Just bought a 521

[datzenmike]

 

If not it will only let rad water out. Leave rad cap on tight while you loosen the rad drain plug and collect in a container. If the contents of the coolant recovery container are sucked back into the rad, you have the right rad cap. This is where the plastic recovery containers are better for seeing what's inside and if they need topping up. 

[mainer311]

I hear you, I was just tired of seeing a cheap plastic milk jug under the hood.

[mainer311]

It hit 40 here today, so naturally the race car came out.

 

[mainer311]

So, the truck had an interesting maiden voyage today. I let it warm up for a long time in the driveway to do a final tune on the Weber, and got it running pretty mint. I pulled out onto the main road and eased into it to see how the Weber reacts to tip-in, cruised for a minute or two, and then hammered on it. There was an immediate bang and then an awful racket under the hood. I immediate killed it and coasted to the side of the road.

 

I popped the hood to find that my fan blade caught the bottom of my plastic radiator shroud and split it into two pieces. The fan blades melted on the tips and shredded the shroud pretty good. Luckily I had a brand new Benchmade knife on me and was able to cut the bottom of the shroud off. I fired it back up and went home to wash my bloody hands off, then went to go do my errands.

 

The Weber is nice. Great throttle response on the low end, and when the secondary opens, there’s a nice low growl from the exhaust.

 

That knife saved my ass already.

Edited February 23, 2020 by mainer311

[DanielC]

How are your motor mounts?  Did the engine move?  Was the fan shroud loose?  Why did the fan contact the shroud?  There is normally plenty of clearance.

[mainer311]

It must have been how I reinstalled it. I had the radiator and shroud off when I rebuilt the head, and the first thing I noticed when I popped the hood was that the bottom of the shroud was bowed out towards the crank pulley.

[mainer311]

 

 

Much better. Just fits under the hood. Got lucky.

Edited February 27, 2020 by mainer311

[wayno]

I had to go back 9 pages to find a photo/photos of this truck, good looking truck.

[banzai510(hainz)]

there is a 1.75 inch tall one for the taller L20 motors with carb adapter incase they hit the hood with the standard sized one. Of coarse its more restrictive.

 

be honest I wish Weber or somebody mad e a throw away filter for those Weber carbs.   I hate oiling them up and they do wear out. 

Edited February 27, 2020 by banzai510(hainz)

[mainer311]

Yeah, I'm not really a huge fan of oiled filters either, but I like the general appearance of the K&N with acorn nuts and not those stupid metal clips. I'm running that inlet radius piece on top, so I need the taller filter to clear it. I was pretty bummed to find that the smaller K&N kit doesn't have any room for an elbow fitting to hook the valve cover breather up. I'll likely just run a piece of tubing down the side to the bottom of the truck. 

[datzenmike]

Be sure to put one of those cute little blue filters on the end. In normal operation filtered air enters the engine from that hose, drawn in by the PCV valve. It can reverse but mostly in.

[mainer311]

Hmm, okay. If it's mostly in, maybe I'll keep it in the engine bay a little bit further.

[banzai510(hainz)]

is there room to drill out the bottom plate to put the Elbow for the breather?

 

I also run a tube down on my 510   witrh sidedrafts

 

 

be amazed how much air those flow back and forth

Edited February 27, 2020 by banzai510(hainz)

[mainer311]

53 minutes ago, banzai510(hainz) said:

is there room to drill out the bottom plate to put the Elbow for the breather?

There’s no room 😞

[mainer311]

I need a Weber DGV guru. I took my truck for a longer drive today and noticed that there’s a pretty good flat spot just beyond idle. If I’m cruising along at a steady speed, and then slightly press the gas, there’s a noticeable hesitation/stumble before anything happens. It’s the most noticeable if I’m maintaining speed and then slightly press the gas. If I’m maintaining speed and then punch it so that the secondary opens, there’s no hesitation.

 

I did a little bit of reading, and it said two things: that my idle jets may be a little small, or my best lean idle adjustment is actually a little bit too lean. I currently have a 55/50 on the idle jets, and my best lean idle is 1-1/3 turns out.

 

The stock idle jets were 55/55, so I removed the 50 on the secondary and put the 55 back in, and opened the idle adjustment up to 1-1/2 turns out. I haven’t tested it yet.
 

Does anyone else have any input?

Edited March 1, 2020 by mainer311

[banzai510(hainz)]

I’m not a true expert per say.

I got a 60 for my idle.

have you tried adv the timing? Distributor new or worn?

maybe it has more to do with accel pump volume as you hit the gas.

be honest I always have to readjust my carb in winter with the lights on then again later when the weather warms up

 

stock carbs when they work and are new are very SMOOTH !

[mainer311]

Yeah, my Hitachi was pretty smooth. Timing is somewhere between 12-15, and I’m not running vac advance. The dizzy is a matchbox, and used. I never had any issues with it before.

[mainer311]

Well, I did some testing today, and no change. I pulled one of the plugs and it’s running way lean, no matter what I do with the idle mixture screw. I even used my Gunson Colortune and verified it’s lean. I might try a 60/55 on the idle jets and see what happens.

[banzai510(hainz)]

If you have a manual choke try pulling the choke slightly to riches up the circuit and see if it still does it.

i forgot why I went to a 60 on the idle but think it was the mixture was right off the bottom on the screw . swap another distributor  if you have one.sometimes it makes a difference.

 

Edited March 1, 2020 by banzai510(hainz)

[mainer311]

My idle mixture is currently set to 1.5 turns out for best lean idle, which by the Weber instructions, is perfect. They say the idle circuit comes into play for a majority of the carb’s working range, yet my carb seems to be staying lean. 
 

I’m going to order a few jets from Pegasus. Kinda fun to experiment, if nothing else.

 

I snagged a pic of it while waiting for it to come up to operating temp this morning.

 

Edited March 1, 2020 by mainer311

[mainer311]

After some searching, it seems like the "Weber stumble" is something that a lot of people experience. I stumbled upon this article from an MGB guy, which is interesting. He modifies the idle/transition circuit by drilling a 3rd hole in the casting to "lengthen" the duration of the transition to allow the primary jetting a chance to kick in before the engine sees a fuel shortage as the butterfly opens.

 

http://bradleyrestoration.com/technical_resources/weber_dgv_carbs_on_mgbs/

 

I'm not sure I'll go that route yet. I ordered 60 and 65 main "idle" jets from Pegasus to see if that makes a difference. After looking at this schematic, the main idle jet not only controls the quantity of fuel at idle, but also through the entire transition period. Since the butterfly covers the transition holes at idle, the bottom screw can still be used to fine tune the best lean idle adjustment, even with a bigger idle jet (within reason). The secondary idle jet is of much less importance since it only comes into play when the secondary opens. I didn't realize this when I first started messing with it. No wonder the change back to a 55 from a 50 made no apparent difference.

 

[banzai510(hainz)]

I tried that experiment while driving steady and hit the gas and I couldnt duplicate the proplem  I believe I have a 60 idle in there.

 

maybe it more pronounced on a hill with a load

[Stoffregen Motorsports]

Maybe I missed it, but is the Weber new? Or is it old? If it is stamped with "5A" it is newer. Maybe you can get a pic of the stamping for us. The reason I ask is because Weber went through a design change about 20 years ago. Anything "5A" or newer has the modified fuel circuits and should not have the stumble you described. If it is a newer carb and has the stumble, it's jetting or timing curve related. If it's an older carb, scrap it and get a newer one.

[mainer311]

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).

[d.p]

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.