Old problem

[1967 GTX 440]

I have 1967 gtx with 77 440. Motor was rebuilt before it was installed. It ran good for about five years. Out cruising one night, ignition cut out and came back on, muffler exploded. limped it home. new muffler and msd distributor. Though it was fixed. Then had off line stumble. Check valve train, no problems. Then took cylinder heads to machine shop, they changed valve springs and r & r valve guides. Now runs ok but down on power. What could be wrong? Thanks

 

[GetX'd]

Welcome to FBBO from SoCal

 

[440Coronet500]

Welcome from Michigan, the Motor City! 440'

 

[khryslerkid]

Welcome!

Are you using a Holley on top? Power valve?

 

[Jerry Hall]

Welcome from Alabama, 67 GTX's my favorite. Did the accelerator pump on the carburetor get changed or repaired after the backfire?

 

[1967 GTX 440]

Welcome!

Are you using a Holley on top? Power valve?

Holley 750 now edlebrock 750

 

[1967 GTX 440]

Welcome from Alabama, 67 GTX's my favorite. Did the accelerator pump on the carburetor get changed or repaired after the backfire?

Holley 750 now edelbrock 750

 

[polywideblock]

g'day from Australia

 

[turbine68rt]

I have 1967 gtx with 77 440. Motor was rebuilt before it was installed. It ran good for about five years. Out cruising one night, ignition cut out and came back on, muffler exploded. limped it home. new muffler and msd distributor. Though it was fixed. Then had off line stumble. Check valve train, no problems. Then took cylinder heads to machine shop, they changed valve springs and r & r valve guides. Now runs ok but down on power. What could be wrong? Thanks

Check your timing, could be a bit late. Also check a/f ratio to make sure it's not running overly rich.

 

[Big Bad Dad]

Check your ballast resistor to make sure it isn't cracked. I had similar issues years ago, and found that simple cheap and easy fix after going through a bunch of other stuff...

 

[Hey-O]

Welcome from Missouri!! I suppose if enough unburned gasoline collected it could blow up your muffler. Bad spark plug wires, shorted coil, fuel mixture problem or a cracked distributor cap. Good luck!!

 

[Budnicks]

welcome to FBBO

was the power loss same time ?,
when you went from a Holley to the Edelbrock ?

that may be a really good hint right there

there's so many things it could be, related to fuel delivery, filter,
clogged sender/pick up sock or restricted lines, bad pump

wrong ignition timing, bad coil, too much air-gap (needs 0.008-0.010")
on the pick up, bad wire/s, bad plugs, etc.
did you do any kind of compression test ?
or any other types of diagnosis ?
anything to actually narrow it down ?

are the simple things covered, plugs wires cap rotor all good ? etc.
do you still have a restriction in the exhaust ?
all these things needs to be addressed in you new thread

maybe start a new thread in another/proper specific forum section
or even the general discussion section
this is the welcome wagon & not a Q&A tech section
far less viewers too

good luck

 

[khryslerkid]

Stamped or adjustable rockers?

 

[HD539]

Welcome from the Pacific Northwest

 

[mr. b]

welcome to FBBO from Pa

 

[68sprtsat383]

Welcome