im about ready to burn this truck to the ground

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It’s just a mechanical vehicle and the make or model doesn’t matter. Find the issue and fix it. It just isn’t that hard. Spark, fuel, etc.

They are just simple machines.
 
ok guys, finally got some time to address this again

i replaced the cap with one a buddy had sitting on the shelf and it is better, but not good (maybe its not even better, but less bad?)

i can plow with it again, but im not trusting her to run down the street, across town to do the Church's parking lot
it still backfires and dies under heavy load

Post 12
Those rotors can burn through letting the spark jump right to the metal advance assembly underneath.
From the looks of the button in the cap and the metal contact on the rotor the spark has been jumping around a little.
With a problem like that the spark gets forced to find another path, and does as you add load to the motor.

Most people don't realize it but the higher the cylinder pressure goes, the harder it is for the spark to get to and jump the plug gap.
And especially with HEI it WILL find another place to go.
Normally on that type of distributor that is straight down through the rotor.

i took the rotor off and looked, no holes or anything else that looks iffy

TFI module? Timing where You left it??

the truck has been converted to a GM style HEI ignition (stupid thing is almost too big for the engine) so no TFI module
i have not yet checked my timing but i have checked to make sure the distributor hold down is tight, and it is

I would check fuel pressure/volume.

What’s fuel pressure at? What pump and regulator are you using?

Maybe a bad fuel pump?

Just a thought.

Good luck. Eric

im not sure what fuel pressure im running, ill see if i can change my vacuum gauge over to fuel pressure or not
best i can tell, there is a stock mechanical pump on there, no regulator
(i realize the 87 bronco should have injection and electric pumps, but the previous owner "rebuild" it with a carb and mechanical pump)

is it a holley carb ?
did you blow the power valve?
yes, it is a truck avenger 670
i did not dig deep enough into the carb to see if the powervalve got damaged or not
(to be honest, i was confused on where it was and when i had the carb of and was checking what i thought was the power valve, i was actually checking the secondaries diaphragm)

If it backfired that violently, I would be looking for a blown off vacuum hose. A large one. Such as the power brake booster. Or any other large manifold vacuum hose.

there are 3 vacuum port on the carb and one vacuum T on the intake
i capped all of them off during my trouble shooting session saturday and it made no difference

It’s just a mechanical vehicle and the make or model doesn’t matter. Find the issue and fix it. It just isn’t that hard. Spark, fuel, etc.

They are just simple machines.

i kinda figured the basics apply the same across the board, a SBM 360 with a stuck lifter should act the exact same as a SBF or and SBF with a stuck lifter

thats why i decided to share this with you guys (and to air out some frustration)

i think i will dig out my timing light and see if i can figure out if timing is where it should be
find a way to check fuel pressure and keep looking for a vacuum leak

i might even throw an old edelbrock on there, to see if that makes a difference

i also came across this video, which claims i can check a powervalve by turning the idle mixture screws all the way in, ill try that too



thanks for all the help guys
 
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Some of the old Fords had an EGR plate under the carb, it'd eat thru, and cause issues.
Not sure it's on that vehicle.
FWIW.
Good !uck
 
The Exhaust might be plugged. Backfire might have dislodged something. Is there a Cat? Catalytic converter? What caused the back fire in the first place?
 
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