Ok, so my car was running great all day today. I was driving my car for 25 miles on the freeway at 3000 rpm at 60mph. Now, when I got off the freeway at the 1st street light, the engine starting running 400 rpm higher and I noticed the shifter shaking really bad. So I did a quick rev to try and clear any weirdness from the steady freeway rpms. No luck.

I drove it to my gf's house. When I got here, it would idle at 1300 rpm and it didn't sound very good, and like it wasn't firing on 8 cylinders. Could it be as simple as a fouled plug or plugs? I am leaving it alone overnight and will try an early morning repair. I was going to leave for a 50mile ride to a Chevelle Club meeting :(

It shouldn't be anything serious right?

Sounds like either the distributor came loose and the timing went advanced real far, maybe a vacuum line came off and you have huge vacuum leak. I have also had the secondary linkage stick open a bit.

Dave

Well I checked the distributor and it was tight.

Sounds like a serious vacuum leak to me.

If it's not a vacuum hose and or PCV hose that just came off i bet it's an issue with the mech adv in dist being stuck ,breaker plate in dist could also be stuck , or vac adv could have hung up .

Any one or combination of those things will cause the idle timing to be in mid 40s to in an extreem case be 50+ deg.

If thats whats happened it will increase idle and also make it run jumpy/uneven/kinda misfiring due to way too much timing at idle & or lower engine rpms just above an idle.

Scott

Ok guys, well after checking my timing, spraying soapy water everywhere trying to find a vacuum leak, and going crazy, I felt something was wrong internally with my motor. In the 90s my dad rounded off a lobe on a camshaft in this motor, so I thought something may have happened to my cam again (we replaced that bad one). As a gee-whiz, I thought I'd take the valve covers and watch the movement of the rocker arms with the engine idling to see if something was way out of adjustment or if there was damage to the cam. Thank Babe Jesus when I took off the passenger side valve cover I saw this!!

http://twitpic.com/36r0d and http://twitpic.com/36rme

My damn rocker nut had backed out and the rocker arm fell off! Is this the intake or exhaust valve?

Anyways, I took off the nut, cleaned everything, put locktite on the threads, and put it all back. Started her up and after some blue smoke for a bit, she ran great! I feel good I was able to diagnose it. I will be ordering a new nut asap as I hear once these back out, they're toast. Thanks to everyone here and at my Chevelle Club meeting this morning :)

Man ohh man did you get lucky ! ! I would watch it when ya put it back to make sure a lifter didnt go bad. You running solids or hydros....? Just a thought.

That was the intake valve.

Thanks Phil. What's the way to tell which valve is which?

The intake valves are inline with the intake ports and the exhaust valves are inline with the exhaust ports on the manifolds.

Thanks for shining a light on my dim valve brain. Ha. Anyone think my lifter could have been damaged or should I be ok as long I monitor the engine really carefully?

Sounds like you dodged a bullet....you might want to replace all the nuts or use the locking kind. Are you running a solid lifter cam..I noticed they were 840 heads so i assumed hi-perf application....good luck.

wilma

Trash the std nuts and invest in posi-locs. Std nuts always seem to come loose at one point.

...and if one came off completely chances are you might have a few more loose ones too.

I will replace them with the posi-lock nuts. And I'm not sure if I have a solid lifter or hydro. Is there a way I can find out by looking somewhere?

A solid lifter cam will have a definate "mechanical" or "metallic" sound....the hydraulic should produce no audible valvetrain "clatter"...the solid lifter cams were used on the hi-perf 396 and 427 engines...since you have the 840 heads, I assumed you had a solid cam. Perhaps others can explain this better...wilma

ps...you will want to know before you cahnge those lock nuts;)

I ran those same rockers on my 396 and the same thing happened even with poly locks. I won't run them again.

Yea I think I'm running a solid lifter cam. And damn Mark, that sucks these rocker arms back the nut out. Which rocker arms did you go with? Rollers have less friction which mean more power right?

Yea I think I'm running a solid lifter cam. And damn Mark, that sucks these rocker arms back the nut out. Which rocker arms did you go with? Rollers have less friction which mean more power right?

I went with Crane Golds. Better geometry and they hold the lash just fine.