Chevelles.com banner

1 - 13 of 13 Posts

·
Premium Member
Joined
·
157 Posts
Discussion Starter #1
To start out, this carburetor has roughly 250 miles on it. 750 dp, on a 396.

I just pulled the carb. off today to check the secondaries transfer slots and to install an allen head adjuster screw. Here's the issue: I noticed when I adjusted the secondaries to get my .020 at the slot, the throttle blades would not completely close leaving the transfer slot way over exposed. I could push at the throttle linkage to get it to close the rest of the way. The spring seems fine. And, if I let the throttle snap back quickly, it closes good.

Now, if I keep adjusting the secondary accelerator pump, I can take out the slack and the blades will eventually close on their own. But I think that I'm putting too much pre load on that accerator pump.

If I get my .015 at the acc. pump the sticking happens.

Has anyone seen this before or is this happening just because there is no load on the throttle linkage.

Also, the car has been running rich. The main reason for me to check the trans. slots.

thanks
 

·
Registered
Joined
·
1,260 Posts
Never mind. I just wrapped the secondary throttle blade shaft spring another time around. fixed.
That extra spring sure does help. Do not try to set the rear sec blades on the Holley baseplates @.020, the problem is that the slots on the sec side are shorter than the pri side. If you have a 4 corner setup it's the same thing. The best carbs for setting both the same are the aftermarket baseplates and the Demon carbs, both transfer slots are the same length on them.
 

·
Boldly procrastrinating
66 El Camino 57 Chevy pickup 2004 Tahoe
Joined
·
28,949 Posts
the secs don't normally need any TS exposed. That's for off-idle idle tip-in, when the secs open you're usually way past tip-in.
 

·
Premium Member
Joined
·
157 Posts
Discussion Starter #5
That extra spring sure does help. Do not try to set the rear sec blades on the Holley baseplates @.020, the problem is that the slots on the sec side are shorter than the pri side. If you have a 4 corner setup it's the same thing. The best carbs for setting both the same are the aftermarket baseplates and the Demon carbs, both transfer slots are the same length on them.
the secs don't normally need any TS exposed. That's for off-idle idle tip-in, when the secs open you're usually way past tip-in.
What are the sec. T slots for then ?

Shouldn't I adjust my idle with the secondary allen head adjuster screw I installed. I was just getting ready to prime up the carb. re time and adjust the carb.

yes, 4 corner set up.

I don't mean to open up a can of worms here. Thanks for the help.
 

·
Registered
Joined
·
1,260 Posts
What are the sec. T slots for then ?

Shouldn't I adjust my idle with the secondary allen head adjuster screw I installed. I was just getting ready to prime up the carb. re time and adjust the carb.

yes, 4 corner set up.

I don't mean to open up a can of worms here. Thanks for the help.
I am not sure what Holley's thinking was when they came out with the sec. idle circuit and didn't make the slots longer. We used to add out own sec idle by drilling the baseplate and all the other holes ourselves but I have always noticed Holley's do not seem to have much sec. idle adjustability compared to other carbs I own. I have at times used a small fine tooth saw blade and made them the same as the pri. side and it does work but it's tome consuming. The sec side is just supposed to be cracked open enough so it does nor stick, but I like to open it further to get some control over the pri. side and close those blades back to the .020-.030 as needed to clean up the A/F mixture.
 

·
Registered
Joined
·
13,788 Posts
Back blades should only have the set screw in a 1/4 turn, just enough the lift the blades off the bore to prevent sticking. I would make sure the shafts aren't seizing or stiff - should move very smooth. Only other thing to watch for is that the shaft isnt twisted somehow or the blades weren't aligned correctly due to a sloppy rebuild by somebody.

Shouldn't have to wind the spring anymore to force them closed.
 
  • Like
Reactions: 1775SS

·
Premium Member
Joined
·
157 Posts
Discussion Starter #8
I am not sure what Holley's thinking was when they came out with the sec. idle circuit and didn't make the slots longer. We used to add out own sec idle by drilling the baseplate and all the other holes ourselves but I have always noticed Holley's do not seem to have much sec. idle adjustability compared to other carbs I own. I have at times used a small fine tooth saw blade and made them the same as the pri. side and it does work but it's tome consuming. The sec side is just supposed to be cracked open enough so it does nor stick, but I like to open it further to get some control over the pri. side and close those blades back to the .020-.030 as needed to clean up the A/F mixture.
Back blades should only have the set screw in a 1/4 turn, just enough the lift the blades off the bore to prevent sticking. I would make sure the shafts aren't seizing or stiff - should move very smooth. Only other thing to watch for is that the shaft isnt twisted somehow or the blades weren't aligned correctly due to a sloppy rebuild by somebody.

Shouldn't have to wind the spring anymore to force them closed.
I have my primary's set at .020 and I should keep the sec. a 1/4" up from totally closed, not exposing the T slot at all ?

Not being able to see where the blades are in comparison to the T slot before I pulled off the carb to see where it was at and to add that allen screw .......so I could get my idle under control is what I was trying to do.

I'm definitely willing to set up this Holley the way you guys are saying. Once i get my timing set, should idle adjustment come from the primary idle screw, sec screw or both ?

And I will adjust my a/f screws to the highest vacuum at some point, I think after pri/sec idle adjustment.

Hopefully I'm in the ballpark with my battle plan here.

I did purchase this new from Holley back in 2018 and I don't believe the sec blades were sticking then. Not sure why they are now. It's not much and it's on the way back to close when the stick, about an 1/8" from horizontal.
 

·
Registered
1969 Chevelle 2 Door Sport Coupe Malibu COPO clone
Joined
·
5,369 Posts
:cool: Holley has a few videos on how THEY believe THEIR product should be tuned/set up. With all respect to all posters, I'd try what the MANUFACTURER says.

Yes, I run a Holley and I love it. It runs fantastically.

PS Holley also has human tech advice available.
 

·
Premium Member
Joined
·
157 Posts
Discussion Starter #10
:cool: Holley has a few videos on how THEY believe THEIR product should be tuned/set up. With all respect to all posters, I'd try what the MANUFACTURER says.

Yes, I run a Holley and I love it. It runs fantastically.

PS Holley also has human tech advice available.
Thanks Bruce
I've been watching many videos on the 4150. I just wanted to clean up the idle a bit. Other than that it has been a great carb.

Just looking for some tips that go beyond what Holley recommends and I know TC is the best place to get it. :thumbsup:

Then the sticking secondary's reared its ugly head. Still not sure what's going on there.
 

·
Boldly procrastrinating
66 El Camino 57 Chevy pickup 2004 Tahoe
Joined
·
28,949 Posts
carbon can build up in the throats or on the butterflies to both.
 
  • Like
Reactions: 1775SS

·
Premium Member
Joined
·
157 Posts
Discussion Starter #12
They look fairly clean, but I will check that out. Only a couple hundred miles on the carb. I would hope carbon build up wouldn't be a factor yet. I think I have some CLP in my gun cabinet. :grin2:
 

·
Premium Member
Joined
·
6,694 Posts
The linkage is supposed to close them, might need some adjusting.
 
1 - 13 of 13 Posts
Top