Engine Missing

[Roger S.]

My engine, 1973 L-82 w/ automatic, has started running a little 'rough' and has less acceleration. I changed the rotor, cap spark plugs. The idle is 1000 rpm, the timing is 21deg & the dwell is 30deg. After installing the new items it still is running rough. I took the plug wire off the distributor one at a time. There was no speed change when #1 and #4 wires were removed. I put new wires in for these two cylinders. Even after the new wires there was no speed change when #1 & #4 wires were removed. I removed the valve cover on the drivers side and the valves for #1 cylinder were moving as the other three sets of valves. I checked the #1 cylinder for compression and it was 135, similiar to what was checked about three years ago.
Any ideas as to what is wrong or things to check/do???
Roger

[Craig S.]

Re: Engine Missing

Roger - I would do a leak down test vs compression to evaluate the health. In addition, I would check for lobes going away on the cam, remove the valve covers and check the lift on each valve for uniformity. Frequently, when a cam goes away, lobes start wearing out after the surface hardening goes away and they wear rapidly. Frequently the symptoms you describe can be caused by camshaft wear.... Craig

[Clem Z.]

did you check the plugs on #1 and#4???? *NM*

[Roger S.]

Re: did you check the plugs on #1 and#4????

With the old plugs and wires in #1 & #4 appeared not to be firing.
Changed the plugs and #1 & #4 plugs still don't appear to be firing. Put new wires on #1 & #4 and there was no improvement.
I have not verified that each plug fires. Do you just remove the plug from the head and hold it against the exhaust manifold to look for a spark?

Roger

[Rob Dame]

Re: did you check the plugs on #1 and#4????

Check for vacuum leaks where the intake meets the heads near those cylinders and around the base of the carb. Rob

[Clem Z.]

Re: did you check the plugs on #1 and#4????

if the wires were bad it could cause the plugs to foul even if the plugs were new. pull them out and make sure they are not black

[Roger S.]

Re: did you check the plugs on #1 and#4????

The plugs looked good. The compression test showed #4 cylinder with 0 compression. I assume since the plugs look good that I have a valve problem. I will try to figure out which valve.
Roger