Classic/Antique Car Repair: gutless 67 caddy, straight pipes, insulation material

Question
QUESTION: Hi Brad, and thanks for answering my last question on a leaky tran.  I pulled it out and had it rebuilt so no more leaks!
The newest problem is my Caddy has no power at all.
Idling is fine, snapping the throttle is fine, but put it in gear and it starts to backfire, pop and almost stall.( I saw a bit of flame coming out of the carb and it stalled) I feather it to get it moving but it's gutless?
Points are fine.
Timing is fine.
Trans was recently rebuilt but this was happening before too.
Fuel filter bowl is full.
Jets are squirting two healthy streams into the primary.
Do you have a checklist of things to tackle?

Thanks in advance,
BL

Much Appreciated.
BL

ANSWER: The way that I would approach this problem in my shop would be to first run a compression test on the vehicle to eliminate an intake valve problem or a leaky head gasket. Then I would look for a crack in the distributor cap or plug wires jumping from one to the other. Retarded timing can also cause this problem. Hmmmm, the distributor cap is on the back of the engine, right? Don't suppose that the engine dropped down when the transmission was removed and distributor cap got cracked on the fire wall, do you?
Brad

---------- FOLLOW-UP ----------

QUESTION: Thanks Brad,
I played around with the timing and no difference.
The engine is backfiring frequently.  Here is more background that might help.
I remember back two yrs ago when I last drove it, that when I revved the engine I blew out one of the mufflers(I have straight pipes running back to independant mufflers).
After I welded the side back on the muffler, I started it up a week or two later and tried driving up and down the road and it was gutless then.  Then I lifted the hood and saw that the insulation material from the underside of the hood had dropped onto the open carb while I was driving! Oh no!  I pulled off the insulation and couldn't see anything in the carb?  This leads me to your questioning the intake valves?
Now the car idles fine but a steady, irregular 'pop' can be heard coming from both tailpipes.  If I floor it, it backfires out of the carb sometimes?
Any ideas?
Thanks,
BL

Answer
It is time to verify the condition of the engine. Time to take a compression test. That way you either have found the problem or ruled out a problem and then can go on to the next test. Gotta have compression to have anything that resembles normal operation.
Brad