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

[Drew Pojedinec]

LOL, can now close the thread    

hahaha, right?

For my daily driver, I'd seriously consider a hydraulic roller.  For my Galaxie, I just wanted that SFT sound

[wayne]

So you can run a solid roller on the street if get the spring pressure ok.

[blykins]

Sure.

It won't have the life expectancy of a hydraulic roller or a flat tappet, but it will work.   The degree of how well it works will depend on the cam lobes, spring pressures, and the quality of lifters.

[Falcon67]

So you can run a solid roller on the street if get the spring pressure ok.

Pressure oiling lifters are a must.  Spring pressure should be set based on the cam requirements IMHO.  I know guys running pressure oiling type lifters in race cars that they run a lot and they are getting good life out of them.  As much as two seasons running big springs and turning big RPM.  I still hear of the occasional fail but really not seeing much roller fails as I used to see maybe 5~6 years ago.  Better parts ad probably better maintenance.

[plovett]

I think I am going to use a solid roller on my next build.  The main reason is I want the ability to change cams on the dyno, or in the car later, with no issues.

I also think the roller will make more power, even with the fairly mild duration (245+) I intend to use.

I could probably use a hydraulic roller, but I have a mental hang up with those, and I want to run a little higher rpm, maybe 6500 rpm.  I'm sure that is doable with a hydraulic roller with careful selection of parts, but it's a easy done deal with a solid.

paulie

[blykins]

The ability to hot swap cams is the main benefit for you.  I don't see the roller making a discernible difference in power, but then again, it comes down to lobe designs for both cams. 

What size engine is this going to be again? 

If the engine is going to peak at 6000 or so, I wouldn't run the risk of running a solid roller on the street.  There's no benefit in them in that situation and there's more risk than reward.  For a lower rpm engine, I would either do a solid flat or a hydraulic roller. 

[plovett]

It's not so simple as saying "it comes down to the lobe designs for both cams".  Sure, it is possible to have a flat tappet that is more aggressive and has more area under the curve, than a roller.  But, there are downsides to that, as well.  If you have a very aggressive flat tappet, you need more spring pressure to control it, unless the rpms are kept low.  Since increasing spring pressure eventually becomes problematic with flat tappets, that can be an issue. 

I once used a very aggressive solid flat tappet cam, 270/240/152 on the intake side.  Had some trouble controlling the valve train with the initial setup.  It started going uncontrolled around 6000 rpm.  We had to change to springs with more pressure and eventually went with titanium retainers.  The motor ended up peaking at 6200 rpm and pulled well to 6500 rpm.   I can't remember the exact pressures, but I think we started with around 360 lbs open and ended up around 390 lbs open pressure. 

I now run just over 400 lbs open pressure (150 on the seat) with another solid flat tappet combination.  I also have a nitrided cam, EDM'd American made lifters, and run good oil with a ZDDP supplement.   So yeah, it's doable to make a flat tappet run with a roller, up to a point, anyway.  But there are some downsides unless it's pretty mild engine.  So it's not so clear cut, in my opinion.

My current cam is 279/252/162 on the intake and 287/260/169 on the intake. Those are 0.020"/0.050"/0.200" numbers.  Lift is 0.340" on both.

Even if I use a extremely mild solid roller lobe like Comp High Energy 288, I can get 244 @0.050 and 158 @0.200.  The High Energy 300 gives you 255 @0.050 and 170 @0.200".  So I can get more at 0.200" but pay a penalty in longer advertised duration.   That's comparing an aggressive flat tappet to a very mild roller.  Peak lift isn't everything, but of course it's higher too.

Anyway, I'm not ruling out a solid flat tappet.  There's a Harold Brookshire (Berkshire?) flat tappet design with 277/244/157 degrees that I like.  I think that'd make a nice intake lobe. 

This will be a 471-474 inch motor if all works out well.  I know the cams I pick should peak lower, but the heads I have seem to help.  My old 240/246 cam peaked at 6200 rpm in a 433 inch version, for instance.

So long story short.  Yes, a solid flat tappet makes sense, and so does a hydraulic roller.  I don't like hydraulics and I want to be able to easily swap cams on the engine so I'm thinking solid roller.  I think it'll make more power with the roller unless I get fairly crazy with the flat tappet.   Of course it depends on the exact lobes used, but there you have it. 

Sorry for the hijack!   

paulie

[blykins]

It's not so simple as saying "it comes down to the lobe designs for both cams". 

Of course it depends on the exact lobes used, but there you have it. 

paulie

You started off rough, but came to your senses at the end......

Yes, it absolutely comes down to the lobe designs on each cam, if you're trying to compare a solid roller to a solid flat tappet.  You have placed emphasis on a magical duration that doesn't exist where the designs intersect and one takes over and is "better".  I will tell you first hand, based on more dyno scenarios than I can recount with both solid flat tappets and solid rollers, that it just doesn't happen like that.

So, you run a lazy solid roller and you lose hp plus you're still running solid roller lifters that, statistically speaking, can take a dump on you at any time, and at the very least will require an inspection at intervals. 

If you run a wilder solid roller, you're having to run stiffer valve springs, which put more stress on the rockers and will most likely require a different rocker arm setup so the studs won't be yanked out of the heads......AND.....you run an even higher risk of wearing the lifters out, which shortens your inspection interval. 

You're zooming in way too tight on this flat tappet vs. roller comparison.  You can't make blanket statements because every camshaft is different.

Switching subjects, your 433 inch engine with a 240/246 cam peaked at 6200 because it's a small engine.  You can't expect a 470 inch engine to do the same, even with 5 more degrees duration.  By the time you account for the duration you're going to lose because of lash, that 470 inch engine is going to peak at about 5500, based on what I've seen on the dyno.  That's a complete waste for a solid roller setup.  You're setting this combination up to be a long distance cruiser or a semi-daily driver, but you're considering parts with a short life cycle. 

Other than the fact that you already have a set of solid roller lifters, I don't understand the aversion to a hydraulic roller, because it seems to fit every bullet point of your presentation.......hot-swappable.......long life......extremely low maintenance, and you absolutely can put the peak hp and shift point where you want them.  A set of factory non-adjustable rockers with lightweight dual springs or beehives will get you there.

[plovett]

Oh my gosh, Brent.  We must be twins separated at birth.  I can say it's greenish-blue and you'll say "no, it's bluish-green".   I could say the sky is up, and then you'd stand on your hands and say, "no it isn't."   I'm sure I'm as bad as you are. 

The main reason I might use the solid roller lifters is to be able to swap cams.  I agree that a solid flat tappet or a hydraulic roller makes sense in most purely rational ways.  I just like driving down the road with solid tappet cam in my FE, ya big dork!  I'm gonna give you a wedgie when I see ya.   

[My427stang]

Paulie, my experience with solid rollers was from the early 2000s before pressure fed rollers, but I had a good bunch of street-driven Rat Chevies that I undid the carnage in Las Vegas when I was stationed there.  The group had their motors professionally built locally about the same time, and they all lost solid rollers.  They all got them rebuilt by me, and they ended up with a combo of SFT and HFT depending on the combo.  They were 500-600 hp machines, 462 cid and under.

When they did fail there was no warning, a little clickety-clack, then the wheel failed, jammed the body into to cam and took out big dollar cranks, spun a bearing on one, one chipped a block and made a general mess.  At the time, I called Comp and they said "75 passes" and they should be sent back to them.  Think of that in miles, then quadruple it, or multiply it by 1000 for the oiled pin, still is scary to me on a street car.

Does that apply here?  Lifters are better, Rats load lifters differently, oil fed rollers didn't exist, so maybe not, but I am still unwilling to run a roller wheel with lash in an engine that periodically runs low RPM, and would never do it if I don't have an oiled pin...regardless of whatever good luck other guys have

Truth in advertising though,, I will say though a buddy with a street solid roller in a 351C that ran forever, sold the motor and it kept running for years, same with Wes and a bunch of other guys.  I am just gun shy because of the lack of warning and the effects if they fail.

[blykins]

Oh my gosh, Brent.  We must be twins separated at birth.  I can say it's greenish-blue and you'll say "no, it's bluish-green".   I could say the sky is up, and then you'd stand on your hands and say, "no it isn't."   I'm sure I'm as bad as you are. 

The main reason I might use the solid roller lifters is to be able to swap cams.  I agree that a solid flat tappet or a hydraulic roller makes sense in most purely rational ways.  I just like driving down the road with solid tappet cam in my FE, ya big dork!  I'm gonna give you a wedgie when I see ya.   

I'm not trying to be argumentative or difficult.  But when I was in engineering school, there was a saying......"Theory doesn't always mesh up with reality." 

It's nice to sit and run Desktop Dyno sims and compare durations at .200" lift, but putting combos together and dyno'ing them is what truly builds up the database.   

I'm just trying to help, as is Ross with his statements about solid roller lifters.  Quality, pressure-fed lifters can make a tremendous difference, but they still fail.   And you don't know when it's going to happen.  If you're setting your car up with a high rearend gear so you can go cruising on long trips, a solid roller just isn't the best scenario.    You can pick a lazy lobe and you can pick low spring pressure, but lifter failure is inevitable, and if you have to wimp-out on the cam to make the lifters last longer, what good is that?

If you like the idea of a hot solid flat tappet, run a nitrided cam with some tool steel EDM valve springs.  I've popped the lifters in and broke in cams without even reducing the spring pressures. 

[plovett]

All good points, Ross.  I said "I think" am going to use a solid roller in my next build.  And I might.  I do have Morel bushed solid roller lifters that I got from Brent.  Good deal, by the way.  Thanks!

I would also use a milder solid roller profile.  I know that gives away some of the advantage of using a roller.  And the rpms would not be too high, so I would be able to use lower spring pressure.

And I would be able to swap cams on the dyno or later, which I something I think I want to do.  My engine with the heads it has peaks higher than most other people's with similar cams, so I'm not totally confident in my cam selections. 

I could end up with a solid flat tappet.  It makes sense and I'm not against it by any means.  I'm a guy that checks his valve lash pretty frequently.  I would likely do it more so with a solid roller, and I don't think the bushed lifters typically disintegrate catastrophically with no warning?

I'm listening, though. 

How much open and closed spring pressure do you all think this cam would need if running to say 6200 rpm on an FE with 11/32" 2.20/1.68" valves and Harland Sharp rockers?  I'd like to run steel retainers, but I'm not averse to titanium as I've been running them for years. 

http://lunatipower.com/Product.aspx?id=2284&gid=284

I know it seems small for a 470+ engine. 

thanks,

paulie

[plovett]

Oh my gosh, Brent.  We must be twins separated at birth.  I can say it's greenish-blue and you'll say "no, it's bluish-green".   I could say the sky is up, and then you'd stand on your hands and say, "no it isn't."   I'm sure I'm as bad as you are. 

The main reason I might use the solid roller lifters is to be able to swap cams.  I agree that a solid flat tappet or a hydraulic roller makes sense in most purely rational ways.  I just like driving down the road with solid tappet cam in my FE, ya big dork!  I'm gonna give you a wedgie when I see ya.   

I'm not trying to be argumentative or difficult.  But when I was in engineering school, there was a saying......"Theory doesn't always mesh up with reality." 

It's nice to sit and run Desktop Dyno sims and compare durations at .200" lift, but putting combos together and dyno'ing them is what truly builds up the database.   

I'm just trying to help, as is Ross with his statements about solid roller lifters.  Quality, pressure-fed lifters can make a tremendous difference, but they still fail.   And you don't know when it's going to happen.  If you're setting your car up with a high rearend gear so you can go cruising on long trips, a solid roller just isn't the best scenario.    You can pick a lazy lobe and you can pick low spring pressure, but lifter failure is inevitable, and if you have to wimp-out on the cam to make the lifters last longer, what good is that?

If you like the idea of a hot solid flat tappet, run a nitrided cam with some tool steel EDM valve springs.  I've popped the lifters in and broke in cams without even reducing the spring pressures.

Yeah, I didn't think you'd agree, Brent.      I am already doing the nitrided cam, EMD'd lifter thing.  My lifters aren't too steel, though.  I run somewhere between 400-405 lbs open pressure on my flat tappet and have for years and several thousand miles.  It seems like it's pushing it to me.

And yes, I do agree that real world experience trumps a desktop dyno.  I don't have one by the way, but I get the dig.    That's why I posted a couple of real examples. 

Post some of yours,

paulie

[blykins]

If not titanium, you can run tool steel. 

That's a pretty aggressive lobe.   Most "street rollers" have 38-50 degrees intensity and a lot of them can be used as a hydraulic roller....

I have ran a 428 to 6500 with a custom Comp solid roller, with 225/525 lbs of spring pressure. 

[My427stang]

I will default to Brent on spring pressure, but your repeated referencing to a 240s-250s cam in a stroker as being "small" hurts my feelings

Please don't tell my Mustang, because at this point it acts like it has plenty of cam and I don't want it to know the truth!