1989 v-8 302ci f150

Base timing is set at 10 degrees below TDC.
seems to idle ok not perfect.
any throttle under load brings on several backfire pops up through the carb
replaced carb base gaskets
checked vacuum lines again, still good

I am completely lost. any ideas on what it could be?

 

How healthy is the accellerator pump? Do you get a good squirt in the primary boars when you pump the throttle? Power piston in the carb could also be stuck.

 

Did some one convert from Fuel Injection to carb?
If so how was it done?
The miss can be from several causes.
The base timing should be 10° before top center, not after.

 

I apologize. Yes before. I am no mechanic. Learning as I go.
also yes this truck was converted from fuel injection to a carb.
Here is a pic of the #5 sparkplug I pulled out.

 

Yes it appears to be a good healthy gas guzzling dump. After the good spray immediately following there are a few drips. Is this normal?

 

That cylinder could have a problem but still not cause the backfire.
You need to do a thurogh diagnostic of the ignition, vacuum gage testing to see the relitive health of the cylinders, fuel and timing action to uncover what the cause is.
Vacuum gage testing is a science based on how the needle acts and related to specific problems that cause the peticular needle actions you see as well as vacuum levels.
Otherwise you need some luck.

With fuel injection, an EEC test could tell the relitive health of the cylinders by an internal test option set up with a code reader and some knowledge of how and interpet the results of the test codes.

 

hat's what I believe it is anyway. The rockers are going up and down except for one.

How do you free a stuck lifter?

 

Ok I figured out what it was. 2 lifters were stuck grinding down on the camshaft. Two lifters toast. One cam toast. thanks for your help along the way!