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Old 03-15-2001, 07:23 PM   #1
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CAM TECH: ROLLER VS. FLAT TAPPET

Theoretically speaking. How much power and torque does a roller cam offer over flat tappet? Comparing 2 cams identical in lift, duration, and overlap.

With rollers you get more agressive ramps more lift and less friction.

In a typical 204/208 stock cam how much power would the roller offer over flat tappet? 5hp? 10hp?

How much did GM say the 87'up small blocks gained in hp due to the introduction of stock roller camshafts?

I ask because I am going from a roller cam to flat tappet cam (for a number of reasons).


------------------
1986 CAMARO Z28 ->
151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, B&M Ripper shifter, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframe connectors, all bushings are urethane, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.22@ 106.4MPH 3300lbs less driver and speakers Next mods-> Extreme Energy 268 cam, Holley street dom intake.

1987 TRANS AM ->
73,000 miles, 305TPI, auto, gutted air box.
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Old 03-15-2001, 07:58 PM   #2
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Just out of curiosity, why are you going from Roller to Flat Tappet?

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Old 03-15-2001, 08:06 PM   #3
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I would really like to keep the roller setup but, I'm just finishing up my 2nd year in college, money is pretty tight right now.

Here's the thing. My lifters are shot and they are about 200 bucks for replacements. A new cam alone is going to run me 250, that's 450 for just cam and lifters. I priced out a flat tappet swap and came out to 400. That price is for cam, lifters, pushrods, rockers, springs, gaskets, timing chain, etc. I figure for the price, power, and application the flat tappet is the way to go. And in the future if I want to swap back I can because the provisions will be there.

Now....can you answer my question? Click the image to open in full size.

------------------
1986 CAMARO Z28 ->
151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, B&M Ripper shifter, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframe connectors, all bushings are urethane, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.22@ 106.4MPH 3300lbs less driver and speakers Next mods-> Extreme Energy 268 cam, Holley street dom intake.

1987 TRANS AM ->
73,000 miles, 305TPI, auto, gutted air box.
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Old 03-15-2001, 08:17 PM   #4
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Typically on a street car you will not see a noticable difference, however, rollers offer less valvetrain stresses and friction and offer longer life.

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Old 03-15-2001, 08:20 PM   #5
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whoa....that was not what I expected. Are you sure? If so that's suprising. I'm not questioning your knowledge but what is your source? Thanks for the reply.

------------------
1986 CAMARO Z28 ->
151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, B&M Ripper shifter, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframe connectors, all bushings are urethane, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.22@ 106.4MPH 3300lbs less driver and speakers Next mods-> Extreme Energy 268 cam, Holley street dom intake.

1987 TRANS AM ->
73,000 miles, 305TPI, auto, gutted air box.
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Old 03-15-2001, 09:45 PM   #6
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JDM,

An important thing to remember is that two cams can be "identical in lift, duration, and overlap" but have entirely different profiles and subsequent flows. A roller cam enjoys a smaller radius of contact, and can open the door to a lot more aggressive and better flowing profile.

This exaggerated diagram shows how the same specification numbers can result in a totally different profile, and totally different behavior from the engine:

Click the image to open in full size.

The left lobe is most like a flat tappet design, while the center lobe is most like a roller tappet design, with much better overall flow, or "area under the curve" than the flat design. The right lobe is shown as an example of an "economy" grind, with a large opening ramp and rapidly closing valve. (Remember, the cam rotates clockwise as viewed from the front.)

I hope this helps illustrate why the extra $50.00 for parts is worth every penny. And if you shop around a bit, you can probably get a better price on a complete roller kit, like a Competition Cams "K" Kit.

If you want stock roller lifters, you can get a set for $120.00 instead of $200.00 for aftermarkets. A Comp Cams 12-388-4, 12-402-4, or 12-404-4 each sells for $117.00 at Summit, and they're a hydraulic roller design. The 12-404-4 is a .464/.464, 222/226, 114 LSA grind, and the others are a bit more mild. You might get a lot of cam for a little cash if you're not careful.

Shop around a little before you make your decision.

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Old 03-15-2001, 10:26 PM   #7
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Wow Vader, I was just having a discussion about the profiles being different for cams that spec out the same this past weekend! I'm gonna print out that pic to make my point clearer!

------------------
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Old 03-15-2001, 10:37 PM   #8
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Wow, my sources? Alot of reading, alot of tinkering and numerous discussions with engineers, designers and builders. When I was building my first GTA I actually harassed John Lingenfelter on a few issues, this being but one. I will grant you that those conversations took place over a decade ago, but I keep finding concurring data in magazines and books. You will note I said in typical street cars, and that would include slightly modified motors. When you start tinkering in the 350+ HP 400+ lb/ft range or high RPM ranges, then you will have serious reasons for the roller cams, for many more reasons than just power.
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Old 03-16-2001, 12:13 AM   #9
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well it all depends on the specs of the whole engine as to how much difference it can make.
I'd say on a typical hotrodded street engine you could see anywhere from 0 to 10% power gain by switching to a hydraulic roller.
I definately prefer hydraulic rollers because of the expanded usable power range.




------------------
*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
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Old 03-16-2001, 08:36 PM   #10
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Vader, I thought those cam profiles were made up for the shape of the lifter. A roller style lifter is more likely to have the center of the lifter follow the cam than a flat tappet type. If you take into account the way a flat tappet lifter would ride the cam, the lift would be close to the same no? As it comes up, it will grab the corner before the center and the going down it will grab the other corner instead of the center (not the exact corner but favoring toward it from the naturual center). The roller lifter will have more of an ability to stay aligned on the center....that's just my thoughts.

Rollers are nice for their high RPM potential. Even if you're not making unstreetable power, with the correct engine combo, nothing is like taking a SBC to 8500.

[This message has been edited by 84FTA (edited March 16, 2001).]
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Old 03-16-2001, 08:57 PM   #11
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Rollers definitely allow for a more aggressive cam profile than flats. That's why all of us have been using rollers in really high-performance motors for so many decades, since long before the factory "discovered" them.

If you look at how a flat-tappet lobe approaches the bottom of the lifter, you can see that as you increase teh steepness of the ramp, you can reach a point at which the "point of contact" between the lobe and the lifter ceases to move smoothly across the lifter face. Once you get to that point, long-term survival of the whole system is impossible. Since a roller doesn't have a flat surface for the ramp to come up to and "slap" into, there's proctically no limit to how steep you can make the ramps. The limit becomes how much beating the rest of the valve train can take.

They also allow for much higher cam lobe loads and therefore spring pressures, allowing higher RPM before the valves float.

Most of the time, people get 5-8% more horsepower out of a roller, compared to a flat with equal lift, .050" duration and advertised duration specs.

A flat tappet lifter doesn't ride the center of the cam. It rides the edge of the lobe that's toward the rear of the engine, ideally about 1/16" from the edge of the lifter. This does 2 things: it forces the lifter to rotate since the lobe is trying to wipe across it so far from the center, and it forces the cam rearwards in the block. That's why with a roller you have to run a cam button, and instead of that simple and cheap and time-tested fix, the factory put that stupid retainer plate thing in the front of the block.

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Old 03-24-2008, 09:03 PM   #12
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

hello everone here is my question basicly i have a 1989 camaro with a 5.7 tuneport. it has roller lifters already. i just bought a cam and lifter set for the car and it cam with a cam of course and flat lifters...not the roller ones. my question is can i just use the cam that i bought and then re use my roller lifters that are already in the car???? please help asap thank you

Last edited by 06andersen; 03-24-2008 at 09:07 PM. Reason: Automerged Doublepost
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Old 03-24-2008, 09:19 PM   #13
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

No you cannot do that. See RB83L69's description of the shape of the lobe, for why. A roller lobe is parallel to the cam axis, but a flat-tappet one is tapered, with the edge closer to the rear of the motor taller than the edge closer to the front, by a couple of .001"s. Mixing the 2 systems is a 100% ironclad guarantee of a wipe-out.

Sell or return the flat-tappet cam and get a roller one. Pick one that's SPECIFICALLY for TPI; not just, the cheeeeepest thing that says "cam" on the box, or what "everybody" is running, or that "lopes alot". None of those cam-picking methods is any more successful than a dartboard.
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Old 03-24-2008, 09:26 PM   #14
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

thank you im glad u told me that before i went out and did all that work to find out that it wasn't going to work....i basically already did that i installed a cam out of a 76 5.7 with flat lifters and put it in my car with the roler lifters found out it runs good till u hit the high rpm's so ya. if im going to replace the cam for money wise its prolly better to just get a bigger cam??
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Old 03-24-2008, 10:40 PM   #15
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

I'd be willing to bet that the cam is ruined, since the lifters can't sit flat on it, but will only ride on their edge....

But yeah, it'd be a good idea to get another cam. This is one that's known to work well in a mostly stock 350 TPI. http://store.summitracing.com/partde...2D08%2D501%2D8 It'll DEFINITELY need new valve springs, if you haven't already changed tehm; follow Comp's recommendations, at the minimum.
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Old 03-24-2008, 11:27 PM   #16
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

new valve springs??? how come??
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Old 03-24-2008, 11:47 PM   #17
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

im looking to put a cam in my 88 l03 tbi engine and im looking for a cam where i can pull the old, slap in the new, put new springs in without having to tune the ecm. Does anyone have any suggestions on what brand i should be looking at? Sorry to jump in on the thread but its something ive been looking at for a very long time, and seeing as i already bought the wrong cam... Got a flat tappet instead of a roller...
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Old 03-25-2008, 01:08 AM   #18
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

Just wondering, but if your upgrading to 1.6 rocker arms could you upgrade from regular steel rocker arms to roller rocker arms without out having to change anything else?
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Old 03-25-2008, 07:34 AM   #19
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

jdm you can get a set of z28 springs brand new roller lifters and a zz4 rollercam for right around 225 on ebay

every day of the week
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Old 03-25-2008, 10:51 AM   #20
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

JDM posted this over 7 years ago.....

I'm betting he's either figured it out and got a cam, or has got out of this hobby, in all that time....

Meanwhile, you need new valve springs, because stock ones - ANY stock ones, including the "LT4" ones, or the "Z28" ones, or ANY other stock ones - are lame. Used stock ones are worse, being about as limp as a dishrag. A modern, aggressive, performance roller cam snaps the valves as far open as fast as the mfr dares, up to the point of pulverizing valve train parts; holds the valve as far open as possible for as long as possible; then drops it as rapidly as possible back onto the seat. Reason being, POWER comes from BURNING FUEL MOLECULES; fuel molecules require AIR to burn; therefore, the more air you can get into and out of the cylinder, the more power PER CYL FIRING you can make; and the only ways to get more of anything through a time-porportioned valve, is to open the valve FASTER, open it FARTHER, hold it open LONGER, and close it FASTER when it's done.

One of the main enemies of engines, which will DESTROY parts faster than almost anything else, is valve float. This is the condition where the springs no longer keep tension on the valve train, but instead, allow the parts to float around freely in space, and then COLLIDE abruptly whenever they touch again. Of course if you think about the force of a spring under compression, it's weakest at its longest extension, which in the case of valve springs, is at the point where the valve is fully closed. Float most often occurs here: the valve literally bounces off the seat. The more aggressive the cam's ramps, which results in the valve dropping back onto the seat faster, the more it will tend to cause this kind of float, and the more spring you need to prevent it. The harmonics produced in the spring by this pounding are strong enough to break it, just like hitting it with a hammer. In fact, it IS the same thing as hitting it with a hammer, if you want to think of the head casting as just an unusually-shaped hammer.

Typical hyd rollers require 130-140 lbs on the seat to prevent valve float.

Typical worn stock springs produce less than 80 lbs on the seat.

"Z28" or "LT4" springs produce 100-110 lbs on the seat, WHEN NEW; enough, BARELY, for typical mild stock cams like the LT4 HOT cam or the ZZ4 cam, WHEN NEW, but not enough for aggressive aftermarket rollers, and not enough after a few thousand miles. Cheeeep springs are a false economy: the difference in how a motor runs is sometimes AMAZING from just replacing weak springs like that with good ones.
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Roughly paraphrased into modern English, and applied to figuring out what's wrong with your car:

The simplest explanation that fits all the facts is probably the right one.

Last edited by sofakingdom; 03-25-2008 at 10:55 AM.
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Old 03-25-2008, 02:08 PM   #21
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

That's a pretty good write-up, except for one little mix up:

Quote:
it's weakest at its longest extension, which in the case of valve springs, is at the point where the valve is fully closed. Float most often occurs here: the valve literally bounces off the seat.
There are two different cases of valve control: One is Float, the other is bounce.

Bounce occurs when the valve bounces off the seat due to incorrect seat
pressures. This causes cylinder pressures to bleed off at IVC (intake valve
close) while the piston is compressing the mixture. Exhaust valves may bounce
and cause gas to revert.

Valve float occurs when the lifter lofts off the nose of the opening side of
the ramp and the vave is then suspended without suffient open pressure
to push the valve, lifter, rocker, and pushrod against the closing side of
the lobe.

While the valve is suspended, hanging open, the piston rushes up and tags
the valve. This is mostly a problem on the exhaust valve during exhaust valve
closing (EVC).
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Old 03-26-2008, 01:47 AM   #22
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

As usual, Sofa's right on the money with his advice on springs. I was going to run the ZZ4 cam in my L98, and I bought the orange colored, factory ZZ4 springs to use with it. I figured since they were specifically listed for the ZZ4 engine, they should be more than adequate. That was before my machinist checked the seat pressure on them and told me they were barely at 90 pounds! Then I proceeded to read a bunch of posts on here where the same orange "ZZ4" springs were breaking on almost new engines. I said the hell with that and upgraded to Isky's 235D springs, which are stock diameter, and have 130 pounds of seat pressure. They cost a lot more than the GM springs did, but they're FAR superior. I'd rather spend the extra money on good springs than spend $60 for springs that'll break and end up destroying lots of things.
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Old 03-29-2008, 09:09 AM   #23
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

sofa is always on the money with the info

if you are going to keep the rpms under 6k the z28 springs will work with a mild roller cam

if you get all kinds of wild and lopey you need to spend more cash
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Old 03-29-2008, 12:45 PM   #24
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Re: CAM TECH: ROLLER VS. FLAT TAPPET

Quote:
Originally Posted by 06andersen View Post
thank you im glad u told me that before i went out and did all that work to find out that it wasn't going to work....i basically already did that i installed a cam out of a 76 5.7 with flat lifters and put it in my car with the roler lifters found out it runs good till u hit the high rpm's so ya. if im going to replace the cam for money wise its prolly better to just get a bigger cam??
That cam and likely the roller lifters are now toast, along with metal in the oil, best to get all new roller lifters and the proper cam to go with them. And anybody that can't afford good parts and needs to buy used or cheap flat tappet junk just to get a Camaro running should be driving a gas sipping Honda instead.

Last edited by DartByU; 03-29-2008 at 12:48 PM.
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