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Need help tuning my carburetor #1029312 07/10/11 01:57 PM 07/10/11 01:57 PM
Joined: Jun 2007 Posts: 1,184 clarks summit pa 73cuda340 OP super stock
73cuda340 OP super stock Joined: Jun 2007 Posts: 1,184 clarks summit pa	I have a holley 650 double pumper on my 318 with headers, edelbrock performer rpm air gap and 3" true dual exhaust. This is for my 85 w150. If I step on it quick off the line it will bog really bad and I have to back off of the throttle to get it to stop. Also, whenever the truck is under load going up a hill, or if I give it full throttle even while moving, the truck hesitates real bad and will backfire out of the carburetor and pop out of the exhaust. When cruising down the road the truck runs fine. Timing is set at either 14 or 15 initial (cant remember) and 36 total. I adjusted the mixture screws for highest vacuum reading and Im getting a strong shot out of the accelerator pump as soon as I hit the gas. Any help appreciated, 1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip, (JA5) Silver Frost Metallic 1973 Challenger Rallye 340 1985 W150 Power Ram prospector 1986 Camaro IROC-Z 305 tpi

Re: Need help tuning my carburetor [Re: 73cuda340] #1029313 07/10/11 03:30 PM 07/10/11 03:30 PM
Joined: Apr 2010 Posts: 4,154 bethlehem pa M mikemee1331 master
mikemee1331 master M Joined: Apr 2010 Posts: 4,154 bethlehem pa	you might want to check your power valve.

Re: Need help tuning my carburetor [Re: mikemee1331] #1029314 07/10/11 04:07 PM 07/10/11 04:07 PM
Joined: Jan 2003 Posts: 9,826 las vegas 70AARcuda master
70AARcuda master Joined: Jan 2003 Posts: 9,826 las vegas	check your acelerator pump linkage...as soon as the linkage moves the squirter needs to squirt gas... check the rear pump also...but it will not squirt gas until the rear throttle blades begin to open,,,, also..at wide open throttle there should be .015 clearance between the pump arm and pump linkage... Tony 70 AARCuda Vitamin C 71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield) 71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas) 71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)

Re: Need help tuning my carburetor [Re: 70AARcuda] #1029315 07/10/11 04:11 PM 07/10/11 04:11 PM
Joined: Jan 2003 Posts: 9,826 las vegas 70AARcuda master
70AARcuda master Joined: Jan 2003 Posts: 9,826 las vegas	http://www.youtube.com/watch?v=k-Nx5HEzvlY Tony 70 AARCuda Vitamin C 71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield) 71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas) 71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)

Re: Need help tuning my carburetor [Re: 70AARcuda] #1029316 07/17/11 06:08 PM 07/17/11 06:08 PM
Joined: Jun 2007 Posts: 1,184 clarks summit pa 73cuda340 OP super stock
73cuda340 OP super stock Joined: Jun 2007 Posts: 1,184 clarks summit pa	Im starting to think that this is an ignition/ electrical related problem. Some days it will run absolutly awful and just cut out for a second and backfire when you give it gas and other times it will be fine for the entire trip. Does this sound right? 1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip, (JA5) Silver Frost Metallic 1973 Challenger Rallye 340 1985 W150 Power Ram prospector 1986 Camaro IROC-Z 305 tpi

Re: Need help tuning my carburetor [Re: 73cuda340] #1029317 07/17/11 11:28 PM 07/17/11 11:28 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Some quick thoughts; assuming float level(s) good. ported or manifold vac? check dist pickup gap/plugs/wires/firing order/disconnect vac adv & see if that helps/hurts/no ch. Always done this (since built) or recent prob? live every 24 hour block of time like it's your last day on earth

Re: Need help tuning my carburetor [Re: RapidRobert] #1029318 07/19/11 09:56 PM 07/19/11 09:56 PM
Joined: Jun 2007 Posts: 1,184 clarks summit pa 73cuda340 OP super stock
73cuda340 OP super stock Joined: Jun 2007 Posts: 1,184 clarks summit pa	Quote: Some quick thoughts; assuming float level(s) good. ported or manifold vac? check dist pickup gap/plugs/wires/firing order/disconnect vac adv & see if that helps/hurts/no ch. Always done this (since built) or recent prob? The problem just started recently and seems to get worse. The problem happens the most when it's under load going up a hill or when it shifts into third. The plugs are good, and the cap and rotor are new. When I open the sight plugs the front slowly trickles out but the back is just below the sight hole. The advance is hooked up to ported vacuum. What I don't understand is with the advance unplugged it is at 34 total advance but it runs like absolute garbage and misses and backfires nonstop. With the advance hooked up it reads 52 total but runs a lot better (only misses and backfires every now and then) and theres no detonation. 1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip, (JA5) Silver Frost Metallic 1973 Challenger Rallye 340 1985 W150 Power Ram prospector 1986 Camaro IROC-Z 305 tpi

Re: Need help tuning my carburetor [Re: 73cuda340] #1029319 07/19/11 11:28 PM 07/19/11 11:28 PM
Joined: Jun 2006 Posts: 257 albemarle, NC D dusterbd13 enthusiast
dusterbd13 enthusiast D Joined: Jun 2006 Posts: 257 albemarle, NC	it honestly sounds like you jumped time. how many miles on this thing? theres a way to check for timing chain stretch without pulling it all apart. i remember reading it in old manuals, and ill do my best to accurately relate trhe info. but remember, this is many moons ago, and ive slept since then. take the crank pulley bolt. turn it until the rotor button begins to turn. then turn the other way until the rotor button begins to turn. if you rotate your breaker bar morew than 1/8(?) turn, youve got excessive slop. may have also wiped a cam, might be a bad ecu on the igbition, or possibly a bad egine ground. hope that goves you some things to check Michael Crawford CSP 1970 plymouth Duster back under construction: http://www.pro-touring.com/showthread.ph...ouring-makeover 1964 el camino beater shop truck 96403-project-drivabeater-2-0-64-el-camino-this-time

Re: Need help tuning my carburetor [Re: 73cuda340] #1029320 07/19/11 11:47 PM 07/19/11 11:47 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: What I don't understand is with the advance unplugged it is at 34 total advance but it runs like absolute garbage and misses and backfires nonstop. With the advance hooked up it reads 52 total but runs a lot better (only misses and backfires every now and then) and theres no detonation. take off the cap & good visual of the pickup/gap etc for anything abnormal esp gap way larger than ~.008" then bump the starter till a tooth is dead even w the magnet then pull the vac can thru it's travel w a Mityvac (or similar) & see if the gap is still close to normal. The operation of the can is affecting it so likely the prob is nearby. Rotor phasing (which is only changed w vac adv arm operation on the eccentric pivot) may have been right on the edge of misfire but for it to occur that fast something else is going on. possible jumped timing gear tooth or slipped dampener but very rare on the dampener and might not even run w a slipped tooth & pretty rare there also. Holler when you find something EDIT if you hand pump it up, as you pull the magnet w the vac arm you will need to loosen/move the housing to keep the tooth lined up w it & see that the gap is not way past ~.008" then retime it w your done Last edited by RapidRobert; 07/20/11 12:14 AM.

Re: Need help tuning my carburetor [Re: 73cuda340] #1029321 07/20/11 01:18 AM 07/20/11 01:18 AM
Joined: Jan 2008 Posts: 553 DE Ply72rr mopar
Ply72rr mopar Joined: Jan 2008 Posts: 553 DE	Weak ignition will cause a miss or stutter under load.You said cap/rotor are new. Have you checked your plug wires,coil etc... If you have access to a old oscilloscope and can make it miss/stumble while loading against the brakes you could confirm or eliminate the ignition system as the problem. Good luck. A lean condition could make it pop out the carb but shouldn't backfire out the exhaust. If the timing chain was off a tooth you would not have a intermittant problem,it would run weak and like crap all the time I would think. Let us know what you find. Last edited by Ply72rr; 07/20/11 01:24 AM.

Re: Need help tuning my carburetor [Re: dusterbd13] #1029322 07/21/11 07:33 PM 07/21/11 07:33 PM
Joined: Jun 2007 Posts: 1,184 clarks summit pa 73cuda340 OP super stock
73cuda340 OP super stock Joined: Jun 2007 Posts: 1,184 clarks summit pa	It just hit 102,000 miles. My original guess was the ecu went bad, because I had to put a new one in a little while ago and it wasnt long after that the problem started; but last night I installed a new one and it's still the same. 1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip, (JA5) Silver Frost Metallic 1973 Challenger Rallye 340 1985 W150 Power Ram prospector 1986 Camaro IROC-Z 305 tpi

Re: Need help tuning my carburetor [Re: Ply72rr] #1029323 07/21/11 09:35 PM 07/21/11 09:35 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: If the timing chain was off a tooth you would not have a intermittant problem,it would run weak and like crap all the time my mistake, a slipped chain and or dampener would stay that way not magically go back & forth from functional to bad. Yes holler what it ends up being & I'll further guess coil or dist pickup live every 24 hour block of time like it's your last day on earth

Re: Need help tuning my carburetor [Re: RapidRobert] #1029324 08/07/11 09:46 PM 08/07/11 09:46 PM
Joined: Jun 2007 Posts: 1,184 clarks summit pa 73cuda340 OP super stock
73cuda340 OP super stock Joined: Jun 2007 Posts: 1,184 clarks summit pa	Still trying to figure this out. I just installed a new coil and it's still the same. The backfiring mostly went away when I reset the floats; it doesnt really do it that often anymore but its still there. The misfire is definatly worse though. 1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip, (JA5) Silver Frost Metallic 1973 Challenger Rallye 340 1985 W150 Power Ram prospector 1986 Camaro IROC-Z 305 tpi

Re: Need help tuning my carburetor [Re: 73cuda340] #1029325 08/07/11 09:52 PM 08/07/11 09:52 PM
Joined: Jul 2003 Posts: 1,212 Canton, Ohio Crazy68Dart pro stock
Crazy68Dart pro stock Joined: Jul 2003 Posts: 1,212 Canton, Ohio	What is your vacuum at idle and is the needle steady? Stock cam? Is the carb out of the box or have you tweaked with the PV and jets? 383, Hemi 4-Speed, AlterKtion, D60

Re: Need help tuning my carburetor [Re: 73cuda340] #1029326 08/08/11 11:11 AM 08/08/11 11:11 AM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: What I don't understand is with the advance unplugged it is at 34 total advance but it runs like absolute garbage and misses and backfires nonstop. With the advance hooked up it reads 52 total but runs a lot better (only misses and backfires every now and then) and theres no detonation. Might check rotor phasing/pickup gap as the vac can affects phasing/gap esp as it should not b acting up w 34 deg. post any news! live every 24 hour block of time like it's your last day on earth

Re: Need help tuning my carburetor [Re: RapidRobert] #1029327 10/02/11 07:26 PM 10/02/11 07:26 PM
Joined: Jun 2007 Posts: 1,184 clarks summit pa 73cuda340 OP super stock
73cuda340 OP super stock Joined: Jun 2007 Posts: 1,184 clarks summit pa	I found out the backfiring and missing were caused by the sockets on the plug wires going into the cap. They loosened up and some werent making a good connection so I just changed the wires. My new problem now is that if I try to just start up the truck and go it will stall unless warmed up. The truck will stay running but as soon as you put it in gear and give it gas it will stall and has a bad hesitation. Nothing else has changed to make it do this. It has an air gap intake and since there is no cossover I expected some drivabilty issuses during cold weather, but it will even do this on a 75 degree day. Any help is appreciated. 1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip, (JA5) Silver Frost Metallic 1973 Challenger Rallye 340 1985 W150 Power Ram prospector 1986 Camaro IROC-Z 305 tpi

Re: Need help tuning my carburetor [Re: 73cuda340] #1029328 10/02/11 09:38 PM 10/02/11 09:38 PM
Joined: Jan 2003 Posts: 541 chatham, Ilinois F fox super street
fox super street F Joined: Jan 2003 Posts: 541 chatham, Ilinois	You need to check the choke adjustment.

Re: Need help tuning my carburetor [Re: fox] #1029329 10/02/11 10:42 PM 10/02/11 10:42 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: You need to check the choke adjustment. plus pump squirt/float levels and especially if the jetting is lean live every 24 hour block of time like it's your last day on earth

Re: Need help tuning my carburetor [Re: fox] #1029330 10/03/11 05:21 PM 10/03/11 05:21 PM
Joined: Jun 2007 Posts: 1,184 clarks summit pa 73cuda340 OP super stock
73cuda340 OP super stock Joined: Jun 2007 Posts: 1,184 clarks summit pa	Quote: You need to check the choke adjustment. Truck has a manual choke and stalls no matter if the choke is on or off. 1973 Cuda 528 all aluminum Hemi, 4 speed, 3.23 Sure-Grip, (JA5) Silver Frost Metallic 1973 Challenger Rallye 340 1985 W150 Power Ram prospector 1986 Camaro IROC-Z 305 tpi

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