flat tappet hydraulic vs. hydraulic roller cam

69 Mach I · #1 (**permalink**) 10-05-2006, 02:54 AM

assuming the power band remains the same, do you make more power with a roller cam? I am pulling my heads and intake for porting and I figure that if there is any real benefit to a roller cam, the time to do the swap is during the porting.

the cam I have now is this one.

http://www.crower.com/misc/cam_spec/...15237&x=25&y=8

Some people tell me I might see upto 25 extra hp with a roller cam because of the more aggressive lobes.

Curt C. · #2 (**permalink**) 10-13-2006, 05:46 PM

Most say the answer is yes. A roller has less friction and offers in the neighborhood of 15 - 25 HP on the Windsors. So I have ready anyway.

Tommy · #3 (**permalink**) 10-13-2006, 06:19 PM

Flat tappet lifters are also more likely than roller lifters to damage cams when using modern motor oils. Modern motor oils don't have the same amount of anti-scuff additives as oils did when flat tappet lifters were common.

Excaliber · #4 (**permalink**) 10-13-2006, 11:13 PM

I think 25 hp is likely on the LOW side of what could be expected. Of course there are tons of variables, but still, I'd bet you would gain better than 25 horse.

That said, I prefer solids. I would NOT run a roller solid, but would consider a hydraulic roller. But like I said, I prefer solid, flat tappet. It keeps me in touch with my car, it just seems more, hmmmm, 'manly'.

While it's true the new modern oils can be problematic there are ways around that and a long life for a solid cam CAN be assured. But it's certainly not as easy as it was 'back in the day'.

speedracer67 · #5 (**permalink**) 10-16-2006, 11:27 PM

As long as you use a race oil that has the Zinc additives you need there is no problem.

KevinM · #6 (**permalink**) 10-19-2006, 11:38 AM

Shell Rotella T synthetic has a good zinc content and is recommended by Comp Cams. If you are running a flat tappet cam, DO NOT use modern passenger car oils!

A Comp XE282HR would be a comparable cam in a hydraulic roller.

http://www.compcams.com/technical/Ca.../72-75_230.pdf

RPM is limited to 6,500 max if that is an issue. There are custom grinders who will grind a HR cam that can rev higher. But to do it, they have to back off the ramp rates, so you somewhat defeat the purpose.

Kevin

Excaliber · #7 (**permalink**) 10-19-2006, 11:47 AM

Vintage side oiler blocks only accept flat tappet, there is no provision for a hydraulic cam of any kind.

...must have been created by 'real men'. Hey, thats a joke!

Wayne Maybury · #8 (**permalink**) 10-19-2006, 12:04 PM

I am not 100% sure but I don't think that Rotella T is a synthetic oil. However, Rotella T is one of the better oils to use with a flat tappet cam.

The additive that has been greatly reduced in oil is ZDDP. The reduction was at the request of the EPA, I believe. I contacted STP who told me that their "STP Oil Treatment" contains a high level of ZDDP so adding a can of STP with each oil change should increase the level of ZDDP in your oil.

If you like a really thump, thump, thump, sounding idle, then stick with the flat tappet cam. I find that many engines equipped with roller cams have a much more civilized sounding idle.

I assume it has to do with the overlap and the profile of the lobes.

Wayne

rdorman · #9 (**permalink**) 10-19-2006, 12:28 PM

I use full synthetic 5W-40 Rotella T in my flat tappet car.

Back to the original question. A roller will generally make more power all else being equal. But it is all in the cam design for the application. Higher opening and closing rates are possible (with cooresponding higher loads on valve train components) with rollers so if we where to compare a flat tappet at the highest practical ramps with a roller again with the highest possible rate of open and close, the roller would make as much or more power in the same power band as the flat tappet with less duration. Higher cost is a factor but overall the roller is a superior design. Don't pick the cam yourself. After your head work is done and you have that data, talk to the experts. And then pick a cam. Be sure your geometry is right on the money. Circle Track ran a good article a while back (this year) on how to check and correct this. While you are at it, the new beehive springs are showing a LOT of promise in the area of valve train control.

69 Mach I · #10 (**permalink**) 10-20-2006, 03:25 AM

These are the flow numbers after porting:

Intake/Exhaust .100" 79/61
Intake/Exhaust .200" 145/121
Intake/Exhaust .300" 198/168
Intake/Exhaust .400" 241/178
Intake/Exhaust .500" 279/196
Intake/Exhaust .600" 284/205

I have 3.70s in the back and a 2800-3000 stall. I am thinking that this would be a good cam to go with it:

Comp Cams part number 35-426-8, grind no. XR288RF-HR (Hydraulic roller)

Adv Dur:
Intake: 288
Exh: 294

Dur at .050
Intake: 236
Exh: 240

valve lift with 1.6 rocker
Intake: 555
Exh: 576

Do you guys concur with this selection?