Possibly to an EA81 2. Build a free flow exhaust system 3. Remove some wieght from the flywheel 4. Port and polish the heads So why are these mods a good idea? And if they are, Why did Subaru not do them in the factory. They seem to be simple things but Subaru must have had very good reasons to do things the way they did. Cheers. Quote Link to comment Share on other sites More sharing options...
Quidam Posted November 29, 2009 Share Posted November 29, 2009 (edited) "Before I do this I need convincing that it is a good idea. What are the pro's and con's?" Hook your vacuum gage up, go to your private race track, and floor it. Wind her out to 5200 rpm. Look at the vacuum gage. If it reads 0, you don't need a bigger carb. Take your compression gage and test it, if it's not good enough, you won't see a lot of up-side to any of these mods. Why? The ring seal is the only thing pulling the intake charge into the cylinder. It then pushes it up for compression. Next, it delivers the power and then evacuates the cylinder. If you have poor compression numbers, it can't do any of those other things well, either. "Things that I would like to do in the near future are: 1. Upgrade the carb. Possibly to an EA81 2. Build a free flow exhaust system 3. Remove some wieght from the flywheel 4. Port and polish the heads" If you're keeping the car awhile and your exhaust needs replaced, slap on a better one. Less weight can be good. Well, they weren't building a little hot rod. Doug Edited November 30, 2009 by Quidam Quote Link to comment Share on other sites More sharing options...
Dirk Posted November 30, 2009 Author Share Posted November 30, 2009 (edited) Is this what I should look for? http://www.trademe.co.nz/Browse/Listing.aspx?id=256542104 What the hell is this?! http://www.trademe.co.nz/Trade-Me-Motors/Car-parts-accessories/Performance/Carburation-induction/auction-257127206.htm Edited November 30, 2009 by Dirk Quote Link to comment Share on other sites More sharing options...
Turbone Posted November 30, 2009 Share Posted November 30, 2009 What the hell is this?! http://www.trademe.co.nz/Trade-Me-Motors/Car-parts-accessories/Performance/Carburation-induction/auction-257127206.htm Its something of a gimmick, I wouldnt waste my money on it. Altho some say it has increased HP a little. Quote Link to comment Share on other sites More sharing options...
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