Weber k662 vs k646

[toshts]

Looking at treating the 81 720 to a little late Christmas gift. Searching Pierce Manifolds for a DGEV 32/36 they have the k662 redline kit for the z20 and z22 and the k646 for the z24. Considering I have the z22 the k662 seems like the obvious choice but I guess I'm wondering if there's any difference in jetting or anything besides the mounting plates? And if there is a difference if there would be any benefit or situation it would be better to run the k646?

[Thomas Perkins]

The K662 is showing to be used with the 80-82 Z-20 and Z-22.I have a 85 4x4 with the 2.4.I use the K646.Mine uses a different linkage than the K662.What is on mine?Redline Weber for some unknown reason does not sell it separate.You can look at both and see this.I believe the K662 linkage rotates the opposite than the K646.It is on the opposite side.

[Thomas Perkins]

Here is the K662

[toshts]

Thanks for the info, that's interesting, does that mean the z22 and the z24 have different throttle setups factory? My throttle cable loops around and attaches/pulls from the passenger side of the vehicle  

[Thomas Perkins]

Here is my 85 2.4

[Thomas Perkins]

[Thomas Perkins]

Here is the linkage that only comes with the K-646 83-85 and Redline Weber does not sell it.You can but the spring to it,I have a bunch.

Edited December 29, 2024 by Thomas Perkins

[toshts]

Looks just like where my throttle comes in on the z22 as well, if the 662 doesn't come with the linkages and is on the opposite side should I go with the 646 then? The 646 kit on Pierce looks like it includes the bottom two linkages but not the top, is there a way to use the one from the stock carb or do I need to source it elsewhere?

[Thomas Perkins]

I believe your throttle cable is different than mine.I would go with the K662.The K662 has different likages than the K646.

[toshts]

This is what mine looks like on the stock carb, sorry for the cramped pic. Throttle pulls towards passenger side

[toshts]

1 minute ago, Thomas Perkins said:

I believe your throttle cable is different than mine.I would go with the K662.The K662 has different likages than the K646.

Gotcha, that would make sense with them recommending it for the z22

[Thomas Perkins]

Sorry but the DG Webers rotate counter clock wise.DF's clock wise.

[Thomas Perkins]

Your cable is the same.

Edited December 29, 2024 by Thomas Perkins

[Thomas Perkins]

 This is from a Forum from what Mike has stated.The stud pattern for the Z24 carburetor is different from the Z22 stud pattern so a Weber kit for a Z24 will not fit a Z22 intake

Edited December 29, 2024 by Thomas Perkins

[toshts]

ahhh alright that makes sense. Definitely gonna go with the k662 then, thanks for all the help!

[Stinky]

If they make one w.a solenoid to shut.off fuel flow, get that one.

[Thomas Perkins]

Get a Empi idle cut off solenoid with a o ring and a big.155 jet.Blue wire for choke and red wire for idle cut off solenoid.To see if idle cut off solenoid is working,take wire off when running and engine will cut of.Dont over tighten it.You can get the jet from Pegasus Auto Racing,Empi from Ebay, o rings from Harbor freight.I tried the redline idle cut off solenoid and it would not work on mine.

Edited January 3 by Thomas Perkins

[toshts]

I'll look into the idle cut off solenoid, I know I'm missing a lot of stuff such as the relay for the fuel pump as mine originally had a mechanical pump and I only have the 2 prong connector for the carb. 

 

Updates:

Webers in and its running so much better. Set the timing to 4-5 degrees advanced, transfer slots just closed at idle pulling no ported vacuum, idle mix adjusted to maximum vacuum at around 21 and it feels like a whole different engine I didn't realize how bad the old carb was running. 

 

 

 

 

On the topic of throttle linkage, my k662 kit came with all the proper linkage and opens counter clockwise as well but the linkage was put on upside down from how the "factory" carb was. 

 

 

Install was super simple, I ended up deleting the vacuum lines and stuff on the passenger side wheel well but left the charcoal canister. Brake booster on my 720 is routed directly to the intake manifold. Currently have the egr plugged and the ab valved taken off, debating whether or not to keep them on. Looking to maximize the longevity of the engine and more mpg never hurts so I'll be looking into other posts on to keep or not. 

 

 

I ended up flipping the throttle linkage upside down to the orientation it was with the old carb and stole a spring off the old one to use as a return. I reused the original cable holder but put a washer under the bottom screw so it would have clearance with the new carb (just barely doesn't touch even though it looks like they do in the pics). 

 

 

After reading the haynes manual and going back and forth in this post I think someone threw a factory carb from a z24 truck on my z22. Main indicators being the throttle linkage orientation and the fuel inlet. Mine looked like the "later models" in the haynes even though I've got an 81. 

 

 

If anyone has opinions or info on the egr, ab valve or anything else to keep or delete it would be appreciated but I'll dig into the old posts as I'm sure there's tons of info. Thanks for all the help Thomas Perkins, I ended up finding your video on your install which showed me how to place the bracket for the return spring on top of everything on this post. 

[datzenmike]

The AB valve only works on deceleration so not going to affect fuel economy. EGR is off when engine cold, idling or full throttle, basically it only works at part throttle introducing varying amounts of inert exhaust gasses. By inert I mean exhaust where all the oxygen has been burned away. This small amount of inert component just takes up room in the combustion chamber and this reduces the output slightly also reducing the peak pressure and temperature that causes the nitrogen in the air to combine with the oxygen. You won't notice this small loss as you would automatically just increase throttle. It could be argued that the throttle is now more open than it would be without the EGR presence and the engine has less work to do pulling air past the carburetor restriction, reducing pumping losses and very slightly increasing mileage. 

 

EGR does not affect mileage economy so it's removal does not put back something that was never removed in the first place.

 

If you remove the EGR be damned sure you seal the hole with a good block off plate and gasket. Also the exhaust transfer pipe removal means the exhaust manifold needs to be plugged. Or you could just leave the EGR on but deactivated.

[Thomas Perkins]

Great job.I have a 4x4 and just did a mileage check on my 4x4.I got 18.467 mpg on the tank of gas.It lasted 11 days.I checked it the tank before this and got 19.1 mpg.I have been getting this since I had my truck for 30 years.The Weber and stock get the same for me.It's up to you if you want to remove egr and vacuum lines.I am on my second egr.It is a Nissan one.This is my second Weber.First one was from North American Weber site.It had the black choke.I believe it was not a real Redline.On the side it had a sticker with the serial number.The real ones have them stamped on the base.Believe it or not,it came with a Idle cut off solenoid.It ran good.The reason I got rid of it cause  head gasket blew and I thought it was the Weber.I sold it on 720 world.Mine runs Super with all the vacuum lines and egr.Here is a picture with both Webers.I bought a bunch of Weber springs if you need one.

Edited January 12 by Thomas Perkins

[Thomas Perkins]

Okay Mike.Some one just put a new fuel pump and fuel filter in it with New China hoses.But any way.What is your take on his install.Says it runs bad.He has original carb.Should I try and get him to join our world on this site.He said the other fuel pump died and this one stumbles.Could it be a carb issue and not a Fuel pump issue.Maybevother fuel pump was good.

[datzenmike]

The pump either pumps or doesn't. Engine runs on what's in the carburetor and not directly on the fuel pump output. If carburetor is full of gas then it should run.

 

Get him to join. Stumbles???? what at idle? under load? after gear change? when cold? Lots of questions to ask. New pump may be too high pressure.

[Stinky]

The inert gas that goes into the combustion chamber, from the EGR, reduces pressure in the chamber which decreases MPG and power.  

[toshts]

12 hours ago, datzenmike said:

The AB valve only works on deceleration so not going to affect fuel economy. EGR is off when engine cold, idling or full throttle, basically it only works at part throttle introducing varying amounts of inert exhaust gasses. By inert I mean exhaust where all the oxygen has been burned away. This small amount of inert component just takes up room in the combustion chamber and this reduces the output slightly also reducing the peak pressure and temperature that causes the nitrogen in the air to combine with the oxygen. You won't notice this small loss as you would automatically just increase throttle. It could be argued that the throttle is now more open than it would be without the EGR presence and the engine has less work to do pulling air past the carburetor restriction, reducing pumping losses and very slightly increasing mileage. 

 

EGR does not affect mileage economy so it's removal does not put back something that was never removed in the first place.

 

If you remove the EGR be damned sure you seal the hole with a good block off plate and gasket. Also the exhaust transfer pipe removal means the exhaust manifold needs to be plugged. Or you could just leave the EGR on but deactivated.

Okay thank you, I'll probably leave it installed but plugged for now at least and leave the AB valve off. For the transfer pipe I'm looking into getting a plug for it, if it's too rusted into the manifold to remove I might just pinch the metal and use some exhaust "weld" in a tube on the edge. 

[toshts]

5 hours ago, Thomas Perkins said:

Great job.I have a 4x4 and just did a mileage check on my 4x4.I got 18.467 mpg on the tank of gas.It lasted 11 days.I checked it the tank before this and got 19.1 mpg.I have been getting this since I had my truck for 30 years.The Weber and stock get the same for me.It's up to you if you want to remove egr and vacuum lines.I am on my second egr.It is a Nissan one.This is my second Weber.First one was from North American Weber site.It had the black choke.I believe it was not a real Redline.On the side it had a sticker with the serial number.The real ones have them stamped on the base.Believe it or not,it came with a Idle cut off solenoid.It ran good.The reason I got rid of it cause  head gasket blew and I thought it was the Weber.I sold it on 720 world.Mine runs Super with all the vacuum lines and egr.Here is a picture with both Webers.I bought a bunch of Weber springs if you need one.

Thanks! I think the spring I threw on there should work well enough but if I run into problems I might send you a message. That's pretty good mpg, hoping to get a little more since I've got a 2wd but well see. Running good is the biggest priority right now. Also hoping my head gasket lasts me a while longer I think I've hit my fair share of head gaskets in the past few years though I do have a z22 which is less known for blowing them? Need to do more driving with it to see if not having an idle cut solenoid will give me problems.