The only reason not to use a roller cam today is if you can't afford it.

More power throughout the range, better driveability.

Flat tappet cams are fine with the right oil and spring pressure.

If you're not set on rebuilding your motor, get a used roller-cam engine and base your build on that.

 

you all have me scared now. i put a crane roller in my vet and i do like it !! it was proabably only half money related for me but probably more so the ease in which i could slip in a standard hydraulic in my camaro that i went that way.

its been in there for 9 months and i do thrash it. both cams probably are about the same Hp (400-450) . it has not wiped out yet so ill keep my fingers crossed. i use castrol edge oil.

another point i would like to make is both motors feel very similar. they both have same heads, carb, slightly different manifolds .both in front of Th350,s with a 2500 and 3000 stall respectively . the only big difference is one is a hydraulic roller and the other hydraulic flat tappet so i cant say i buy into the theory that rollers are WAY better .....not when no lobes are wiped of your flat tappet anyway.

 

no they are way better, however when you have to go into your engine twice because you wiped a lobe on break in the price isnt so bad for the roller now.

 

Apart from the added peace of mind (NOT wiping lobes) a roller cam CAN provide better performance because the ramp rate can be faster than a flat tappet cam.... reliably!

Look at this image.... same cam duration at 0.050, same lift....



The flat tappet cam rises at slower rate, and sits near max lift for only a few degrees on the peak of the lobe.

The roller cam, however, due to the reduced frictional load on the cam/lifter interface, can rise (and close) much faster, and sits near max lift for a greater angular displacement.

Keep in mind the flow rate of your head at various valve lifts, and you then easily see the value of running a roller cam. ( the image above is lift at lobe... actual valve lift will be multiplied by rocker ratio (eg 1.6:1)

This combination of greater air flow provides better intake filling and consequently more power throughout the rpm range.

In practice, with a roller cam, you can run less duration to get the same horsepower as you would with a bigger duration flat tappet cam, and that provides slightly better manners on the street.

 

The Hyd rollers are great IF RPM isn't going to get crazy. In a small block that means a little under 7000 RPM usually if you have good parts. Big Blocks can get in the 6500 range pretty comfortably.

They will pump up the lower rpm power over a flat tappet that makes equivalent power. Just to give some examples:

In the 555" motor I just did for Doug *Snowman* for his C-3, I tested a *good* solid flat tappet against a HR and a SR. The Flat tappet had .696 lift, the HR had .720 and the SR had .788 on the intake sides. The flat had 270*@.050, the HR had 254* and the SR had 268*. Now of course you have to add some for the fact these are solids against a hyd cam. Anyway, as you can see they were all pretty healthy.

They were all able to break 800HP on pump gas. The solid flat and the HR made almost identical peak HP, but the HR was up about 20-30 ft lbs in the lower ranges. The HR peaked around 6300RPM and the flat tappet peaked around 6500 rpm. At the end of the day the big solid roller was only about 30-35HP or so tops over the solid flat as long as I had equivalent intakes and carbs on it.

The advantage of the solid flat was that it could rev to the moon with no drama. Same as the solid roller. The HR was signing off in the 6700+ rpm range.

So it all depends on application. If you will never rev too high when you want to play, the HR makes sense. If you ARE willing to rev it when having fun, the solid flat could walk away from the HR in the above motor because it could *hang on* much longer. They were both in the 700+ ft lbs area...so low end power wasn't an issue anyway.

At the end of the day Doug selected the HR for his combo and even with the smallest intake and carb setup (hood clearance) he's still in the 775+ HP range as it sits in the car.

JIM

 

Anyone that's ever actually looked at the difference in lobe profile is going to see just how significant the power gain will be with a roller...even if they somehow managed to miss all the dyno runs and the fact that virtually every in-block cam engine uses them today.

A roller allows a far steeper ramp than a flat-tappet - this means the valve opens far more quickly and creates an effective increase in duration.

The hot flat-tappet cams today use a near-roller profile...and it is this, along with the attendent high spring pressures and the introduction of GF-4 spec oil (due to OEMs virtually all using roller cams) that caused the cam problems we saw. A properly broken-in flat tappet with the correct oil and reasonable spring pressures is not going to wipe a lobe and the fear-mongering is overblown.

 

Thanks Zwede and Beejay, for the info. now on the cam gear is that for gm roller cams or all roller cams. being different bolt pattern?

mejetdrvr

 

It's for all LT1 and LT4 cams. Remember that the LT series was GEN II and as such very few parts directly interchange with a traditional small block.

 

I believe roller cams were introduced in the GenI engines around '88. The LT4 Hot Cam was a cam to upgrade the '96 LT4 (Gen II) engine.

 

.... thats why for the camaro i chose a well respected cam profile from the early 90,s and it hammers. i have heard enough bad stories with these new cams.

 

When the roller cams were introduced modifications were done to the block. A cam sprocket from a roller block will not work on a earlier block. The front of the block where the cam sprocket spins is completely different. You would need to do some welding and machine work to the earlier block to be able to use a roller cam sprocket. Most including myself elected to go with a retro roller cam that uses the earlier compatible cam sprocket.

 

Ah, now i understand the retro term..thanks guys for the great info. As always you guys on the forum are loaded with best info..

 

The retro roller cam is designed to use the earlier style timing chain set. You still need to control the back and forth movement of the cam due to the fact that the lobes are not ground with a slight taper as are the standard non roller cams. This slight taper forces the cam to be pulled to the back of the block. With a retro roller cam you need to install a cam button to control forward movement and a special hardened shim behind the sprocket that acts as a wear area between the sprocket and the block. The shim is about .030" in thickness. The cam sprocket should be sent to a machinist to have .030" machined off the back of the sprocket. Some will install the cam without the shim but you risk possibly gouging the the block where the cam sprocket is spinning. If you setup the cam endplay to around .005" then you will help to control the back and forth movement of the cam thus eliminating any possible future damage. The biggest mistake made is in not setting up the correct endplay.

 

I've been running a solid roller in the 427 sb ,billet,small base circle,
and recently pulled it and noticed 1 lobe was wiped out,not as much like a flat tappet but some evident wear,

Then theres talk of the rollers not getting enough oil at idle,I wonder if this is what caused it,I still do not
know the cause and I'm concerned if this would happen again.

Now they have the roller lifters that have a oil feed hole to the roller itself. Get these if your gonna run a roller.
My engine had about 25,000 on it.

 

my take is cam makers are just making ****-poor flat-tappet cams now days, not everything due to oil, problems seem to be on new cams not those still running original cam, especially seems comp cams wiping out mostly or maybe that is the one everybody buys. kinda like msd....lots of hype and advertisement on tv, mags etc.

 

i had read somewhere that cam blanks were only made by a few different companies,
so a cam from comp or a cam from lunati might have started out from the same stock.

any truth to that

 

im hearing what everyone out there is saying about wiping out their cams. it does seem like the percentage of new installations that go sad seems quite high but im wondering for how many wipeouts im hearing are other people having no problems. im just not convinced its always the cams fault . so much has to be right on cam installition from excessive cam lube on cam and lifters,pre oiling before start up,spring pressures, use of proper running in oil, adjusting the revs between 1600 - 2400 periodically,valve and pushrod adjustment and the list goes on. not to mention babying it for the first 200 miles.if everything is done right even with these RISKY new age cams everything should be ok.

 

A lot of you are missing the real issue. Reduced Hydraulic intensity numbers are the main reason more cams are failing. A roller cam can have a fast ramp as shown in the graph above. Actually a better graph woul have the duration @ .050 aligned and the area above the curve and lift would show up much higher in the roller cam. Modern cam designers are trying to achieve a profile close to a roller cam on a flat tappet cam because of the advantages in power, off idle response, broader torque curve, better vacuum. This requires a faster ramp. I have read a couple articles about this, one by Harvey Crane, the other by David Vizard. While neither one really points the finger at this David Vizard does reference that this is an issue. If you want roller cam performance use one. If you want to use a flat tappet check the duration @ .050 against the advertised duration. Factory flat tappet cams had a hydraulic intensity of around 70. If the duration @ .050 was 230 the advertised duration would be around 300. Modern profiles are much steeper ramps to give you the above noted advantages. David Vizard says that a hydraulic intensity of 50 to 55 is the smallest recommended "safe" intensity for a flat tappet. The Voodoo cam the OP referenced has a duration @ .050 of 241/245. The advertised duration is 284/292. This is a hydraulic intensity of 43. This is roller cam intensity in a flat tappet. This is beyond a safely engineered hydraulic intensity. I am not picking on Lunati. All the manufacturers are designing these type of lobes. They have to compete. The customer wants it, they build it. This combined with lower zinc levels in oil. improper break in, incorrect spring pressures, bad geometry and the customers using that new power has lead to the failures you are seeing. Actually the cam cores of today are far superior to the originals in the C3.

http://www.harveycrane.com/duration.htm

http://www.enginebuildermag.com/Arti...r_failure.aspx

 

OEM roller cams use a stepped nose, this stepped nose engages with a retainer plate that bolts to the front of the block behind the timing chain sprocket. The retainer plate is why OEM rollercams do not require a nose button to eliminate walk. Once the sprocket is bolted on the cam is unable to walk fore or aft.

Because of the smaller diameter face of the cam presented to the sprocket the bolt radius is smaller on the OEM roller cams.

Most mfrs will indicate if their cam has a stepped nose or not for OEM applications.

The stepped nose on my cam can be seen clearly in the lower left of the image below

 

Order your flat tappit cams with the hardened cam core.

Pro Plasma " Nitriding "

36 hour Nitriding process uses pulsed nitrogen plasma, in a vacuum controlled environment, to inbed
chains of nitrogen ions into the camshaft surface approximatly .008 to .010 deep. This newly fortified outer layer (not a coating or polish) strengthens the camshaft's lobe surface 100 percent reducing the chance of premature lobe wear. Pro Plasma " Nitriding is available as an added service for all COMP cams flat tappit cams.

If the cam companies were worth a damn all of there at least quicker rate cams would come with this standard.