Can't get rid of bog

[rda1218]

Hello,
I have an 85 square-body K5. She has a 305, the motor is solid for a 35-year-old engine. The compression is within specs, valves are adjusted and timing is right on at 8 degrees before. The distributor is original and is electronically advanced and not vacuum. I had a major bog issue which I corrected with a rebuild of the original Rochester Quadajet, but there is still a lack of power under load and it pops sometimes when the accelerator is hit hard while idling. I am down to having someone else look at the issue like a local mechanic with all the wizbang tools, any suggestions on what to look at beforehand?

all work done so far:

timed with light and retimed after major adjustments or replaced parts. (8degrees btc)
new wires
plugs
coil
valves adjusted
carb rebuilt (even used a reman which turned out to be part of the problem)
tranny rebuilt
carb adjusted to make sure the vacuum is good
no vacuum leaks


(Wish I could remove smog stuff but still in commie cali)

 

[squaredeal91]

Sounds like you're on the right track with what you've checked so far. Could be a number of things. Possibly a flat cam or accelerator pump not squirting . Or maybe ignition system not working properly. ? ESC system? They can bog when not working properly.

 

[fast 99]

backfire into intake:

lean, ignition misfire, valve train issues, weak or broken valve spring

 

[rda1218]

I checked the springs when I adjusted the valves, and I did not see any issue there, other than the mess I made with the engine running during adjustment. I am leaning toward a distributor issue, maybe the counterweights are binding. I am not sure about lean, but the issue of power especially on an incline does not sound like a lean fuel problem. I have good acceleration on level ground with no draw on the engine, the bog only occurs when I try to wot or heavy throttle.

 

[squaredeal91]

Knock sensor?

 

[rda1218]

I have no knock sensor on 85 quadrajet carb, that i am aware of.

 

[rda1218]

I am trying to find a correct vacuum diagram for my California emission engine with an electronic spark advance. Does anyone know where i can find that diagram it is not on the vehicle.

 

[rda1218]

Update: I am now leaning toward an exhaust blockage. I have done everything else. I don't know the complete status of the exhaust as I bought this vehicle after it had been sitting for almost 6 years.

 

[Ricko1966]

Post a pic of your distributor. Put a timing light on the distributor but not to time it,use it to verify advance and retard use timing tape or make your own timing tape. Rev the engine see how far you advance,make sure advance is coming up and going down smooth. Disregard the 12 posts after this telling you to get a light with adjustable advance. If you are feeling up to it, here's a backyard method for checking the cam. Lay a business card up against a valve spring mark the height on your card,turn the motor until the valve is fully open,you'll know,just put your finger on it when it quits moving its fully open. Now make another mark on your card.Compare cards a flat cam lobe will be apparent by the difference in the hash marks on the card. Your intakes and exhausts are liable to be different nbd. Compare intakes to intakes,exhausts to exhausts.

 

[fast 99]

Update: I am now leaning toward an exhaust blockage. I have done everything else. I don't know the complete status of the exhaust as I bought this vehicle after it had been sitting for almost 6 years.

Easy to diagnose, install a vacuum gauge to manifold vacuum. Under a load will decrease to almost zero or loosen header pipe, drive around the block.