Jump to content
rcv

First start today!

Recommended Posts

25 minutes ago, 240260280 said:

Measuring the fuel level in a small jar by pouring in the top is brilliant an is  great for ensuring both fuel levels are exactly the same but this is basically for 0psi fuel pressure.

If you apply 3.5 to 4psi, you will find the valve opens and the fuel level goes up higher.  Measuring on a running car or with a head of fuel does not have this issue.

Ah yeah you're totally right, I was just setting the fuel levels with my funnel while my gas tank was in the shop.  I re-adjusted yesterday during the brief period that my fuel pump actually worked, and and had to make minor adjustments as you'd expect.

 

4 hours ago, 240260280 said:

Column of water or fuel in a vertical hose can do this w/o needing a pump.

Just out of curiosity I calculated how high that vertical hose would be to get to 4psi:

p = ρ g h

Using ρ=750 kg/m3 for the density of gasoline and 4psi = 27579.04N/m2 for our pressure we get a column height of ~3.75m = 12.3'. That's a lot of hose!

Share this post


Link to post
Share on other sites

As always, I've got some good news and some bad news.  The good news is that I installed a new K&N fuel pump, and the process couldn't have gone better. The float syncs are now showing near perfect fuel levels in the bowls, with the bonus feature of being able to tune the levels without Hoover's ladder.

The bad news is that something is still very off with the mixture.  Using the standard 2 1/2 turns down on the mixture knobs the car will barely start, runs very rough, and pours enough dark smoke out of the tailpipe that people on their afternoon strolls cross to the other side of the street. Good thing they're already wearing masks.  

As I turn the mixture knobs leaner and leaner, the car runs better and better.  I bought myself a Gunson Colortune, and verified that even with the mixture knobs cranked all the way up I'm still running rich (see video below). I made sure that the chokes are pushed all the way up, so I don't think that's the problem.  I suppose the next thing to check is that the needles are seated properly in the carb piston, or possibly the needles are just totally wrong themselves.  Anyone have any other debugging advice I could try?  Is it possible that my timing has something to do with this?  I'm pretty sure I'm somewhere between 15-20deg advanced, but this is honestly my first experience with a timing gun so it's possible I'm screwing that up. I tried shifting the timing around a 5deg each way and didn't see an appreciable change in the spark color.

EDIT: I just had another thought.  I have no idea what the story is with the coil on this car, but it looks like it's the factory original one. Is it possible that my mixture isn't actually rich, but I'm just not fully combusting because of a weak spark from an aging coil?

 

 

Edited by rcv

Share this post


Link to post
Share on other sites
56 minutes ago, heyitsrama said:

You say the float level is spot on, what are they set to?

My set point is 23mm down from the roof of the lid, which comes out to 14mm up from the base of my Float Syncs. I'm actually maybe 1mm off from that, but if anything I'm a little low so I can't imagine that's my problem.

 

IMG_2734.jpg

Edited by rcv

Share this post


Link to post
Share on other sites

Ok, so I replaced my OEM ignition coil / ballast resistor today with a Pertronix Flamethrower coil and new resistor.  The car seems to run a bit stronger, but the mixture is still way too rich.  My colortune is showing bright orange even with the mixture screws all the way in.  Backing them off at all just causes the motor to bog down and run like junk. 

I also tried re-seating the needles according to the Z-Therapy DVD instructions, but that made no difference.  I'm not really sure where to go from here.

Edited by rcv

Share this post


Link to post
Share on other sites

The needles looked ok to me when I pulled them out today. No pitting or scratches as far as I could tell. I didn’t see any markings on them to indicate what kind of needles they were though. It was getting dark though, so I could check again in the morning. Should they be marked on the shoulder?

Share this post


Link to post
Share on other sites

I believe SM's are the standard needle. I don't know if they are all stamped. If the float level is right and holding then needles would be my first suspect

  • Thanks 1

Share this post


Link to post
Share on other sites

The factory standard needles are N-27, but a lot of people install SM's instead. That decision works out well for some people and some others report running rich.

The number is either stamped or inked onto the hilt and is only able to be seen with the needle removed from the suction piston. However, if they are inked (and not stamped), the ink printing is pretty fragile and is often destroyed with handling or chemicals. In other words... It would not be unusual for you to pull the needles and find only remnants of the number stamp and not be able to tell what they are from the ink printed mark.

It's easy to make the carbs run lean, but it's usually a little more difficult to make them run rich*. To run rich, it takes deformation of a needle or a nozzle, or the installation of incompatible parts.

Did you ever get in touch with Paltech and ask what needles he used?

 

* Assuming, of course that the float levels are OK and the nozzles are not sticking down with the choke.

Edited by Captain Obvious
  • Like 2

Share this post


Link to post
Share on other sites

I’m going to text him tomorrow and see if he’ll get back to me. I actually have the stock needles from my original carbs now that I think about it. I’ll try swapping them in tomorrow while I’m waiting for Jeff to get back to me. 

  • Like 1

Share this post


Link to post
Share on other sites

Swapping in a pair of known stock needles would be a good test, and something relatively easy to try.

I know you said you are already positive that your float levels are on target and your chokes are not sticking down at all. And with those two things not causing a problem, I'm having a hard time coming up with a scenario that would result in running rich without some sort of damage to a nozzle or a needle or a wrong part installed.

Like I said, lean is easy. Rich is more difficult assuming you have already ruled out the easy ways to run rich (float levels and sticky chokes).

  • Like 1

Share this post


Link to post
Share on other sites

What is the history of the nozzles?

And who did the alignment of the nozzles after the rebuild process? Is that something you did, or did they come to you already aligned?

Share this post


Link to post
Share on other sites

I got the carbs and intake manifolds from Paltech and just bolted them on as-is.  I really have no idea what their history is, as I just bought the full set from him rather than having him restore my originals. I’m assuming he aligned the nozzles. The pistons drop freely with a nice solid clunk at the bottom when I pull the oil damper out, so I’m assuming the alignment can’t be terrible right?

I’m going to swap those needles in an hour or two and I’ll post an update. 

Share this post


Link to post
Share on other sites

Like the Captain said it could be the nozzles too. If you have a couple of good matched sets, you might want to swap out both

  • Like 1

Share this post


Link to post
Share on other sites

As well as identifying what needles are in there, it may be a good idea to see if the nozzles are stock 100s. I see that Ztherapy sells different diameter nozzles. I know little about the different nozzles available or how to identify them, but if the PO installed larger nozzles it would run pig rich.

  • Like 2

Share this post


Link to post
Share on other sites

I just tried pulling the needles out of my old SUs, but both needles were stuck hard in the cylinders. I ended up just dropping the old cylinder + needle combo into rebuilt carbs on the car and ... drumroll ... it runs much better!  The car won't start anymore with the mixture screws all the way in, but runs great around 2 turns down with a nice blue-ish spark from my colortune. I'm very pleased.  I'd like to get a new set of needles if possible - does anyone know a good source these days? It looks like MSA is out of stock on their N-27s. 

 

By the way, here's what the needles I pulled out look like - the pitting is worse that I had thought, and I'm guessing that was effectively "thinning" the needle causing the rich condition:

 

Share this post


Link to post
Share on other sites

Well I may have celebrated a little prematurely. I had only color tuned the rear carb before my last post. I just went out and tried tuning the front one and it’s still rich, even with the mixture cranked all the way in. 

Share this post


Link to post
Share on other sites

1 hour ago, 240260280 said:

Beware! Some 240z repair kits with gaskets and needles sold for early 240z are too rich.  The needles may be made for later 240z with flat tops or even another SU application such as the roadster. Both @Captain Obvious and I had these. The rest of the kit was ok.

Was that the "black dragon" kit I remember reading a bunch of crap about?

Share this post


Link to post
Share on other sites
4 minutes ago, rcv said:

Just the pistons. I want super rigorous about testing their drop rates like the ZTherapy dvd recommends, but they seemed roughly ok. 

 Are the drop rates still ok with unmatched pistons and tops?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.