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NewTechnicIan Fri May 20, 2016 5:37 am

Howdy all,
I just got my 1679 build started and run in a week or so ago, but haven't gotten it to idle yet.
My specs:
:arrow: 1679 pistons
:arrow: ACN L3 Heads
:arrow: Eagle Mileage Cam
:arrow: German Solex 34-pict 3 carb, rebuilt and jetted at 55 idle and 125 main (recommended by John at Aircooled)
:arrow: rebuilt DVDA distributor, all vacuum hoses hooked up to the carb, timing DEAD ON at 5 ATDC (checked with timing light and made sure #1 TDC was where we thought it was)
:arrow: Sidewinder header and hideaway exhaust
:arrow: Stock crank and conrods


more info on the cam:


Anyway, the run in was at 2000 RPM but in order for it to get there, I had the choke closed and the throttle up on the last notch on the choke cam. I let it go for the time being during that run-in because I wanted to get it run in nicely and Then I could make it run well.

After buggering around with it all last night, we came to some conclusions:
:arrow: We could only get the car started with the choke on and the throttle up
:arrow: If we took the choke off and tried to start it, it would spew fuel out the top of the carb after trying to start, which I see from some research is a sure sign of it being lean
:arrow: We got the thing running with the choke on and slowly turned the screws 1/2 turn each at a time until they were both bottomed out and heard no difference in the way the thing was running

Okay, all that to explain my situation. Now, we're down to 2 possibilities:
:arrow: Vacuum leak - the thing needs the choke on to limit the air coming into the system because it's got a ton coming in from somewhere.
:arrow: I don't think it's this because all my vacuum ports are plugged into the distributor and my vacuum port in the manifold is plugged until my air cleaner gets installed. I also have my carb torqued down nicely with a new gasket, new boots on the Dual port fittings and new gaskets torqued correctly at the heads.
:arrow: I have not tried the method of spraying starter fluid around the various joints or even looking for a cracked manifold, so I could do that.

Other possibility:
:arrow: Jets too small - the mixture is so lean that it needs the choke on to richen it up. Even with the screws turned all the way in, we heard no difference in the way the engine ran or improvement in the idling situation. This is what I'm guessing is the case but I'd love all y'all's input on that.

Remember, the thing will run but I just can't let the choke off more than a tooth on the choke cam without losing it. I feel like that would have to be a heck of a vacuum leak, like I'd hear or see it for it to be that.

Anyway, Thanks everyone!

67rustavenger Fri May 20, 2016 6:53 am

Get your timing correct before proceeding. It should be 7.5* BTDC not 5* ATDC when using an SDVA dist. Use a strobe type timing light to verify your settings.
John @Aircooled is a very knowledgeable guy. He helped me with timing problem when I thought
that I had a crab issue.
Good Luck.
EDIT
Never mind. I misread your dist type. You have DVDA. Sorry

NewTechnicIan Fri May 20, 2016 7:19 am

Haha all good man. Yeah I'm realizing that SVDA is way more common than DVDA. Is there a reason why on that? And would I need a new distributor or just a new vacuum can to convert the thing to SVDA if I wanted to?

More importantly, Any idea on the question at hand then? vacuum leak or jets?
Thanks!

67rustavenger Fri May 20, 2016 7:28 am

Did you check that the retard side of the vac can is functioning? I have heard that they are the first thing to go on those dist.
I have no idea why the SDVA is so popular. There just seems to be an abundance of them out there. And they all seem to have problems, including mine ATM.
Pull the dist cap and check the function of the retard circuit.
I'm no dist expert so I can't advise you to far down the road. Tsab or Glenn will more than likely have an answer that can help ya.
Good Luck.

74 Thing Fri May 20, 2016 8:27 am

I say vacuum leak at the head/manifold connection or a plugged idle jet or something set wrong in the carb. I would pull it off and clean it out. Did you check your fuel pressure-I assume not since you are having trouble getting it to idle.

[email protected] Fri May 20, 2016 8:40 am

you need to get a vacuum gauge on the intake and see what it's pulling. Also, a lot of guys don't know that SVDA and DVDAs time the SAME if you disconnect the retard hose from the DVDA.

DVDA: 5ATDC = 7.5 BTDC Retard Hose Disconnected.

Knowing this you can see if the retard diaphragm is operational or not. A lot of guys have the retard diaphragm go bad, they just put a SVDA pot on and time to SVDA specs and keep driving.

Also do a compression test and see if you have a tight or leaky valve.

NewTechnicIan Fri May 20, 2016 9:00 am

Taken before the Run-in:

Compression:
#1 - 115 psi
#2 - 120 psi
#3 - 125 psi
#4 - 120 psi
Looked great to me when I checked it.

John, so to test the vac retard I just get the thing running and then disconnect the vac retard and see if that changed the timing? if the vac retard is dead, I just buy a SVDA can then?

How do I test/what am I testing for with a vacuum gauge? Plug into a vacuum port on the carb or the manifold or both?

74 thing, I haven't checked fuel pressure. Does the problem indicate that it might be too high? I didn't add any additional paper shims under the stock mechanical pump, but I did add the stock paper gaskets below the plastic stand and between the stand and pump.

[email protected] Fri May 20, 2016 12:55 pm

Those compression #s are decent (if still valid). You are chasing a problem, I'd re-check them to see if the engine is still mechanically tight.

If the timing changes at idle with the retard hose on/off I'd consider it working. It SHOULD retard 12 degrees. (7.5BTDC to 5ATDC).

It's important to note that you could have difficulty if you are trying to use a SVDA carb with a DVDA distributor.

Vacuum; you want something in the 15-18" range, with no flutter. If it's fluttering or lower than that, you have a problem. I check for a vac leak with starter fluid, takes 30 seconds. You'll hear an RPM change if you find the leak.

NewTechnicIan wrote: Taken before the Run-in:

Compression:
#1 - 115 psi
#2 - 120 psi
#3 - 125 psi
#4 - 120 psi
Looked great to me when I checked it.

John, so to test the vac retard I just get the thing running and then disconnect the vac retard and see if that changed the timing? if the vac retard is dead, I just buy a SVDA can then?

How do I test/what am I testing for with a vacuum gauge? Plug into a vacuum port on the carb or the manifold or both?

74 thing, I haven't checked fuel pressure. Does the problem indicate that it might be too high? I didn't add any additional paper shims under the stock mechanical pump, but I did add the stock paper gaskets below the plastic stand and between the stand and pump.

Frank Bassman Fri May 20, 2016 3:23 pm

I think you're probably lean. I mean I'm at sea level so I do have to run my car richer but regardless it doesn't make much sense to me why your larger than stock motor is running smaller jetting than a stock motor would, AND while running a freer flowing muffler.

I could be missing something.

Time it right, see if it will run good. If not, I suggest a 57.5 or 60 idle with a 130 or 127 main jet. Even 130 may be marginal.

I too use a DVDA on my 1699 type 1 motor and love it.

Also... Make sure your points gap is good.

Good luck.

-Frank

NewTechnicIan Sat May 21, 2016 12:20 pm

OK a few things:

:arrow: I got a vacuum gauge, plugged it into the port in the intake manifold for the air cleaner pre-heat. It read a steady 20" as the engine was running. Now, what's interesting about that is that I still don't really have it "idling" and the vacuum obviously goes up and down with throttle.
:arrow: I was still nervous about a potential vacuum leak, as stated above it was a quick test to spray starter fluid everywhere from the carb to the intakes on the heads and I really didn't hear a noticeable difference in engine revving. So I don't think it's a vacuum leak. I tightened things up a bit anyway and it still didn't sound like it improved anything.
:arrow: my vac retard might be broken because it doesn't change the timing when I unplug it. I double checked that static timing is 5ATDC and it looks really close to 7.5BTDC when it's running, obviously advancing more than that with throttle. Is this correct except for the vac. retard? Where should I be when I pull the cap off at #1 TDC and where should I be when I'm idling?

[email protected] Sat May 21, 2016 12:52 pm

have you backed out the idle mixture screw yet? Start "too rich", and lean out as you adjust. Go out 5-6 turns as a start.

Which 34-3 do you have? Does the throttle plate have the hole in it?

NewTechnicIan Sat May 21, 2016 1:51 pm

Yeah I've been up at 7 turns out on the idle screw haha. Where should the volume control screw be when I'm that far out on the idle screw? And it's "too rich" when the idle screw is all the way in, correct?

Edit - wait what do you mean by idle mixture screw? You're talking about the big screw right? The bypass screw? Or are you talking about the screw on the throttle lever?

NewTechnicIan Sat May 21, 2016 1:53 pm

Oh, and my 34-3 does have the hole in the throttle plate

63single Sat May 21, 2016 2:35 pm

Just to make sure:

Is the idle cut off valve powered and working? you will never get it to idle with out it working or bypassed.

NewTechnicIan Sat May 21, 2016 2:51 pm

Heh, uhh, not sure? :oops:
This is my first rebuild. Just to be clear here, if the cutoff valve doesn't get power while the engine is running, that will prevent it from idling? Because I haven't been powering it...

63single Sat May 21, 2016 3:02 pm

Yup..you have to power it to pull the plunger back to allow air flow. Take the power from the coil same as you did for the choke.


[email protected] Sat May 21, 2016 3:22 pm

there you go!

You need 12V to the choke and the idle shut off valve when the key is on. Take it from Coil 15.

NewTechnicIan Sat May 21, 2016 3:31 pm

Ahyup! That worked wonders! I got it down to the last notch on the cam but it died as I put it down to the final running position. I'll tune it tomorrow but I think that was the key! Thanks a million all! I'll have to spread the word on that

Lingwendil Sat May 21, 2016 3:32 pm

NewTechnicIan wrote: Heh, uhh, not sure? :oops:
This is my first rebuild. Just to be clear here, if the cutoff valve doesn't get power while the engine is running, that will prevent it from idling? Because I haven't been powering it...

#-o

Hook up the solenoid ya big goof!

:D

NewTechnicIan Sun May 22, 2016 2:22 pm

OK that definitely got us closer, but unfortunately no cigar quite yet. I'm on the last notch on the choke cam before I'm bottomed out at idle, but I just cannot seem to get it closer than that. :cry:

I can definitely hear the thing throttle down as it steps down the steps on the cam but it just can't keep itself running when it hits that last step.

Just to make sure, the richest mixture possible is with BOTH screws turned IN, correct? Or is there a "stubborn motor" starting point on this carb that will get it idling, but just not well? Like if what I'm scared of is correct and my jets are too small, what can I do to compensate for that?

Most places say to start 2 1/2 turns out on the small volume control screw and 4ish turns out on the big bypass screw, but that doesn't seem to be this motor's happy place right now.

Thanks for the help all!



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