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lauko

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  1. Well, it took some time but today I finally went for a test drive. I put in the new F7 emulsion tubes and the thing now accepts WOT from 1600rpm on! This really made a huge improvement. I only hope that this change hasn't caused my rich "cruise" to be even richer...gotta borrow a wideband again. At the same time I also ordered a set of 36 chokes but now I don't think I'll even try them!
  2. Well after what you wrote I think I will do the following. First I will try with some low-rpm-enrichment emulsion tubes. F7 look like the ones I need, I just hope that these will not make idle / cruise too rich. Is anyone here running F7 or at least tried them? Second step: 36mm chokes.
  3. That is exactly my problem - how to make it richer at low rpm acceleration, but not elsewhere (cruising etc). - Other (richer at low rpm) emulsion tubes would make it run richer in general, not depending of the throttle position - cruising would also get richer. Or am I wrong? - Bigger pump jets are a band-aid i think; as this solution only masks the problem. This doesn't help if the acceleration phase takes long (high gear high speed acceleration uphill for example - you will run our of the pump jet "shot" before getting to 3000rpm). - More progression holes: sounds good in theory, but would keep it as a last resort option. - Other idle jets: here I also think I found the right ones, as idle & cruising the AFR is almost spot on. Maybe a tad too rich, but with leaner idle jets the bog / hesitation at low rpm acceleration gets even worse. - Smaller chokes: I read a lot about the "golden rule" of having chokes between 70-80% of the carburetor diameter; with DCOE45 that is 32-36mm. If these are bigger than the recommendation the booster signal gets weak. But how would that feel while driving it? Would it also impact low rpms or only high? This is currently my best bet, as I could always return to 38 chokes if the smaller ones wouldn't help. @jonbill thanks for the link; I read this a while ago but was a good thing to re-read anyway. There is also a very good FAQ on https://240260280.com/Tech/Carbs/Weber/DCOE Theory Operation and Tuning.html
  4. I heard of drilling additional progression holes, but really hoped I will find another solution (drilling would require a precise machinist and in any case its a one-way trip). I hoped a different jetting (maybe different idle jets or emulsion tubes) could have a similar effect as additional progression holes? My cam is quite mild so peak power is at 6600 rpm, from there on power goes down. I never rev past 7000. What cam did you have in your engine to not restrict such a combination (L29+39 chokes)?
  5. Hi guys, I'm starting yet another topic on DCOE 45 jetting for a modified stroker L31 engine. The reason is that I would really like some feedback from someone else with a similar setup as after 2 years of driving / tuning / jetting it I still have not managed to get rid of the "bog" if flooring it below 2500 rpm. Engine specs: L28 bored / stroked to L31, ported head & intake manifold, MSA 6-1 headers with 2.5" exhaust, Schneider "270-80F" cam (270/280 duration, .460" lift), 10.5 to 1 compression, ZX dizzy, a set of rebuilt Webers DCOE 45 DCOE jetting: 38 chokes, 155 main jet, 185 air corrector, F11 emulsion tubes, 55F9 idle jets, 60 pump jets, closed back-bleed valve So the engine runs nice, dyno showed 242 HP@6600 rpm (calculated crank), AFR is around 11-12 at idle and cruising, 12-13 at WOT. If I floor it below 2500 rpm the AFR gets really lean and all power is gone. I tried to fix that with a bigger pump jet (60) and a closed back-bleed valve and it helped a bit, but didn't really solve the problem. As the idle/cruising AFR is already on the rich side I don't want to increase the idle jets. My theory is that the 38 chokes are a bit too big, or that the cam is too mild and doesn't produce enough flow to correctly draw fuel at low rpms. Any other ideas how I could improve the low rpm acceleration phase? Any other hints on the jetting setup? Many thanks for all the help! :)
  6. Yes it may be good for a turbo, but I am building a NA engine. I bought then a LD28 crank which changes the compression ratio from cca 8.5 to cca 10.5. I will be using a 2mm head gasket - else the CR would be even higher! I hope that with CR ~10.5 I'll be able to get some more power from the engine. 8.5 sounds a bit too low, and I could find no one with that combo...so I have no idea what power could be achieved with that.
  7. OLDZZZ you are very good at describing my dreams, ha! Both the engine compartment as the interior look fantastic! Do you have any data regarding power/torque?
  8. Interesting info regarding C and W versions - and yes your explanation matches with the ratios! Thanks! Otherwise the 4-bolt driveshafts are as it looks almost impossible to find, so I'll probably go the easy way and keep searching for a 280ZX box...
  9. Great, thanks for the info! About the power...I can't tell anything yet One more question...the FS5C71B has an 4-bolt output flange, not the splined shaft like the other boxes (including my original 4-speed manual). Is there an easy conversion between flange type output -> spline type output? Is it possible to remove / replace the final output shaft of the gearbox? Otherwise I guess I might also need a matching prop shaft... Peter
  10. Hello! I was searching for a 5-speed transmission to put into my '72 240Z. Although I aimed for a 280ZX box, I have now found an EU 240Z 5-speed, a two-piece-case FS5C71B. The engine of my car is being built right now and will be a 3.1 NA stroker. I am wondering if the 240Z box will be able to hold the torque. Is a 280ZX box any stronger than the 240Z box? Thanks, Peter
  11. Hi! Yes of course the head work is a crucial part of the build. But even with a good head work the 9.3 CR seems to me a bit too low to get some serious power. I imagine that also a good exhaust and intake / carbs can't help you much if the CR is not a bit higher than only 9.3. Am I mistaken...? Peter
  12. Oh, interesting. So maybe we will soon have another L28 / KA24 engine build thread, where the owner changed his mind? Anyway, I sent JelmerPatrol a message about the crank. I'm still curious about the KA24 combo, if anyone has some experience, please do share! Thanks, Peter
  13. Hello fellow Z guys! It's my first post here so I hope no one minds being a technical question. I have been following some of the threads here for some time now and finally found a question with no answer. I have seen the combination L28 + L24 rods + 89mm KA24 pistons in a few threads (and on some other web forums), but everywhere it was just described as a possible option or as a "plan for doing a build". I want to hear some hands-on experience from someone who has already build it and drove it. And the most important question: would he build it again? The 3.0 that you get from that combination of parts sounds very nice to me (especially because there is no way to find a LD28 crank in Europe), what bothers me is only the cca 9.3:1 compression ratio that you get with the N42 head (probably the best option regarding CR). I am not sure if that is enough for a "performance" engine. Thanks, Peter
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