Hello everyone. I'm looking for recommendations on a set up for my holley 850DP mech. secondaries carb. The engine is a BBB 462, 10.5:1 cr., ported iron heads w/stage 1 valves, 290-08H cam installed @ 106 ICL, SP 1 w/ 4 hole 1 inch spacer, TA headers- 1 7/8 prim. 3 1/2 collectors. Thanks.
Hi Tim. First of all, you car will like a bigger carb, 950 or 1050 if you can. If the 850 is the only option, then make sure you put jet exensions in the rear, and plug the rear vacuum diaphram. Make the rear jets about 6 sizes bigger due to this. As far as jet sizes, can't help you there. Those change everywhere you go based on local altitude and stuff. Good luck.
I am going to have to disagree with Mark. The 850 will work fine, I found little difference between a good 830 and a 950 on a very similiar setup. If starting from scratch would go with a bigger carb but no reason to change at this point. Good basic setup: front jets 78 with 6.5 power valve, rear 84 if no power valve. 34 squirters with pink cam. This should be in the ballpark and can work on the tune from there.
I agree Doug. I tried to say in there that if you only have an 850 and no options, it will work. We went from 800 to 950 and will go to 1050 as soon as we can afford it. Our build is similar.
Thanks guys. I would like to put a 1000 or 1050HP on it but it's not in the budget right now, which is why I was asking. The carb is currently jetted with 82 fronts and a 3.5PV, 90 rears PV plugged and jet extensions w/notched float. I have 78 and 84 jets that I can try. Does anyone run idle feed restrictors and or have the throttle blades drilled for additional air for better idle? What about opening up the air bleeds a little?
Mark, Guess that was not much of a disagreement :grin: Tim, Each carb and combination is a little different. My guess would be that you could be a touch rich but you have to run it to see or have an AFR guage. A good running Buick usually have almost white spark plugs. Problem is much of the new fuel available is very hard to do a traditional plug reading with. What area of your tune are you working on? It is my opinion that none of the carb tuners have really addressed the idle feed issue on 4 corner idle holleys. I think they all run to big of an idle feed restriction. Was going to work on that with the Bigs 950+ that I was using but have switched to a blow through carb from QuickFuel. Have not run that carb yet. The Bigs was very good but could have used some idle work for the street. It wanted to be a little rich on the bottem and over 2000 rpm cruise. But that was also true of the QuickFuel 950 and the Baker 830 I tried. All are very conservative to make sure that you do not lean out on WOT. Bigs did not use any holes in the butterflys, the Baker 830 and the QuickFuel 950 did. The QuickFuel blow through does not use any holes.
Tim, Just noticed you are from Algonac. Need to get more of the MI performance Buicks together. Think about it next year. We have pretty much run out of this season.
Doug, I hear you on that. I have gone to car shows and cruises where I'm the only Buick in attendance. Then someone will ask me what year Cutlass that is!ou: Now that I have a 200R4 in it freeway cruising is nice and easy. It would be cool to have a meet with all the Michigan Buick guys. Count me in! As far as what I am trying to accomplish with this carb would be getting the idle mixture right due to the rich smelling exhaust and better part throttle cruise milage. The engine runs well, but I'm trying to see what others are running as far as jet sizes and if they checked there A/F ratio with a wideband 02. I do realize that jetting changes with altittude, but just want to see if I am in the ballpark. I didn't mention in my previous post that I have a .010 piece of wire in all four idle feed restrictors and a .060 hole in all 4 throttle blades, and if I put my finger over just one of the idle air bleeds the engine will want to stall, leading me to believe it wants more air. If I enlarge the hole in the blades I'm concerned about not being able to get the idle speed low enough. Maybe I should open the idle air bleeds a little bit, but not sure as to how much. Thanks, Tim
Tim, Going to be real interested in how restricting the idle feeds works out. Most of us using the 4 corner idle carbs find that the idle adjust screws are very sensitive and usually require only 1/2 turn on each screw. The first goal is to try and get the idle adjust to be happy at 1 1/2 turns out then put in smaller idle air bleeds. Never got there myself. I think my new QuickFuel has screw in jets for the idle feed so could be easier to experiment with. Here is where I linked to an article on tuning for better millage with a Holley. http://www.v8buick.com/showthread.php?t=160671 At this point I am starting all over on carb tuning. Just got a blow through QuickFuel 650. According to QuickFuel this carb should be good for 750HP with my blower.
Holley says that if you can screw the idle mixture screws in and make the engine change rpm by doing it , then the idle mixture can be leaned out to get rid of the rich mixture.... but , i think that the rich smell is caused by the cat pee gas that we are forced to use now.... it will not completely burn before it gets pumped out the exhaust pipes.....:Brow: :Brow:
