340 tunnel ram issue

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sups2nick

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i have a 1973 dart with a mild built 340 and 4 speed. the 340 has a weiand tunnel ram setup with dual holly 4brrl's. i don't know all specs on motor because i did not build this car and previous owner got it in on a trade and i got it off him, you know the story. anyways my issue is that the car ran great when i got it but lately now i cant get it to do much at all. the car will start and run but will seem like it is missing and when you go to give the car gas it will pop and stumble and sometimes backfire and sometimes backfire from the front carb on the tunnel ram. i have checked the plugs and changed them already and also tried to play with the timing. another weird thing about my issue is it seems like when i mess with it and i think it's about right ill test in neautral and rev it no real issues so i go to drive the car and as soon as i let clutch out fully and goto give it gas it will do same as before back to backfiring, quiting, missing. just seems like anything rolling over 1k rpm has issue. i am lost and getting annoyed with it haha. i need some help please...
 
Check where the intake is bolted to the heads and under the carb's to check for vacumn leaks. Check to make sure there are no open ports or cracked vacumn hoses on the motor. Do this while it is running and you might want to rev it up a little.
 
you probably need to do some tuning...

check the plugs...check the plug wires...check the timing..

the carbs...look down them and see if the acelerator pump is working...and then check the adjustment on them...

you dont say what kind of carbs they are...double pumpers or vacuum secondary...

double pumpers check all 4 acelerator pumps are working and adjust them right
 
could be..
xcelerator pump diaphram bad=lean on take off=pops out of carb

ignition

power valve blown 'old holleys'

what kind of compression does this thing have?

will it go/rev ok if you baby it?

does it surge at cruise?
 
If you use carburetor cleaner to check for vacuum leaks, you may as well just use gasoline in a spray bottle. That's the most dangerous advice to give someone. Don't use anything flammable to check for vacuum leaks. Use water in a spray bottle. Trust me, you'll KNOW if you hit a leak.
 
checked plugs, changed plugs, same issue. and it wont go at all down the road i am lucky if i can move it to and from my garage. it will idle still but seems like still missing, but as i stated before anytime you go to let clutch fully out and give car gas "1k - 2k+ rpms' it will spit and sputter and jump hop and stop, backfire you name it! if you dont try to move car it will do about same when giving it gas off and on. but sometimes it will seem like its fixed and you go to move it and back to square one. i will get carb info tomorrow and also test for vac leaks.
 
whats your initial timing set at?,what carbs do you have and what size squirter?check to make sure the accelerator pump is working.......
 
i dont hear any weird pings or knocks / noises. but i dunno? i am going nuts over it about to either pull intake and replace it and carb and do away with tunnel ram or i am about to sell car and be done messing with it. i just dont know why it wont even drive down street yanno? and that is what makes me so annoyed. i am going to check plugs, wires and also for vac leaks yet again tomorrow and also get carb info and spray them with cleaner.
 
might have to clean carbs, some dirt in the jets would make it run like crap under load, at idle no load
 
id really hate to see you throw in the towel over something that could only a tuning issue.i run a t-ram on my car and it runs well.you say it ran good when you first got it......as in no hesitation,good low end,tire burner?id really start by checking your initial timing.......
 
Do you have points or electronic ignition? Point gap wrong will do this. Bad condenser can cause this kind of weirdness too.
 
Back to basics. Break it down. It ran good when you got it. It started running bad when?
Did you get a back fire on a shift and then it started running bad? Did it run great one day and the next day nadda? Did you swallow a bird or small child at 7 grand?
You have Holley carbs, it could be something as simple as a blown power valve or a vacuum leak. What type of ignition system? Bad points? Bad ballast resistor? The tune up problem you're having doesn't really care if you have a two barrel carb or eight strombergs on bathroom plumbing. Just relax and work through the basics. You'll be glad you did.
 
msd blaster 2 coil, hei msd dist, msd street fire wires 8mm, and it ran fine no issues untill one day. ex: drove it all day no issues, parked next day went to start car and noticed this. all i have done so far is check plugs, check wires, and play with timing and i did timing by ear not with a gun. prev owner told me he just replaced plugs and they are autolite's and he said he used short plugs not long ones that were in it before. i have not tried to change plugs since they are new and if it were plugs why would it drive good one day and not next? wouldnt it do it from when he changed them to new plugs?
 
pull the plugs and see what they look like. Were they the same heat range as before?
 
StrokerScamp said:
If you use carburetor cleaner to check for vacuum leaks, you may as well just use gasoline in a spray bottle. That's the most dangerous advice to give someone. Don't use anything flammable to check for vacuum leaks. Use water in a spray bottle. Trust me, you'll KNOW if you hit a leak.
Click to expand...


I use starting fluid, if it does catch fire, it burns so fast it won't light anything else!

8)
 
today i started back to basic's since i had time to calm down and cool off about my issue. so i plugged plugs and they looked fowled and covered in black so i changed plugs from autolites to ac delco rapidfires. i fired car up and it was woken up and issue seemed to be gone, i reset time, and i then cleaned carbs with carb cleaner. anyways issue is now resolved and car is running pretty good i must say. i however now have a issue with my clutch but ill post that in the transmission section haha.

thanks, nick
 
Just from what I was reading, it sounded like the plugs were changed, something about short to long plugs(?). Could be the heat range got screwed up on the replacements. Ran good on first day but died on fire up the next day. Not gospel, just what I thought these old eyes saw. Keep an eye on them plugs for a few days and see how they do.
 
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