Roller vs. Flat-Tappet Cams! - Engine Masters Ep. 16 Motor Trend Channel

[427HISS]

I know,...there are many threads, video's and books about this very same discussion, but not by me. 

Please note, that I'm not talking about top high performance, same cam specs or exact apples to apples, but debating a fairly mild 500 HP, costs vs power vs sound vs feel, is 21.4 HP worth the added expence of a roller engine.

Say, $250 flat tappet vs $1,000 mechanical roller.
Having to lash valves vs seldom.

Also weigh in on this question.

Working on engines is fun, almost theaphy, so I don't mind lashing my valves a few times per season.
This question shouldn't be in this thread, but is there a difference betwern your muscle car, hot rod etc vs your race car, in having to lash your
 valve train ?

Or, to some it's a pain in the butt, so you have a buddy or a mechanic do it for you. No,...shame with that.

The guys on this video are split, and I am too.

What would change your mind ?

 Is gaining 21 HP worth the added money for the sound and feel of a roller motor ?
 No or yes and why ?

At what gain in HP is worth the expense, sound & feel ?

Doesn't matter, rollers rule !
Rollers suck and are too expensive !

What's your thoughts ?

https://m.youtube.com/watch?t=17s&v=8VjFZMKvEwY

[Drew Pojedinec]

I don't think 21hp is some sorta hard fast rule....

If you have a hotrod street cam that is .550 lift and 240@.050 that is vastly different than .900 lift, etc
For a daily driver, the only negative to a flat tappet is break in.  More aggressive lobes would make that harder.

I think you are approaching this all wrong, I wouldn't start a cam search based on type, I'd figure what I needed out of the engine and the type of cam would eventually be apparent, or at the least narrowed down.
That said, I drive a 63.5 Galaxie, and a solid flat tappet is what I wanted, so that is what that is. 

[My427stang]

I have to ask too, which cam needs to be lashed regularly?

Loaded question because I don't think they are any different.  Lash on solid flat tappets rarely change unless you have loose rockers or damage and solid rollers you should check periodically to head off potential roller carnage if one fails (more unlikely nowadays, but when they fail, they fail big)

So I would say adjustment is rare with both and good to check periodically with both, so no real change.  More than once per year would be ral strange to me if you have good rockers

I will add this too, my 489 has been together with a flat tappet since late 2006.  Although I have checked it annually, and tightened them to make the cam act a little better, I have never had lash change from one adjustment to the next in 11+ years, and I run it all over Nebraska and never slowly, especially on I-80

That being said, Drew gave you good info.  Cam for use, if you need the very high RPM capability of a solid roller, go for it, if you don't need it, go solid flat tappet, or if you intend to stay under 6000 rpm, go hydraulic, either roller or flat.

[scott foxwell]

Hyd rollers have come a long way and are making big power and big rpm these days. More benefits to a hyd roller than just lack of needed adjustments. The roller never leaves contact with the lobe so there is no jack hammer effect at the adjuster, albeit small. The hydraulic plunger in the lifter acts like a small shock absorber and helps with valve train harmonics. Shorter pushrods. Most hyd rollers are .700-.800 taller than a solid and therefore use much shorter pushrods. That's always a good thing. Quietness and smoothness of operation and yes, simplicity of not having to adjust lash. New lifter technology these days allows for higher rpm and higher spring pressures. I have hyd roller engines out there with 270#seat pressure that spin 7800 (not limited travel) and I think we can go further than that. There's also the availability of different levels (cost and performance) of lifters to meet different budgets. Street series "OEM" style lifters, drop in retro-fit, "pro" level .903". Cost is always a consideration but most of the time we're building an engine that isn't a "necessary" expense in the first place. Save a little longer, drink a few less beers...whatever... the difference in cost between a FT and roller is usually not a big percentage of an engine's budget but IMO the benefits are well worth it. As far as power, well...you can make the same power with either up to a certain point so IMO that really isn't the question. I personally don't like the risk associated with flat tappets these days and the failures are well documented, especially since the OEM's quit using them. For me, anything up to .650 lift and 6500rpm, a drop in retro hyd roller lifter will be my choice. Above that, for the FE, we might have to play some games to get a "good" hyd roller lifter but it can be done.

[plovett]

Here's another take on it.  The size or duration of the cam makes a difference in deciding whether a flat tappet or roller is better, too.

Flat tappets have basically unlimited acceleration and limited velocity.  Roller tappets have limited acceleration and basically unlimited velocity.  What that means is flat tappets can actually get off the base circle of the cam quicker, but the roller cam can catch up and pass it before too long.

In a practical sense, this means that the bigger the cam (duration), the bigger the advantage for rollers.  For a small cam, a roller may gain nothing.

In very general terms, I'd say for cams under 230 degrees @0.050" there is little or no performance advantage to using a roller compared to a modern flat tappet.  Somewhere around 240 degrees @0.050" the roller starts making significant gains.  Over 250 degrees, the roller is dominant.   

That's just looking at performance.  A small roller can be worth it to avoid wear issues and for the tiny reduction in friction.

JMO,

paulie

[machoneman]

Here's another take on it.  The size or duration of the cam makes a difference in deciding whether a flat tappet or roller is better, too.

Flat tappets have basically unlimited acceleration and limited velocity.  Roller tappets have limited acceleration and basically unlimited velocity.  What that means is flat tappets can actually get off the base circle of the cam quicker, but the roller cam can catch up and pass it before too long.

In a practical sense, this means that the bigger the cam (duration), the bigger the advantage for rollers.  For a small cam, a roller may gain nothing.


Paulie did a good job of summarizing why hydro rollers are the best of all worlds unless this is a real racer. Hydro rollers have, for example, run millions of miles in later model 5.0/5.8 Windsor motors, many with aftermarket wild cams using the OEM Ford rollers, dog-bones and spyders. The advent of drop-in rollers now even eliminates the dog-bones and spyders. The FE also benefits from the same advantages.

[plovett]

That's funny because I'm the guy who can't bring himself to put a hydraulic roller in an engine.  I also can't put fuel injection in a hotrod.  Electric cars can out accelerate my old Cougar, but I just can't do it.  Still, I get that hydraulic rollers make sense for 95% of applications. 

Don't count flat tappets out for some combinations, though.  If, for instance, the engine in the Engine Masters video had cams with 224 degrees @0.050", the extra $700 for the roller couldn't be justified.  You could make more power spending that $700 somewhere else.  Or if they compared an inexpensive modern solid flat tappet to the 244 @0.050" hydraulic roller, you'd have seen a different result.  It's not so clear cut, is what I'm saying.

paulie

[blykins]

In very general terms, I'd say for cams under 230 degrees @0.050" there is little or no performance advantage to using a roller compared to a modern flat tappet.  Somewhere around 240 degrees @0.050" the roller starts making significant gains.  Over 250 degrees, the roller is dominant.   

You can't make general statements like that regarding duration.   Displacement and cylinder head design have a huge bearing on what durations will do what. 

If you're going to try and make comparisons like that, you need to base it on rpm rather than duration, and even then, there's too many variables to do so reliably.

The whole solid flat tappet argument all comes down to budget, long-term durability, and race rules. 

[plovett]

Yes.  That is why I said "very general".  LOL!  Are you talking about a 2.0L engine or an 8.0L engine.  I think most people here deal in 350-500 cid V8 engines.  And even then I use "very general".   Don't miss the forest for the trees, so to speak.  The point, which you know very well, is the duration of a cam significantly affects how much advantage a roller tappet has. 

JMO,

paulie

[blykins]

The point, which you know very well, is the duration of a cam significantly affects how much advantage a roller tappet has. 

Ehhhhhhh..................may want to rethink that statement.   

That's like saying long stroke engines won't rev.....

[blykins]

  Don't count flat tappets out for some combinations, though.  If, for instance, the engine in the Engine Masters video had cams with 224 degrees @0.050", the extra $700 for the roller couldn't be justified. 

Whoops.....thought you were talking about the EMC.  I get that you were talking about the video now......

[scott foxwell]

Yes.  That is why I said "very general".  LOL!  Are you talking about a 2.0L engine or an 8.0L engine.  I think most people here deal in 350-500 cid V8 engines.  And even then I use "very general".   Don't miss the forest for the trees, so to speak.  The point, which you know very well, is the duration of a cam significantly affects how much advantage a roller tappet has. 

JMO,

paulie

Aren't the valve events what really matters? Does the valve really have any idea what's making it go up and down? I don't think it really matters how one type of cam does that compared to another until we get to where one method is compromised and another is more efficient. Until then, I don't see that one has any more "performance" benefit over the other as far as getting the valve events accomplished. If both can accomplish a goal, say 450hp, will one be able to make more power under the curve than the other? Both can achieve fairly good peak power numbers up to a certain point, but within that limitation, what about average power numbers?

[TJ]

I know next to zero about cams so hope I'm not asking something too silly.  I think scott foxwell's comment about average power is similar to the question on my mind.

Can either cam make a wider powerband than the other?  In other words if a roller cam and a flat tappet peak at 450hp.  Can the roller cam be cut to make a flatter/broader torque curve than the flat tappet due to how a roller contacts the cam?  The reason I ask is if this is true, perhaps this would cause someone to lean more toward one type of cam versus the other.

[blykins]

I know next to zero about cams so hope I'm not asking something too silly.  I think scott foxwell's comment about average power is similar to the question on my mind.

Can either cam make a wider powerband than the other?  In other words if a roller cam and a flat tappet peak at 450hp.  Can the roller cam be cut to make a flatter/broader torque curve than the flat tappet due to how a roller contacts the cam?  The reason I ask is if this is true, perhaps this would cause someone to lean more toward one type of cam versus the other.

The shape of the hp and torque curves are really more dictated by the specs themselves than the type of lifter that's used.   

With that being said, there's a ton of variables there too.   At a lower rpm range, however, you'd probably be hard-pressed to find a difference between the two lifter types.   You can make a very aggressive roller lobe, but the valvetrain requirements (and performance) may be compromised as a result. 

One thing to make note of, is that the advertised durations of a roller cam are often longer than a flat tappet.  That's a general statement, as there are differences between solid rollers, hydraulic rollers, and variations of the like, but if you compare hydraulic cams for instance, your flat tappet will probably have a much shorter advertised duration (roller will be much longer) and the engine will need to be designed with that in mind, as it affects fuel requirements, vacuum requirements, etc., etc. 

[Falcon67]

I have one flat tappet engine left here - if it ever gets a cam change, it will be roller.  The expense is well worth not having to sweat the break in anymore.  IMHO, most of the expense is in the solid roller tappet area because you really want to pop for pressure oiling.  Hydros tend to take care of themselves.  And we hit 6500 regularly with hydro rollers so it's not that much of a limiter.  I will not be using flat tappets anymore - there is just better tech out there.  As for the "$1000" I think we have about $700 in the 351C in the Mustang for the cam, lifters and springs.

As far as power, a roller can get the valve open quicker and keep it open longer so builds a lot more area under the open curve for things to happen - vs a flat tappet.  So in most instances a roller has the potential to make better use of the heads than a flat tappet grind.

Lash - use quality components and you should not have to tinker with a solid roller or a solid flat tappet setup.  I've run my solid roller all year and not had to make any adjustments.  The last solid flat I ran went two years racing, lash never changed.  Get it right from the get-go and you really don't need to budget any extra time to mess with a solid cam setup.  You do throw a feeler gauge under some once in a while - any change notes a problem.  But here I've yet to see one.