POLL: Why use a flat tappet over a roller cam?

The biggest concern with a roller cam and decent Alum heads?

Not block durability.

It's that the budget gets spent on the sexy parts, and the fuel system is overlooked. Then it's leaned out and detonated, wipes the bearings out and the "HP" parts get blamed.

And I have found that the Hyd rollers sound about the same, and share similar idle characteristics with the Hyd flat tappet cams. They are only slightly better. Only the solid rollers, with the much more aggressive ramp rates, idle noticeably better for a given duration.

Going in, I thought the same thing, but with a dozen HR builds thru the dyno now, I don't think that anymore.

The only downside is cost.. the cost of the parts going in, and also the support hardware for the fuel system and such.

JW

 

Unless you want originality - go roller! (Re: flat tappet over a roller cam?)

Dear Paul, Jim, and V-8 engine gurus,

This is out of my league but I have been reading this thread with considerable interest.

I keep harping on this theme, but it seems worth repeating:

A roller cam isn't really increasing engine horsepower at all. All it is doing is what any bearing system does: reduces friction.

So switching from a flat tappet to a roller cam is making your engine more efficient. If Jim's reports are correct, that extra 60 horsepower is at least in part from the reduced friction in your engine. So you are simply getting more "bang" from a "less powerful" engine, because more of the power that was used to rotate the cam around is instead reaching your wheels.

Other advantages are a longer engine life, better fuel economy and subtle things like a quieter engine.

There has been a considerable amount of grumbling over the additional cost in this thread, but considering the cost of a new engine for most folks around here, the increased engine life and reduced fuel costs (however slight) will probably pay for the hydraulic cam - unless you insist on (and can afford to) rebuilding/replacing your engine very few years.

To answer Paul's original question, there is only one case where I think the choice of a flat tappet cam is undeniably better: folks wanting a original working engine. Even this is somewhat dubious nitpicking since the cam type isn't visible from the outside, but originality freaks will be originality freaks. I don't think any other reason really stands up to scrutiny.

Cheers, Edouard :beer

 

From a durability standpoint, we cannot equate this aftermarket lifter design with the OEM (original equipment manufactured) rollers in our cars nowadays. To me, these aftermarket lifters have little to do with the OEM other than they have a roller tip. They look like race lifters with hydraulic guts.

OEM did severe durability tests so that your car has a chance to go 150K miles.

The aftermarket lifters have us to try them, unless more data gets shared.

That being said, my next build may very well be with a TA hydraulic roller cam.

Devon

 

I believe no drought that the roller cam is better but it is hard to cover 4 times the cost on a stock build. A nice hyd flat tappet $250.00, as posted above Hyd roller , lifters, button, cam gear $1100.00 and that does not include push rods or rocker arms. That $750.00 will go a long way to a complete the stock build. I just feel if you go with a roller cam you might as well go with the roller rockers to take full advantage but there goes another $800.00 or so. You will have 2K tied up in a full roller setup. <o></o>
That said I went Hyd roller, roller rockers and all on my 496 but I am also running Brodix heads to make it all worthwhile. <o></o>
It for sure takes some consideration no matter which direction a person takes.<o></o>
<o></o>
Nelson<o></o>

 

I may do one....next time. 60 hp seems a bit hard to believe, though.

Jim....any direct back to back tests with comparable cams? Maybe I missed that part of the discussion......

 

Am I missing something or did the 413 cam make only 23 hp less ? This was after the roller cam was twisted to 6000 rpm .

mark

 

I was just looking at the same thing.uzzled:

 

Okay I stand corrected! (Re: flat tappet over a roller cam?)

Hi Larry and V-8 Buick engine gurus,

*Heavy sigh*, I knew I should have just kept my big mouth shut! ou:

Okay, the Lunati page is especially interesting and the curve and associated illustrations really drive the point home. But my point isn't entirely incorrect. The benefits in acceleration arise from the way in which roller camshaft eliminates friction. I never thought of the tappet "digging" into the camshaft. That is a particularly nasty kind of metal surface to metal surface "bearing."

Thanks for straightening me out! :TU:

Cheers, Edouard :beer

 

Re: Okay I stand corrected! (Re: flat tappet over a roller cam?)

That Why they came out with cam saver lifters has a little hole for extra oil to the bottom of the lifters to save the cam..

 

The 413 made 577 @ 5700 rpm
The 413 roller cam made 608 @ 6000 rpm and still climbing.
Thats 31 hp difference.

The 413 is 234/244 duration, .516/.516 lift on a 113 lobe center

The 413 roller is 234/247, .574.584 lift on a 113 lobe center.

This is a good comparison for just the cam change alone.
I won't speculate on how much the roller rocker is worth over the stock 1.55 ratio.

Paul

 

Roller vrs. flat tappet .... the roller cam can provide more lift @ less duration than a flat tappet. Roller lifters allow the use of aggressive lobe profiles & the lower intensity number , preformance should increase ( as long as the valvetrain stays stable).

Flat tappet (mech & hyd.) .... the flat tappet cam can only provide so much lift @ a given duration before the duration needs to be increased to allow for more lift & then the power band takes a hit! Some flat tappet cams are useing a more aggressive(faster) lobe profile to get a lower intensity number , once again preformance should increase over a flat tappet with a (slower) higher intensity number. (as long as the valvetrain stays stable)

From the standpoint of lower intensity numbers (more power) & a stable valvetrain ( spring pressures ) & being able to follow the lobe profile without damage to the cam itself .... The roller wins hands down!

The big question in my mind is how much horsepower is gained with the roller over a PROPERLY set up hi-intensity ramped flat tappet camshaft ? & whats the cost per horsepower gained ?

If all I used my car for was strip use ,the flat tappet would be fine ... however if I wanted to drive on the street & have the engine run 100,000 miles I think the roller would be a better choise , as long as the lifters hang in there.

Mark

---------- Post added at 12:46 PM ---------- Previous post was at 12:37 PM ----------

BQUICK ..... Larry wants his 29 hp back ...LOL

Mark

---------- Post added at 12:57 PM ---------- Previous post was at 12:46 PM ----------

Paul, I think the differance in the horse power came from the fact that Larry used a differant camshaft in the 2nd engine . 231*/238*112 LSA 550"/571" lift Correct me Larry if I am wrong

Mark

 

Boy you guys are tough...

Yes, 30ish HP over the 413

but 75ish over that Lunati stick... that's how much you leave on the table if you try and run that fast ramp stuff.

Larry's second roller was just about the same size as that Luanti Voodo cam. Intake duration for sure are very similar, and that's really where it's at.

So I rounded to 60ish for the whole test..

Next time I will go look it up.

I might suspect that Edouards, and several other I have done here recently, were worth more than 30HP over a flat tappet, but that's just a gut feeling. No data.

And I like what I read in someone's tag line.."Without data, your just another guy with an opinion".

JW

 

It would be interesting to put roller lifters on a flat tappet cam just to see the frictional hp gain. I think most of the hp comes from being able to run a different lobe profile.

 

Larry

It depends on if we are talking about the difference between going to a roller cam and roller rocker from a flat tappet cam and stock rockers
or in your case where the only change was the cam and both cams had the advantage of the roller rockers.
I'm not going to speculate what the difference is if the rocker change was part of the equation but we know it's worth something significant.

Where the 60 hp difference can possibly come in is if you look at Edouards 500+ hp combination.
The cam is a 215/225@.50 on a 115 LC mid .500 lifts.

Because of the short duration, a hyd flat tappet version of this roller cam will be restricted to lifts under .500

This engine made 509 hp at 5500 rpm with no signs of backing down. It would have hit near 515 hp if the pull would have continued to 6000 rpm.
Now remember this engine is only 448 cu in, not a 470.

Now put in a 215/225 flat tappet with stock rockers at lifts in the .475" region and see what the hp difference is.

It turns out that the roller cam and rocker combination is even more beneficial to the group building Buick engines dedicated to street use.

I'm looking forward to seeing the results of the 350 JW is presently building with a roller version of the TA 212

Paul