Talk to about carb needs

[PurpleBeeper]

Thanks! I’ve decided also to measure and see if I can switch holes in the carb linkage... there’s one hole for the ball-pin that is closer to the throttle shaft, which should mean it requires less travel of the pedal to effect full rotation of the linkage... we’ll see if it is workable. I’ll almost certainly have to trim down the cable to use that one, so I wanna be sure I can before I make it permanent.

The hole in the red circle is the one I’m aiming for.

View attachment 629328

That is a very reasonable approach. The carburetor "throw" will be less, but the cable "might" have to be anchored lower so it can "pull downward" near full open throttle...maybe, so check... and re-read coloradodave's post & check the Lokar instructions in my opinion too. You will get there.

 

[///Matt]

That is a very reasonable approach. The carburetor "throw" will be less, but the cable "might" have to be anchored lower so it can "pull downward" near full open throttle...maybe, so check... and re-read coloradodave's post & check the Lokar instructions in my opinion too. You will get there.

So I switched the cable pin to the more centric hole... I had to drill it out a hair to fit the pin, but it went well. The cable alignment was good, cable pull is straight (straighter than the original hole, actually) and shorter. The difference between throws at the carb is about a 1/2” of cable, which is enough that now my pedal can go full closed to full open, instead of closed to 80%.

Looking forward to driving it tomorrow and seeing how much it’s woken up, but also anxious to see how much cleaning/tuning I’ll have to do on the secondary. The secondary wasn’t getting used, so it’s fouled all up. The secondary acc pump doesn’t work at all (can’t even manually depress it) so I’ll have to see on the road whether I’m fixing only that or taking apart thay whole side and cleaning/replacing all the metering.

 

[PurpleBeeper]

So I switched the cable pin to the more centric hole... I had to drill it out a hair to fit the pin, but it went well. The cable alignment was good, cable pull is straight (straighter than the original hole, actually) and shorter. The difference between throws at the carb is about a 1/2” of cable, which is enough that now my pedal can go full closed to full open, instead of closed to 80%.

Looking forward to driving it tomorrow and seeing how much it’s woken up, but also anxious to see how much cleaning/tuning I’ll have to do on the secondary. The secondary wasn’t getting used, so it’s fouled all up. The secondary acc pump doesn’t work at all (can’t even manually depress it) so I’ll have to see on the road whether I’m fixing only that or taking apart thay whole side and cleaning/replacing all the metering.

Boo-Yah! Honestly, if the secondary accelerator pump is "frozen" it's either A. The arm in the accelerator pump housing itself or B. The rear accelerator diaphragm is rock-hard. I know you're almost there, but I suggest you fix that first before you floor it so it doesn't start leaking fuel all over your engine while driving OR bend up the lever on the carb base that actuates the secondary accelerator pump lever.

You can buy the accelerator pump diaphragm off the shelf at O'Reilly (& others). You'll need a 90-degree bent "Z-style" phillips screwdriver (if you have phillips head screws) to take off the rear accelerator pump. Use a mirror & maybe a safety pin & some carb cleaner to make sure the little "trapped ball" is moving free. IF you have the "hour glass shaped" (name?) screws on the accelerator pump, then take off the rear fuel bowl & use the special screw driver (or driver bit) & then you'll need the rear metering block gaskets too (double check application, but probably off the shelf at O'Reilly too).

 

[///Matt]

Boo-Yah! Honestly, if the secondary accelerator pump is "frozen" it's either A. The arm in the accelerator pump housing itself or B. The rear accelerator diaphragm is rock-hard. I know you're almost there, but I suggest you fix that first before you floor it so it doesn't start leaking fuel all over your engine while driving OR bend up the lever on the carb base that actuates the secondary accelerator pump lever.

You can buy the accelerator pump diaphragm off the shelf at O'Reilly (& others). You'll need a 90-degree bent "Z-style" phillips screwdriver (if you have phillips head screws) to take off the rear accelerator pump. Use a mirror & maybe a safety pin & some carb cleaner to make sure the little "trapped ball" is moving free. IF you have the "hour glass shaped" (name?) screws on the accelerator pump, then take off the rear fuel bowl & use the special screw driver (or driver bit) & then you'll need the rear metering block gaskets too (double check application, but probably off the shelf at O'Reilly too).

Thank you!

 

[beanhead]

See how you like it once the carb and throttle stuff is fixed, and go from there. You are, most likely, down on compression but the carb is definitely NOT too big. With your mods it should still be a nice torquey driver if all is working right. The limiting factor for real power with 440s is always the heads..the factory used the same heads for a given year on everything from hi-performance R/Ts to 2-barrel C-body cars..just some food for thought. Big cams help but then the whole personality of the engine changes. To swap heads you'll need to get the headers out to access the lower row of bolts..always a good time

 

[///Matt]

See how you like it once the carb and throttle stuff is fixed, and go from there. You are, most likely, down on compression but the carb is definitely NOT too big. With your mods it should still be a nice torquey driver if all is working right. The limiting factor for real power with 440s is always the heads..the factory used the same heads for a given year on everything from hi-performance R/Ts to 2-barrel C-body cars..just some food for thought. Big cams help but then the whole personality of the engine changes. To swap heads you'll need to get the headers out to access the lower row of bolts..always a good time

Sweet! They (the headers) don’t have to come “out” though, right? Just unbolted and maneuvered around?

 

[beanhead]

Sweet! They (the headers) don’t have to come “out” though, right? Just unbolted and maneuvered around?

They should come out...you can try it but getting in there with a ratchet and then a torque wrench is next to impossible especially on the passenger side. You may even have to jack the engine up to get space in front of the shock tower areas

 

[///Matt]

They should come out...you can try it but getting in there with a ratchet and then a torque wrench is next to impossible especially on the passenger side. You may even have to jack the engine up to get space in front of the shock tower areas

Boooo

 

[///Matt]

What do you in the brain-trust think of the Street Avenger 870cfm? I’m thinking that instead of repetitively screwing with the 750DP til it’s good, I’m going to switch to a brand new carb with vacuum secondary, and just worry about dialong in the tune instead of trying to make the carb work right and THEN dialing in a tune. I’m thinking this one in particular : https://www.summitracing.com/parts/hly-0-83870

Since my Satellite is a heavy car, with a fairly low-stall auto trans, it doesn’t really fit Holley’s description of a car the DP is best suited for. Is this one a better option for me? And apparently my cam is .284/.484, all the info the PO had for me.

And also: if I switched to the 870 avenger, do I need to source a linkage for kickdown, or is it already compatible?

 

[///Matt]

Ordered a 770 avenger... (not 870, after researching various places about “right carb size” and Holley’s carb selector tool.)

Anyone want a 750DP that needs elbow grease, provided by someone who has more experience with carbs than I do?

 

[Paul_G]

I dont see the "Chrysler adapter" on the carb. Holley part #20-7 throttle lever adapter.
It is a must have to correct the geometry.

 

[///Matt]

Thanks for everyone’s input!

I replaced the 750dp with a new 770 Street Avenger. I used holley 20-2 kit to relocate the stud as shown in the picture. Relaced the cable bracket with an updated Lokar one, adjusted all the cables, and tune idle mix... and now she’s fun. I get full range of throttle, good kickdown performance, and wayyyyyy more power with the properly-functioning carb. All winning!

I may re-jet some, but I’ll have to watch the plugs a while first and see how she’s burning. But this was the alarm clocl kit she needed to wake up.