Mechanical Roller Cam Breaking On The Street, Why ?

[427HISS]

Some people are saying not to use a mechanical roller cam on the street, as all the low idling will break the lifters, destroying the engine.
I can maybe see a cheaply made lifter falling apart, but what about the higher dollar, better made brands ?

What exactly breaks and why ?
Is their any videos or good drawing showing what happens ?

Thank you.

[Katz427]

The fellow about 2 miles from here had a 57 Chevy all aluminium block AFR heads and a Comp solid roller. Mainly street driving about a 8 mile circuit he would follow. One night I did not hear him return, a couple lifters broke and did considerable damage. I think incidents like that started the solid roller tales of woe. Lots of spring pressure with a solid roller cam.

[Joe-JDC]

At low engine speeds, there is not a lot of oil being thrown around by the crankshaft, rods, and windage to keep an adequate supply of oil to cool and lubricate the roller bearings in the rollers.  Because of the spring pressures, they tend to push any oil out, and heat up, and heat destroys.  The needles will go flat, wear quickly, or groove, the race housing.  A chattering roller will wear quickly, and throw out a needle, and then things escalate very quickly.  BTDT, and the needles will sling out like shrapnel and destroy piston skirts, cylinder walls, and take out the camshaft in a hurry.  Sometimes the needles get caught in the oil pump and lock it up.  Catastrophic failure will result in some cases.  Joe-JDC

[jayb]

Back in the 80s I ran some roller cams on the street, and despite being careful to rev the engine in traffic to keep the lifters splash-oiled, the lifters still eventually went bad.  The needle bearings would fail, and then take out a cam lobe or worse.  I probably got 1000-1500 street miles out of a set of lifters.

However, nowadays there are better options available.  The pressure oiling to the needle bearings that is available with many roller lifters goes a long way to making them live on the street.  I've gone as long as 10,000 miles on a set of Crower HIPPO mechanical roller lifters on a Comp 308R roller cam.  And of course with the bushed lifters that are now becoming available (no needle bearings, just bushings), I'd guess things are even better.

One thing about mechanical roller lifters is the lash required automatically means that once every two engine revolutions, the lash is taken up between the roller wheel and the cam lobe.  Crashing the wheel into the cam lobe has got to eat into the lifetime of the lifters.  Hydraulic roller lifters don't have this problem, of course; with a hydraulic roller the roller wheel is always in contact with the cam lobe (unless you float the valvetrain), so there is no hard contact.  As a result hydraulic roller lifters should last a lot longer.

Valve spring pressure will come into play as well.  The more spring pressure required for the cam, the harder it will be on the bearings in the roller lifter, and probably the shorter time it will last.  On the 308R mechanical roller that I mentioned earlier, if I recall correctly my spring pressures were 200 on the seat and 560 over the nose.  The 504" FE currently on my dyno uses spring pressures of 290 on the seat and 750 over the nose.  No way those lifters are going to last as long as the ones with the lower spring pressure.

Whether or not you use a mechanical roller on the street should be based on the number of miles you want to drive, and how radical the cam lobe and spring pressures are.  A lot of us don't put much more than 1000 miles per year on our FE cars; with a reasonable cam and spring pressure, I wouldn't be afraid to go 10 years before checking the lifters in a situation like that.  On the other hand, if you plan to drive 2500 miles per year and you have open spring pressures exceeding 700 pounds, I think I'd be installing a new set of lifters each year, just to be safe.  As Joe mentioned, when the needle bearing versions go bad, they can cause a lot of damage...

[wowens]

I think unless they are high dollar pressure fed needle or bushed with very good hot idle oil pressure they are destined to fail. I lost a comp roller 2 years ago at 900 miles, external pump, 40 psi hot idle, 80 psi above, 600 over the nose. Pressure never went below 40.

[cjshaker]

How many RPM's does a "short travel" hydraulic add over a standard hydraulic? They seem like they would be a fairly good compromise between a standard hydraulic and a solid, on a regular street engine.

[chilly460]

As others stated, without pressure fed oiling they don't hold up.  I never ran one but helped buddies tear down and check their lifters, generally one or two would start to feel rough at 1000mi or so and need to be rebuilt.   One trick was to put a small groove in the lifter body above the bearings, that seemed to help a bit but was by no means long term effective.  Basically a "poor man's" pressure fed. 

[Falcon67]

X3 or 5 as above - only buy pressure fed solid rollers and check them every year.  Street or race, same deal IMHO.  What happens is easy - the shaft gauls and fails, releasing the little roller pins when then pretty much chew the carp out of the motor.  At the very least you can lose the cam.  But scattering hardened steel pins through a running engine is also contra-indicated.  Some higher end stuff - Isky I think - comes with bushings.  Either way, good lifters that last aren't cheap.  But they can be reused when you change cams and they can be rebuilt, which protects your initial investment. 

[scott foxwell]

I'll be the odd man out here and say that most roller lifter failures are not the lifter's fault...as long as we're talking about a decent quality lifter. I hear roller lifters getting a bad rap year after year (both hyd and solid) but most of the time when you really get the whole story...it wasn't the lifter's fault. Pressure fed oiling is definitely a big plus. Bushing lifters not so much. A lot of people believe that a bushing lifter is a "drop in and forget" lifter and is the answer to every roller lifter problem. A bushing lifter is a wear item that will require constant maintenance, just like a bronze distributor gear. They have very low tolerance to dirty oil. The ONLY benefit that a bushing lifter has over a needle lifter, and by design, is that it will not go into catastrophic failure mode. They will give you a warning when they are failing, seen in a lash check. This was their sole purpose when Morel designed them back in the 80's. It's unfortunate that others in the industry are selling these lifters as the holy grail of lifter design. They really aren't.
Things that affect lifter life; rocker geometry is a big one. Overall valve train condition and design (bigger pushrods are better). Lifter bore condition (clearance), placement, perpendicularity to the cam, etc. Proper spring pressure. Using the right oil. Cam lobe design and of course, type of use.

[427HISS]

Morel "Black Mamba" Roller lifters.

http://morel-lifters.com

[scott foxwell]

Morel "Black Mamba" Roller lifters.

http://morel-lifters.com

That's a great lifter. Gives the Chevy guys on a budget an .842 lifter that can handle just about anything you can throw at it without having to spend money on expensive machining to upgrade to a larger lifter. Designed for extreme racing. It's not a bushing lifter. It actually rides on an oil wedge just like the crank and rods. Upgrading to a larger dia. lifter with a larger wheel is a better option but not always feasible.

[Tommy-T]

I ran a 308R in my car for a while. I must admit it made more more power than any flat tappet I've run, but the roller deal has it's "quirks".

I was running Dove rockers and the stock-style 4 bolt hold downs, so I decided to keep my open pressure 550 or so. Worked great, zipped up to 6500, and all was well.

The problem is when the springs go away. That beats the shit out of everything and parts start to fail rapido!

I don't drive my car anywhere near 1000 miles a year. More like 500...if that. So if you want to run a solid roller on the street, and NOT use the race T&D's...here's my recipe:
A quality roller rocker system, I use POP's
A blue spring oil pump so there's lots'a oil fling'n around
Normal Comp roller lifters. The pressurized stuff good but pricey.
Quality pushrods
550 open 200 closed. This is a minimum but must be maintained or else parts are going to start bashing into each other.

Normal maintenance is change the valve springs EVERY year, and the lifters every 3rd.

[jayb]

Morel "Black Mamba" Roller lifters.

http://morel-lifters.com

That's a great lifter. Gives the Chevy guys on a budget an .842 lifter that can handle just about anything you can throw at it without having to spend money on expensive machining to upgrade to a larger lifter. Designed for extreme racing. It's not a bushing lifter. It actually rides on an oil wedge just like the crank and rods. Upgrading to a larger dia. lifter with a larger wheel is a better option but not always feasible.

Scott, I'm anxious to learn anything you know about those lifters.  The reason is that I'm in the process of designing my own SOHC rocker arms, which of course have a roller lifter wheel on the side that rides on the cam.  I have settled on the same approach used by those Morel lifters, to provide full time pressure oiling to a bearing surface.  In fact, last week I just made up my first set of roller wheel axles on my lathe; pic below:



They need to be heat treated and finish ground, yet, but you get the idea.  The small hole on the side gets oil from the rocker body and the larger hole on top distributes it to the bearing surface.  The groove at the right side on top is for a pin, to hold the axle in place so that the hole in the axle stays lined up with the oil hole in the rocker body.  FYI, SOHCs have a 1" diameter roller wheel that rides on the cam.

Do you happen to know what material the pin in the Morel lifters is made from?  Looks to be some kind of a bronze alloy.  My axle is tool steel, and the roller wheel itself is bronze bushed, so that I can size the diameter for the proper clearance.  Any experience with the longevity of these lifters?  I've had it with the T&D rocker needle bearing failures I've experienced over the years in the SOHC, have wrecked a couple of dry sump pumps when needle bearing shards have gone through the pump...

[preaction]

Jay, have you identified the reason for the SOHC lifter failures ?

[jayb]

The SOHC rockers don't have pressure oiling to the needle bearings, they rely on splash.  If you sit in traffic at low speeds there isn't enough splash to keep the needle bearings oiled and they fail.