New Truck - '71 521

[andyZ00m]

28 minutes ago, datzenmike said:

Preferably use the Hitachi.

im assuming I use the same hardware from the Weber but use the hitachi plate? 

[andyZ00m]

Got the carb in. She runs great! Got idle and speed set and timing is at 8 TDC with the idle/speed I like and this new carb. I think Mike said the L16 are meant to be at 12TDC. Will adjust timing once I get the carb dialed.

 

What are the rest of these pieces? Where do I mount throttle return spring on these thingys.

 

 

 

Also, I had to run a curly fuel line as the hard line is just so that the hose is likely kinking. I can probably bend it a little...  Need to figure out a better situation for this.

 

[datzenmike]

 

Cable mount, cable, the mount on the throttle arm and the return spring should be in a straight line. Return spring anchor should be over towards the valve cover at about horizontal. Make a bracket and bolt it to that intake manifold bolt.

 

Should have used the Hitachi crank. The stock cable would have fit right on. Cut cable clamped between two washers will fray from all the flexing. 

[thisismatt]

The plate w/gasket is an EGR block-off plate you shouldn't need

[andyZ00m]

55 minutes ago, datzenmike said:

 

Cable mount, cable, the mount on the throttle arm and the return spring should be in a straight line. Return spring anchor should be over towards the valve cover at about horizontal. Make a bracket and bolt it to that intake manifold bolt.

 

Should have used the Hitachi crank. The stock cable would have fit right on. Cut cable clamped between two washers will fray from all the flexing. 

 

Putting the hitachi on there would have been better for sure. This angle is less than ideal. I honestly was having trouble figuring out which parts to use for it. First time doing this.

 

I mounted the spring to the little bracket on the valve cover bolt. Works great.

 

 

 

 

[andyZ00m]

So I got timing and idle/speed set back up and the idle return spring is working pretty well. 
 

Did a test drive and once past idle it has a ton of power and feels great. Sounds like it’s sucking a lot of air!! Haha. 
 

Accelerating out of idle has a bit of lag. There is hesitation from initial throttle. Any ideas? I checked all the stuff in the troubleshooting guide from pierce. 

 

Video link to acceleration issue: https://i.imgur.com/NQkYSPV.mp4

Edited December 18, 2023 by andyZ00m

[datzenmike]

3 hours ago, datzenmike said:

 

 

Cable mount, cable, the mount on the throttle arm and the return spring should be in a straight line. Return spring anchor should be over towards the valve cover at about horizontal. Make a bracket and bolt it to that intake manifold bolt.

 

Of course this will... work, but not optimal. It's pulling sideways on the throttle plate and butterflies adding wear to them. 

 

 

 

[andyZ00m]

23 minutes ago, datzenmike said:

 

Of course this will... work, but not optimal. It's pulling sideways on the throttle plate and butterflies adding wear to them. 

 

 

 

 

Yeah its not ideal. Gunna try and find a better solution tomorrow.

 

A buddy suggested the throttle issue might be a jet issue. But this kit is supposed to have the right jets for this engine/truck, but could be that.

 

Gunna mess more with idle/mix tomorrow and see if I can dial it in.

 

[datzenmike]

 When driving hesitation when stepping on the gas from low speed or idle is because the air in the primary obviously isn;t moving fast enough to produce a vacuum signal at the venturi. No or low vacuum means gas cannot be sucked in and too much air and not enough gas means a lean condition and no power. You could just step very slowly on the pedal and this would allow time for the air to speed up matched to the engine's needs. But that's no fun. To remove this lean condition a mechanical pump called the accelerator pump squirts raw gas into the primary.

 

Take the air filter off and look down the carburetor with the engine off. Have someone step on the gas. You should see a strong stream of fuel into the primary.   

[banzai510(hainz)]

I would have used the Hitachi linkage on the carb and use the stock cable end on there!!!!!!!!!!!!!!why ruin a good cable.

 

or buy this park for the weber

[andyZ00m]

1 hour ago, banzai510(hainz) said:

I would have used the Hitachi linkage on the carb and use the stock cable end on there!!!!!!!!!!!!!!why ruin a good cable.

 

or buy this park for the weber

Im a newb and I went with the “easy” thing. Even though now I’m realizing it was probably easier to use the hitachi.. 

 

I still have the little cylinder for the end of the cable. Could solder it back on there and use the hitachi still. I think the way the return spring is set up would be much better too. 

[datzenmike]

Solder will never work. It's for making electrical connection not mechanical ones. Just replace it and be done with it.

[banzai510(hainz)]

24 minutes ago, andyZ00m said:

Could solder it back on there and use the hitachi still.

Nope its DONE Broke!!!!!!!!!

[Stoffregen Motorsports]

The return spring would mount to the bottom of the cam type linkage piece, pulling it towards the cable bracket. It's not too late to get one of those piece, or to make a piece that hangs off the bottom of the bracket you have. Got a welder?

[andyZ00m]

9 minutes ago, Stoffregen Motorsports said:

The return spring would mount to the bottom of the cam type linkage piece, pulling it towards the cable bracket. It's not too late to get one of those piece, or to make a piece that hangs off the bottom of the bracket you have. Got a welder?

That’s a good idea. I think this would work. I was looking at some other types of cable attachments for the Swiss cheese thing. There are a ton of options. The washer sandwich is kinda wobly. 
 

Once I get the return spring dialed and the idle acceleration issue figured out then I’ll get the linkage attachment cleaned up. 
 

Regarding the accelerator pump, it’s def dumping gas in there on first acceleration. Pump is working. 

[andyZ00m]

Spoke to Pierce and they gave me some good advice. Got it pretty close and the idle acceleration is pretty good, not perfect. 
 

Dave at Pierce said that if I can’t dial it with the mix/idle then it’s likely I need to go up in idle jet. 
 

Thanks Stoff for the idea on the return spring. Made a little bracket thingy. 
 

 

[mainer311]

A lean spot at throttle tip-in is VERY common on Weber carbs and it has to do with the way the progression holes are drilled on the idle circuit. As the butterfly is cracked, there is moment in time where air rushes in prior to the accelerator pump squirting any fuel. If the next progression hole is not uncovered in time, then the air rushing in creates a lean condition. It only takes a fraction of a second. You won't ever be able to "tune it out" unless modifications are done to the carb. The idle circuit on these accounts for 80% of the driving you'll do. It covers both idle, and the entire transition to the main venturi below a certain RPM. 

 

 

[banzai510(hainz)]

see if changing the timing will make it better.

when it comes for smoothness the stock carb is always better. But once they wear outI go with the weberDGV for simplicity

 

I have messed with changing the idle jets but really the ones with the carb are about fine. (50 I think they are)

[andyZ00m]

1 hour ago, mainer311 said:

A lean spot at throttle tip-in is VERY common on Weber carbs and it has to do with the way the progression holes are drilled on the idle circuit. As the butterfly is cracked, there is moment in time where air rushes in prior to the accelerator pump squirting any fuel. If the next progression hole is not uncovered in time, then the air rushing in creates a lean condition. It only takes a fraction of a second. You won't ever be able to "tune it out" unless modifications are done to the carb. The idle circuit on these accounts for 80% of the driving you'll do. It covers both idle, and the entire transition to the main venturi below a certain RPM. 

 

 

 

So what can be done to improve this? Are you saying thats just how these carbs are?

 

48 minutes ago, banzai510(hainz) said:

see if changing the timing will make it better.

when it comes for smoothness the stock carb is always better. But once they wear outI go with the weberDGV for simplicity

 

I have messed with changing the idle jets but really the ones with the carb are about fine. (50 I think they are)

 

Regarding timing, I have it set to 12TDC at idle while warm. Should I go up or down?

Edited December 18, 2023 by andyZ00m

[andyZ00m]

Alright, I played around with timing up and down and idle/mix. Got a good higher idle which is fine as I still have the 35A alternator in there. Ended up with timing around 13 over TDC and got the mix set so its really responsive and there is a VERY slight hesitation off idle.

 

Feeling pretty good about where its at.

 

Thanks for all the help!

 

[mainer311]

1 hour ago, andyZ00m said:

 

So what can be done to improve this? Are you saying thats just how these carbs are?

 

Yes and no. Ideally, the butterfly position at idle should be set to cover the first hole, not close in front of it. By doing this, the moment the butterfly is cracked open, it uncovers the first hole, and you immediately get fuel along with the air. The issue is that, to do this, you have to crack the butterfly open at idle, and then your idle speed is much too fast. You can partially remedy this by retarding the idle timing, but then it runs like crap. 

 

The other option is to drill an extra progression hole such that it coincides with the edge of the butterfly when the butterfly is completely closed. This solves both problems, but can be easy to screw up if the hole is not located properly. This is actually how I fixed my DCOE's.

 

See here: 

 

Essentially, what you have currently is "B." But you need to get to "A," while still having a decent idle RPM.

Edited December 18, 2023 by mainer311

[Stoffregen Motorsports]

I suppose you could radius or chamfer the hole so the opening is closer to the butterfly.

[mainer311]

Here’s my DCOE. The top-most hole is a 0.050” hole that I drilled, which is covered by the edge of the butterfly when closed. It comes into play ever so slightly sooner than the hole next to it.

 

[andyZ00m]

35 minutes ago, mainer311 said:

Here’s my DCOE. The top-most hole is a 0.050” hole that I drilled, which is covered by the edge of the butterfly when closed. It comes into play ever so slightly sooner than the hole next to it.

 

Dang!! SO is this an inherent design flaw in the Weber?

[Crashtd420]

1 hour ago, andyZ00m said:

Dang!! SO is this an inherent design flaw in the Weber?

I think yes and no..... 

It can be tuned around, mainer was successful drilling....

I run a single side draft and I was able to change emulsion tunes .... 

 

For the most part people say you just have to drive the truck like the weber likes because the tune is close enough..

 

So you can either start down the rabbit hole or just don't stomp the floor with the throttle peddle like your trying to drag race just ease into it then floor it once past the progressive holes....