Where did my power go?

[GotSomeRust]

I went to the drag strip this weekend. My car ran 11.2s two weeks ago. This weekend it was running high 11.6s to low 11.7s. The only thing I did to the car between trips to the track was change the oil, charge the battery, & adjusted the tranny brake. I'll confess that I pulled a bonehead move and tried to start the car with the carb cap still on. I only did it once. The car runs OK, it's not right. Why did I lose 4.5 tenths? Car info and things I've tried are below. The only other thing, is that 2 weeks ago I was getting a puff of smoke sometimes when lifting off the gas at the end of the quarter (exhaust guides maybe going bad).

Car info:
1983 Cutlass
Chevy 350
Proline Heads
Victor Jr Intake
Holley 750
MSD 6-AL with external 2-step
MSD Blaster 2 coil
2-spd powerglide with tranny brake
Ford 9 inch rear with 513's
30x9x15 slicks

Things I've tried:
reset the valves
adjust the timing
swapped distributors
swapped 750 carbs
replaced 3 spark plugs that looked a wet
verfieid battery voltage.
This week I'm going to try changing all the plugs and putting a new set of plug wires on the car.

Help?!?! What else should I try. Where'd my power go?

Thanks

[jmarksdragster]

Oil change ond plugs.

[Tod74]

WHEN YOU RESET THE VALVES WAS THE LASH STILL WHERE YOU SET IT?I had this happen once and blamed it on the weather and everything else...but it got slower every pass up until a lifter broke and destroyed the engine. Looking back I think it got hurt the week before and it was telling me there was a problem (slowing down) and I ignored it...payed for it too. If any of them were loose I would look at the lifters if it is a solid roller.

[GotSomeRust]

WHEN YOU RESET THE VALVES WAS THE LASH STILL WHERE YOU SET IT?I had this happen once and blamed it on the weather and everything else...but it got slower every pass up until a lifter broke and destroyed the engine. Looking back I think it got hurt the week before and it was telling me there was a problem (slowing down) and I ignored it...payed for it too. If any of them were loose I would look at the lifters if it is a solid roller.

Yeah, lash was still OK. I'm running a solid roller. Only a few were slightly off from where I'd set them last time. Nothing to fire off any alarms...

[Tod74]

I Wonder if the converter is about to take a dump?

[GotSomeRust]

I Wonder if the converter is about to take a dump?
Guess it's definitely a possibility...

[cepx111]

I definetley change "ALL" the plugs out.
If you had some that were wet from the cap being left on the carb its a strong possiblity that the others arent in the best of shape, change them out and go back with your original set-up, I.E< carb, dist, timing etc.

Goodluck, Charles

[jrthone]

Temprature??????????????

[promodjohn]

I am wondering if you created a leak in the intake manifold or the carb. gasket when you tried to start it with the carb. cap on.

An easy way to check this is an old backyard method take a can of shaving cream,start the car and put a small amount around the carb.gasket and intake manifold gasket pay close attention if you see the shaving cream dissapear somewhere, you have a leak.

P.S. don't feel bad I did the same thing several years ago good luck.