Triple carb install = won't start!!??

[benn9090]

New annoyance: Although I am using the longer carburetor throttle levers and the shorter holes on the main linkage shaft, I have still had to shorten my pedal stroke by 1.5" by lengthening the throttle stop under the pedal. The result is a very "hair-trigger" throttle.

Is this simply the way things are, or is it possible my '74 has a different linkage ratio than the earlier Zs this kit was p;ossibly originally designed for?

-MB

[Doehring]

Benn,

look 3 posts upwards to the link to zhome.com. Perhaps the tips there will help you

Rolf

[EricB]

Very interesting ben9090's latest post as I believe I am having similar issues....

So first let me tell you that I did finally get my FPR (It's a Holley brand) from Fedex. Put that on and within a half hour took a reading of my fuel pressure from the electric pump only (yes I removed the mech pump alotgether and blocked it off) - we are looking at 3.5-4psi of fuel.

I started the car with a dash of ether - it still resists to starting on its own on a cold motor. Let it run for a while, shut it off and turn it back on and it will fire up with only the slightest turn of the ign key.

i had my throttle mixture screws turned out to 2 1/4 turn from seated as recommended. My carbs' throttle plates are hooked up via the Cannon linkage levers' outer most hole - this results in a very short pedal travel and yes I did check that I am getting a full range at the carbs (closed to WOT).

Now I had to drive 50miles to get to my fav muffler shop on only the 6-2 open header and I really couldn't believe that a stock I6 could be SO LOOOUDDD... it was getting painful to the (muffled) ears by the 40mile marker.... Amazingly I did not get pulled over... Maybe the "Historical Vehicle" license plates and the hazard flashers had something to do with that...

I HIGHLY recommend Eastside Muffler in Palmdale on Palmdale BLvd to any one in the SoCal area. The prices are fantastic and the workmanship is always spot on. Brothers Joe and Gabriel are the two guys that run the shop. Joe did my work. With that said.

Being at high altitude when I arrived in Palmdale I did not think it wise to spend time adjusting the carbs, but suffice it to say that my idle was around 1800 and no I don't think they are synched at all. What made me curious though is that if I pressed on the accel pedal with anything else but the slightest progression then I would first get a big cough and only then would the revs rise progressively. On the straights in the desert on the way to Angels Crest I tried some WOT in 3rd, 4th and 5th gear and the car dit not seem like it was HUGELY more powerful over my stock '73 flattop SUs... Yes I know I still need to tune the triples but still..... It maybe only felt 20-30% better... does that seem right?

Also in addition to the big cough I just told you about above the car seems to now have a bit of a sticky throttle which it never had before. Around town after having pressed on the gas from a light or so the throttle will want to stay around 2500 to 3000rpm. I'll have to go in, place my foot under the gas pedal and nudge it back up to gt back to 1800rpm idle.... I've lubricated all the throttle linkage joints, off the car the webers open smoothly and close firmly... ideas???

Also at idle with the hood open, if i place my hand under each carb (where the four screws that hold the bottom cover on, or where the velocity stacks meet the carb body) i can feel a slight

perspiration" of gas.... it is moist with gas there as if it was still dripping out of the velocity stacks but only in the slightest amount.... "perspiration" really is the only thing I can liken it too - what do yall think....

oh and yeah with the FPR I am not getting the dribbling I had last week with only the IGN set to Accessory (ie fuel pump on but engine is not running) so that problem's been solved.

I also had the muffle shop weld on an O2 bung so I can take O2 sensor readings now and I am guessing will get full rich right about now in its state of non-tune....

-e

[HS30-H]

Hi Eric,

Glad to hear the car actually runs and you can drive it now.

Forget about that start-up trouble meaning anything - I think you are still a long way off needing to worry about that yet, and it will surely improve when you get in the ball-park with your mixture and synchronisation.

If the full exhaust system is now connected up and finalised you can progress to fine-tuning the settings. First thing to sort out sounds like that linkage problem; I have no idea at all about the Cannon brand except that I presume many others in the USA use them - so it must be possible to get them working OK. What kind of throttle return springs does it have? Surely it does not just rely on the built-in spring of the pedal or the butterfly return springs inside your Webers? That's a no-no.

The better makes of Japanese manifolds I have experience of ( like the HARADA or SANYO versions ) have a fully-adjustable spring setting that allows you to set the amount of power that the return spring exerts on the linkage. In this way it is also possible to change the "feel" of the pedal to softer or harder depending on your preference. Whatever the Cannon has, you will have to make sure that you have enough power in the return spring system to bring the butterflies positively back to the idle setting position. You need to have proper screw-adjuster throttle stops on the end of each throttle shaft ( the Weber bodies have provision for this but I do not know whether you still have them or not ).

I think it best to imagine that the whole of the throttle linkage DOES NOT EXIST for the purposes of setting your idle and the synchronisation of the three carbs. It should be possible for you to get a decent idle around 800 rpm with all three carbs in balance WITHOUT THE LINKAGE CONNECTED. Then you can connect up the linkage with the carbs and sort out your pedal travel and feel ( presuming you will be able to adjust the Cannon linkage ). One thing you MUST remember is to make sure that the "Wide Open Throttle" position is finalised with a stop AT THE PEDAL, and not transmitting torque to the shafts and butterflies past the point where they would naturally stop. This would be a sure-fire way to twist the shafts and make it IMPOSSIBLE to ever set a synchronised idle. There is a throttle-pedal stop on the floor of the car, and it is adjustable. My advice is to make sure and get that setting right before its too late.

Its plain from your latest post that you do not feel that the settings are yet in the ball-park. Without getting the linkages correctly set and the throttle-stops set, you will not get anywhere with this. However, you are saying that you notice an increase in power. If you got a "20% to 30%" increase in power from your relatively stock engine just by bolting on the Webers then I would be VERY surprised. I would have estimated something much LESS than that. You have to be realistic about this.

I don't really know what to think about the "perspiration" that you are experiencing on the underside of the carb bodies. They really ought to be bone dry, and if they are not then I can only imagine an assembly mistake or gasket problem. Is it REALLY gasoline, and not condensation? ( quite often seen as "icing" on carburettors due to the difference in air-density between the inside and outside of the carburettor body ). Sorry - but if it really is gasoline you need to cure the leak. Its not natural to have gas OUTSIDE any part of the carb during running. You said you had eliminated the leaking / flooding since installing the Pressure Regulator - so I am surprised that you have what still seem to be leaks...............

The mixture settings are still way out by the sound of it, and you will not get close to curing that by experimentation until you get nearer to synchronising the throttle-stops and the return spring problem. Once you cure that you can start on the experimentation process to pin down the mixture settings.There's a set procedure to this but you cannot start with it until you get those other things ticked off.

If the car is now driveable, would you consider taking it to a dyno / rolling road tuner that is not too far away? He would probably spend 30 minutes to make the kind of improvement that would take you days to get near...............

Keep at it,

Alan T.

[EricB]

Alan,

Absolutely good points. For the first time in a long time I think I am going to have to swallow my pride and turn it over to the local expert, two towns away because I have never done this before and am definitely fishing around....

To answer your question, yes the Cannon manifold linkage I have was indeed relying on the springs of the webers as well as those of the accel pedal to shut the throttles - there is no external return spring - a situation I could remedy to relatively easily. And yes the Weber throttle stops are still present and being used by the Cannon linkage.

FYI I set the throttles with the car off and some one in the car pressing down on the accel pedal all the way to set WOT. I then checked to make sure that with the given range of motion they did shut completely (apparently not totally completely...)

I say I am going to hand it over to a pro for the following reason. With the idle at 1800 and with the aide of a Unisyn gauge I saw that of course the amount of air drawn in by all three carbs was vastly different. Removing the sparkplugs only confirmed this.

Adjusting the idle mixture screws 1/4 turn at a time inwards from 2 turns 1/14 out from seated did do a bit of an improvement on the AirFuel ratio gauge but did not bring the idle down to less than 1300. It also did very little to change the amount of air drawn in by each carb.

Just to give you an idea of the specs as they stand now before I take it to the local pro.

The front carburetor has spark plugs that look a-ok, the unisyn gauge having but three major gradations drawn on its plastic cylinder shows for the front carburetor something roundabout half of the first gradation.

The middle carburetor has full rich sparkplugs and the unisyn gauge reads the maximum 3+ gradations.

The rear carburetor shows sparkplugs that are about halfway between normal and rich, and has a unisyn reading of roughly 1 1/2 gradations.

Thanks for the help everybody.

Hopefully the weber pro won't mind showing me what he does so I can learn from him...

-e

[HS30-H]

Hi Eric,

Amen to all that. I think it will be money well spent having a pro look at it, and fingers crossed you will be happy with the result.

Its very frustrating sitting here thinking that I might be able to help a little more if only you were more local to me. I've learnt the hard way, and it really pains me to think that I might have been able to point out an obvious point if I could only get my head into your engine bay..........

Once again, good luck and let us know how you get on.

Alan T.

[EricB]

as invariably happens i started over one more time and from scratch, re-read the weber book front cover to back cover, and i made progress. idle is at 1000 and three carbs are more or less drawing in the same amount of air and i was able to lean it out some so it wasn't coming out black and rich out of the tailpipe. phheewwww

i have an appt set for early this week with the local pro so i am curious to see how far or how close I've ended up... thanks again to all.

-e

Vive la France!

[benn9090]

Rolf, thanks for the pointer to the "get rid of the jerk" link on ZHOME.COM. I need to accomplish something similar, although I may do it by cobbling the Weber linkage itslef as opposed to the Datsun linkage itself.

BTW, here is a fantastic website regarding O2 sensors and using them for jetting purposes. www.wps.com/LPG/o2sensor.html

Eric, I'm afraid I have a similar situation - though I ported the head, purchased a 274 cam, and installed the Webers and the N42 echaist manifold (as opposed to my crappy 260 manifold with smog ports), I have what amounts to a 5% power increase over my old DGV setup.

Here's to hoping things improve if I dial things in a bit more precisely ....

-Mark

[halz]

EricB - did you get your webers sorted out by a pro? How's the Z running now? I'm sure we's all like to know...