I have a 406 with about 3500 miles on it. It has a small retrofit roller cam from Speedpro. The lifters are Comp Cams. I took my first long drive with it over the 4th of July weekend. About 900 miles round trip. It ran very strong until about the 700 mile mark where it developed a miss. Gas mileage dropped off and by the time I got home there was a distinct "clack" coming from #1 cylinder that I hoped meant it just needed an adjustment. The Vortec heads on the motor are fresh but the rocker nuts have an unknown history. I hoped they just loosened on number 1. When I pulled the valve cover, number 1 intake rocker was not even moving. The nut was rather high on the stud so it raised hopes of needing an adjustment. As I slowly brought it down, it became apparent that I had sustained some kind of damage because the response was zero. As best as I can tell, the stud is not pressing out of the head. I fear it must be a flat lobe but how on a roller cam? You just never hear that. And if the lifter is barely rolling on the flat lobe, what must be happenning to the lifter it is attached to? That bar must be at some extreme angle!! #1 exhaust seems to work fine. Takes an adjustment like a champ. And why did just one lobe in 16 go bad? I just changed the oil to my first belly full of Mobil One (8 darn quarts) and it looks dirtier than a change that was done 900 miles ago. Raises more suspicions of a flat lobe. Any ideas?

 

you already know the answer, you trashed the cam. even if you trashed a lifter it's safe bet the cam got cought up in the mess too.

 

There's a clue right there....

Retainer smacking into the top of the valve guide?

 

Thanks for the confirmation, fella's. I was hoping someone would tell me there was a pill you could put in your oil that would fix that. Remember those from JC Whitney? LOL

I guess I wanted to know how often does that happen to a roller cam. I have never heard of roller cams going flat. My first thought is I did think that it was strange the Speedpro cam was cast. I have never seen a cast roller cam. I remember reading that a cast iron casting would not hold up well in roller applications but I thought "Why would a first class outfit like Speedpro sell a part that would not hold up"?

RB83L69,
The cam is a real baby cam. Only 440 lift on the intake/ 460 on the exhaust. Well below the recommended maximum lift for Vortecs. But you did spark a thought. The heads were used when I bought them. New guides and a fresh valve job were in order with some pocket porting and valve back cuts thrown in. I did reuse the springs. My car has a 4:10 posi. It doesn't like being pushed past 70 miles per hour. The punishment for such bad behavior is crappy gas mileage (secondaries begin to open) and she really drops off after 4000. I thought it was from lack of air/fuel volume but now I bet I'm running her right up against valve float. After 900 miles on the threshhold, I probably killed the cam.

 

Virtually all hydraulic roller cams, including factory ones, are cast; just like virtually all street flat tappet cams.

I've never seen a roller cam lobe go down, except when there's an interference problem or valve float; coil bind is what usually does it. But the Vortec heads are a little bit of a special case.

No little blue pills for cam lobes to make them stay longer and harder for longer, sorry.

 

I have to admit, my experience with roller cams is short. I've noticed many rollers from friends that run their cars on the strip and they were all steel.

I am addressing the valve float issue with a new set of factory springs. I am having a new Extreme 4 X 4 (.447 In/.462 exhaust)cam rushed in from Summit because this motor is going into my Suburban when the new motor for the IROC is finished. (A long rod 350 more suited to the 4:10 gear). Can you tell me what the obvious signs of retainer interference might look like?

 

The retainer is harder metal.... so I'd look for a big retainer stamping on the top of the valve guide.

{edit} On the roller cam thing - most if not all real racing rollers are billet steel. That's different from street rollers.

 

Cool man..thanks for the info! I want to have some kind of idea what I'm looking for and some information to give the machinist if I need to go that route. So basically I would rather look like a dumb --- to you guys than to a guy I'm going to be paying my hard earned dollars to!

 

Wow! Here's a twist. Took apart the top end this weekend. There in the lifter valley was my #1 lifter pair sitting there with it's tie bar torn from one another. I expected to see that so no big deal. What was strange is that when I pulled the pair out, #1 exhaust was still in it's correct position. With a flashlight, I could see no damage to #1 lobe. Of course, #1 intake was side ways and there was plenty of lobe damage. I went ahead and pulled the heads, both because I felt I needed to change to new springs and to check bore condition. The bores all had perfect cross hatching, no scuffing....shew! Pulled the cam and #1 exhaust was perfect. That sucker ran true WITHOUT the tie bar attached. How in the world.....? Cam bearings looked great.

My head machinist checked for retainer contact...none found. Computated the valve lift from the cam card and said retainer to guide clearance was more than adequate. Also NO CHANCE OF VALVE FLOAT because the old springs were good for 85 lbs of pressure at the seat. I never got above 4500 rpm on the trip, so the pressure was adequate to control the valve train. I replaced the springs anyway. So.....It appears that the whole problem stemmed from the tie bar breaking between the two lifters. The lifters were used off of EBAY so I guess they might have been horse whipped by their original owner. I'm calling the whole set suspect and trashing them. Lesson learned: Only buy used components that are easily changed out and not require mayjor surgery to retreive. Did I pass MASTER?!?:hail:

 

Yuck....

I'd still scope out the valve guides real carefully, just in case that was what stressed everything.

It does sound like some kind of luck though, that a lifter stayed put without its link bar intact. Might be the only time in your life that it will happen! You just used up all your luck (well, all your good luck anyway).