I have a 69 charger se 383 with a/c fully restored and am haveing troubles with the engine.It has kb pistons,stock 440 closed chamber heads,purple camshaft 284,480,mopar dual plane intake,electonic ignition conversion,edlebock 750 cfm carb.At low idle it runs good engine shakes a bit,if i open carb ever slightly to bump idle it struggles then revs no matter where timing is.Cant increase idle slightly enough to increase so i can use a/c at idle without going from nuetral to drive without slamming gears.when its warmed up the engine will increase on its own sporatically like a vacuum leak.When driving the car it serges down the road like cam loaping even at higher rpm (2000).When i stomp on it it takes right off and when i pull up to a light it serges.It doesnt seem to be predictable.Now here is what i have checked.Vacuum is low and bouncy 6-8,plugged all vacuum lines,set timming everywhere.replaced plugs 3 different brands,new distributor (mopar),new control module,new dual ballast,replaced intake 3 times,once with just pan twice with paper on both sides of pan with high tack,switched manifold with stock and mopar,switched carb to holley,checked firing order several times,new coil,compression is 140 on all holes at 4500 ft of elevation,2 different sets of wires.When i installed the cam i lined up the marks but did not degree.Any thoughts
help
- Thread starter greek
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RustyRatRod
Well-Known Member
Sounds like a vacuum leak. I think you nailed it. Some will say to use carburetor cleaner to spray around the carb and intake but don't. That's dangerous. Get a small squirt bottle with water and spray around the carb base and intake gaskets and where any vacuum lines or hoses attach. When you find it, you'll know it.
It acts like a vacuum leak but after changing gaskets a few times with no resolve the chances of it being manifold after tring everything short off welding it to the heads makes me think its something else like cam timing
RustyRatRod
Well-Known Member
Does it have power brakes?
I had a similar issue with the same Edelbrock carb. I bought the calerbration kit and changed all jets, metering rods, and springs and tried every combination possible but never did get the stumble out. I put a used 850 double pump Holley on and have never looked back. The Holley really woke my 440 up too!!
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I think RustyRatRod may be on to something. Low manifold vacuum in the 6-8" range is an indication of a major leak. If you have P/B plug the line to the booster and watch the vacuum gauge.
just an update on vacuum leak possibility.Brought a smoke machine in and guess what,no leaks anywhere.Now back to square one.The vacuum readings were done with all vacuum lines plugged.Just last night after warming it up i pulled the fuel line off the carb and the gas was very hot,possibly boiling gas issue?As far as carbueration it does the same thing with a holley 600 vac secondaries that works perfectly on another vehicle
The other question that arrises about the hot gas possibillity is that it would not affect vacuum,nor would it make it not idle adjustable in small increments when it is cooler.The biggest stumper in this is that the vacuum readings are low yet there appears to be no leaks anywhere in the car after doing the smoke test.The cam is not that big
Jim Bob The Dancing Bear
Well-Known Member
Fuel pump? It seems like there have been a rash of fuel pump rods wearing out. Clogged filter or lines? Dry rotted rubber hoses sucking in air?
How did you do a smoke test? I've not heard of this. Was there any problem on either intake manifold getting the intake bolts to line up with the threaded holes in the heads? (Wondering if the heads or block surfaces were cut excessively, causing a mismatch with the intake.)
RustyRatRod
Well-Known Member
If there are no vacuum leaks, I would suspect low initial ignition timing. Also another source of a low vacuum signal.
Thanks for all the input,the smoker blows heavy smoke into any vacuum line and finds any leaks,another possibility that I am persuading is fuel boil especially on this edlebrock.the bowls are on the sides as apposed to front and back'and the heat transfer ports are not plugged.i noticed on my stock manifold underside when I took it off the paint on the transfer port was very brownish from heat,with less than 10 miles on the engine.The port runs the same direction as the bowls.the underside of the carb is also browning,which indicates a lot of heat,no heat spacer also.i have the stock exhaust manifolds with the heat riser valve,possibly adding to the problem.keep in mind also our great fuel is 85/15 ethanol.in the edlebrock manual it addresses this issue having drivability and idle issues because of the internal venting spilling into carb.the step up rods have lose springs for low vacuum but I may put the 5 and under springs in it leaning it at idle,also lowered floats to allow for more fuel expansion.tommorow I am going to block ports,wire open riser,try a 750 Holley because it does not have step up rods,bowls run opposite ports,heat space.am I nuts any thoughts
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