Looking at the pictures it’s possible to see the bottoms of several are gone. The rubbing surface needs to be convex on surface shape not flat nor concave which I see on some of them. air the lifter face is gone so is it’s mated cam lobe to some extent extent.
The way these cast iron parts wear is more like grinding the pieces are extremely small to microscopic. There isn’t going to be a flood of pieces big enough to be stopped at the oil pump pick up screen and probably small enough the average 30 to 50 micron filter won’t catch them. So to a large extent these partials are to small to do much damage, where they do it will look more like the mating parts were wet sanded rather than carved and gouged.
As for new cam you can put in anything you like with in the limits of having to change stall of the converter so the high idle RPM isn’t pulling hard against the brakes. That is a condition where even with power disk brakes it becomes physically tiring applying enough force such that the engine isn’t spinning the rear tires while standing still or drags you past the intended stopping spot. This is dangerous as one lapse in concentration or the slip of your shoe on the pedal will quickly put into a crossing pedestrian or cross traffic. So if your Monte has a 1350 stall converter the typical lopey cam with a 900-1000 RPM idle is going to be pulling very hard and the closer it gets to converter stall speed the harder it will tug against the brake till it exceeds the brake’s holding power then the rear wheels will spin if the vehicle is unable to move. The rear brakes being drum this they are not as powerful as the front disks. In the “good old days” doing this at the start of a drag race was known as “torquing it up”. In this condition when the brakes are released the vehicle leaps forward with a vengeance. As Paul Stookey a mid to late 20th century song writer, singer and humorist said in his routine of Mr Business Man meets the Kid at a stop light. A semi quote follows——The car is internally hemorrhaging as Mr. Businessman steps on the brake and floors the accelerator to get an extra fast start.
So to get a cam that provides a lopey idle the converter stall is the upper limit. So with the tight converter you have a 900 RPM idle engine will tug hard against that 1350 stall to get to the idle rpm it wants or the engine well constantly stall at these low in gear RPMs The more you speed the engine’s in gear idle to keep it running the harder the pull as the engine speed closes in on the stall speed. This is not an all or nothing situation. For the most part the factory sets the converter stall speed at about half the RPM of in gear hot idle speed of the engine. So your 305 has a cam that is designed for a 650 RPM idle against a 1350 stall. At this RPM the hydraulic transfer force through the converter is easily held with light brake application. From here the force output through the converter geometrically increases with RPM until the stall speed is met. At that point the hydraulic coupling acts like a solid connection. If the output is stalled as in locked then the engine‘s RPM gain is halted with all the twist force the engine is mustering contained in the converter. Needless to say this is nothing less than an oil filled bomb. A stock converter outer case at the least can balloon from the hydraulic forces, with a big enough power input the converter can be forced to explode in a gush of torn steel and scalding hot if not flaming oil.
So these are the constraints on your desire for a lopey cam. Without a converter stall change you can kind of press into the bottom limit of a cam where the idle picks up a little bit of stagger. That point is about has a cut off of about 215 degrees intake at .050 inch lift. If you tighten up the LSA so it is less than 110 degrees the stagger idle sound is more pronounced for that intake duration. After about 215 @.050 duration things get hairy very fast. While cams in this 215 degree range are sold as acceptable with a stock stall converter this is pushing hard on acceptable drivability.
As far as lifter life and spring strength limits are low the older factory cam designs of the 1960’s where durations are fairly long and lifts are pretty low. These old cams used a lot of ramp to ease the coming and going of the valve train with fairly low lifts so spring pressures didn’t eat cam lobes and lifters.
So basically you can’t have a rough idle cam without a lot of other changes.
Bogie
