Hey all, I'm making good headway on my 1965 Olds F85 with a 496 BBC. I have this car relatively mechanically sorted, and bought this AFR gauge as insurance to prevent the nitrous shot from melting an engine. So, until the engine is AFR tuned to the top, I'll be holding off on spray. But first I need to get it there. So here goes... https://www.v8buick.com/index.php?threads/1965-olds-f85-“snowflake”.364098/ Holley 850 cfm Double Pumper, 1851 or something First Run: Idle Afr- 14.1:1 Part Throttle Cruise- 12.0:1 Couldn't safely ease into the throttle to full without seeing 17:1 + Primary jets: 80 Secondary Jets: 82 Primary power valve: 4.5" Secondary power valve: 3.5" New setup to test: Primary jets: 76 Secondary jets: 84 (or higher?) Power valves the same No squirter change yet Anyone have any tuning advice on what to shoot for? Remove power valves? I've never done a Holley, so what's up?
High numbers are lean, lean= nfg Don't be too concerned with idle numbers that are really fat, 10 or even lower. WOT numbers are your priority. Shoot for 11-13ish, no higher. Connect a vacuum gauge to ported manifold vacuum and adjust your four corner idle mix to attain the highest vacuum numbers ya can first , then adjust your idle rpm. Be good to know how much vacuum your motor/ cam combo is making. Then you can move onto Air Fuel Ratio adjustment via jet changes. Run the numbers on that carb and post them. Someone will have the book with it's specifications. Be nice to know what jets it was born with. Get a jet kit and a jet screwdriver. Most 4150s with dual power valves run the jets square, that is same front to back. Those with a PV in the Primary Metering and not in the Secondary usually run 8-10 jet sizes larger in the rear. I think you are going the wrong way with your second setup. 17 is way too lean , in my opinion..... JIM
I would agree. Lean at 17.....I think dual pv complicates thing alot. As stated. Pv add enrichment of about 8-10 jet sizes. I think you will want you pv adding fuel a little earlier too..........I dont know how big of cam your 496 has.......but most carbs do will with a 6.5 up front and non in the rear. 82/90 jets is a decent start. Make sure you pump arms move exactly with the throttle......sometimes there is too much space in them causes a delay and lean bog.... What fuel are you running through this.....what is your timing set
Thanks Jim, the engine combo makes 8” of vacuum at 1000 rpm. Idles at 900-950 warm. I have manual brakes. I did look up the carb number before and believe it was born with squared 80s and a 6.5 power valve. Cruising at 45 mph had the carb down in the 12.0:1 afrs, which is certainly too rich for cruise. I’m now aiming for around 13.2-13.5.
I’ll probably just remove the rear one and plug it at this rate. The cam makes 8” of vacuum at 1000 rpm. Pump arms are tight, but not too tight. Fuel is 93 on the street, probably a 50/50 blend of 110 at the track, or just straight 110. Timing is locked at 34*
So with 8" of vacuum at idle the cam has some overlap. A pv around 4 or 3.5 should be close. I assume this still has progressive linkage What cc pump and squirters are you using? Make sure your jets are installed with a jet tool not a screw driver.....if the slots get deformed which happens with a flat blade it will effect the flow of those just. They are more than just a drill size......
should be a carb list# of 4781 followed by a -1 or -3 or -5 etc . that'll be your series ( age ) . first couple series should be 2 corner idle I believe although I have an early -3 that is 2 corner . FYI - lower power valve number = slower opening rate . memory - newer 850's seem to be 80's for jets all the way around and 6.5 PV's front and rear . some early ones as high as 8.5 and 10.5 ? I'd have to check book after work if I know series . info online too .
-6 should be unless someone has changed something . base , body and metering block all have to match to be 4C .
So would you suggest running it that way, or 80/88 and 4.5" in the front power valve, while blocking the rear?
That should be close to start. If 4 corner idle i would set each mixture 1 5 out, ibwould make sure to open the rear blades some......to let a little more air through and make certain that the front blades are not too far open.......if there is no screw to open rear blades......I would start wit putting a 1/16 hole in all 4 blades........but only if no rear blade adjustment.
the rear adjustment is under carb right below throttle shaft on pass side . P-I-A . plus good luck with adjustment , small recessed screw and usually not too cooperative . aftermarket bases use a dif top side adjustment setup . or can be added to stock base . I usually start with idle screws turned 1.0 full turns out . it's a guess but I'd say start at oem spec jets and P/V and when you get your NO2 going do some homework on the NO2 setups , then maybe bump rear jets and P/V .
Make a custom stubby screwdriver like this, or buy a secondary idle screw & bracket.... https://www.ebay.com/itm/HOLLEY-ADJ...-/163970145901?_trksid=p2349624.m46890.l49292 Or this one.... https://www.ebay.com/itm/Adjustable...-/192056216272?_trksid=p2349624.m46890.l49292
In the meantime, I tried: 76/84 Primary PV: 5" and secondary PV: 4.5" It was 11.5:1 rich at cruise. And I learned that it likes a lean/hot idle of about 14.5-15.5:1 And still I could not even begin to put the pedal to the floor. It was showing nearly 17:1 for a 1/4 second at 3/4 throttle, so I completely backed out So what will happen is this: 80/90 Primary PV: 3.5" and secondary blocked
Your going the wrong way with the pv. If you want more enrichment sooner you need the power to go up in numbers. The way they work is the spring in them over come engine vacuum at that rated number and provide more fuel from then on. The other thing that might be happening is if the squirter shots stops too soon b4 the main meter takes over it can go lean........ So if it does dead lean when throttled in...you need more from the pump......a bigger nozzle or a faster ramped cam......if you need the pump shot to last longer you need either a small nozzle or a larger cc pump. Does it respond quickly when throttled then go lean like it runs out.......if so you need the pump shot longer or does it fall flat lean and never come back..........if so you need more fuel from the pump sooner If it bogs. But eventually lives up you need less pump. Another fudge that helps pull fuel quicker or easier is raise the float levels......does your have sight glass or plugs...... You said your motor is only pulling 8" at idle.......if the needle choppy and bouncing or a steady hold. Mine idles about 5 and the needle moves so fast its hard to really see......5 just seems to be the middle number.......I run a 3 pv in it but because of this when I'm around the pits say 2500 I can tell it' rich.....I even pulled the air bleed completely out in the intermediate circuits to see........and it was better......but that would also lean out top end so I never ran it more thsn in pits........when I on it it does just fine even from a foot brake........its just fat at 2500ish under light throttle
What I believe is happening is that the power valve is opening up at cruising speeds and throttle positions. The needle is pretty choppy between 7-9" at idle The floats are properly set with plugs I have 31 squirters in it, 30 cc pump in the front, 50 cc pump in the rear, so I will definitely start to watch the way the tip in goes. At the moment, it never recovers from going lean, and continues to go further lean the more the throttle is opened.
