Moparts
1970 440-6 problems
Posted By: Anonymous
1970 440-6 problems - 08/02/08 03:42 PM
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.
Posted By: DemonKyle
Re: 1970 440-6 problems - 08/02/08 03:45 PM
Whats the timing set at?
Have you tuned all three carbs?
Edit: Oops completely Missed it
Posted By: Anonymous
Re: 1970 440-6 problems - 08/02/08 03:55 PM
as I said in the first question the timing is set at 12 and 36 and yes the carbs are set
Posted By: jbc426
Re: 1970 440-6 problems - 08/02/08 04:52 PM
Sounds like a fuel control/float level issue to me. Did it just start doing it or has it always done it(dirt/contamination)?
Posted By: Anonymous
Re: 1970 440-6 problems - 08/02/08 05:31 PM
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
Posted By: DemonKyle
Re: 1970 440-6 problems - 08/02/08 05:43 PM
Sounds like the timing is off to me. Or fuel mixture.
Maybe loading up too much in one cylinder?
Posted By: postbody65
Re: 1970 440-6 problems - 08/02/08 06:13 PM
check your firing order and timing your airgap start on basics
Posted By: Anonymous
Re: 1970 440-6 problems - 08/02/08 06:20 PM
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.
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...
Posted By: Anonymous
Re: 1970 440-6 problems - 08/02/08 09:12 PM
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
Posted By: Challenger 1
Re: 1970 440-6 problems - 08/02/08 09:14 PM
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.
Posted By: Anonymous
Re: 1970 440-6 problems - 08/02/08 09:49 PM
we did an extensive check for a vacuum leak and found nothing
Posted By: anmracing
Re: 1970 440-6 problems - 08/02/08 10:00 PM
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.
Posted By: Anonymous
Re: 1970 440-6 problems - 08/03/08 08:55 PM
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.
Posted By: 69440
Re: 1970 440-6 problems - 08/03/08 09:05 PM
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.
Posted By: Anonymous
Re: 1970 440-6 problems - 08/03/08 09:12 PM
the vacuum advance is plugged. That was one of the first things suggested. Can you tell me about the power valve?
Posted By: anmracing
Re: 1970 440-6 problems - 08/08/08 08:43 PM
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.
Posted By: anmracing
Re: 1970 440-6 problems - 08/08/08 08:53 PM
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?????
Posted By: BHuey
Re: 1970 440-6 problems - 08/09/08 02:19 AM
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.
