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Chasing dreams with a ball bat
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Discussion Starter · #1 ·
hey all,

I know this had been debated several times and I've read the posts. However, here's an interesting little tidbit.

I am using a trial version of the Engine Analyzer Pro (sweet program, BTW), and was doing some research using both my babies, a 350, 10.5:1, and a 406, 9.9:1

Started fooling with different cams and such and it would seem that a hydraulic roller with the same @ .050 duration is only worth a few HP and a few ft-lbs. talking like 10 or so in each case - the average numbers also fell about 6 HP and 8 ft-lbs, telling me that the overall torque and power curves fell slightly. So there is a slight performance advantage, even on paper. And that program does take into account friction. I compared a mild hyd. roller with an aggresive hyd. flat tappet, perhaps not entirely fair, but hey.

So let's see, a roller cam: $275, roller lifters : $450, roller cam buttom, stiff front cover etc, $50 (not to mention different pushrods) Versus a flat tappet voodoo or xtreme NRG from comp with aggresive lobes (which can get closer to a hyd. roller valve actions) for $150-175 with lifters.
Roller: $775, flat tappet $175. $500 for 10 HP hurts baby! :spank:

Get nitrous instead. :mwink:

I feel raped. :embarrass

Anyone else have a different take on that? Perhaps Engine Analyzer is lying to me???? :evil:
 

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Hotrodders.com Moderator
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dyno program

Where did you get the trial sample???? Can you pm me the link??

I have some opinions about this issue but i would like to play with the program first...

Also if you compaired one cam to another and it wasn't a parallel test then you cannot say for sure what the results are...more agressive flat to a mild roller....

One thing to figure in..... If you loose a lobe on a flat tappet cam and need to remove the entire engine,dis-assemble, remove cam bearings and freeze plugs hot tank,grink or polish crank, new main and rod bearings...... The $600 for the roller starts looking like a deal!!!!!IMO


Keith
 

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Bottle Fed
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k-star said:
One thing to figure in..... If you loose a lobe on a flat tappet cam and need to remove the entire engine,dis-assemble, remove cam bearings and freeze plugs hot tank,grink or polish crank, new main and rod bearings...... The $600 for the roller starts looking like a deal!!!!!IMO
Keith

I agree 100%. I personally will never run a flat tappet cam in a performance oriented engine ever again.
 

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It's simple, and Engine Analyzer Pro is very smart and accurate.

IF you model a camshaft lobe profile that is basically the same between a roller and a solid flat camshaft of course the numbers will basically be the same. All it's looking at is the lobe profile that you asked it to model. There will be some allowance for friction reduction which might be accounting for some HP gain and that can be verified via the analysis data.

The benefit to the roller profile is to get the valve lifting faster, as well as in most cases higher, in a shorter amount of time. In other words the amount of degrees of camshaft rotation to get to .100, .200 and so forth is less with a properly designed roller profile. That is the advantage to using a roller.

As you can see, and Engine Analyzer confirmed this, if there is very little or no difference in lobe profile there will be very little or no difference in power.

As for loosing a lifter. If you ever loose a roller it's a mess as well. Granted, there is no break in on a rolller but when they go, the spew debris as bad as a solid, if not worse. That's not something with a hyd though I'd be concerned about.

K-Star www.performancetrends.com

Follow the links to the Demo. This is a great program and we use it all the time. We have EA software that links between the flowbench data, cam doctor and then into the Engine Analyzer Pro. Without exception every race motor is designed this way and most of the high performance street stuff. As long as all the data is accurate the end result numbers come out very close to our actual dyno verification. If they don't, we know something is amiss. All of the Performance Trends software is excellent. The guys that work their are all brainiacs when it comes to this stuff, very hard core.
 

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Bowtie or Die!
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k-star said:
Where did you get the trial sample???? Can you pm me the link??

I have some opinions about this issue but i would like to play with the program first...

Also if you compaired one cam to another and it wasn't a parallel test then you cannot say for sure what the results are...more agressive flat to a mild roller....

One thing to figure in..... If you loose a lobe on a flat tappet cam and need to remove the entire engine,dis-assemble, remove cam bearings and freeze plugs hot tank,grink or polish crank, new main and rod bearings...... The $600 for the roller starts looking like a deal!!!!!IM




You nailed it! Happend to me before. No flat tappets for me.
 

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Save a horse, Ride a Cowboy.
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Any upgrade requires the corresponding upgrade in valve train components. Heavier weight roller lifters require stronger valve springs = more friction, more power to compress, which in turn requires a better roller lifter to stand the pressure.
More lift requires full roller rocker arms, stouter springs, and better pushrods.

There is a lot of additional expense to cam upgrades, some more, some less. It becomes a snowball.

It's hard to beat an hydraulic roller if done properly.

Flat tappets generally can stand a maximum of 300 lbs. over the nose of the cam if there is going to be any degree of longevity.

Power production is not the only consideration.
 

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hotrodf1 said:
hey all,

I know this had been debated several times and I've read the posts. However, here's an interesting little tidbit.

I am using a trial version of the Engine Analyzer Pro (sweet program, BTW), and was doing some research using both my babies, a 350, 10.5:1, and a 406, 9.9:1

Started fooling with different cams and such and it would seem that a hydraulic roller with the same @ .050 duration is only worth a few HP and a few ft-lbs. talking like 10 or so in each case - the average numbers also fell about 6 HP and 8 ft-lbs, telling me that the overall torque and power curves fell slightly. So there is a slight performance advantage, even on paper. And that program does take into account friction. I compared a mild hyd. roller with an aggresive hyd. flat tappet, perhaps not entirely fair, but hey.

So let's see, a roller cam: $275, roller lifters : $450, roller cam buttom, stiff front cover etc, $50 (not to mention different pushrods) Versus a flat tappet voodoo or xtreme NRG from comp with aggresive lobes (which can get closer to a hyd. roller valve actions) for $150-175 with lifters.
Roller: $775, flat tappet $175. $500 for 10 HP hurts baby! :spank:

Get nitrous instead. :mwink:

I feel raped. :embarrass

Anyone else have a different take on that? Perhaps Engine Analyzer is lying to me???? :evil:
I think you're lying to Engine Analyzer. You need to put real data in for the cam, not just switch the selection from flat tappet to hydraulic. You'll never get the same area under the curve from a flat tappet cam that you can get from a roller.
 

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Chasing dreams with a ball bat
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545 Posts
Discussion Starter · #9 ·
k-star said:
Where did you get the trial sample???? Can you pm me the link??

I have some opinions about this issue but i would like to play with the program first...

Also if you compaired one cam to another and it wasn't a parallel test then you cannot say for sure what the results are...more agressive flat to a mild roller....

One thing to figure in..... If you loose a lobe on a flat tappet cam and need to remove the entire engine,dis-assemble, remove cam bearings and freeze plugs hot tank,grink or polish crank, new main and rod bearings...... The $600 for the roller starts looking like a deal!!!!!IMO


Keith
Don't forget - plenty a guy has fragged a roller lifter as well!! It happens. In fact, Comp Cams says that you should periodically check the rollers, axles, bearings for cracks, wear, etc when you get a set of their Magnum lifters.
 

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Chasing dreams with a ball bat
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545 Posts
Discussion Starter · #10 ·
onovakind67 said:
I think you're lying to Engine Analyzer. You need to put real data in for the cam, not just switch the selection from flat tappet to hydraulic. You'll never get the same area under the curve from a flat tappet cam that you can get from a roller.
I would agree with you - physically, the roller is better. I understand getting the valves open quicker should allow more air to flow compared to a flat tappet variety that opens the valves more slowly. I just thought it would be worth more power than that.

As far as inputting the right info - when the computer spits out the result it gives you a duration @ .200" lift as well - and when I change the cam type (mild hyd roller, agg roller, mild flat, aggr flat) you can see that the numbers change. That suggests to me that the program is in fact taking into account more and less aggresive lobe profiles.

What I'm suggesting here is that all the money spent on going roller (which I thought was going to be worth every penny) was perhaps not spent in the right spot for me.

I did input real data for the cams. Actually tried to get a "best" run from each type, (which of course meant choosing different adv. durations), but when it was all said and done - I could have chosen the right flat tappet cam and been within 10 or so HP throughout the powerband. When you change the type of cam in the program, it just simulates a more aggresive lobe - which allows a comparison of two cams with the same @ .050" durations.

If one is looking for a more radical valvetrain, the roller (hyd. or especially solid) would be the way to go - however, on a street vehicle with any manners, that sort of cam is not necessary so I'd say the flat tappet is just near as good at that point.

If my 406 was 12.0:1, I could run that 306/314 in there on pump gas - DCR would be close to 8:1 - and she would fly. However, there are -20cc reverse dome pistons in it that give me 9.9:1. The 306/314 is just tooooo big.

I would have been better off buying an LM-1 and tuning the engine properly - you can gain way more than 10 HP and probably several MPG too. :thumbup: Course I bought one anyway. I have learned SOOO much from mine. LOVE IT!
 

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Roller cams act like a hydraulic cam 10 degrees smaller in manners. I can run a mechanical roller with 246/252 @ .050 and still have plenty of vacume for the power brakes. Same with the hydraulic roller having manners like a much smaller flat tappet hydraulic. Since you can run a cam 10 degrees larger and have the same street manners, it seems that it would be fair to run the test with 10 a degree larger roller cam.
 

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To do the calcuation correctly you need to confirm either off a Cam Doctor test or via the cam manufacturer what the .200 duration numbers are for the compared camshafts.

Again, of course if you simulate two camshafts that have basically the same lobe profile they are going to A) look exactly the same to the valve they are lifting, and B) basically make the same power.

It's as simple as that. Unless your going to take advantage of the benefits of the roller within the lobe profile there really is no reason to go roller. For the exact reasons you mentioned. Taking advantage of the roller design and lifting the valve off the seat quickly and to a high lift is where you gain the power.
 

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hotrodf1 said:
Don't forget - plenty a guy has fragged a roller lifter as well!! It happens. In fact, Comp Cams says that you should periodically check the rollers, axles, bearings for cracks, wear, etc when you get a set of their Magnum lifters.

Yes roller lifter failure is something that can happen, but in the mild hyd roller cams i think it's a none issue...I would bet you can't find 5 guys on this site that lost a roller on a mild hyd roller cam,,,but you can find 10 times that amount that lost a flat tappet lobe...IMO the odds are against you on that one...

Now a solid roller with 1000 lbs over the nose,,,thats another story!!!

keith
 

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Chasing dreams with a ball bat
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Discussion Starter · #14 ·
I re ran the numbers the morning, checking everything over.
Somehow when I ran the flat tappet yesterday the SCR got changed to 10.6 . Ihave no idea how that happened, but that's what scewed the results.

Tried it again today to see if I could prove myself wrong: Used the same specs at .050, same LSA, same ICL, just changed the type from mild flat tappet to aggresive hyd. roller (which should be maximum benefit) to see what would happen. The roller returned with a little less torque on the bottom end at up to 4000 RPM, but then the roller started to shine 557HP at 6000 RPM versus the flat tappet's 541 HP at 5500RPM (after which Engine analyzer said the lifters were pumped up). At 6000 RPM the flat was only making 483 HP, which is due to lifter pump up - I don't think that is represented correctly, but oh well.

So then, just for fun, I jacked the flat tappet duration until the @ .200" duration was the same and reran it. It got closer to the same peak HP (as expected), but the torque in the lower end was way down, and the idle vacuum would be 9" Hg. So it would be really too hot for the street I think.

Someone suggested I try running the roller with an extra 10 deg. of duration - so I tried that too. Unfortunately, my SCR doesn't support that very well, but I still came up with 565 HP at 6000 RPM, while loosing torque up to 5.5K. Idle vacuum dropped to 9.9 (the flat was 11.8 which suggests more street friendly). Clearly the first roller was better in almost every aspect at this SCR of 9.9.

SO there you have it - the roller reigns supreme if you want to be streetable and have enough cam to make those big heads breathe. Sorry for posting inaccurate data - I should have been paying more attention. :drunk:

If budget is an issue, the street racer would do the flat tappet and then use the "extra" money for nitrous. Or else build a mild big block 496 :evil:
 

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http://teamrfc.gospelcom.net
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Here is another comparason. These are the same motor except the cam used. To me, this seems like a good way to compare the two cams. The common factor in each cam in the duration @.050. Recommended powerband is also very similar. 1600-5800 for the hyd flat tappet and 1900-5600 for the hyd roller. both cams have 224 230 @.050 duration.

Hyd flat tappet.

made 342 hp @ 5000 RPM
413 ft lbs @ 3800 RPM
http://www.compcams.com/Technical/DynoSheets/XE268H-10_001.asp


Hyd roller

Made 373 hp @ 5200 RPM
427 ft lbs @ 3700 RPM
http://www.compcams.com/Technical/DynoSheets/XR276HR-10_001.asp

The two cams performed in very similar powerbands, which I would expect with the same duration @.050, but the roller made more hp and more torque.

Here is the list of all the dyno tests on the comp site
http://www.compcams.com/Technical/DynoSheets/

Adam
 

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don't remember, but I read somewhere that some big engine builder guru like David Vizor(spelling?) said a roller cam was not worth it with anything under 270 advertised duration cams.....just a vague memory though...
 

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Resurrecting this old thread, as I'm looking at both cams types right now and have read and searched all kinds of old posts without really finding the answer I'm looking for.
Two posts up there's an A vs B comparison.. but it's not quite the apples/oranges, as the roller has more lift.
I've found roller cams that have the desired lift and duration that I'm looking for, but can't seem to transfer that same setup into a flat tappet cam. Like the above comparison... it seems that every flat tappet cam I find with the desired duration @ .050 has less lift than I want.
If you want higher lift in the flat tappet... you have to have the longer duration too it seems. Is there a reason for that? Will a similiar profile in a flat tappet cam not work properly due to the ramps or something?

(Just to be specific... the roller cam I'm trying to duplicate is 0.510 int./0.525 exh. and 219 int./225 exh. @ .050)
 

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Rod...from a Chrysler?
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You'll need 1.7 rockers with a hydraulic grind to get that lift at such a short duration.

Comp has a bunch of standard lobes. I just custom ordered a mild roller myself using the grinds available. I checked different lobes on my Engine Analyzer.

Very pleased with my results. Everything from the EA was bang on.

Check the PDF on the link below of lobes available. Plug in the numbers and see how that goes for you.

http://www.compcams.com/Technical/Catalogs/LC2007/2007LobeCatalog.pdf
 

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You need to look at this a little differently. The flat tappet design by its nature is limited to the rate of lift (as you have verified). Apply lift too quickly and at worse the edge of the lifter contacts the lobe and digs a trench.

The best thing about roller cams is the additional lift without sacrificing idle quality or low RPM drivability. Long term durability on the street for a flat tappet dictates maximum lifts around .500", while the roller will yield the same life with maximum lift around .600". Even if you don't utilize the additional lift of the roller, the roller is opening the valve much faster and keeping it open longer. It is also doing this with the same amount of closed time on the valve. Except for the initial cost, it is definitely a win-win situation with the roller.

edit: As 123pugsy pointed out, you can use a higher ratio rocker, but this is still no where near the area under the curve available with the roller -- and the high ratio rockers also extend the duration of the FT cam you are using. For that matter, you can use a high ratio rocker with a HR, and have even more area under the curve if you desire.
 
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