Hey,
I have a 68 dodge charger w/383 motor, it has a rv cam,1"7/8 primary hooker headers, in line edelbrock 6.5 lb. fuel pump, new pug wires,plugs,distributor,1406 edelbrock carb, painless wiring harness all items new. Motor is new w/2300 miles and trans is a 727 TCI 3 sp auto on colum. Having trouble with launching: idle-5000rpms seems to stumble like its starving for gas or timing at 3500-4000rpms in 1st gear. have tried every combination of jets,springs,rods in the carb. getting 15 lbs of manifold vac. at idle with no change, tried advancing timing from 6degrees to 20+ with no luck. Have had 3 different distributers on it including electronic, 5 different mechanical and electric fuel pumps, it has a new gas tank and sending unit, new fuel lines and filter. Tachs out fine if I start at 2500-3000rpms when moving but not from a stand still. But it does have a stock iron intake manifold with the four holes under carb. Any advice? Intake leaks possible?

 

I would try and borrow a carb from someone. If for no other reason as to eliminate it as a problem

 

I'd be thinking torque converter, from how it reacts at the different R.P.M.'s.

 

Have you checked fuel pressure at full throttle? Might be starving for gas

Rig a voltmeter to your ignition supply voltage and make sure it's getting good voltage. Without knowing the condition or type of wiring, you may have a problem with the 'ol bulkhead connector, or even an ignition switch going south

What does it do "out of the throttle? If it clears up, this kinda indicates fuel/ ignition as opposed to something like really weak valve springs, or a pushrod/ rocker combo that is holding the valves open or causing early float.

So first thing I'd do is "rig" a fuel pressure gauge, even if temporary

If that checks out, a carb swap IS a valid step, because it might at least change the symptoms.

Any chance, something simple, a dodgy coil, bad coil wire, dirty cap, bad wire/s to the plugs, or just bad plugs?

Any chance of a big restriction in the exhaust?

Headers? Uncork 'em and see if it changes the situation

 

yes have had 2 holly 600 carbs and 2 600 edelbrock carbs on it with every jet and spring/rod combination and nothing seems to work. Have 1"7/8ths primarys hooker headers long tubes, tried 2 coils a normal and a accell high spark no luck, have 2"1/2 in exhaust with flowmaster 40s no cats. have the fuel pump (edelbrock 6.5 lb electric pump wired into ignition new voltage regulator, have tried to wire it like painless diagram says will run different but wont charge have a externaly reg. dual field alt., also found that most of the system is grounded at contacts with key off alt. fields volt reg. terminals and ballast resister contacts. Is this correct when the key is off? I'm leaning towards a electrical issue but not sure...any and all suggestions will be tried to fix this problem.

also just installed a weiand alum. intake 0-6500 stock height.

 

ran PERFECT in the rain no issues what so ever temp stayed at about 165 going to try a seperate trans cooler instead of being on the radiator. possible trans fluid getting to hot and not letting it go like it should????

 

changed filter and trans fluid, the old fluid w/1000miles on the new TCI 727 it looked very dark and burnt also found a lot of shavings in pan and a cap looking thing that fell out when i took the filter off. TCI has no idea where or what that cap is for. It still does the same thing AFTER driving it 25mins or so after warmed up. but ran perfect in the rain the other day. going to try a trans cooler. I think its a tranny problem... Any othher advice?
Thanks

 

trans rebuilt by TCI they found a bad sprag in it but still having same problem, what about the differential??? temp it was 140degrees on bottom of case checked w/lazer gauge after a 20min ride at 70 on interstate? is this normal and around turns it seems to have a vibration like the diff(2.76 open) could it be the diff holding it back or a bad axle berring or gears??? only having trouble at take off 0-4500rpms in first only no trouble in 2 or 3 kicksdown good 3-2 have no idea revs perfect in park nutral 2,3,drive except 1st.....

 

A MISS will usually manifest itself under heavier and heavier load, IE run good in 1st, less well in second, worse in 3rd, etc

Is it actually missing, or more "bogging?" Might just be too much throttle for the RV cam and high rear gear

I don't know why you are running an "RV" cam. For me, any street machine that deserves a BB especially with headers AT LEAST should have the equivalent of the old Road Runner/ Super Bee cam, and maybe more.

One thing I'd do is CONFIRM that your timing marks are correct using a piston stop, then degree (or buy timing tape) so you can tell what the timing is ACTUALLY doing. I'd run more advance, and AFTER you confirm the timing marks, set the total mechanical timing (no vacuum) to 35-38 or so, then back it down a little if it wants to detonate.

 

140 on the temp is good, some may say too cool, but you certainly aren't over heating it.

I was about to say: measure lobe lift at the push rod to confirm no flat lobes, confirm dist isn't off a tooth, valves adjusted properly? , but a perfect run in the rain confirms that is all well.

you did everything under the sun and then some. I would measure coil tolerances, and resistance in wires.. make sure intake air isn't being overheated by header?

Sorry i don't have more.. You got me stumped... need to hear it...