Just bought a 521

[Stoffregen Motorsports]

21 hours ago, mainer311 said:

It's brand new. It was part of the "K657" kit for Datsun L series, so it came pre-setup with all of the jets that are baselined on here, with the exception of the secondary idle being a 55. If you search on here, the baseline idle jets are 55/50, but it came with 55/55 installed. Besides that one small change, I pulled it apart and verified every jet matched the baseline.

 

After running it for a while, plug #1 was dead white, not the chocolatey-brown that I'd like to see.

 

Timing is set somewhere between 12-15 at idle (750rpm), vac advance removed, and I'm running a late 70's matchbox. I get about 30-35 total advance, but I don't really know what the curve looks like. (And I ALWAYS run 91 or better in it).

Dead white? Just on one cylinder? Hmmmm. You sure it's the same type of plug as the rest? How is your valve lash? .010"/.010" cold is where I set them, unless it's got a big cam, and then sometimes tighter.

 

1 hour ago, d.p said:

Its weird because with my weber it always (and still does) runs rich.  Plugs are usually always black or dark, never the brownish/tan everyone speaks of.  I just live with it at this point as I am too lazy and have no interest in fighting the battles I did with the previous weber.  

 

Interested to see if re-jetting solves your problem.  

Do you ever wring it out? or just cruise? If you're just cruising around without ever getting into full throttle or high RPM's, it wouldn't surprise me to see dark coloration on the plugs.

[d.p]

37 minutes ago, Stoffregen Motorsports said:

Do you ever wring it out? or just cruise? If you're just cruising around without ever getting into full throttle or high RPM's, it wouldn't surprise me to see dark coloration on the plugs.

 

Honestly not really, mostly just cruise around.  Will try to throttle it around when the weather warms up to see if it changes anything.  

[mainer311]

3 hours ago, Stoffregen Motorsports said:

Dead white? Just on one cylinder? Hmmmm. You sure it's the same type of plug as the rest? How is your valve lash? .010"/.010" cold is where I set them, unless it's got a big cam, and then sometimes tighter.

 

BP6ES across the board. All of them are white. I put my colortune on cylinder #1 and it's running whitish blue. It should be blue on the verge of yellow.

 

I lapped the valves, but haven't adjusted lash yet. I can't imagine it's very far off, since it runs like a champ otherwise. Setting the lash is on my radar, I just haven't had a chance yet.

[Stoffregen Motorsports]

The P means projected tip, and while it can help increase the burn rate, it can also lead to detonation. I always run B6ES in any street driven L motors. They allow you to run more timing without the added worry of detonation.

[mainer311]

I've always run the BP's in both my L16 and R16. Running 91, with not a very high compression ratio, and modest timing, I haven't experienced any knock.

 

In other news, my jets are out for delivery. Going to swap in the 60 and see what happens.

[mainer311]

Well, I put the 60 idle jet in, so now I’m running 60/55. I’m 1-1/8 turns out on the idle mixture screw and only 1 turn in on the throttle stop.

I went out for a spin around town with varying levels of tomfoolery, the hesitation is still somewhat present.

 

I’m no spark plug reading expert, but here they are. #1 still looks lean. #2 and #4 seem to match, and #3 is sooty around the threads, but the electrode looks okay. Pics are in order front to back.

 

 

 

 

 

Next step is to check the valve lash, and run a compression test I guess.

Edited March 5, 2020 by mainer311

[d.p]

I don’t know man. I went through the same shit when I switched to a Weber.  Obsessed about the plug color and in the end I just said fuck it and drove the truck.  
 

 

[demo243]

When did you pull the plugs? Ive always read to truly understand  whats going on you need to shut the engine off while running it at the level you want to check... don't quote me on that...  but I feel like that is what I have read...

Or go wideband AFR and know whats going on all the time.

 

OR as D.P. said...just drive it! hahah

 

 

Looking forward to true driving season! Got some good miles in over the weekend in the 620. Hopefully we can get the northeast crew back together this spring!

Edited March 5, 2020 by demo243

[banzai510(hainz)]

whats your gap? I think with a Matchbox one runs about .044  pertronix or points is .032.

 

PS I never gap them and just stick them in.

 

try another distributor(or adjust timming ) if you have a spare if it bothers you that much

[mainer311]

I have a matchbox, so I just use them right out of the box (.043"?)

 

I'm going to check the valves tonight, and pay special attention to #3. If I have a valve that's being held open on #3, that could explain why it's slightly more rich than the others. 

 

I've read that the DGV likes advanced timing at idle. It keeps the rpm's up enough that you can close the primary butterfly so that it doesn't interfere with the idle circuit progression holes. I can retard a few degrees, but the RPM'S will come down. I may give it a shot anyway, and see what happens. 

 

The other thing I thought of is that I removed the vac advance. I may hook that back up and see if it changes any of the carb's characteristics.

Edited March 5, 2020 by mainer311

[Crashtd420]

8 minutes ago, mainer311 said:

I have a matchbox, so I just use them right out of the box (.043"?)

 

 

I think this is wrong....

If you are using bp6es they are .032 out of the box....

Bp6es-11 or b6es-11 are .043....

[DanielC]

You must adjust the valves before setting idle mixture.

 

If you look at a cam timing diagram, you will notice the intake valve closes a long way past bottom dead center, 48 degrees in one diagram I looked at.   This gives you more power when the engine is running at a medium to higher RPM.  At idle, the air is moving much slower, so the piston can actually push the intake charge back into the intake manifold, partially, and remember at idle, there is high vacuum in the intake manifold.

Having valve adjustment off even a little can affect the timing on the intake valve closing, and that can have a big affect on idle air mixture, and filling of the cylinder at idle speeds.

[mainer311]

6 minutes ago, Crashtd420 said:

I think this is wrong....

If you are using bp6es they are .032 out of the box....

Bp6es-11 or b6es-11 are .043....

 

Baulz, you're right. Well, looks like I have a laundry list of things to try tonight.

Edited March 5, 2020 by mainer311

[datzenmike]

White is no good. Check the jet you have isn't part blocked. This will act like a smaller lean jet.

[mainer311]

20 minutes ago, datzenmike said:

White is no good. Check the jet you have isn't part blocked. This will act like a smaller lean jet.

 

I read on a racing website that the center ceramic is NOT a good indicator of mixture (jetting), but rather the ends of the threads should be looked at for jetting clues.

[mainer311]

Well, no good news. I retimed the dizzy from 15 back down to 12, reconnected the vac advance, put a new set of plugs in gapped to .044”, and lashed all the valves cold: 0.010” for intake and 0.012” for exhaust. (They were all pretty tight to begin with.)

 

I then reset the best lean idle, which didn’t require any changes, set 750 rpm and went for a ride. The stumble off idle is worse. It falls on its face and then takes back off again. 
 

I came home and pulled the new plugs. There’s no color on any of them except for #3 which is slightly darker. 1, 2, and 4 are all pretty clean and show little to no color.

 

I put the 65 idle jet in and pulled the 60 out, then called it quits for the night. Tomorrow I’ll reset the idle and go for another spin. It’s possible that the 60 jet I got isn’t quite right. I figure going up 2 sizes will make more of a difference, and let me iterate faster.

[datzenmike]

Was the jet clean or maybe part blocked?

 

Universally a darker porcelain is rich and a lighter is lean. Usually there aren't plug threads showing inside the combustion chamber, or maybe one at the most, because they are sharp edged, get hot and can become a pre ignition source.

 

A correct fuel air will cool the combustion chamber and there is less chance for pinging under load. Lean mixture will do less work and the engine will be sluggish and you will have to press down more on the gas to maintain the same speed as it did when running properly. Lean mixtures tends to backfire out the carburetor more.

 

I can't look back to see what carb you have but try setting the choke on to force a richer condition. If it runs better and stops 'falling on it's face' then it's way too lean.

[mainer311]

It’s a brand new Weber 32/36 DGV-5A. All signs point to it being lean, all the time. I figure, the idle mixture screw only sets the idle mix. Once the primary butterfly is open, even slightly, it starts using the transition circuit, which leads me to believe that a larger idle jet should fix the lean problem.

 

Other forums are saying that throwing bigger idle jets at the problem usually never fixes anything, and that it’s likely the main jet needs to be larger, or there’s a vacuum leak somewhere. I bought one that’s one size bigger in case I wanted to try it.

 

I will say that there is a very loud hiss inside the cabin once the butterfly is cracked open. I’ve never had a Weber, so maybe that’s normal? I’ll use the carb cleaner trick if I have to.

[banzai510(hainz)]

webers are just LOUD.

 

I think I would drive it with more miles on there and see what color the spark plugs turns out in color.

 

what I unsderstand the weber comes with a 140 main jet and that should cover the L16 /18 for sure.  I seen them low as 130main jet back in the day.

the 510Again Bible said

L16 was 130 main

L18  135

L20 140

[Charlie69]

Does your engine idle rough?  If not unlikely you have a vacuum leak.

 

Spray some wd40, brake clean, or carb clean around the base of the carb and other likely vacuum leak areas, if the engine picks up in RPM you have a vacuum leak.

Edited March 6, 2020 by Charlie69
spelling

[mainer311]

That’s the thing, I can get it to idle great. It’s the off idle hesitation that is driving me crazy. If I downshift to take a turn and the rpm’s drop off, when I go to hit the gas again it stumbles for a few seconds and then recovers. 

[Stoffregen Motorsports]

Check the float level.

 

Add fuel (bigger main jet).

 

I would try those two things first.

 

But timing curve and valve lash also are very important.

[DanielC]

I am too lazy to look back in your thread and see what engine you are running, L-16, 18, 20-B, and I also do not know if the Weber carb has a mechanical or vacuum secondary.

A carburetor depends on manifold vacuum, and air flow speed through the venturi to accurately meter the gas into the air at the right fuel to air ratio.

if you suddenly floor the gas pedal at low RPM, with a mechanical secondary carb, especially on a L-16, the manifold vacuum drops almost to zero and the engine simply is not drawing in enough air to get a decent air flow speed through the venturi.   This is overcome by the accelerator pump on the carb.

 

Again, the last thing you do in setting up a carburetor is do a full tune up on the engine.  Is the compression good?  Valves adjusted?  Ignition timing set?  A little more advance can help off idle, and low RPM performance, provided the engine is not too far advanced.  If you hear knock, the ignition timing is too advanced under those conditions.

 

Now, for the carb.  The most important parameter on the carb is the float level.  Too low, or too high float level will affect every every different fuel circuit in the carb.

 

The beauty of a manual transmission is you choose the gear you are in, and you can in anticipation choose a gear you will need coming out of a corner, while you are still deep in the corner, or even before entering the corner.  An automatic transmission can only react to present driving conditions, not anticipate them.

 

With a stock 521/L16/four speed transmission.  The gear ratios are not really that good, there is too large a gap between 2nd and 3rd gear.  With a mechanical secondary carb, you have to learn to ease into the throttle as RPM of the engine increases, and the engine can take the air flow of the carb.

 

 

No fair, I actually started this post before Stoff.

Edited March 6, 2020 by DanielC

[mainer311]

But I’m not flooring it out of the corner. I’m easing into it and it’s stumbling. It actually stumbles less if I just put it to the floor. 
 

It’s a mechanical secondary. Aside from a compression test, absolutely everything on the engine is already setup.

 

As far as float level, the carb is brand new. Aren’t they set from the factory?

[mainer311]

Well, I made a breakthrough. Going up in idle jet sizes was the wrong thing to do. I pulled the 65 out and went back to the stock 55. Stumble is almost completely gone. I’m wondering if downshifting with the throttle closed was causing the very rich condition due to high vacuum, and then when I’d throttle out after taking a turn, it was recovering from being rich. The spark plugs are still light in color. It’s just an L16, so I would think the primary jet is fine, but this Offy manifold may be doing something funny.