4 corner idle carbs?
 

I talked to the owner at custom rebuilt carbs.com and he was telling me about a Holley 850dp with mechanical secondaries and 4 corner idle circut. Anybody have one of these, and would it be a pain to tune? He told me that with my 467 motor and Crane 296 cam it would be a good choice for smoother idle and be awesome for WOT! Thanks!

Re: 4 corner idle carbs? (467-Ratman)
 

I have one of those carbs with annular discharge nozzles. I have a stout solid roller cammed 454 and it is a very good carb for my motor. If you have basic tuning skills it is not to much of a pain in the butt.

Re: 4 corner idle carbs? (69 N.O.X. RATT)
 

69 RATT, What size jets are you running, and does the carb ever foul the plugs? I am really wanting to go with the mechanical secondaries and the 4 corner idle sounds good to me. My cam is hydraulic, crane 296-2 lift is 551 and 571 with duration at 50 thousands 243 and 250. I have merlin rec port heads with 119cc combustion chambers and 310cc intake runners. Thanks for the input!

Re: 4 corner idle carbs? (467-Ratman)
 

To be honest I forget the jet sizes, besides it does not mean it would be the right one for your motor anyway. The carb does not foul the plugs if it is tuned right. Mechanical secondarys are very streetable, if tuned right. I would start with the stock jet sizes and keep an eye on the plugs and adjust accordingly. The hardest part for me is tuning the idle A/F mixture. make very slow turns on the adjustment and take your time. I have a problem with my car heating up the carb and fuel then the car does not want to idle, makes it difficult to adjust it then.

Re: 4 corner idle carbs? (467-Ratman)
 

I'm running a Holley 950dp from Holley's pro shop. The 4 corner idle adjustment really helps the L88 behave much better at idle. I heartily endorse it! The L88 cam measures in the mid 270's at .050", about 360 degrees at the seat.

Chuck

Re: 4 corner idle carbs? (Chuck Harmon)
 

Another vote for 4 corner idle. My Barry Grant modded Holley DP idles right after start-up and it has no choke. It also delivered a .35 reduction in my 1/4 mile ET. Probably the best single part I've put on the motor.

Re: 4 corner idle carbs? (Les)
 

i have a four corner idle carb. kicks butt. idle was much better then with other carbs. :yesnod:

Re: 4 corner idle carbs? (QuickVet)
 

Thanks all for the info, I know for sure that this old 780 is out of here soon. The idle really sucks and the cam is not that wild, 550 and 570 lift and 236 and 246 duration at .050 lift. Can't wait to enjoy the extra power that the 850 and mechanical secondaries will give me. Anybody wants this carb let me know!

Re: 4 corner idle carbs? (467-Ratman)
 

I have 2 of them on my bigblock. All double pumpers run richer because they are more performance oriented. The problem I find is the idle circuit. It is way too rich. I always drill about .100-.125 holes in the throttle plates but only the plates with it's own idle circuit so in this case all 4. The placement of these holes is critical. I also lean out the idle mixture with .015 wire struck in the 4 idle circuit metered holes. The main jets are 80 stock all around and you can run these IF you lean out the idle circuit. The idle circuit, the transfer slots and the main jets control the cruising mixture. To do just the main jets leaves the idle mixture too rich. Work on the idle mixture and the cruising circuit will look after itself.
I run 2 of these carbs and still get 12 mpg around town.
https://temp.corvetteforum.net/c3/st...gages_good.jpg

Re: 4 corner idle carbs? (467-Ratman)
 

Looks like I am going to get the 4 corner idle carb for my car, I have tried adjusting my Holley 780 and the car will not idle until it reaches about 180 degrees. My hot air choke seems to be working fine, but the car just dies if I am not working the throttle. The idle is about 1100 rpms.I have checked for vacuum leaks and dont seem to find any. I have drilled my throttle plates and have the adjusting screws for the idle circut turned out about 3 turns. Can I make this carb work with my motor, or should I forget it and buy the Holley 850 dp 4 corner?

Re: 4 corner idle carbs? (467-Ratman)
 

Hate to say it but i think you will have a harder time with that dp than with that avenger. Anyone you know that might be able to take a look at it for you? Sounds like your choke isn't set right.

Re: 4 corner idle carbs? (Fevre)
 

When you watch the choke operate with the air cleaner off, it seems to open properly, but it does take a long time to open fully. Untill it heats up the space that it opens looks small , if you try to flip it open more it dies for sure. do I need more fuel with the idle circut to keep the motor running?

Re: 4 corner idle carbs? (467-Ratman)
 

Don't get me wrong I think with your set up the 850 dp would rock but it has a lot more things to adjust than the avenger carb. There should be a way to adjust to choke richer. I have an electric choke and am not familiar with the hot air type but if it dies when you open it then I would say it is lean.

Re: 4 corner idle carbs? (Fevre)
 

At lunch time I adjusted the choke arm, made it straigher making the choke close a little farther, seems to have helped. I am also going to adjust the idle circut screws tonight and make it a little richer. Thanks for the suggestions!

Re: 4 corner idle carbs? (467-Ratman)
 

No problem. Too bad you don't live closer I would let you try out my 750 dp just to see if you like the mech sec. I am going to rebuild it this weekend and to try on my little 350. Overkill for sure but might be good for the track once in a while. I plan on doing a 383 in the next few years so it should be better for that project.

BTW Although the choke tower is no go for performance, it is nice to have for warming up the car.


[Modified by Fevre, 2:58 PM 8/22/2002]

Re: 4 corner idle carbs? (Fevre)
 

Fevre, Keep me posted on how you like the 750dp on your 350 motor. Last year I had my 350 with an LT-1 intake and solid lifter cam, and my holley 780 carb, you will like the 750 dp on that motor, big fun!!!