283 popping thru the Carb on Acceleration?

I had my 55 out for a spin today, it has developed a pop thru the carb on medium to hard acceleration,if I feather it slowly no problem but when I get on it a little it pops pretty good.does this sound like a intake valve?
What do you think it might be?
thanx,xtra.

 

Of course, it could be any one of a number of things, but since it's easy to pull the valve covers, run it with them off and see if any of the rocker arms are barely moving, signifying a worn cam lobe.

 

definately worn cam lobe, identified with valve covers off and as said previously, it wont be moving up and down much, or as much as the others.

 

Hi again....
If it has been setting a while it could be as simple as a chunk of carbon lodged in the intake valve holding it slightly open....
Take a windex bottle [with water] in it and spray it in the carb top as you rev the mill up...it may take a few shots to steam it out....Good luck.....

 

Easiest way to find it is to pull off one spark plug wire at a time and drive it. When you pull off the right one it will stop popping. Just make sure you put the good ones back on.

 

It'd be worth checking the dist cap and plug wires first on this since it's ok until under load. Increased load means it takes more voltage to fire the plug, more voltage means a marginal ignition part will act up only under load. Could just be crossfiring in the cap.

 

i'm no mechanical genius, but i agree with bigdog. i'd try to look at the easy stuff first, like making sure your ignition system is up to snuff and when that can be taken out of the equation, then move on to what the rest of the guys have mentioned...

just my two cents
-s

 

If you determine that it doesnt have a flat lobe on the cam, do a compression check on it to see if a valve is leaking.

 

Change your oil...sounds like you have a collapsed or collapsing lifter.

Flat lobes on cams will do what you say...but the problem doesn't just sneak up on you... if the car isn't run a whole bunch.....and possibly even runs a little rich, your oil is probably gased down and thin and has lost it's viscosity.

 

Sounds like a bad cam.

 

don't forget about bent pushrods

 

I would look at plug wires first. If it spits and pops outa the gate and under a load or going up hills 9 times outa 10 its the wires.

 

I had this same problem with my motorhome (1987 460 w/4bbl).
Because I hoped it was something simple it took me months of BS before a simple compression test that I should have done to begin with revealed the obvious...a bad intake valve seat.

It would idle OK, I could accelerate with no load, but as soon as I put it in gear to try and drive it it would pop and backfire.

Do yourself a favor, do a compression test first, then go from there.

 

check timing & your distributor cap & rotor.
JimV

 

Wait for Squirrel's answer, but it sounds like bad gas or lean condition to me. It it runs OK except when you accellerate I doubt it's real serious. Do the compression check to make sure.

 

Or a bad coil.

Eliminate one at a time and you'll find it.

Fuel tank to the engine.

Coil to the engine.

Then mechanical. Everything has to follow a path. Good luck

 

Flat exhaust lobe (little to no valve action on exhaust rocker, seen w/valve cover removed), crossfiring wires (look at em in the garage with the lights off perhaps while someone carefully power brakes it for a load), crossfiring inside the dizzy cap (carbon tracking), head gasket blown between 2 cylinders (2 low compression cylinders right next to eachother), lean misfire (worse when cold?), etc

 

Thats what I was gonna say!! FUNNY!

 

Any Updates?

Keep us posted as to what you discover is giving you problems.

 

Here's what we found & what we did.

First off changed the oil & filter, I think it did break down a little even though it didnt have 500 miles on it.
Found a hose off the back of the carb, and one plug wire was not all the way on the dizzy.

We also did a compression test and found compression around 140 per hole.
The highlight was putting in the Petronix Flamethrower dizzy, timed it,and then tuned the carb and it seems to run much much better, a whole lot smoother,idles nice.
As far as a big difference in performance, about the same and I didnt expect the flamethrower to make much difference there.

So It runs pretty good, I am hoping to get body & paint work done soon and interior next year.

Thanx again for all your tips guys they were helpful and very useful!

I'd post a couple pics but still having resizing issues! I resized them and they still are to big??