bad cam shaft?

[packers05]

follow lee's advice

[slikside]

Not sure about cam issues, but assuming it is your carb, just how hard are you getting on it when it bogs? The accelerator pump only supplements the primaries. If you are getting on it and opening the secondary side, your air flaps may not be adjusted properly via the adjustable tension spring, or the the choke pull off (which also regulates airflap opening rate) may not be adjusted either. Cliff's high performance recommends 1/2 to 3/4 turn clockwise on the spring tension after it just barely closes the airflaps. If your motor is stock or nearly so, the choke pull off should go from fully compressed to wide open in 2-3 seconds, and faster if a higher performance motor.

I have just rebuilt my q-jet and mine is set up this way for a stock motor, but I have yet to reinstall it and have it running. I got this info (and much more) from his book on rebuilding carbs. Also, be aware that q-jets are widely misunderstood carbs, and a great many mechanics do not know how to tune them properly. I may not either, but I am not a mechanic...just and eager learner want'n to get his truck back on the road.

[Sillyoldman]

Forgive me if I repeat anything. I have not read the replies. Pop the valve covers and watch the rockers for a dead lobe. It's obvious. Nexts start off by adjusting the valves correctly. Not with the engine running. Any mechanic that has to bash others work is either a liar or desperate to justify their own work imo.

[Danomt]

I am with the silly old man. After hundreds of engines I still have never adjusted a lifter with engine running. Now for the Accel pump issure. look into the carb and jack the throttle. Does it have a healthy squirt into the front two venturies? So flat cam, timing issues or carb squirt, Fix what is wrong and the cruise. DanO

[Painter D]

Originally Posted by LONGHAIR

I would do a little more investigation before jumping off of that bridge.
A "leak-down" test can tell you a lot. Removing the valve covers and visually inspecting the rocker arm movement would be good too.

If in-fact the cam has lost a few lobes, it is going to take a total rebuild to fix it. Do not let anyone tell you that the rest of the bottom-end will be "ok" and just cut corners into a top-end job. When a cam goes flat, even on just a few lobes, the oil circulates all of those metal particles through everything. It take a total rebuild to get that cleaned out. If you don't it will happen again, much more quickly.

Originally Posted by LONGHAIR

Not so, this is the exact advice I caution against. "Worn enough to cause a problem" means virtually any wear at all. Cams and lifters are "case hardened" which will stand for almost no wear at all. This is why that "failures" are sudden and seemingly fairly extreme. Once a cam makes it through the break-in process and is at least adequately lubricated, it will last a very long time. Once the wear "starts" it goes very quickly, the case hardening is very thin. Think of it like chrome plating on a bumper, one you get through that outer layer, it's just raw steel.
You will not get "enough wear" to cause a performance issue until the castastropic failure. At that point, as stated before, it needs a major rebuild. Hot tanking the block and starting from the ground up. Trying to "refresh it" with a new cam will result in a quick failure.

Originally Posted by LONGHAIR

Probably in more than one way. You may see the silver metallic sludge before even turning the engine over to watch the rocker-arms.

All of this is correct and probably the best advice you will receive.

[rsavage]

Not trying to get in a pissing contest, but I suggested two different ways to adjust the hydraulic lifters - static or running. I'm an old guy too (59) and was taught 40+ years ago how to adjust them running. Quite frankly, a young inexperienced guy can more easily wrongly adjust lifters using a static method by cranking a rocker arm down when the valve isn't closed then he can with the motor idling. It can be messy but it is actually more accurate and is fool proof. I have a set of 67 and earlier valve covers with the centers cut out which cuts down on the oil. I also used to have a set of clips for the rocker arms which would reduce the oil splash but I can no longer find them. The valve covers work better. When I put an engine together I set them up static and then readjust warm and running. The fact that someone has never adjusted Chevy hydraulic lifters with a warm engine running does not make it advice worth dismissing.