Stock 340 Rebuild - Roller Cam?

[73440]

If the polishing of the lifter bottoms is to help rotation, would smoothing and polishing of the lifter cavities help also ?

[Shane Kelley]

If the polishing of the lifter bottoms is to help rotation, would smoothing and polishing of the lifter cavities help also ?

That's not the reasoning for it. Cam break in should really be called lifter break in. The bottoms of the lifters have machine marks on them and that is what you want to remove so it doesn't chew on the cam. When that happens lobes will go down. So the way most people do the break in is having the motor start right up and run at 2000rpm for 30 minutes. Basically that is polishing the lifter bottoms. The problem with that process is ruining header coatings (excessive heat) and hoping there isn't a leak or problem where you have to shut it down.

[Cudakiller70]

If the polishing of the lifter bottoms is to help rotation, would smoothing and polishing of the lifter cavities help also ?

That's not the reasoning for it. Cam break in should really be called lifter break in. The bottoms of the lifters have machine marks on them and that is what you want to remove so it doesn't chew on the cam. When that happens lobes will go down. So the way most people do the break in is having the motor start right up and run at 2000rpm for 30 minutes. Basically that is polishing the lifter bottoms. The problem with that process is ruining header coatings (excessive heat) and hoping there isn't a leak or problem where you have to shut it down.

After polishing lifter bottoms do you still do a traditional cam break in?
So lifter and cam lobe aren't really being seated together like piston rings and clyinder walls are done?

[Shane Kelley]

If the polishing of the lifter bottoms is to help rotation, would smoothing and polishing of the lifter cavities help also ?

That's not the reasoning for it. Cam break in should really be called lifter break in. The bottoms of the lifters have machine marks on them and that is what you want to remove so it doesn't chew on the cam. When that happens lobes will go down. So the way most people do the break in is having the motor start right up and run at 2000rpm for 30 minutes. Basically that is polishing the lifter bottoms. The problem with that process is ruining header coatings (excessive heat) and hoping there isn't a leak or problem where you have to shut it down.

After polishing lifter bottoms do you still do a traditional cam break in?
So lifter and cam lobe aren't really being seated together like piston rings and clyinder walls are done?

Nope. After you polish them you are done. No need for the 2000 rpm for 30 minutes needed. It's not a seating process.

[Cuda Cody]

That's a neat trick.  I've never heard it before and it makes sense.  I'll try it next time I build an engine.

[Cudakiller70]

  hmm doing a flat tappet cam now

[Shane Kelley]

That's a neat trick.  I've never heard it before and it makes sense.  I'll try it next time I build an engine.

I know what you mean. I have a Chevy friend that's a big engine guru and he kept telling me this for years on how he does it and never had a problem. But I had never heard of it or even read about it. Then he showed me. There it was right in a old GM racer manual like he said. I have been doing it this way ever since without issue. I done at least a dozen motors this way.

[Shane Kelley]

Left one straight out of the box with raw machining. Right one polished.

[HP_Cuda]

You do want to seat the rings and ensure everything is operating smoothly.

If the polishing of the lifter bottoms is to help rotation, would smoothing and polishing of the lifter cavities help also ?

That's not the reasoning for it. Cam break in should really be called lifter break in. The bottoms of the lifters have machine marks on them and that is what you want to remove so it doesn't chew on the cam. When that happens lobes will go down. So the way most people do the break in is having the motor start right up and run at 2000rpm for 30 minutes. Basically that is polishing the lifter bottoms. The problem with that process is ruining header coatings (excessive heat) and hoping there isn't a leak or problem where you have to shut it down.

After polishing lifter bottoms do you still do a traditional cam break in?
So lifter and cam lobe aren't really being seated together like piston rings and clyinder walls are done?

Nope. After you polish them you are done. No need for the 2000 rpm for 30 minutes needed. It's not a seating process.

[Cuda Cody]

That's a big difference.      

Left one straight out of the box with raw machining. Right one polished.

[HUSTLESTUFF]

An old racer friend of mine used to put sticky sand paper on glass to sand his lifters if he used a different cam.  I don't know of any sticky 1000 grit but you could probably tape some down.  Glass is very flat to sand on.  Mike

[Cudakiller70]

An old racer friend of mine used to put sticky sand paper on glass to sand his lifters if he used a different cam.  I don't know of any sticky 1000 grit but you could probably tape some down.  Glass is very flat to sand on.  Mike

Spray glue or contact cement works for sticking sand paper to glass.

[Shane Kelley]

An old racer friend of mine used to put sticky sand paper on glass to sand his lifters if he used a different cam.  I don't know of any sticky 1000 grit but you could probably tape some down.  Glass is very flat to sand on.  Mike

I just hold the sheet on a flat surface and work the lifter over it. It really doesn't try to slide around. The 1000 grit comes in half sheet size. I use 1 sheet for every 2 lifters.

[Cudajason]

That's a neat trick.  I've never heard it before and it makes sense.  I'll try it next time I build an engine.

I know what you mean. I have a Chevy friend that's a big engine guru and he kept telling me this for years on how he does it and never had a problem. But I had never heard of it or even read about it. Then he showed me. There it was right in a old GM racer manual like he said. I have been doing it this way ever since without issue. I done at least a dozen motors this way.

That is very interesting. 

I have wanted to change the cam in my 360 for a few years, and after all the horror stories I have heard of wiped lobes, I did not want to risk destroying a perfectly running engine.

I wonder if this the ticket?

Jason

[Cudakiller70]

That's a neat trick.  I've never heard it before and it makes sense.  I'll try it next time I build an engine.

I know what you mean. I have a Chevy friend that's a big engine guru and he kept telling me this for years on how he does it and never had a problem. But I had never heard of it or even read about it. Then he showed me. There it was right in a old GM racer manual like he said. I have been doing it this way ever since without issue. I done at least a dozen motors this way.

That is very interesting. 

I have wanted to change the cam in my 360 for a few years, and after all the horror stories I have heard of wiped lobes, I did not want to risk destroying a perfectly running engine.

I wonder if this the ticket?

Jason

It's only a piece of the ticket to a successful cam change. I can't speak to polishing the lifters, but I do know oil type, not just a high zinc plays a big part in wiping out cam lobes. with change back.