roller lifter

[joey74]

what the differents between a roller cam and stock cam? The reason i'm asking is i have the parts for roller lifters. I've been told that with roller lifters you have to use a roller cam.

 

[alwaysFlOoReD]

A roller cam will have steeper ramps. So that the valve is lifted off the seat to full open quicker, making for more time for fuel and air to get in the combustion chamber. A cam for flat tappet lifters will have a gentler slope. You could probably use roller lifters on a flat tappet cam, but not the other way. The edge of a flat tappet lifter will dig into a roller cam and ruin it quickly.

 

[19Walt93]

Don't use roller lifters with a flat tappet cam, it might work but if it doesn't you'll have metal particles throughout the engine. Then the engine would need to be completely stripped down and the block hot tanked by a machine shop before it can be reassembled.

 

[don4331]

Roller cams/tappets and flat tappet cams are incompatible to mix. You might get away with it short term, but eventually it will destroy the cam and/or the lifters. And maybe take the rest of the engine with them.

Why you ask?
A flat tappet isn't actually "flat" it just appears so because the radius of the curve is so large*. But if you put them on a sheet of glass, you will find they rock slightly versus sit solid. The corresponding cam has the lobs ground with a very subtle taper. The combination of the taper and the curve results in the tappet rotating in the lifter bore. That way the contact position is constantly changing on both the lifter and the cam, so wear is very, very slow. The larger radius and subtle taper allow the the oil film to distrubute the load

In contrast, as roller cam is machined flat to match the flat of the roller in the roller tappet therefore maximizing the contact surface.

If you put flat tappets with a roller cam**, the contact postion on the tapper never changes and after very short period the tappet wears and metal shavings fall into oil causing expensive damage.

If you put roller tappets on a "flat" tappet cam, only the edge of the cam is in contact with the roller and after short period, the tappet wears the cam or vice versa and again metal shavings fall into oil causing expensive damage.

* This assumes your cam manufacturer knows what they are doing. Failing to machine taper/radius is most common issue on reground cams/lifters, 2nd is grinding through the hard surface - most cams/lifters are only induction hardened a few thousands. They heat the cam white hot, then oil quench. But the heating was such a thin amount, you can handle the cam with bare hands right away. Its actually scary to watch the 1st time - someone handling cam that was white hot a moment ago.

**If your roller cam lift rate is so radical that it exceeds the edge of the flat tappet, the tappet will dig into the cam and failure will be almost instant.

 

[alwaysFlOoReD]

Roller cams/tappets and flat tappet cams are incompatible to mix. You might get away with it short term, but eventually it will destroy the cam and/or the lifters. And maybe take the rest of the engine with them.

Why you ask?
A flat tappet isn't actually "flat" it just appears so because the radius of the curve is so large*. But if you put them on a sheet of glass, you will find they rock slightly versus sit solid. The corresponding cam has the lobs ground with a very subtle taper. The combination of the taper and the curve results in the tappet rotating in the lifter bore. That way the contact position is constantly changing on both the lifter and the cam, so wear is very, very slow. The larger radius and subtle taper allow the the oil film to distrubute the load

In contrast, as roller cam is machined flat to match the flat of the roller in the roller tappet therefore maximizing the contact surface.

If you put flat tappets with a roller cam**, the contact postion on the tapper never changes and after very short period the tappet wears and metal shavings fall into oil causing expensive damage.

If you put roller tappets on a "flat" tappet cam, only the edge of the cam is in contact with the roller and after short period, the tappet wears the cam or vice versa and again metal shavings fall into oil causing expensive damage.

* This assumes your cam manufacturer knows what they are doing. Failing to machine taper/radius is most common issue on reground cams/lifters, 2nd is grinding through the hard surface - most cams/lifters are only induction hardened a few thousands. They heat the cam white hot, then oil quench. But the heating was such a thin amount, you can handle the cam with bare hands right away. Its actually scary to watch the 1st time - someone handling cam that was white hot a moment ago.

**If your roller cam lift rate is so radical that it exceeds the edge of the flat tappet, the tappet will dig into the cam and failure will be almost instant.

Thanks for the refresh. I had forgot most of that info...

 

[joey74]

Thanks guys what would be a good cam and what size should I use 5.0 bored 40 over?

 

[scotts90ranger]

did it come stock with a flat tappet cam or roller cam? The overbore makes less difference than you would expect, porting the head along with a mild cam will make more difference than anything I'm pretty sure...

Buying lifters anymore is gambling, I wasn't in the mood on my Explorer last year so I just re ran the stock roller lifters but threw in a mild cam and heavy valve springs...

 

[85_Ranger4x4]

And end use of truck is huge in cam selection...

 

[joey74]

did it come stock with a flat tappet cam or roller cam? The overbore makes less difference than you would expect, porting the head along with a mild cam will make more difference than anything I'm pretty sure...

Buying lifters anymore is gambling, I wasn't in the mood on my Explorer last year so I just re ran the stock roller lifters but threw in a mild cam and heavy valve springs...

It has flat tappet

 

[joey74]

And end use of truck is huge in cam selection...

daily driver

 

[don4331]

What heads, what intake, what exhaust?

 

[joey74]

What heads, what intake, what exhaust?

gt40p edelbrock 2 plane dual with glass packs

 

[joey74]

gt40p edelbrock 2 plane dual with glass packs

anybody have a roller cam for sale?