I have a 79 chevy malibu with the 200 V6. The the engine rattles when you accelerate and lacks power. It feels like a timing advance problem. Do you know where I can get a vacuum hose diagram? Also any advice would be appreciated. Thanks, Bill

it is not the valves that are rattling under load but detonation in the combustion chambers from incorrect air/fuel mixture and ignition timing
The rattle is the pistons being slapped against the cylinder wall and the rings taking a pounding in the ring grooves
detonation is the untimed spontaneous combustion of a weak air/fuel mixture ( diesel action) before the spark ignites the mixture
It can melt the top out of the piston because it sends the combustion temperature up to 200 degrees c higher than normal
Evidence of detonation in an engine can be seen in the crown of the piston as small pit marks as if being pounded by ball bearings
How to fix --- drop the advance timing of the ignition back to 12 btdc ( standard on chev motors) or better back to 10 degrees btdc
increase the main jet sizes in the carbys or make sure that the power valves are operational in the carbies
The correct air/fuel mixture is 15:1 and that should be maintained at all times unless under acceleration when it can go up to 17 or 18:1 but if it drops below 14:1 when the throttle is wide open and the fuel is not increased to compensate ( accelerator pump or power valve ) then detonation will occur

Pre-ignition or knock maybe. Ignition timing over-advanced, fuel mixture weak, or possibly the plugs. Faulty knock sensor?

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c1528026924c Here you are.

sounds like a catalytic converter - runs good but lacks power - the back pressure keeps the engine from being able to accelerate under load - good luck :O)

full power is only achieved when the engine is fully warm(operating temp).so if you accelerate more than, say, a third of the gas pedal,the car will feel sluggish.
this is more apparent when first starting the car in the morning in winter.almost like the car is going to stall.
most wear in the engine is leaving it to idle when cold you should always drive the car straight away from cold.then when hot turn on the a/c if required....

I suspect your ignition timing is too advanced and the rattling sound is actually detonation (VERY VERY bad for your engine). Have your ignition timing set and your valves adjusted.

fuel lines inside the intake plhenum may be cracked and leaking inside the plhenum. same thing happened to my 1992.sonoma. they are made of a plastic material and tend to crack right in the bend of these lines.

make sure that the timing advance mechanism in the distributor is working freely.

Possible bad motor mount(s) --only thumps or rattles when power is going to the wheels.

i believe it's around 80, but anything higher than 60 should run it somewhat, just lacking power, and dogging out while accelerating, like a running out of gas symptom.