I posted my question in the wrong area first...I think.

Anyway, my question was: Can you run roller lifters with a non-roller cam in a street app?

This motor will not have too steep of a lift (about 400) and not a very long duration (about 290). The only thing I was looking for in this motor is to be the heart of a semi tuff street car.

The app notes that I have found is that you can not run roller lifters with a non-roller cam. This does not make any sence to me...I would under stand that using friction lifters with a roller cam would cause problems because of the ramps...but...a roller lfter following the contour of the lobe would cause a problem???? I know that a roller cam has harder lobs and a steeper opening and closing ramp, but would rollers cause a problem?

No , the lobes on a roller cam are wider because the roller has a small contact area
a flat tappet cam rides on the edges when the valve is in motion, you would have the same advertised lift but your lift at 50 thou, 100 thous, would be way down.
http://www.supermotors.org/getfile/163978/fullsize/cam%20lobes.jpg
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1972 Camaro 350 factory heads 1.94/1.5 street driven full interior
93 octane everything works 7.59
89.54 mph
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[This message has been edited by Mwilson (edited December 09, 2004).]

[This message has been edited by Mwilson (edited December 12, 2004).]

Flat tappet cams have a taper on the lobes, so the roller wouldn't be touching on much of the cam lobe anyways. Plus a roller cam is much harder than a flat tappet cam to deal with the hard rollers.

Ok....So, the duration will be cut in half...thats not good. Has anyone ever done this?

<font face="Arial,Verdana" size="2">Originally posted by sheriffpridg:
I posted my question in the wrong area first...I think.

Anyway, my question was: Can you run roller lifters with a non-roller cam in a street app?

This motor will not have too steep of a lift (about 400) and not a very long duration (about 290). The only thing I was looking for in this motor is to be the heart of a semi tuff street car.

The app notes that I have found is that you can not run roller lifters with a non-roller cam. This does not make any sence to me...I would under stand that using friction lifters with a roller cam would cause problems because of the ramps...but...a roller lfter following the contour of the lobe would cause a problem???? I know that a roller cam has harder lobs and a steeper opening and closing ramp, but would rollers cause a problem?</font>

The biggest physical reason you can't run a flat tappet cam with roller lifters is the lobe placement. Roller cams have the lobes centered under the lifter bores, flat tappet cams are offset to promote lifter rotation.

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<font face="Arial,Verdana" size="2">Originally posted by Mwilson:
you would have the same advertised lift but your duration would be cut in half!

</font>

How's that?

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well i didnt mean it like that the duration would be the same the lift at any given duration would be way down

<font face="Arial,Verdana" size="2">Originally posted by Mwilson:
well i didnt mean it like that the duration would be the same the lift at any given duration would be way down</font>

OK.

How's that?

A hyd cam is a hyd cam. Changing the lifters (besides other problems as mentioned) from flat to roller wouldn't effect the characteristics of the cam. The flanks' profiles would stay the same, as well as the lift.

Well, I have also posted this in troubleshooting section of the message board. I have been getting feedback there too. I got some info last night telling me that if the lifters has the stabilizing bar on them they would work. But, I know that a non-roller cam is ground so that it would promote the lifter to rotate and the lobs are not centered. I see how that would cause an emotional moment.

yes, the cams profile is the same when you swap lifters, but here's the thing.
With a flat-tappet cam, the base of the lifter is the full width of the lifter bore. The edge of the lifter rides against the cam, so it follows the part of the cam that is directly under the edge of the bore.
With the roller cam, the point that the roller contacts the cam is closer to being under the center of the lifter bore because the base of the lifter is curved (the roller wheel).
This is why the roller cam lobes look very square compared to the tapered lobes on the flat tappet.

I'm not sure if this describes it well. Someone once posted a pic that shows everything ion a profile view, so you can see why the roller lobes have to be so much different.

Yeah it would, take a regular cam(flattappet)
stick it in the block rotate the cam with a roller lifter in one hole and flat tappet in another the flat tappet starts moving when the edge contacts the the lobe immediatly after the lobe passes base circle, the cam will rotate farther before the roller of the roller lifter starts contacts this area, ever look at two cams with the same specs, only one is a roller the roller cam will have much wider lobes yet both cams have almost identical specs. The flat tappet would open much sooner and higher all the way to max lift than the roller if you put them on a flat tappet cam.



[This message has been edited by Mwilson (edited December 10, 2004).]

It,s a very bad idea anyway you look at it and no matter who you are.

Look into Shuebeck lifters. I use them in my sprint car (VERY large flat tappet cam). The base is made out of ceramic and the rest is hollow. The face of the lifter never wears out, and can be interchanged to any lobe without affecting the cam. I've ran the same set for three years on about five different cam profiles with no problems. They weigh about half of what a normal solid is. They also make a radiused ceramic lifter for using on Roller cams.

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[URL=http://www.ncmaracing.com
http://www.ncmaracing.com

Here is an illistration

infopop.com (http://www.supermotors.org/registry/vehicles/showmedia.php?id=163542)

[This message has been edited by Mwilson (edited December 10, 2004).]

Gotcha. I see what you're saying.

I guess your sarcasim threw me a little. http://www.nastyz28.com/ubb/wink.gif

I can attest to that being true. I was degreeing a cam in a 350 I was building and got lazy and used a roller lifter I had laying around. THAT didn't work.

It wasn't off by a whole lot since a flat tappet does have a convex surface, but it was enough to throw off the .050" duration enough to cornfuse me. http://www.nastyz28.com/ubb/confused.gif

Once I realized that wouldn't work that I asked "Where's my sign?" http://www.nastyz28.com/ubb/smile.gif

Well, the roller lifters will not be ran. Thank you for all y'all imput. I was not clear about why til now. I have been putting the pressure on my brother-in-law on what was being said here...Needless to say the roller lifters are out of the Trans Am til he can get a roller cam.


Thanks for all y'alls help
Russell