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jonbill

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jonbill last won the day on March 11

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About jonbill

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    260z

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  1. Ah right, the 42 DCOEs! I still think it would be helpful to have one out and measure it. Perhaps after you've checked the float levels. Is there a gap between the two progression holes, or will the throttle plate start uncovering the 2nd as soon as it finishes the first? Do you think you can position thr throttle pedal at the problem point while the car is stationary? You could get someone to look at the progression holes for where the throttle plate is when the problem occurs. after the 1st hole or after the 2nd.
  2. yes. the choke size determines the air speed and suction at the main jet outlet, which determines when the main jet comes in (in part). so with a big choke, you can run out of progression holes before the main jet kicks in and it goes lean and the answer is to fit smaller chokes or possibly add progression holes or if its marginal you can get away with just larger idle jets and make the progression phase richer to cover the transition to main jets. with small chokes, you're probably just lean through the progression phase and bigger idle jets/richer idle holder wil fix it (and you turn down the idle screw so its not too rich at idle). why do you say your chokes can't be changed?
  3. take a choke out, it'll either be marked or you measure it. assuming you're opening the throttle reasonably slowly, your 18:1 is on the progression holes or between the progression holes and the main jets. progression holes are supplied by the idle jets.
  4. so when you accelerate from cruising at 13.5:1? what size chokes are they?
  5. I have 0.58 mm clearance in my engine. I originally had 0.56 mm and a piston just kissed the head.
  6. yes, or the hottest plug you can that doesn't melt.
  7. real world, if you put a bpr8 in a stock Z engine it will foul badly, because combustion isn't hot enough to get the plug hot enough to self clean. if you put a bpr6 is a high compression tuned engine, the tip of the plug will melt because combustion is too hot. the right plug for the engine is one that doesn't foul and doesn't melt.
  8. both EFI and carbs will produce the same power assuming both setup well. As ZH said, the big difference is the EFI can be much easier to setup. You would need to give more detail on the build specs to be able to talk about how much power it might make.
  9. does the cam have much lift? I damaged my cam last year. Based on what I learned here https://forums.hybridz.org/topic/130549-valve-spring-seat-pressure/ I concluded the cause was idling below 1000.
  10. 3.5 psi is a good pressure, but if you loose pressure with the return line open, maybe the pump isn't moving enough fuel. can you install that pressure gauge so you can see it when you drive? it would be informative to know what happens with the pressure when you have that lean condition. if thats a pain, I'd be inclined to try adding a cheap inline electric pump. you've probably got wires for one down at the fuel tank sender.
  11. I never heard of adjusting the pressure of the mechanical pump. I'd start with getting a pressure gauge and inserting it in the fuel supply line to a carb. if it passes that test, then maybe take the top off one, including the valve and check theres a good flow of fuel when the valve is open.
  12. I don't know, my car only has the mechanical pump from the factory, so my pressure is regulated by an Aeromotive FPR.
  13. maybe your float valves are sticking or your fuel pressure is too low. I reckon full float chambers allow you to drive gently for say 3/4 mile. so a couple of full throttle runs might empty them, and then if the valves are blocked or no fuel pressure it could take 15 seconds to fill again at idle. should be easy to prove.
  14. confusing. you don't want to be running it much at 8 and 9, you'll have a sump full of fuel! if you lift off and close the throttle at 4000, its ok for it to go to 22. there's no load and only enough fuel for idle. As the revs come down towards the idle range the AFRs should come back down until its idling as it was at the start. is it staying at 22 when the tevs are back down to idle speeds? I don think it would be sticking float valves. how old is you wbo2 sensor? flipping between super rich and super lean might be a dead or clogged sensor.
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