Im almost at my wits end on this engine.

Refresher:

Engine is a 90k mile original 400-2v in a 73 Dodge Truck. The engine lacks power and pops and backfires in the intake when attempting to accelerate,even under light acceleration.Has very little power,but will drive normally if you "baby" it.

The Dizzy Cap,Rotor,plug wires are all new,the firing order is correct on the cap and on the plugs. The plugs,although not brand new,have a nice normal dry brown color to them.Checked the timing and its correct.

Under advisement of someone,I replaced the Timing chain and gears,thinking this may have been the cause of the trouble. Once I did this I realized the old timing gears and chain were probably just fine.Put it all back together and the truck still pops in what sounds like the intake when attempting to accelerate.

Ive pulled the Valve cover on the drivers bank of the engine and the inside of the valve cover and the valvetrain looks VERY Clean... Not one bit of Sludge. Ive pulled the rocker shaft on the drivers side and removed and inspected the Pushrods on that side one at a time,theyre all straight on the drivers side.

I have pulled the valve cover on the passenger side,but ran out of light,so ill have to pull the rocker shaft tomorrow so I can inspect the push rods.

"IF" I inspect the pushrods on the passenger side and they all appear straight and normal,where else can I look to try and figure out whats causing this engine to run so poorly?

Could the cam have gone flat on a lobe? Stuck lifter? Bent Valve?

Any assistance would be greatly appreciated.

(1) vac leak (2) borrow another known good carb for a road test

Don't recall if you've verified that all lifters are going up and down through earlier posts?

No I havent verified the lifters are going up and down properly yet.I did go back out and pulled the Rocker Shaft off the passenger side and all the pushrods appear normal.

Im gonna install the rockershafts back on tomorrow and see if I can get someone to crank it over while I watch the rockers move.

If im not mistaken,watching the rocker movement will show if a lobe is flat,by the rocker moving very little...Correct?

If all that checks out,Ill button it all back up and pull the carb off the 360 on my 72 Fury Wagon(same carburetor) and see if that makes anything better.

Ill keep you all posted on my findings,and hope I can cure this issue. Thanks for the suggestions!!

Im racking my brain on this issue,and even though it probably wasnt necessary,I now know how to R&R a timing chain and gears on a BB Mopar.

Vacuum leak, Coil, ballast resistor, Electronic Control Module, and my personal favorite... some sender wire that's grounding out in the engine compartment somewhere can throw a false signal to the coil causing erattic timing (don't ask me how I know).

Well the ECM,ballast Resistor,coil and even the vacuum leak all seem pretty simple to R&R with known good parts.Ill check all these if everything else checks out ok...Again all the suggestions are very helpful thanks everyone!!

Its NOT a vacuum leak. When symptoms like this occur, its nice when it is that easy. When a popping up through the carb is detected, it is often something else. Exhaust is being forced into the intake. The cause is one or more worn EXHAUST lobes on the camshaft. During normal light duty cruise, cylinder pressure is low. The limited opening of the exhaust valves poses little problem. When you lay into the throttle, cylinder pressure increases. The cylinder cannot evacuate the exhaust as normal. The popping you hear happens when the piston is on its upstroke during the exhaust cycle. When any cam lobe is worn, the valve opens late, lifts less and closes early. In your case the piston is still rising. when the intake valve opens , the trapped exhaust gases are forced into the intake tract. this makes you lose power .
Remove the valve covers again and run the engine. Pay close attention to the rocker arms to each exhaust valve. Look for one or more to have less movement than the intake rockers next to them. You should find the problem there.

Try another carb that's really easy. I think its a carb/fuel issue.

Remove the air cleaner and watch down the carb for a squirt of fuel while you open the throttle. Sounds like a bad accelerator pump. No cost to try and easy to do. If not that bad power valve or its equivalent if not a Holley. Smooth running if you baby it is a clue.
Ron

burnt valve,IMHO

Collapsed Lifter or bent pushrod. Pull the plug wires off one at a time until you find the one that changes the sound. I had this happen to me last year on a 87 318 in a van while pulling a hill. I wasn't stomping on it, just driving it. It did exactly as you described. The lifter collapsed and the pushrod was stuck in the lifter. The motor only had 80,000 miles, 1 owner (me) and never abused.

comp test is in order first to see the cyls across the board
'
then a leak down test

had a couple do this,sure cant tune a bad valve/miss out of an engine with a tune up

Well I have taken a :40 second video of the engine running with the valve covers removed. I see about equal movement of all rockers,although if you focus on one particular rocker it appears the others arent moving.

If you guys will take a quick look at my video clip and tell me if the movement of the rockers is normal or weak,and maybe conclude whether I have a flat cam or not...This would be appreciated.

Link to the video:

http://www.youtube.com/watch?v=BxHTp6SuO68

They're moving alright, but that thing is hurtin for oil on top.

EGR valve is stuck open ...check it

The intake has an EGR Block off plate on it.

looking at the rockers they all seem to stop and go at times

looking at 1 it does it like you mentioned so I looked at a couple diff ones and it seems to do it on all of them looking one at a time

does look dry also

my vote is still on a comp test and burnt leaky valve or collapsed lifter

Ok so who's braniac idea was it that this issue could be a Vacuum leak? I want to thank you for that suggestion.

I was working on swapping the carb on the truck,had the known good carb pulled of my Fury Wagon and was ready to pull the carb on the truck.

It was then that I noticed the mounting bolts on the carb on the truck were VERY loose.

I tightened those back up and hooked everything back up and the truck runs MUCH better,still have some fine tuning to do but im figuring things out.

As far as the truck not having power...

Well it finally dawned on me that Im driving a HUGE truck and cant expect this thing to really haul A**. So I just have some personal adjustments to make on how this truck performs.