i have a 91 5.0 w/ 88,000 miles. i havent done anything but a tune up so far, but noticed that the spark plug in cylinder#7 was drenched in oil. and upon heavy acceleration the pipes are coughing smoke. however very little to no smoke at idle. i havent got a compression check yet, and have heard a couple ideas of what the problem may be....valve spring, valve, and piston rings. somebody told me to take off the oil cap, press my hand on it firmly for a few seconds to check for "blow-by". i didnt feel much if any, but it did lower the idle by 100rpm or so w/ the cap off. can anyone help? any ideas?

mods on car are H-pipe w/o cats, flowmaster cat-back, 65mm edelbrock/bbk t/b, k&n filter, short throw shifter, aftermarket clutch upgrade of some sort.

 

taking your oil cap off while the car is running, creates a metered air leak... thats why your RPMs dropped

FWIW...

Blue smoke = Burning Oil
Black Smoke = Excessive fuel
White smoke = Steam (water in the exhaust) can also be caused by a blown headgasket

Blue smoke while:
Acceleration = Bad piston rings
Engine Deceleration = Worn valve guides
Cold startup = Valve seals

(valve springs don't make you burn oil)

 

yeah the smoke is only under acceleration. i am thinking of just having the block punched to a 306 if it is the rings. would i have to purchace new pistons as well or could i just buy rings? thats for ur help.

 

you really need to get new pistons when you go overbored. ive seen someone use a different ring set, just to come out of their rebuild with a motor that had piston slap like a m'fer, and in the end it ruined the block.

also, get the pistons first, and have the machine shop balance your rotating assembly, and match bore the block TO the pistons.

due to manufacturing tolerances, a .030 piston, may not actually be 4.030"