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1970 440-6 problems #98484 08/02/08 11:42 AM 08/02/08 11:42 AM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	when I accelerate lightly I get a surge and when I come off the highway I get a lot of backfiring through both exhausts. I have glass packs, Taylor plug wires, Auto light 85 plugs, Mopar pointless distrbutor, timing is 12 and 36. No vacuum leaks but may have an exhaust leak. Any ideas? At 65mph the car seems to run great. I have about ninty miles on the car right now.

Re: 1970 440-6 problems #98485 08/02/08 11:45 AM 08/02/08 11:45 AM
Joined: Jan 2005 Posts: 3,312 Marine Corps Base Hawaii DemonKyle USMC LCPL
DemonKyle USMC LCPL Joined: Jan 2005 Posts: 3,312 Marine Corps Base Hawaii	Whats the timing set at? Have you tuned all three carbs? Edit: Oops completely Missed it Last edited by DemonKyle; 08/02/08 12:00 PM.

Re: 1970 440-6 problems [Re: DemonKyle] #98486 08/02/08 11:55 AM 08/02/08 11:55 AM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	as I said in the first question the timing is set at 12 and 36 and yes the carbs are set

Re: 1970 440-6 problems #98487 08/02/08 12:52 PM 08/02/08 12:52 PM
Joined: Mar 2007 Posts: 3,285 West Coast, USA jbc426 master
jbc426 master Joined: Mar 2007 Posts: 3,285 West Coast, USA	Sounds like a fuel control/float level issue to me. Did it just start doing it or has it always done it(dirt/contamination)? 1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's 1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)

Re: 1970 440-6 problems [Re: jbc426] #98488 08/02/08 01:31 PM 08/02/08 01:31 PM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	always do it and I just took the three carbs off and cleaned them inside and out. They have ninty miles on the and now they have four miles on them so I do not think it is a fuel issue

Re: 1970 440-6 problems [Re: jbc426] #98489 08/02/08 01:43 PM 08/02/08 01:43 PM
Joined: Jan 2005 Posts: 3,312 Marine Corps Base Hawaii DemonKyle USMC LCPL
DemonKyle USMC LCPL Joined: Jan 2005 Posts: 3,312 Marine Corps Base Hawaii	Sounds like the timing is off to me. Or fuel mixture. Maybe loading up too much in one cylinder?

Re: 1970 440-6 problems [Re: DemonKyle] #98490 08/02/08 02:13 PM 08/02/08 02:13 PM
Joined: Aug 2005 Posts: 216 clearwater,fl P postbody65 enthusiast
postbody65 enthusiast P Joined: Aug 2005 Posts: 216 clearwater,fl	check your firing order and timing your airgap start on basics 4592918-IMG_0029.jpg (120 downloads) [url=http://www.postbody65@yahoo.com

Re: 1970 440-6 problems #98491 08/02/08 02:20 PM 08/02/08 02:20 PM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	maybe disconnect front and rear carb.-vehicle should run smooth on center carb.-if it does then you have a problem with one of the outboard carbs.

Re: 1970 440-6 problems #98492 08/02/08 04:54 PM 08/02/08 04:54 PM
Joined: Feb 2004 Posts: 7,196 Harrisburg, Pa. screamindriver master
screamindriver master Joined: Feb 2004 Posts: 7,196 Harrisburg, Pa.	Good Lord don't disconnect the secondary carb linkage...They'll open up and you won't be able to close them...If the surge is RPM specific it might be the distributor mechanical advance curve in action...Or it could be a slight lean surge and the center carb needs bigger jets.. No way to tell sitting here for sure.. Is the exhaust poping or really cracking ???? Exhaust leak upstream will sometimes pop like that or simply the glass packs are doing their thing...

Re: 1970 440-6 problems [Re: screamindriver] #98493 08/02/08 05:12 PM 08/02/08 05:12 PM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	that is interesting because I was wondering if the glass packs were the popping I was hearing. It is more a poppomg than a backfire and I do have an exhaust leak where the exhaust manifold connects to the exhaust, just have not had a chance to fix that yet

Re: 1970 440-6 problems [Re: screamindriver] #98494 08/02/08 05:14 PM 08/02/08 05:14 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Quote: Good Lord don't disconnect the secondary carb linkage...They'll open up and you won't be able to close them...If the surge is RPM specific it might be the distributor mechanical advance curve in action...Or it could be a slight lean surge and the center carb needs bigger jets.. No way to tell sitting here for sure.. Is the exhaust poping or really cracking ???? Exhaust leak upstream will sometimes pop like that or simply the glass packs are doing their thing... Sounds lean for sure and the back fire could be from being lean or a vacuum leak. Doubt if it has anything to do with what kinda mufflers you have. Could be the exhaust leak you have at the manifold causing the back fire on decell. Last edited by Challenger 1; 08/02/08 05:23 PM.

Re: 1970 440-6 problems [Re: Challenger 1] #98495 08/02/08 05:49 PM 08/02/08 05:49 PM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	we did an extensive check for a vacuum leak and found nothing

Re: 1970 440-6 problems #98496 08/02/08 06:00 PM 08/02/08 06:00 PM
Joined: Jun 2008 Posts: 120 Arizona A anmracing member
anmracing member A Joined: Jun 2008 Posts: 120 Arizona	It sounds like a lean issue... The popping is cool air sucked in from the exhaust manifold leak on decel is my bet.... Glass pack sound awesome and they will pop on decel too..... I would love to hear a sound clip of your car.

Re: 1970 440-6 problems [Re: screamindriver] #98497 08/03/08 04:55 PM 08/03/08 04:55 PM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	at this point nothing is clearing up the problem could you explain to me what a bad power valve in the center carb would do.

Re: 1970 440-6 problems #98498 08/03/08 05:05 PM 08/03/08 05:05 PM
Joined: Oct 2007 Posts: 1,064 Washington 6 69440 super stock
69440 super stock 6 Joined: Oct 2007 Posts: 1,064 Washington	This is just a shot in the dark, but try disconnecting the vacuum advance, but be sure to plug off both sides. If you see any difference, then you can be safe to assume it's within the dist.

Re: 1970 440-6 problems [Re: 69440] #98499 08/03/08 05:12 PM 08/03/08 05:12 PM
A Anonymous OP Unregistered
Anonymous OP Unregistered A	the vacuum advance is plugged. That was one of the first things suggested. Can you tell me about the power valve?

Re: 1970 440-6 problems #98500 08/08/08 04:43 PM 08/08/08 04:43 PM
Joined: Jun 2008 Posts: 120 Arizona A anmracing member
anmracing member A Joined: Jun 2008 Posts: 120 Arizona	If the PV is bad you would find that your plugs would foul out pretty fast and would be blowing black smoke. It could possibely cause a back fire through the exhaust due to it running a lot richer than it should. That combined with a possible crossed wire could cause a huge exhuast backfire that would wake up the dead...... To answer your question, what it does is the diaphram opens as the vacuum drops when pressing the excelerator causing it to richen up. If you put a plug in place of a PV then you better changer the jets. Boost them up 10-12 sizes bigger.

Re: 1970 440-6 problems #98501 08/08/08 04:53 PM 08/08/08 04:53 PM
Joined: Jun 2008 Posts: 120 Arizona A anmracing member
anmracing member A Joined: Jun 2008 Posts: 120 Arizona	Quote: when I accelerate lightly I get a surge and when I come off the highway I get a lot of backfiring through both exhausts. I have glass packs, Taylor plug wires, Auto light 85 plugs, Mopar pointless distrbutor, timing is 12 and 36. No vacuum leaks but may have an exhaust leak. Any ideas? At 65mph the car seems to run great. I have about ninty miles on the car right now. When you say it surges, what do you mean???? When you give it gas it doesn't do anything (it bogs)and then it feels like it catches and gets moving again?????

Re: 1970 440-6 problems #98502 08/08/08 10:19 PM 08/08/08 10:19 PM
Joined: May 2005 Posts: 126 Groton, MA. BHuey member
BHuey member Joined: May 2005 Posts: 126 Groton, MA.	Does your car have power brakes ? If so don't overlook the vacuum booster, it can cause a surge condition if the diaphram is leaking, brakes can feel OK but vaccuum on a gauge will be low and fluctuating. 70 Challenger R/T Conv. 66 Vette 427 Coupe 61 Vette FI Roadster

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