Sar_moby

for sale- won't be using it. New in package, part number JHS 00120 Made in Japan $35 + S&H from zip 92870 or local pick-up Picture available please reply to this listing or e-mail to scott.rogers@cytec.com Thank you Scott

Well, I took out some accelerator pump shot and re- adjusted mixture and idle speed and most of the bog on tip-in is gone. It still revs better if I run it lean(er) when hot but it is getting closer. When cold it still mis-behaves some and gets better as it heats up- leaking intake or exhaust manifold (It sounds like exhaust manifold as of late, probably #1 or #2 as those are the ones that need the mixture rich to run) When this thing is hot, it runs like a rocket. The 4 speed makes freeway driving kinda loud though. Thanks for the help- will get back to you IF I tear into this motor. Regards- Scott

thanks for the help Hainz- I think it maybe mixture into cyl 1,2 and will see if the accel pump/fuel pump etc. are doing there job and look at changes to see how it runs. Thanks all Scott

mixture set rich, motor cold, pump pedal and starts right up. after 40 sec. the engine is real rich with the choke on, rev the motor to open the choke, choke clears and we are back to the 2 cylinder motor. increase mixture again, increse idle speed, rev a few times and it will hold idle on all cylinders. on accleration, sometimes it bogs at tip in real bad. You can slowly keep opening the throttle and continue the bog ( motor sounds like it is starving). i can't see the float level with the air cleaner on but could fuel supply cause this? anything else? Possibly the accelerator pump is bad( already?) or the pump is not refilling with fuel? It seems that the 2 cylinder problem is air/fuel ratio related( WOT is great) and that for some reason those two cylinders need more fuel to fire. At the same time the extra fuel makes the rear two cylinders too rich and they bog( theory). Makes me think intake gasket is bad. Well as time permits I will keep investigating. Anyone local wants to take a look- I'd be thankful Thanks for the help Scott

In all honesty I think the car is fairly close or has one or two underlying problems that cause the driveability issues. I have to keep in mind that cold start driveability and heat-up transition is why people went to F/I in the first place. I can adjust the car to run great hot (lean= good throttle response), pretty good with the choke on( rich) and only have the problem during the transition from cold to hot (unless quite rich). My in-experience with Hitachi carbs is some of the problem. This being my first Datsun, I have been learning what they like and don't like as compraed to my Toyota experience. I can turn this vehicle in and get paid for it - but it will get crushed( not good in my opinion, a vehicle that runs pretty clean as compred to a SUV) Vacuum secondary looked okay, held vacuum. I will adjust the choke colder and work on the accelrator pump to see what can be changed (more fuel/less fuel). I am wondering if the accelrator pump linkage somehow got bent as the shot doesn't seem real powerful...... hummm Scott

DatzenMike- 78 smog vehicle uses a two port threaded fitting on the #1,#2 intake manifold leg where one manifold vacuum source goes to control the air injection system (fender mounted) and the other ( I believe is the anti-backfire valve?) also located on the fender. I plugged one of them and you get that motorboat sound from the air injection system. hooked them both back up= no change. Now I am looking at the accelrator pump to see if the motor needs more fuel on tip in or less. I am not clear on the best settings and must change the plunger rod setting and the pump lever to change the magnitude of the pump shot.( is there any other way?) Motor starts great with the choke on, then the rpm drops when the choke is out of the way (set choke to colder setting?) and with the rich setting on the idle mixture, as it warms up it appears to run on more than two cylinders. Except for the tip-in the motor pulls quite well. The remaining problem is the bog on tip-in. I have a new accelerator pump in the carb but when looking down the primary it seems to only squirt a fairly small, steady stream of fuel( as compared to my toyota 22R- or my imagination). I appreciate all the suggestions and help. Almost a daily driver Scott

I think the return springs are okay( had not thought about it). I can adjust the idle speed at the screw without problems. Good thought though, thanks Scott

A body shop friend of mine once told me that Mercedes and Porsche have a special extra thick under body urethane coating that works real well and is put on with a heated pressure gun. Might be worth a look as another way to protect the body of the car. Call some body shops to get a quote to compare to bed liner material.

Update- Turned the idle mixture out two turns until the enging idled pretty smoothly and now at tip in the engine stumbles. If I lean the idle mixture, the stumble goes away but I loose #1 and #2 when cold with no choke. After making the mjxture adjustment I pulled the #1 spark plug and did not notice any difference in the idle of the engine. Can this be "normal" on an L20b? Is it possible that the rear two cylinders are running that much leaner than the fron two? I did disconnect two vacuum lines( plugged) and they made no difference. On the EGR, I removed it and the manifold adapter 2 months ago and cleaned out the carbon build-up. I have the vacuum to that and the BPT plugged right now so no EGR at all so I can diagnose the poor idle. I have also tried to spray carb cleaner around the intake with no change to the idle ( may not be able to get to the bottom of the intake manifold). After adjusting the carb, took it for a drive and it pulls well( all cylinders firing but maybe a little rich). Carb is a =DCH 340 with a 103 primary jet. Now, I can live with a rich idle if I can get rid of the bog at tip in. The accelerator pump has two positions for the plunger and three positions on the lever arm. Question: To reduce the shot volume at tip in ( too rich condition especially on #3 and #4) I would assume( dangerous) that I should move the rod toward the pivot (reduce throw). Is that correct? What else can adjust the off-idle mixture? Thanks all Scott

I think mine has a relief valve but not a check vavle, I can try removing it under pressure to confirm if it leaks down when unscrewed from the cylinder hole. Thanks

that is a good point: When I did the compression test, I let it crank 8 revs and then made sure it held the pressure for at least 30 seconds, no leaks noted. Thanks Scott

Well, I sprayed carb cleaner around the #1,#2 intake manifold from the top and sides and did not notice any change. It is very difficult to get to the bottom part of the intake manifold on a smog equipped l20B so it could be leaking from the bottom side, cannot tell. Another thing I noticed but have not tried yet is that the vacuum connections tee goes into that leg of the intake manifold. I will try pluggin both vacuum lines( no vacuum advance) and see if there are any changes. All that would need to happen is bleed enough air into that leg of the manifold to drop the mixture lean and those 2 cylinders would not fire. I will check it and report. The BPT valve is disconnected now as is the EGR to make sure they are not contributing to the problem= no change. Anything else to check? Thanks Scott

I think this problem precedes my ownership( car had a stuck float when I got it). It runs solid at higher RPM so a bad plug wire would misfire at high rpm. I did a hot valve adjustment and got the factory setting on intake and exhaust though I did find #1 intake tight. Rest of valvetrain looks good. I did not yet check the intake manifold but that seems most likely at this point. Will advise when I test this - tonight. Great video Hainz- thanks Scott

Okay, thanks for the thoughts. It does not have points and I did check the mag pick-up clearance( did not wobble the shaft though). I would think a bit of wobble would chew up the mag pick-up pretty fast if it were loose. I will wobble it and try spraying carb cleaner around the intake manifold. I got the link to Hainz video- will look at that as well. Let you know what I find. Scott

Thanks for the quick replies. While the compression test was solid, the intake leak seems most likely. Both of those cylinders are siamesed( I think) and a bad leak would kill both of them. Any other possiblities ? I have the head gasket but it will be awhile( if ever) that I tear this down. I have two cars ahead of it( one with a timing belt and ironically,a second with a head gasket as well= practise?). wife wants the car to "go away" but I keep trying to make it a daily driver. Can't let an old car die without a fight. Thanks- Scott