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Thread: The OTHER one - Gemini #2

  1. #1
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    The OTHER one - Gemini #2

    Have refrained from putting this one up because, well, absolutely SFA has happened over the past 18months or so, but expecting a lot of progress shortly so here goes. Bit of a pic dump to catch up but we will start on some somewhat-related background. Begin Cool Story Bro. A few years ago now I screwed together an L67 powered VS for the nopics to use as a daily. Started with a basket case her dad for some strange reason had sitting in his carport. Photos cannot accurately convey how shit the thing was.





    Went through the whole thing and gave it a quick respray, replaced the whole interior [fucking cats] new suspension etc only for the thing to blow a headgasket a week after being on the road. Replaced dead engine with L67, Berlina trim, new rad, new this, new that, and so on. The result was, for a rush job, surprisingly half decent.





    And then the headaches started. Kept dumping its coolant on shut off – went through three radiators before we discovered it was the cheap aftermarket rads that were causing it – filler neck area wasn’t machined right so once the cap would soften up it would start to leak. Then the auto went. Then two power windows. The seat went into autofullysick mode [it reclines by itself]. Then the exhaust fell off. Then the front brakes caught fire. Replaced them with new ones, then they caught fire again. The roof lining and all the plastic trims around the back window feel down. The ignition barrel broke. Then the panhard mount snapped. Then her brother crashed it.

    /CSH

    So because my nopics is as broken as I am and apparently learnt nothing during the VS Saga, she suggested we get something else and build that instead. Rules were it had to be light, RWD and manual. MX5’s were ruled out early on by the boss as being too girly, K series Corollas too ugly, T series Celicas too hard to find, Z cars too exxy. Which literally left us with the PF perennial favourite the E30, or a Gemini.

    Couldn’t find a decent 6cyl E30 in budget to play with sooo…









    Yes the k’s are legit. Two owner car – retiree for most, young kid for 12months. It leaked water and no longer ran and he didn’t know why – leak was welsh plug at back of block which he never would have found, and he forgot to connect the alternator [runs the fuel pump in these] which is why it wouldn’t run. So out it came, resealed inlet, new sump gasket, new front and rear mains, new water pump, new welsh plugs etc. Basically everything except valve stems and headgasket, which would come to bite me in the arse later.





    Rebuilt the front end with nolathane, new ball joints, Gabriel shocks and a “slight” altitude adjustment.







    Set of 15x7 BBS RS Copies







    And done. Sort of. With what was planned long term, I figured it might be a wise idea to teach the girl how to drive. No13b_Cunt organized a skid pan day, so what better than to drive up from melb to rag on the thing all day long? Did I mention we literally got it registered THAT week and hadn’t driven more than 10km in it? No drama…

    Skids n shit.









    So not only did it survive the merciless thrashing on the pan, but it did it without hiccup and without using more than 8.5L/100. The bug had well and truly bitten the nopics at this point. Next up stereo, the boss demanded the interior appear as near as standard as possible. Never got to finish this but heres what we have/had. It’s a marine stereo so comes with a separate wired remote w/ screen that will go in the centre console, allowing everything to be hidden.





    Sadly at this point, the engine began to expire. Remember me not changing the headgasket and valve stems? It began to consume 4L of oil in under 1000km, which resulted in a lovely letter from the EPA because some tree hugger lagged us in.



    The plan was, at this point, to throw another running stocker in and rebuild the original one with a few mods. This time I thought, for the sake of 90bucks, ill throw a VRS at the “running” engine. You can see where this goes.





    Off to the machinist we go, assembly done by me at home. Is as follows:
    G161z Block/Crank/Rods
    Federal Mogul cast G180z Pistons and rings [2nd o/s, 84.5mm]
    Approx 9:1 CR and 1700cc
    Reground cam to suit
    Big valve [42mm inlet] head, full reco
    HD Valve springs, “mild” cam











    At this point, she-who-whinge-a-lot declared she wasn’t happy with the graze down the passenger side of the car and wanted the whole thing resprayed. No amount of pleading from a mate and I to leave it alone would sway her. She’d also managed to find a photo online of a modified Gemini ZZ/R and demanded I help her make it look like that, just to make my life that little bit more difficult.



    Which means I needed the JDM front apron, the ZZ bonnet vents, hard plastic bars and the rear wing. Fortunately, fibreglass copies exist. Unfortunately, fibreglass is actually the worlds worst material because inevitably you need to spend 11 billion hours getting it right.



    Eg.



    Have spent a few hours with a file removing excess material. Still need to fill in all the gaps and voids etc. Not pictured are OEM ZZ/Z rear spoiler [its ABS plastic! How posh!] and fibreglass bars.



    Wont bore you with a million photos of the same thing, but this is the sort of shit I had to deal with panel wise.



    Painted the bay black while I was at it because this thing will leak oil when im finished with it. Plus ceebs with shiny engine bays, aint nobody got time for that.



    Sent it away to get painted. Was going to do it myself, but selling house etc means I no longer had a garage to do it in.







    In the meantime, kept working on engine. Spec list was pretty devoid of inlet/exhaust details. Heres the what.

    Hi rise turbro manifold with merge collector. Kinugawa turbo, cant remember the spec but its meant for an SR of some sort, was 450ish plus HP apparently. Should be more than enough to see it hit 170ish rwkw. Inlet is Rodeo 4ZE1 runers, “Custom” piece of pipe I mean plenum, XF throttle. GTR injectors are a straight drop in.





    Note: Oil line goes around the back with water lines, I re did it. Also shortened the water lines too.

    Problem is, turbo comp cover needed rotating….which means wastegate mount is now on opposite side to wastegate flap. Fucked around with cardboard and ally on works bender a bit just to see if I could get it to work.





    It does, but I don’t like it. Think I might be better off getting a plate TIG’d onto the front cover.



    Theres an EMS 8860 and loom in there somewhere. Plan is to run a single LS1 coil, using as many GM/Delco parts [sensors etc] as possible. NFI what im going to do about IACV. Steve reckons it wont be a problem, just depends on how lumpy the “mild” [and by mild I mean biggest that could be ground on standard stick LOL] turbo cam goes.
    Intercooler was the bargain of the year, $100 for a custom made Plazmaman to suit Gemini. Would have been a straight bolt in except, having been in a prang before this thing wasn’t 100% up front so had to open up a hole in the radiator support for the cooler piping to fit through. Fits behind the grille too.





    As of this weekend. 2k solid in the original colour [Alabaster White], getting cut back and polished and we should be getting it back Monday arvo.





    Should probably mention that there is a deadline on this too – rego on mrs daily runs out in October. Here we go again…

  2. #2
    Opens AxGT's Avatar
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    Still auto?
    If so, at least it should have enough herbs to poodle around with the turbo
    Dirty Subaru owner

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    Registered User 50RTD's Avatar
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    Tough!

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    Registered User 9triton's Avatar
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    cool story , bro.

  5. #5
    Owns a bucket no13b_Coupe's Avatar
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    “Custom” piece of pipe I mean plenum
    Piece of over price fucking rubbish and easily the worst thing you will put in her car? Probably goes hand in hand with that custom turbo manifold.

    Waits for circle jerks to cry 844543 rivers and facebook e-war.

    Personally keen to see this back together.

    Then we can re-create this 3 years later.



    BF XR6 Turbo - 2L Turbo TE - 75 TX Coupe - Atlas SS

    - PSN: rotacoupe

    This is obviously assuming all your AUX outputs are doing something. Ie idle control, and the other does water spray, and the other updates your Instagram automatically etc.

  6. #6
    Registered User schnitzelburger's Avatar
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    Nice build bloke keep going

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    Quote Originally Posted by AxGT View Post
    Still auto?
    If so, at least it should have enough herbs to poodle around with the turbo
    Nah, auto was turfed for a 5speed when the engine was out. Much more fun being able to clutch it and light em up

    Quote Originally Posted by 50RTD View Post
    Tough!
    Thanx Dan

    Quote Originally Posted by 9triton View Post
    cool story , bro.
    Hansel*. I go by Hansel these days

    Quote Originally Posted by schnitzelburger View Post
    Nice build bloke keep going
    Thanks mate. I have no choice but to keep going. VQ is dieing a death of a thousand cuts so the quicker this gets going, the quicker the VQ gets fucked off.

    Lol Jonno, I dont need to tell you how disapointed she is we wont make this skidpan. As for the CircleJerk manifolds, I had them on the shelf sooooooo meh.

  8. #8
    "The bitches, are wet" Sketchy's Avatar
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    Big fan of those wheels
    Quote Originally Posted by Dimi View Post
    80mm of penetration isn't bad, i wish i had that much.
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  9. #9
    Two years in Lompoc... Lobster's Avatar
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    How's this going?
    Previously known as Lobster, Chuss's brother's anus, Chuss's brother, Lobsook, Lobstersock, Socks, Sockz, MissAmericaImportGirl, ClutchCLobster

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  10. #10
    Registered User Grizzler's Avatar
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    What are the BBS copies worth these days? Does that offset fit ok on your other Gemini?

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    Quote Originally Posted by Lobster View Post
    How's this going?
    Havent done massive amounts on it since it was painted - got put on the back burner a bit and parked under a cover at the wifes pops house while other life shit [finishing my car, wedding, house etc got in the way]. Move into our new place soon so ill finally have a garage to work on it again after almost 18months of nothing. Engines been ready to go for a while, just need to sort out the ignition side of things for it and weld a bracket onto the front cover for the waste gate. Otherwise, mostly just re-assembly.

    Quote Originally Posted by Grizzler View Post
    What are the BBS copies worth these days? Does that offset fit ok on your other Gemini?
    Depends on who makes the copies, these cost the mrs 900 i think from memory. Yes and no - they fit well [especially on the rear] however mine rubs on the front right quarter occaisonally. I had to replace that gaurd when i stacked the car and its a non-genuine one - i have the impression that the arch shape is slightly wrong.

    15x7 ET20 with a gaurd roll would be fine though, unless you hit a giant bump at full lock.

    N-

  12. #12
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    You know the saying out-of-sight-out-of-mind? Well, that kinda happened with this thing. Tucked it away at the back of the wifes grandparents place in the carport behind he garage and shed and left it there. We'd go visit the oldies and because of where it was stashed you'd forget it was even there, and pretty much forget we owned it we did. That is until Nan and Pop decided to sell the house after almost 50years of ownership and build new. Which by extension means this came home end of Jan.



    First things first, make it waterproof. Ive fitted heaps of Gemini front/rear screens over the years and its gotten to the point where im quite good at them - good enough that when I fit them, they dont leak, unlike the one Obriens fitted when my windscreen exploded due to an errant rock on our honeymoon. Did the usual, roped it in and it sat a little bit proud in the bottom corner. Thumped it with my palm [i was having a real bad day at the time] and it must have been under tension because about 30sec after getting it seated it exploded, showering me and the dog with glass.



    Replacement rear which had funky 80s purple tint. Peeling the tint was the easy bit...getting rid of the glue residue fucking took forever, and thats using thinners too.



    Fitted/seated properly



    Tail lights in and bar on, looking more like a car now





    Magna remote boot release is pretty much a bolt on swap for this. Given that it may end up being my daily for a little while i figure this [along with central locking swap] would make life a bit nicer. New carpet inside, seats cleaned and reinstalled [forgot to take photos of all this] and inside is pretty much done. Which brings us to the fire-in-the-hole noisemaker bit. Bit of a discussion with the nopics, we have way too many cars and i dont feel like pouring giant sums of cash or devoting giant amounts of time into this one. I argued that throwing a carb back on it and getting it running is better than it sitting in the back yard and sucking up cash. She reluctantly agreed, so turbo and EFI gear came off and goes back on the shelf. Initial plan was to throw a 32/36 Weber on it except inexplicably people want good money for these, and even the reproductions are 400 odd. Bugger that.

    Found an IDF Redline manifold for $100 local. Good price and the young fella even offered to deliver it to my father inlaws. Decision made. Began the hunt for a second hand set of Dellorto DRLA40s or IDF40s. Bzzt, no dice. Found a few sets of rough as fuck 36IDFs which arguably might have been a bit on the small side anyway but the best part was the fella selling them was asking $450 for the pair of them despite the fact they had black scorch marks all over them and had visibly been on fire. No thanks.

    Bit the bullet and bought a pair of the repro IDF40s. No, i am under no disillusion that these are anywhere near the quality of a genuine Italian made Weber. However, id argue that given they are substantially cheaper plus i dont have to strip them down and rebuild them these should be perfectly ample, even if one carb turns out to be a POS and i need to replace one. Should be relatively straight forward right? Right?!





    Yep. Only I could buy parts made for each other and still have problems....

    So it turns out earlier Redline IDF manifolds had a smaller spacing between cylinders 2 and 3, presumably to get the runners for number 4 away from the brake booster. Except of course, the whole point of going IDFs is because they are meant to clear the brake booster. This smaller gap combined with the throttle shafts being longish means the nuts and linkages were sitting on top of each other.

    Fair bit of fucking around later including manually thinning down the throttle linkages and nuts [nuts were hand filed to half thickness...yes it took ages] plus cutting the throttle shafts down and it all fits.








    Ready.





    Set.





    Go.

    Except, of course, it wouldnt. I cannot describe the feeling that goes through you when you are trying to start a motor you've built yourself for the first time and it refuses to go. Hit the starter and all i got was a tired groan out of it, even though id bench tested it and it tested fine. Added a few more earths and got that cranking nice and quickly, oil pressure light out virtually instantly. Next step, no spark. Worked out id bought the wrong ignitor from the wreckers - N13 Pulsar is meant for a hall effect dizzy, this has a variable reluctor. Fuck, pinch points dizzy out of the gold car and crank it. Nice and fat spark zap now, so time to prime the fuel system. Connect pump to 12V, fuel filter full and...sniff...what the fuck? Can smell fuel.



    Ladies and gentleman, may i present to you 1x Chinese made M10 x 1mm x 8mm barb fuel fitting. Noticed a drip out of the Carb and touched the fitting only to find out it was hand tight. Interesting...turned it with my fingertips and it came off in my hand. Replaced all of the barbs with new ally ones, no fuel leaks. Put coil lead on dizzy and...

    ....it wont fucking start. This is where i begin to pull my hair out. I have fuel, I have spark, I have compression. What i dont have is a running car - what the fucking fuck? Did i get the cam timing wrong when i built the engine? Did i put the dizzy in wrong? Has to be timing surely, it wants to cough and fire. Tried advance/retard, it goes to fire and then dies. Really scratching my head at this point and the swearing and screaming and backfires out the open extractors means the dogs decided shes had enough and taken off round the other side of the house. I swear i used to get more shit done as a smoker; youd get frustrated/pissed off, you'd have a quick ciggie and that 5mins of clarity means you find the problem instead of hurling shit around the garage.

    Has to be timing. Took the dizzy out and decided to time it the same way I do whenever im replacing a dizzy. Turn crank to 5deg BTDC. Dizzy in, rotor pointing at number 1. It should fire. It has to fire.

    It doesnt. Except this time, im looking at the dizzy [known good one] as im cranking it. And as its just about to fire and cough I notice something. You know how you leave the locking bolt a bit loose so you can set the timing? Well. It turns out that on an engine with decent comp when it goes to kick into life, the dizzy moves. Ive effectively wasted an hour trying to start this thing with no joy because the dizzy kept retarding itself.




    Almost there!

  13. #13
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    Suppose were due for an update. I have really done fuck all on this thing over the past year - its basically sat in the garage on stands 90% complete while life got in the way, with me slowly fiddling with bits and pieces here and there, which means i didnt take pictures of shit so youll have to deal with short snapchatesque videos. Gem Nationals coming up again [Easter] and with the house now being sold I vowed this thing will drive out of the garage. Add to that my car being written off means I needed wheels, fast. Nothing like a bit of drama to get you moving then.

    Two things have stopped this thing from moving [I dont mean time and money] - one was the carbs were over fuelly as fuck and i have no real idea how to set them, and the second was it randomly developed a no spark issue. It would kick/fire no worries with my points dizzy, but the other two dizzys i tried resulted in nothing. I tried a variable reluctor setup with both a camira ignitor AND a procomp elec box - no dice. Tried a hall-effect points replacement with Camira ignitor - again, nothing. Bit the bullet and bought a brand new, two wire points replacement which has the module built in and all. Two wires - this cant go wrong! No spark. In the end conceded defeat and stole the points dizzy out of the now defunct brown/gold car and whacked that in, which resulted in this goodness.



    Ordered a synchrometer and got plugging on Friday finishing off a few loose ends like seat belts, throttle linkages, clutch cables. Roddy came down on Saturday and spent a few hours going over the carbs, we bled the brakes out and took it for a whirl. Not going to lie, was nervous as fuck given that the engine was something i built by myself in my garage a few years ago but so far ive racked up around 100km and you can feel it freeing up and wanting to rev. Engine feels good, sounds good and from the short stab of the throttle here and there seems like itll go pretty good.

    Gave the old girl a quick bath and although im not really happy with the paintjob on it, it scrubs up ok





    Need to run the polisher over it and give it a wax, should look ok. Theres still a decent amount of things to tidy up and get around to sorting out before we take off for The Entrance next week. Exhaust is banging on body pretty badly, rear swaybar needs connecting, interior needs finishing off. It drives ok on the carbs but we still need to put a wideband up it, has an annoying small backfire/spit out the carbs if you are slowing down from, say 3500 and then pick up the throttle lightly. Its also an absolute cunt to start regardless of if its hot or cold. Also idles high when warm but way too low when cold. Hooked up the vac advance which helped a little bit, wondering if i need to up the base timing a fraction as its currently on 10BTDC although thats already pretty high.

  14. #14
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    Heres two more shit videos for your viewing. Apparently I can only upload one at a time


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  16. #16
    Eurotrash :D
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    Bbbbbbbbbbbbbbbbbbbbbbbbbbbboooooooooooooooooooooo oooooooooorrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrtttttttt tttttttttttttttttttttttt!!!!!!!!!!!!!!!!!!!!!!!!


    Love it.
    Quote Originally Posted by Marv View Post
    Only be concerned if that Dunning-Kruger Motorsports bloke is there and goes all Captain Damphands McGigglefingers on you after a couple of lemon squashes....


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    The noise is so fucking addictive its not funny, cant wait to actually be able to rev it out properly. Seems to go better than the relatively basic sum of its parts suggest it should.

    Carbs are going to take a fair bit of fine tuning - its an absolute bitch to start cold or hot which it shouldnt be given that it has a relatively healthy amount of timing advance [10btdc] and the vac advance connected too. That said, it actually drives without any hysterics cold without a problem after youve given it 30sec or so on throttle to settle into an idle on first start. Another issue ive got is i still think its a bit rich as the fuel is washing out but theres no black marks on the rear bumper from excessive fuelling so that contradicts itself.

    The main issue at the moment with the carbs is i think its suffering from a bit of spit-back, happens mainly around 3000rpm - say cruising on the highway, back off throttle and then go to pick up the throttle again. Its not a huge backfire out the inlet ala too much timing advance, more like a small cough out of the carbs. So far seen the cause as being described as cam related [possibly, but its not a huge cam so doubtful], lean mixture particularly on progression [again, doubtful as its pretty rich], and carb syncing [they are synced properly, so not that]. Anyone have any suggestions?

    Im also concerned that the main venturi is a bit on the small side - currently has 28mm chokes and it drives ok [caveat being fresh engine so havent revved it hard yet], but all the choke sizing graphs ive looked at for IDFs seem to suggest its way under-sized. Looking at the graph for approx 1700cc and 7000rpm i should need a choke around the 34mm-36mm area, not 28. Could airflow being too restricted be causing the spit back? ie choke too small restricting airflow and leaving fuel mixture still in runner rather than being drawn into cylinder?


  18. #18
    Registered User schnitzelburger's Avatar
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    induction system is titz

  19. #19
    CNGAF rowdytoot's Avatar
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    Best thing about my old rally gem was the noise on twin idfs

    Sent from my G8141 using Tapatalk

    1998 MX5 - Ohlins DFV coilovers, Roll bar,15 x7.5 Konig Litespeeds, Mania Intake
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    Eurotrash :D
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    yep, chokes too small. the prob is, changing those means rejetting everything. id go 36mms and see what it does. have you got a wideband on it?
    Quote Originally Posted by Marv View Post
    Only be concerned if that Dunning-Kruger Motorsports bloke is there and goes all Captain Damphands McGigglefingers on you after a couple of lemon squashes....


    I'M NOT A HOOKER BUT 20 BUCKS IS 20 BUCKS...

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    Non Compos Mentos Gammaboy's Avatar
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    Quote Originally Posted by F3ARED View Post
    The noise is so fucking addictive its not funny, cant wait to actually be able to rev it out properly. Seems to go better than the relatively basic sum of its parts suggest it should.

    Carbs are going to take a fair bit of fine tuning - its an absolute bitch to start cold or hot which it shouldnt be given that it has a relatively healthy amount of timing advance [10btdc] and the vac advance connected too. That said, it actually drives without any hysterics cold without a problem after youve given it 30sec or so on throttle to settle into an idle on first start. Another issue ive got is i still think its a bit rich as the fuel is washing out but theres no black marks on the rear bumper from excessive fuelling so that contradicts itself.

    The main issue at the moment with the carbs is i think its suffering from a bit of spit-back, happens mainly around 3000rpm - say cruising on the highway, back off throttle and then go to pick up the throttle again. Its not a huge backfire out the inlet ala too much timing advance, more like a small cough out of the carbs. So far seen the cause as being described as cam related [possibly, but its not a huge cam so doubtful], lean mixture particularly on progression [again, doubtful as its pretty rich], and carb syncing [they are synced properly, so not that]. Anyone have any suggestions?

    Im also concerned that the main venturi is a bit on the small side - currently has 28mm chokes and it drives ok [caveat being fresh engine so havent revved it hard yet], but all the choke sizing graphs ive looked at for IDFs seem to suggest its way under-sized. Looking at the graph for approx 1700cc and 7000rpm i should need a choke around the 34mm-36mm area, not 28. Could airflow being too restricted be causing the spit back? ie choke too small restricting airflow and leaving fuel mixture still in runner rather than being drawn into cylinder?

    Spit back is progression - the progression drillings are possibly not ideal. May also be accelerator pump, but that tends to manifest when you give it a bootfull rather than just picking back up off trailing throttle.
    I'm running 35mm chokes, 1800cc and ~7100rpm, and a few other mods to the auxilliary venturies to improve flow.

    Get bigger chokes into it (34s), and post up the rest of your jetting.
    Last edited by Gammaboy; 09-04-19 at 12:31 PM.
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

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    Accel pump being set incorrectly should give dumps of black smoke when revving even when stationary, no? And how does one establish if the progression circuit is the problem? Not seeing excess fuel in mirror at night but that doesnt mean shit without getting hard figures from an o2 really - its definitely rich at some point because the oil is washing out. Havent had the o2 on it yet, Roddy is meant to be making an adaptor so we can put it in the tail pipe and check it hopefully this weekend, otherwise ill throw it on a dyno somewhere during the week.

    Max venturi size off the shelf for a 40IDF is 34, so according to the graph still technically undersize but probably ideal to go a little bit smaller given itll live on the street. Jetting sizes are as follows:

    Fuel Press [Recommended] - 2.5psi to 3.5psi
    Float height: 11mm w/ Gasket
    Needle and seat: 200
    High Speed Enrichment: N/A
    Acc pump nozzle: 50
    Acc pump bleed: 55
    Choke/Main venturi: 28
    Idle jet: 55
    Emulsion tube: F11
    Main jet: 125
    Air corrector jet: 185

    If you follow the formulas that they have in print/online everywhere for recommended sizing:

    Venturi size rule of thumb = inlet valve size minus 6mm, so 42mm inlet valve should have 36mm venturi [way, way off]. 34mm is biggest off the shelf available for 40IDF so being 2mm short of ideal has surely got to be a better compromise than being 8mm smaller.

    Idle jet = 1.6 x Venturi size. Current idle jet is way too big for 28mm chokes [1.6 x 28 = 44.8] but bang on for 34mm chokes [1.6 x 34 = 54.4].

    Main jet rule of thumb = 4.1 x Venturi size. Current [4.1 x 28 = 115] is two sizes smaller on the main jet vs recommended, ideal with 34 chokes [4.1 x 34 = 140] is too small so ill either have to go up here or wind the accel pump up?

    Anything else im missing/thoughts?

  23. #23
    Non Compos Mentos Gammaboy's Avatar
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    Quote Originally Posted by F3ARED View Post
    Accel pump being set incorrectly should give dumps of black smoke when revving even when stationary, no? And how does one establish if the progression circuit is the problem? Not seeing excess fuel in mirror at night but that doesnt mean shit without getting hard figures from an o2 really - its definitely rich at some point because the oil is washing out. Havent had the o2 on it yet, Roddy is meant to be making an adaptor so we can put it in the tail pipe and check it hopefully this weekend, otherwise ill throw it on a dyno somewhere during the week.

    Max venturi size off the shelf for a 40IDF is 34, so according to the graph still technically undersize but probably ideal to go a little bit smaller given itll live on the street. Jetting sizes are as follows:

    Fuel Press [Recommended] - 2.5psi to 3.5psi
    Float height: 11mm w/ Gasket
    Needle and seat: 200
    High Speed Enrichment: N/A
    Acc pump nozzle: 50
    Acc pump bleed: 55
    Choke/Main venturi: 28
    Idle jet: 55
    Emulsion tube: F11
    Main jet: 125
    Air corrector jet: 185

    If you follow the formulas that they have in print/online everywhere for recommended sizing:

    Venturi size rule of thumb = inlet valve size minus 6mm, so 42mm inlet valve should have 36mm venturi [way, way off]. 34mm is biggest off the shelf available for 40IDF so being 2mm short of ideal has surely got to be a better compromise than being 8mm smaller.

    Idle jet = 1.6 x Venturi size. Current idle jet is way too big for 28mm chokes [1.6 x 28 = 44.8] but bang on for 34mm chokes [1.6 x 34 = 54.4].

    Main jet rule of thumb = 4.1 x Venturi size. Current [4.1 x 28 = 115] is two sizes smaller on the main jet vs recommended, ideal with 34 chokes [4.1 x 34 = 140] is too small so ill either have to go up here or wind the accel pump up?

    Anything else im missing/thoughts?
    Ok, accelerator pump setup is really done by feel/o2 sensor, you can still be too rich without black smoke.
    Venturi size "rule of thumb" is junk. Ignore.
    Does it respond to idle mixture adjustment? How many turns out is best (smoothest) idle?
    Main Jet size needs to be right, as does air corrector - accel pump is a momentary thing, you can't use it as a band aid for the MJ/MAJ being wrong.
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

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    ive been thinking about this all day, and the more i think the more t sounds like a cam timing issue. does this thing have a vernier pulley?
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    Quote Originally Posted by Gammaboy View Post
    Ok, accelerator pump setup is really done by feel/o2 sensor, you can still be too rich without black smoke.
    Venturi size "rule of thumb" is junk. Ignore.
    Does it respond to idle mixture adjustment? How many turns out is best (smoothest) idle?
    Main Jet size needs to be right, as does air corrector - accel pump is a momentary thing, you can't use it as a band aid for the MJ/MAJ being wrong.
    It does respond to idle mixture but the "window" where it gets better is pretty small. Cant remember exactly how many turns out, will need to wind one in then wind it out again to check but i *think* it was somewhere around 2.5 turns. Really need to get the wideband onto it but my feeling based on driving is idle mixture ok/mixture and main jets ok [based on nothing more than not overly fuelly out the pipe and responsive on throttle] but something wrong to cause it to spit back. The worst part about the spit back is its right in the rev range [3k] where you sit on 100-110 in 5th.

    With the venturis, do you mean ignore the formula or the graph? 28 still sounds small to me based off what other engines seem to be running relative to their engine size.

    Quote Originally Posted by Sloth View Post
    ive been thinking about this all day, and the more i think the more t sounds like a cam timing issue. does this thing have a vernier pulley?
    Standard cam gear so non adjustable, cam zero'd on standard timing marks. I take it your thinking the cam may have been ground a few degrees out?

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    Quote Originally Posted by F3ARED View Post
    With the venturis, do you mean ignore the formula or the graph? 28 still sounds small to me based off what other engines seem to be running relative to their engine size.
    Ignore the "Intake valve minus 6mm" bullshit. The graph is ok. Throw the 28s in the bin (or a lathe - that's how I wound up with 35s with an improved venturi profile) and go to 34s. Alfa 1600s turning to 6,000rpm came with 32s for fucks sake. Not much point trying to set them up for 28s when you're going to change to 34s. 28s are probably ok on a stock beetle motor.
    Fatten up the idle a 1/4 turn and see if it helps with the progression spitback - highly unlikely to be cam timing if it's only a narrow window of rpm it happens in. You can also raise the float height 1-1.5mm to richen it up in the progression (Only just remembered that trick) - it will make it slightly fatter everywhere else as a trade off though.


    Feel isn't a good indicator of air fuel unless you're so far off one end it's not funny - I need to lean off the topend (air correctors) on mine because it's so rich you can smell it from the following car - but it doesn't feel doughy or anything (6-7000rpm range).
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

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    Had a good read of the pdf you sent me this morning [thanks again]. I *think* ive got a slightly better understanding of whats going on. Going to have to order a few main jets and air correctors as well as the venturis i think. So, the spit back issue around 3k rpm - if we are to assume for a moment its caused by lean/weak mixture around the progression phase [based on my interpretation of the problem] the possible causes/fixes are:

    -Too lean on idle jet. Up idle jet or turn up idle mixture screw [like you suggested earlier by 1/4 turn]. Idle jet being a 55 i think thats more than big enough given that the book recommends a 45 or a 50 for similar engines, so may need more turns.

    -Too lean on air correction [185]. Smaller holes is richer mixture so that would mean the air correction must come DOWN a size [to, say 175?]

    -Not enough static advance. Currently set on 10BTDC, may need more? I think this ones unlikely as it pulls across its rev range [keeping in mind im not turning it over 4500 yet] cleanly from 1500ish rpm under load without going stupid

    Now, something else struck me as interesting in the pdf which got me thinking - what are the chances of one cylinder being slightly leaner than the others causing the spit back only on that pot? I have a sneaking suspicion if that is a possibility that it is cyl #2 thats the problem because the idle mixture screw on that barrel is a lot stiffer to turn than the rest. Might give the mixture screws a quarter turn and see if it irons out.

    Im thinking 34mm venturis, leave the idle jet size alone [provided the o2 says idle mixture is ok], up the main jet size to 135/140 from 125 and leave the air corrector alone. If it still acts like a shitcunt and running it richer helps, then drop the air corrector size from 185 to 175

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    Your dissy problem sounds like you are trying to run an electronic dissy off a ballast resistor.

    10deg BTC is not heaps you could bump it up to 16ish provided the total timing is not too much.

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    I wouldn't worry about what the o2 sensor says for idle mixtures - you're adjusting them for smoothest running (and adjusting them independently to get there) at idle - that will probably be a little fat according to the WBO2

    Not sure the Air corrector has much input at those sorts of flow speeds.
    You *may* need to up the idle jet size when you go to 34mm venturis.
    Last edited by Gammaboy; 10-04-19 at 01:01 PM.
    "Where can we get hold of a Vincent Black Shadow?" "Whats that?" "A fantastic bike," I said. "The new model is something like two thousand cubic inches, developing two hundred brake-horsepower at four thousand revolutions per minute on a magnesium frame with two styrofoam seats and a total curb weight of exactly two hundred pounds."

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    Quote Originally Posted by mopar lover View Post
    Your dissy problem sounds like you are trying to run an electronic dissy off a ballast resistor.

    10deg BTC is not heaps you could bump it up to 16ish provided the total timing is not too much.
    I was thinking this too. When i had my first Gemini and fitted a facet electric pump, i couldn't figure out why it kept dying. Turns out because i took the power for it after the ballast, Moved to the other side, problem solved.

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