Time for a road trip!
Probably needs a good drive somewhere. The guy I brought my 69 off said it needed a tune and smelt rich but it never really left the driveway.
I drove it 6hrs home and it ran sweet ever since.

 

Your gas may have gone unstable/bad? Throw some fresh gas in it and drive it. Ethanol is corrosive to many metallic parts in fuel system.

 

Running rough with small backfires could be any number of things. Just a few things that it could be are a cracked distributor cap, a broken rocker arm or bent push rod. See if you can isolate which cylinder could be causing it. Maybe pull one plug wire at a time and see if one doesn't make any difference and focus on that cylinder. It is all just a guess at this point but it may give you somewhere to start. Put a fresh set of plugs in it and see if it helps.

 

in the first place stop driving or starting it up unless you can run it far enough to get completely warmed up. This would be like 5 miles on some kind of highway type road. just don't. you're asking for a flat cam lobe.

put a set of plugs in it before going any further. the fact that the plugs are all carboned up is telling you something. Your engine doesn't want to be operated as you've been doing. again, if you don't have time/license/whatever to get it fully hot just leave it alone. Don't start it up just to hear the sound.

 

All the plugs carboned up. That is the most likely cause of the backfiring. Oil or fuel fouled?
Since all the plugs were fouled, it is most likely fuel fouled. Easy things first:

- spark plugs are too cold heat range. Should be a 5 heat range in NGKs.
- choke sticking on.
- carb flooding due to wear/dirt in needle & seat.
- float has a leak, causes flooding.
- check that float level is 7/16". No gaskets reqd if you are careful when removing airhorn.

 

If you have a flat tappet cam you may have lathed the lobe. I had one happen the same way over the winter started it up after like 6 weeks drove about a mile started popping. Todays oil you need the zinc additive as the newer oils don't stick to parts like the old ones. If it is the cam causing this put a hydraulic roller in the next time around.

 

Thanks guys. I was thinking of a hotter plug or different plug mfgr. This is my 4th set of AC Delco's. (That's over 10 yrs but only 100 miles)

When i said around the block, I should have specified my block is just over 5 miles. Always reaches 195*-200* before I shut it down. Bad part of that is longer idling time getting it warmed up.

It's not a flat tappet engine and it has new gas.

How I hate pulling those plugs again. #7 Arrrrgh!!
Thanks for the good info.
I'll let you know what I find.

 

I've tried to find NGK heat range 5 plugs. The equivalent NGK plug to AC Delco R44T is BP5FS. I can't find them anywhere. Even checked the newer iridium equivalent. The replacements identified are plugs with gaskets and not tapered seats.
Can anyone suggest a next best plug?
TIA

 

Jim, don't wait for it to warm up. That just wastes gas and carbons up your engine along with diluting the oil. Get in, start up and go.

R44T is a bad choice. too cold and not an extended nose plug. R45TS would be better.

have you looked into the various tricky plug wrenchs?

 

Tom, Thanks. I ordered a tricky plug wrench and it should be here tomorrow. I reviewed some comments and found several where guys couldn't use the R45TS due to the length of the plug and the long tube or Hedman headers. I took one of my plugs to advance auto and compared them. The r45ts is a little longer. Based on how close I am now I know they won't work. Can't find a shortly comparable except for an accel plug that is $18 a piece.
Anybody have a different plug they use that is a shortly, with a tapered seat and extended tip?
Assuming someone recommends a plug that is equivalent to a R45TS, can I use just that one plug and the other 7 R45TS?
I'm sure there's only one cylinder that is involved.
Thanks again

 

I would swap out the headers for a set that let me use the proper spark plugs. Seriously - what you're describing is just going to be a colossal pain the entire time you own the car. Fix it properly now, before you get it on the road permanently. I've been there/done that with angle plug heads and headers on a small block. Not worth the trouble.

 

what is a tricky wrench? and why would you need to use one? thanks

 

try taking it for a "good ride" where it might see 5000+ rpms on a 1-2 gear shift.
it will probably run fine after that.

4th set of plugs in 10 years/100 miles?
I have been drag racing my car for 18 years including driving it 190 mile round trip to the track and probably have changed the plugs 4 or 5 times over the years.