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Replacing CD 150 in '69 Alpine

Discussion in 'Huskies, Imps, Rapiers, Fastbacks, etc.' started by Bill Blue, Oct 3, 2021.

  1. Bill Blue

    Bill Blue Platinum Level Sponsor

    Finally fired up, now to find the BIG air leak!

    Bill
     
  2. Shannon Boal

    Shannon Boal Bronze Level Sponsor

    Hope it will sustain an idle while you do that!
     
  3. Bill Blue

    Bill Blue Platinum Level Sponsor

    Currently have trouble getting it to fire, let alone idle. Methinks a massive, intake manifold mount related air leak. Am somewhat befuddled though. First day, got it to run, albeit at a very fast idle and with fuel enricher used. Removed the carb, applied RTV to all gasket surfaces and it refuses to fire. Coincedently, the fuel regulator stated leaking, so I removed it, using 5/16" tubing to bridge the gap. Still would not fire, but it appears the carb can handle the Alpine fuel pump pressure. 53 degrees in the garage does not help. Expecting temps near 60 degrees today.
    Bill
     
  4. Bill Blue

    Bill Blue Platinum Level Sponsor

    Removed carb, filled the built in air leak that is part of the vacuum switch setup. (Good ole' JB Weld). I decided I would just go with my home made ported advance. Decided the intermediate jet was too small. But at .031, is the largest one in the set. So I drilled out the smallest jet (.026) to .032. Reinstalled the carb. Will now idle down to less than 600. Idle lean falloff occurs at about two turns out, cannot adjust rich enough to notice any change. So I'm assuming that I'm maxing out the jet and still way lean, but a lot closer to ideal. Now to pull the car again and enlarge the jet. Hope I have an appropriate drill.

    Bill
     
  5. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, sounds like you are getting close. Most automatics you want about 600RPM in Drive. If the drive line clunks when you put it in gear, slow it down a little more.
     
  6. Bill Blue

    Bill Blue Platinum Level Sponsor

    Jim, this engine simply does not like to run at 600. So my target idle rpm is 800. That is the speed I get with the throttle plate shut and the engine running at optimum fuel mixture.

    I finally got some good luck. Went through my stash of small drills, nothing above .032 that's close. So I drilled the jet out to .038! What an incremental step! I did it thinking that at a minimum, I would be establishing minimum and maximum jet sizes. Fired that baby up, let it warm up a bit, lowered the revs and started the process of adjusting the idle richness. Idles like a champ at 800 with the mixture screw two turns out. Even accelerates from idle very nicely. Tried several times to lean it out a tad, but a quarter turn either way ruins the idle So its going to stay at two turn turns with .038 jet until testing proves it wrong. No clue as to when that might happen.
     
  7. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, Is that idle speed in Park or Drive? Road test and sparkplug color.
     
  8. Bill Blue

    Bill Blue Platinum Level Sponsor

    Jim, this car has a manual transmission. Road test is going to have to be postponed until all the stars are properly aligned. Our house is located on a State highway at the top of a hill with limited sight distance. Warmish day, no salt on the roads, not much traffic, Barb available in case things go terribly wrong. Things like not enough power to climb the hill. :eek:

    Bill
     
  9. 260Alpine

    260Alpine Silver Level Sponsor

    I must have confused your car with another one on this site that has an automatic.
     
  10. husky drvr

    husky drvr Platinum Level Sponsor


    Jim,

    The carb switch is for Bill's '69 Alpine coupe with 1725 iron head engine and manual trans.

    Bill's Durapine II is the car getting the automatic trans.

    Hope this helps,
     
  11. Bill Blue

    Bill Blue Platinum Level Sponsor

    Got my O2 sensor up and operational. It is a 4 wire narrow band, set up as a sniffer at the exhaust pipe exit. The 4 wire sensors have a heater in them for quick warmup, also seems to enable the sensor to be used as a tailpipe sniffer.

    I say it is operational simply because it seems to give realistic response to changes. Having said that, I have a mystery on my hands. The literature for the carb says that large motorcycle engines, up to two liters, should use the .031" intermediate jet and to tune for a 1000 rpm idle that is on the rich side. I have a .039" jet, and an idle speed of 800. The idle rich adjustment screw is 3 turns off the seat, idle is on the lean side. The narrow band started a 40 millivolts with the screw out about 2 turns. 3 turns off the seat and the sensor is pretty consistent at 300 millivolts. Can't wait to get on the road to see how it reacts at speed and load.
    Bill
     
  12. Bill Blue

    Bill Blue Platinum Level Sponsor

    Today was the magic day. In a word, RICH. So rich, it was blubber whenever pressed and was down on power. Reinstalled the .031 intermediate jet, still very rich. Ended up with a .028 intermediate and .070 main. The main is still too rich and kicks in too soon. So will go with a .068 and drill the air bleed to .050" (up from .040"). I decided the only way to live with smaller intermediate jet was to drill the idle mixture hole oversize. Took it from .054" to .062" in about four increments. The engine now idles at about 150 mv (very lean) with the mixture screw out about 3 1/2 turns. At least it idles and takes fuel smoothly. Have a photo of my exhaust sniffer. As stated earlier, it is a four wire, takes a minute or so to warm up, but not all that bad. For tuning a carb, I think a narrow band is good enough. I really like the price - cheap, very cheap. This is a sensor I picked up in a junkyard a few years ago. Can't remember if they even charged me for it. The heater is plugged into the cigarette lighter outlet and the output is read by a six dollar Harbor Freight multimeter.
    Bill
    Oh yes. The carb seems to have done a decent job of waking up the Alpine. Pulls good at the higher rpms. With CD 150, there was no chance of over revving. I'd loose interest at about 5000. How it seems to have plenty of life past 5000. How much past, I can't say. Todays driving probably totaled less than ten miles, just out and back to determine where I was in the tuning effort.
    IMG_8130.JPG
     
  13. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, You'll get it figured out. I'm curious how the cold start and warm start are?
     
  14. Bill Blue

    Bill Blue Platinum Level Sponsor

    Cold starts, noo problem. Hit the gas a couple of times, pull out the fuel enricher and crank it over. Starts second or third time over. Most of my cold starts have been with an empty carb, which confuses the issue. Warm start, have not done many of them, but so far, no issues. Initial start was a disaster, cranked the battery down to almost flat a couple of times. But subsequent starts have been easy. Starting with the 150 was a real crap shoot. Either second time over or a seriously discharged battery.

    Idle richness aside, the S&S has been a good carb to work with. Reacts to changes like it's supposed to and gives repeatable performance on the road.

    Bill
     
  15. Bill Blue

    Bill Blue Platinum Level Sponsor

    We took the car out today for an "extended" drive. We had a lot of rain overnight and there is not enough salt on the area roads to properly season a small order of fries. The "extended" trip was only about 10 miles, but enough to sort out whats lean and whats not. The intermediate jet was lean, but the engine still ran pretty good. No misfiring, sneezing, etc. But still lean, giving a lot of millivolt readings in the 100-200 range. The main was rich, pumping out 800-900 mv. Also coming in too soon, as early as 2,000 rpm's. The intermediate jet should do most of the work up to 2500-3000. So. Changed out the intermediate jet to a .0295, up form .028. Drilled out the main air corrector from .040" to .050", per standard instructions. The smallest main jet was in the carb. After I get the main kick in range correct, I'll solder the orifice shut and drill it to about .060" and go up from there. Currently the car has a .066" main in it.

    All in all, pretty good rough tune with very improved performance over the CD 150. I'd say that now the performance is similar to the Series 1725 Alpines.

    Bill
     
  16. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, Excellent!
     
  17. Barry

    Barry Platinum Level Sponsor

    Bill,

    Sounds like you are gaining on it. How do you "adjust" the RPM where the carb transitions from the intermediate to the main jet?
     
  18. Bill Blue

    Bill Blue Platinum Level Sponsor

    Enlarging the main jet air corrector jet retards the main jet transition. I think that one of the S&S videos mentions it also leans out the main jet. My plan of attack is to leave the main jet very rich which allows me to see its transition more clearly. Currently, the transition appears to be early and abrupt. The last tuning sessions will be leaning out the main jet.

    Bill
     
  19. Barry

    Barry Platinum Level Sponsor


    That is the rational approach; at anything close to WOT, rich is safe and lean is trouble looking for a place to happen.

    Some sources indicate that an O2 sensor should be at least 12-18 inches from the open end of the exhaust to prevent "back flow" from causing an artificially lean reading. Temporarily adding / removing an extension should clarify the issue.
     
    Last edited: Dec 12, 2021
    Shannon Boal likes this.
  20. Shannon Boal

    Shannon Boal Bronze Level Sponsor

    The balance between the main, and air correction jet, creates a mixture vs airflow curve. If the air correction jet is smallish, the curve get richer at max flow; if it is large-ish, you get some high speed leaning. I like a little leaning at high speed. It sounds like you are getting close to good drivability.
     

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