4 Barrel

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The problem: on initial startup engine runs rough then smothes out to a nice idle. On acceleration acts like it's flooding and or dropping a cylinder. The cam lift: 294 in., 441 ex. duration: 276 in., 288 ex. I know that's a little much but I like a little lope.
 
The problem: on initial startup engine runs rough then smothes out to a nice idle. On acceleration acts like it's flooding and or dropping a cylinder. The cam lift: 294 in., 441 ex. duration: 276 in., 288 ex. I know that's a little much but I like a little lope.

Did you change the cam the same time you added the AVS 600?

If so there is your problem.
 
Where is your initial timing set? Oftentimes, a carburetor issue is not a carburetor issue, but a timing issue. That camshaft is going to want a good bit more initial timing than stock.
 
D dart were a rare and significantly different engine design for competition
and not very comparable to the general production engines. Particularly
the low compression versions.

In my opinion a 600 CfM carb would be plenty for his
combination.
 
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D dart were a significantly different engine design for competition
and not very comparable to the general production engines. Particularly
the low compression versions
Yeah they were radical beasts for a 273.
 
The problem: on initial startup engine runs rough then smothes out to a nice idle. On acceleration acts like it's flooding and or dropping a cylinder. The cam lift: 294 in., 441 ex. duration: 276 in., 288 ex. I know that's a little much but I like a little lope.

Something isn't right in your cam specs, but I ran a stock 340 cam with 340 intake and AVS (port mismatch) on a low comp 273 back in the 1990s. Never had any drivability problems.
 
Dual plane or single plane intake? More info needed on the cam specs.
Do the idle mixture screws control the idle: make the engine stall when screwed in; run rough when backed out.
 
I installed the cam and dual plan Perfomer at the same time. I'm not sure what all the cam specs mean.
Valve settings intake .000, exhaust .000
Lift: the same for intake & exhaust @ cam 294 @ valve 441. Advertized duration int. 276, exh. 288
Cam timing: int. opens @0 BTDC, closes @38 ABDC, lobe center 109 int. duration 218.
ex. opens @ 53 BBDC, closes @-5 ATDC, lobe center 119 ex. duration 228.
I'm also checking for a vacuum leak.

Thanks
 
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I'll say it like this: Whatever the issues are, cam, timing, carb setting, bad valves, hole in the piston.... 600 cfm is not to much carb for your engine.
 
Looks like his cam is:

Lift: 441 / 441
Duration: 276 / 288
Lobe Centers: 114

________

Solid lifters, with adjustable rockers?

Or

Hydraulic lifters with stamped steel rockers with the mopar rocker shafts.

______

If you have mechanical adjustable valves, should have around .010 - .012ths valve lash, not .000

If it is hydraulic lifters and adjustable rockers then you need around 3/4 turn after zero lash, for the pre-load.
 
The problem: on initial startup engine runs rough then smothes out to a nice idle. On acceleration acts like it's flooding and or dropping a cylinder. The cam lift: 294 in., 441 ex. duration: 276 in., 288 ex. I know that's a little much but I like a little lope.
Rough running when cold is a choke/ choke pull off adjustment issue. Accelerating smoothly or flooring the pedal? Tough to diagnose over the internet.
 
OK, then you need to set some pre-load on those hydraulic lifters with the adjustable rockers.

Top Dead Center up on compression stroke. Go to zero lash by tightening the rocker while spinning the push rod with the other hand. When the pushrod gets some drag on it, then go another 3/4 turn for the pre-load. On the 2 valves.

Then it's on to the next cylinder to set those valves and so on. Spark Plugs out.

This should help it to run better just getting the valves set right in itself.
 
I did that prior to intial startup. When I tried to start, there was no compresion. I backed out adustment one full turn and it started and ran @ 3000 for 25 minites. I have built a large number of engines, in my over sixty years working on cars and trucks, but I have no idea what was going on with that lifter adustment. I'll go ahead and go over it again as you suggest. I did find a stripped carb mounting thread which possibly is causing a vacuum leak.
Thanks a bunch!
 
It takes a light touch on feeling where that Zero Lash point is as you are spinning those pushrods by hand, and turning down the the adjustable rockers.

The lifters will not be pumped Up after the engine has sat for a period of time.

The thing is the upper disc in the lifter is topped out, this is the point where you want to start with Zero Lash, it is a light touch because the lifter is not filled with oil yet. So back off the adjustable rocker, then slowly work your way down to zero lash.

Then at Zero Lash with the lifter disc at the top, then you adjust the rocker down 3/4 of a turn to get that upper disc down into the lifter a bit so it can float and "actually" be adjusted by the engine oil pressure as the engine comes to life.
 
Are we to assume this is a low compression 273 (not a Commando)?
I believe Toolmanmike is running a high compression 273 with a Holley 600.
 
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