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carb tuning ??? #1220082 04/21/12 09:37 PM 04/21/12 09:37 PM
Joined: Nov 2004 Posts: 3,517 pacific northwest S Stroker Scamp OP master
Stroker Scamp OP master S Joined: Nov 2004 Posts: 3,517 pacific northwest	using and A/F meter my idle is at 18-20, I only have the screws out one turn, other question is whats the best # to look for in the upper RPM range? race motor C-12 fuel, Im just testing parked for now but im getting a 10-11 at 4K, carb is a Holley 950 HP, seemed to think it was 12.5 range, any input would be great, as you can tell im just learning this stuff, Thanks Mike footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip 73 Duster 340 street strip 12.79 @ 105

Re: carb tuning ??? [Re: Stroker Scamp] #1220083 04/21/12 11:47 PM 04/21/12 11:47 PM
Joined: Jul 2004 Posts: 19,317 State of confusion T Thumperdart I Live Here
Thumperdart I Live Here T Joined: Jul 2004 Posts: 19,317 State of confusion	My 470 big-block likes bet. 13.8-14-2 at idle and my wot on the street was bet. 12.5-12.7 when I just ran my best and this is w/VP-100 unleaded at the pump. 72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....

Re: carb tuning ??? [Re: Stroker Scamp] #1220084 04/21/12 11:57 PM 04/21/12 11:57 PM
Joined: Aug 2003 Posts: 43,205 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,205 Bend,OR USA	Mike, I shoot for 14.2 to 15.6 at idle and around 13,8 to 14.8 on part throttle cruise, 12,8 to 13.3 at WOT Best thing is to tune for MPH at the track and watch the spark plug, once you get the best results then look at the AFR readings No two motors will like the absolute same readings Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: carb tuning ??? [Re: Stroker Scamp] #1220085 04/22/12 12:48 AM 04/22/12 12:48 AM
Joined: Jan 2003 Posts: 5,486 SoCal Brian Hafliger master
Brian Hafliger master Joined: Jan 2003 Posts: 5,486 SoCal	Quote: using and A/F meter my idle is at 18-20, I only have the screws out one turn, other question is whats the best # to look for in the upper RPM range? race motor C-12 fuel, Im just testing parked for now but im getting a 10-11 at 4K, carb is a Holley 950 HP, seemed to think it was 12.5 range, any input would be great, as you can tell im just learning this stuff, Thanks Mike Idle screws out 2-2 1/2 turns, block rear power valve and start with 87, 2.5 PV in front and 77 jet. I recommend .035 squirters, and blue pump cams front and rear. Make sure you crack the rear throttle blade enough to let air by the blades. OOTB they are seated in the bores and won't properly allow idle adjustments. A 950 is just too small for that engine though IMO... Brian Brian Hafliger

Re: carb tuning ??? [Re: Brian Hafliger] #1220086 04/22/12 01:16 AM 04/22/12 01:16 AM
Joined: Nov 2004 Posts: 3,517 pacific northwest S Stroker Scamp OP master
Stroker Scamp OP master S Joined: Nov 2004 Posts: 3,517 pacific northwest	Quote: Quote: using and A/F meter my idle is at 18-20, I only have the screws out one turn, other question is whats the best # to look for in the upper RPM range? race motor C-12 fuel, Im just testing parked for now but im getting a 10-11 at 4K, carb is a Holley 950 HP, seemed to think it was 12.5 range, any input would be great, as you can tell im just learning this stuff, Thanks Mike Idle screws out 2-2 1/2 turns, block rear power valve and start with 87, 2.5 PV in front and 77 jet. I recommend .035 squirters, and blue pump cams front and rear. Make sure you crack the rear throttle blade enough to let air by the blades. OOTB they are seated in the bores and won't properly allow idle adjustments. A 950 is just too small for that engine though IMO... Brian currently running 84 squared no power valves, pretty sure 35 for squirters, think i have a cam kit, boy i should have done this long ago,,, brian wont turning it out to 2 1/2 fatten up the idle? footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip 73 Duster 340 street strip 12.79 @ 105

Re: carb tuning ??? [Re: Stroker Scamp] #1220087 04/22/12 01:54 AM 04/22/12 01:54 AM
Joined: Oct 2010 Posts: 2,408 Ambridge, Pa. R rickraw top fuel
rickraw top fuel R Joined: Oct 2010 Posts: 2,408 Ambridge, Pa.	u could drop down ur idle air bleeds about 4 sizes. that should make the scews about 1 1/2 out. that will clean up the idle some.

Re: carb tuning ??? [Re: rickraw] #1220088 04/22/12 11:28 AM 04/22/12 11:28 AM
Joined: Aug 2004 Posts: 2,128 sweden S sshemi top fuel
sshemi top fuel S Joined: Aug 2004 Posts: 2,128 sweden	I tune the idle with a vaccum gauge

Re: carb tuning ??? [Re: sshemi] #1220089 04/22/12 03:04 PM 04/22/12 03:04 PM
Joined: Apr 2007 Posts: 325 Greenville, WI B Big B enthusiast
Big B enthusiast B Joined: Apr 2007 Posts: 325 Greenville, WI	If you have a cam with a lot of duartion then using an O2 meter at idle is useless. My O2 meter says 16:1 at idle but realistically is around 13. If you do a lot of street driving you will need to get a PV and jet the primaries down 6 jet sizes. Otherwise you will be crusiing at 12 afr....not good.

Re: carb tuning ??? [Re: Big B] #1220090 04/24/12 12:25 AM 04/24/12 12:25 AM
Joined: Nov 2004 Posts: 3,517 pacific northwest S Stroker Scamp OP master
Stroker Scamp OP master S Joined: Nov 2004 Posts: 3,517 pacific northwest	is the higher the # fatter or leaner? footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip 73 Duster 340 street strip 12.79 @ 105

Re: carb tuning ??? [Re: Stroker Scamp] #1220091 04/24/12 12:27 AM 04/24/12 12:27 AM
Joined: Aug 2003 Posts: 43,205 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,205 Bend,OR USA	Higher AFR # (15.0)are leaner, lower is fatter,(12.0) just like altitude Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: carb tuning ??? [Re: Cab_Burge] #1220092 04/24/12 12:31 AM 04/24/12 12:31 AM
Joined: Mar 2003 Posts: 2,509 PA moparacer master
moparacer master Joined: Mar 2003 Posts: 2,509 PA	At 18-20 I bet that thing is sipping air somewhere. Is this with open headers/collectors? 67 Barracuda street/bracket car 11.27-119 68 Dart 502 BB 8.70s-152 414 cid SB Dragster 7.65-174

Re: carb tuning ??? [Re: moparacer] #1220093 04/24/12 12:41 AM 04/24/12 12:41 AM
Joined: Nov 2004 Posts: 3,517 pacific northwest S Stroker Scamp OP master
Stroker Scamp OP master S Joined: Nov 2004 Posts: 3,517 pacific northwest	Quote: At 18-20 I bet that thing is sipping air somewhere. Is this with open headers/collectors? i am running bullet mufflers the sensors are in the extension in front of the muffs footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip 73 Duster 340 street strip 12.79 @ 105

Re: carb tuning ??? [Re: Stroker Scamp] #1220094 04/26/12 10:15 PM 04/26/12 10:15 PM
Joined: Nov 2004 Posts: 3,517 pacific northwest S Stroker Scamp OP master
Stroker Scamp OP master S Joined: Nov 2004 Posts: 3,517 pacific northwest	another dumb question but how much does the A/F change under load going down the track? footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip 73 Duster 340 street strip 12.79 @ 105

Re: carb tuning ??? [Re: Stroker Scamp] #1220095 04/27/12 12:01 AM 04/27/12 12:01 AM
Joined: Aug 2003 Posts: 43,205 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,205 Bend,OR USA	Quote: another dumb question but how much does the A/F change under load going down the track? It depends on the fuel system and carb., if it goes lean from the start line to the end of the run then look at what is casuing it. I've seen it caused by the fuel filter being to fine, to small of needles and seats, .110 versus .120 Not big enough pickup in the tank, not big enough fuel line to the front, not good enough fuel pump, fuel regulator too small and the list goes on Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

Re: carb tuning ??? [Re: Stroker Scamp] #1220096 04/27/12 12:10 AM 04/27/12 12:10 AM
Joined: Apr 2011 Posts: 319 jonestown,pa D dmking enthusiast
dmking enthusiast D Joined: Apr 2011 Posts: 319 jonestown,pa	i read it ritchens up under a load. i agree somewhat. i run about 13 to 13.3 to 1 at the track. setting up a street engine i use a vacume guage to see driving vacuum on the flat and then pull a hill to see what the vacuum drops to while pulling the hill. then get a power valve that is higher than that number or around that so it fattens it up pulling the hill. after that i jet for 13.5 to 1 to 13.8 and want 13 or high 12 when the power valve is open on the primarys only for driving. if the power valve is too low a number it will not open up and you will pe pulling a grade with good afr on the flat and go lean as you go open on the throttle. remember when running a air cleaner that is real small you can actually start to build vacuum at high rpms and the power valve will close and relean out the engine and make you chase your ass. (this usually happens when a very low power valve number in in)

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