I have a 1979 Full Size blazer with a 350. I recently bought it and have had to do a lot of work on it. I've been stumped by this one though. It starts right up when the key is turned but as it warms up the idle speed slowly lowers and lowers and then it has problems staying on, and will eventually die out almost like it's not getting fuel.
I recently had the holley carb rebuilt and initially when it was reinstalled it worked okay and didn't have this problem. I can't put my finger on what would have caused this. I have heard that it could be the timing, fuel getting past the filter etc. I have changed the fuel filter but have no idea how to mess with the timing. Any ideas/suggestions would be greatly appreciated.

 

Have you adjusted the warm idle speed via the screw on the driver side of the carb? What model carb is on it? What does it have for a choke (manual, electronic, thermal)? Do you have a tach? If you do, what is the idle speed at right before the last step down in speed that results in a stall?

 

Have you done any checks on fuel pressure? If so does it seems stable or does it drop before it dies?

 

I too had to wonder if the fuel pump (mechanical this far back) may not have been supplying the proper fuel, but that would take quite some time to work through the fuel in the fuel bowls on the carb...

Does it stay running if you lightly hold the throttle open a bit?

 

It's a 4160 Holley, I'll be honest. I've had quite a time trying to figure out how to adjust it. It has an electronic choke, and I have tried adjusting the choke, and unfortunately I don't have a working tach right now so I don't know the RPMS at which it stalls. This blazer is my first real big car project so I'm definitely a beginner. I haven't checked the fuel pressure, and I'm not quite sure how to.And for the final question...it will stay running if I hold the throttle a bit...also, when i push the accellerator it almost seems like the engine bogs a bit then it will rev up. i don't know if that has anything to do with the overall problem however.

 

Wonder if your idle circuits are too rich or too lean...

THIS was the first page I came across. It contains the full manual for your carb and a few other similar models. It should help greatly if you can get through it all. THIS might be a good buy! I used to have a few books on tuning holley carb's, but have since lost the box that contained them and all of the old photos of my Chevelle...

 

can that be adjusted by the idle mixture needles on the fuel bowls?

 

yes, but you really should go through the whole process of setting the carb up... I believe that the manual in the first link I provided should get you the information you need.

How is the accelerator pump? Is it working properly? If not, that could explain the bog off the line. But if the idle circuit is rich, it could also explain the bog as a rich condition + more fuel via the accelerator pump == bog.

 

I'm sorry I'm not much help in answering your questions...I am not sure how teh accelerator pump is, but that would make sense on teh engine bogging down at acceleration.