What exactly are roller rockers?

[tonyk72]

What do they do? How do they increase performance? Can I install them on a stock LT-1? What kind of tools are needed to get this done? How complicated is the install? What can break if the install is not done correctly?

Thanks!

 

[Jack]

Roller Rocker Arms vs OE stamped

What do they do? How do they increase performance? Can I install them on a stock LT-1? What kind of tools are needed to get this done? How complicated is the install? What can break if the install is not done correctly? Thanks!

Roller Rocker Arms replace the stamped steel OE rocker arms with ones that operate with less friction. Friction is a load that reduces horsepower … less friction equates to more power … rolling cylinder / bearing reduce friction. OE stamped have no bearings … they have a simple (but very reliable) fulcrum ball at the rocking point and they simply slide across valve tip (also very reliable). Some aftermarket “stamped roller tips” are also stamped steel and utilize the OE type fulcrum ball but also employ a rolling cylinder that rolls across valve tip. So called “full roller rockers” are typically aluminum extrusions and have a needle bearing fulcrum at the rocking point in addition to the rolling cylinder for valve contact.

Full rollers (those with bearing fulcrums) have relatively tall locknuts (called "polylocks") … their height often will not fit under stock-height valve covers.

With a relatively mild cam as in 72 LT-1 (I think that’s a solid lifter cam), tools needed for rocker arm replacement include: either the knowledge to adjust valves or an instruction manual, a couple of combination wrenches, a set of allen wrenches (for polylocks) and a set of feeler gages (not needed for hydraulic lifters). With a relatively mild cam, the install is rather simple. More radical cam profiles require more attention paid to where roller is located atop valve tip … and may require longer pushrods to “center” the roller’s contact pattern in middle of valve tip … may require special "adjustable pushrod checking tool" to determine proper pushrod length.

If the roller tip is not reasonably centered it can fall off the valve tip and hit spring retainer … causing undue side-loading … causing arm / rocker arm stud / valve stem to break.
JACK:gap

 

[Vettehead Mikey]

What do they do? How do they increase performance? Can I install them on a stock LT-1? What kind of tools are needed to get this done? How complicated is the install? What can break if the install is not done correctly?

Thanks!

Two more important questions to ask:

How much more usable power will they give me?

What is the cost to aquire this usable power?

 

[GerryLP]

Toney and Mike,


I would also like to piggy-back on Jack's statement and add that the advantage comes throught the accurate multiplication of cam lift through the range of motion compared to stamped-steel rockers. Chevyhighperformance.com has an article on tests performed on different types of rockers, and the differences bettwen OEM stamped-steel rockers and aftermarket are significant. Take a look there for more info.

Also, please realize that the implication of being unable to use the stock valve covers translates into unable to mount the AC compressor without extensive modification to the bracket assembly. I am unaware if there are vendors offering after-market AC bracket kits to fit taller valve covers.

 

[Stallion]

I think I read once that with roller rockers you can have a different type of cam because the rockers accept a bigger plateau of the lobe. I'm not 100% sure, but I think I do remember something along those lines. Roller rockers are definitely worth it, though, I think.

 

[Jack]

Two more important questions to ask:
How much more usable power will they give me?
What is the cost to aquire this usable power?

Some claim as much as 15% increase in HP ... I dunno about all that. Cost from about $150 to about $400 a set to fit studs as in sbc vette. Yes, there are claims of lotsa production tolerance variation of RAR in OE stamped ... I've little doubt that variation exists ... but I dunno about how much ... or how noticable that much variation is to someone driving a 250-400 hp street car. Also, I've little doubt there's variation in aftermarket/roller rockers too ... again I dunno how much or if it really matters so much.

I will add this ... I've worked on several aircraft motors ... some WWII era ... in all I've seen (maybe 10 in all) the inards of em had full roller rockers from factory. Keep in mind that what may be de rigueur for an airplane ain't always needed or prudent for a street car. We have full roller rockers in our circle track 355 sbc ... I have only stamped (new ones) in my 388 sbc street-only vette.

edit: Roller rockers and roller lifter cams are apples & oranges. Roller cams' roller lifters permit cam profiles that aren't practical for flat tappet cams.
JACK:gap

 

[tonyk72]

Ahhh, I thought I could neatly tuck these away under my stock valve covers...So If I need taller covers & need to make adjustments for the AC..I'm not sure I'd want to go down that route.
$150-$400 seems kinda steep? Is that for parts and labor? My coworker has a L98 and he just got some roller rockers for right around $120...
Anybody have any dyno results with before & after roller rockers? Where does the power increase come at..across the whole RPM band? What about torque?

 

[Vettehead Mikey]

Some claim as much as 15% increase in HP ... I dunno about all that.


I will add this ... I've worked on several aircraft motors ... some WWII era ... in all I've seen (maybe 10 in all) the inards of em had full roller rockers from factory.

15% increase? So if I'm running a 375 horse motor, I can add 56 hp with these rockers? I wonder why all the combined intelligence of the GM engineering division didn't also know this, and install them from the factory. I protest! Class action suit! John H., where are you, I want an explanation. This is an insult! :L :L :L

BTW, if the aircraft engines you worked on were big round ones with an eagle on the crest, the fellow next to me at work was the QC guy that signed it off the last time it was at the factory. How's that for a small world.:cool

 

[JohnZ]

Well, the marketers are at it again (as usual); the claimed power increases from reduced friction in an ordinary street engine are WAY over-hyped. It stands to reason that after spending $400 for rockers, screw-in studs, guide plates, and pushrods (not to mention new taller valve covers), the spendee WANTS VERY MUCH to "feel" more power. Ain't gonna happen. The other claimed benefit is "reduced valve guide wear" - you MIGHT be able to measure a difference with laboratory methods after 80,000 miles, but I doubt it. Waste of money on a street engine.

Those big Pratt & Whitney R-2800's have rollers everywhere, for absolute reliability and to get the last ounce of power (they also get completely rebuilt every 750 hours or they don't fly). Priced an airplane engine recently? An ordinary unsupercharged 200hp 6-cylinder Continental or Lycoming only runs about $30,000.00. Mikey can tell you what the P&W PT-6A turboprops cost that he deals with every day, but you don't want to know :eyerole

 

[drags1998]

Ill make short and sweet: SAVE YOUR MONEY!!!!!!!!!! Any extra lift,reduction in friction or CLAIMED HP . WONT BE NOTICEABLE and if you screw the install up, IT COULD COST YOU A FORTUNE!!!!!!!!!!!!!!!!!!!!

 

[GerryLP]

A fact is that any engine modifications done alone hardly is the BIG horsepower producer (although, the single improvement producing the most horsepower could be adding a supercharger...).

Emphasis should be placed upon a combination of improvements driven by a particular goal. Is one's goal to race in the local quarter-mile or circle track ? Does one prefer to smoke the tires between stop lights or will the car be a dedicated race car? Once you reach a conclusion (is your goal within your mean$$$$ ???) on these questions, the rest of it should be a straight foward approach.

John and Drags, I sense on your part and maybe others a dislike of vendors, and believe me, I understand very well your sentiments, and I could be misreading you all, but its almost as if you won't recognize that there were many times that high performance vendors drove the production decisions at the big corporations like GM and Ford. Achievements by Edelbrock, Shelby, Yenko and many others helped convince the big auto makers that it made a huge financial sense to produce the muscle cars of the late sixties and early seventies. The taste for these cars never went away, and then came the gasoline crisis. And when the big-three reached bottom by selling cars with the V8-305 or V6 engines in them, a resurgence in after-market demand (or was it low new-car sale totals together with customer uninterest, and big competition from foreign automakers??) may have effected a rebirth in ingenuity on the part of GM to provide us today with the Buick Grand National, the ZR-1, and the ZO-6. It seems to me that the big-three also happen to be the biggest vendors around, So please, and ever so respectfully, lighten-up!

I choose to do my experimentation with an off-the-shelf engine so that I can save my venerable L81 engine block from my own stupidity, yet I will add that knowledge base and experimentation leads to inginuity, so I would encourage everyone who has the desire to research and apply their own ideas through experimentation. There are examples of engines producing large amounts of torque by combining short-duration cams together with high lift lobes and rocker arms, but don't forget that these also involved relatively high compression ratios, high performance fuel systems, and matched intake and exhaust components. It cannot be overstated that engine modification for performance is expensive; however, so its smoking cigarrettes, raising a family, and putting one's own through college. Choose your vice.

Sorry, I'll get off my soap box now...or was it shot-off????

 

[onefast95vette]

Roller rockers improve the performance of the engine by reducing the friction between the rocker and the lifter. That way there's less ambiguity in the valve throe (depending on your cam). Make sure you get the torque requirements from a Chiltons, and I recommend titanium keepers if you're going to get that far into the motor. And get roller lifters. They will also enhance your performance and they don't cost all that much.

Dan

Dan

 

[tonyk72]

Gerry, to answer your question...I'd like to smoke 'em up between stop lights

But the more I think about it, I think I'll leave my stock engine alone and start shopping around for a block to build up from scratch...I'm itching to do some mods & this might be the best way to go. I could preserve the original engine and do whatever I want to my "spare" engine...

 

[Jack]

But the more I think about it, I think I'll leave my stock engine alone and start shopping around for a block to build up from scratch...I'm itching to do some mods & this might be the best way to go. I could preserve the original engine and do whatever I want to my "spare" engine...

I think building another motor is the way to go.

Some claim 15% ... I haven't made such a claim ... again, I dunno how much of such claims (suppliers' marketing) I believe. From my post above, one might surmise that I'm not a huge proponent of roller rockers for everyday use in a street car.

Yes, I've worked on a Pratt radial ... in a Texan bomber-trainer. The most recent radial I helped with is similar to a Pratt ... a Yak-licensed radial in a red chinese Nanchang fighter-trainer. I assist a long-certified AP mechanic (I am not) ... I can't recall any of the Pratt stuff going back for certs ... the Yak stuff probably hasn't seen china in 20 years. Some might characterize it as shadetree ... I don't mind that a bit ... they run well & the warbirds are flying ... not a lotta hours ... they're not commercial ... heck they're barely general ... they're a hobby ... but nobody's augered-in yet. Little doubt that if & when a magneto etc needs a cert, some guy with more "certified" NDT experience than I will sign off on it. To clarify, I'm not a certified airplane engine mechanic ... I simply bring my practical & professional experiences to assist a certified AP man.

I dunno, someone else knows about later vettes etc ... but doesn't/didn't some of the later production vette motors (? LS-something ?) ship from GM with full roller rockers & roller lifters? I'm certain that GM sells them with a GM P/N ... like most factory parts, they're manufactured by another supplier.

JohnZ has it dead right ... airplanes have rr's for exactly the reasons he stated. Same goes for what John says about most street cars' need for rr's.

Stamped rockers have limitations ... load them heavy enough & they'll flex. Real careful here ... average sbc C3 came with valve springs from factory that PROBABLY have a seat pressure of NO MORE than ABOUT 95 psi ... PROBABLY closer to 75 psi. When going to heavier springs (for more aggressive lobes) ... seat pressures go up. Simply an estimate here, but when seat pressures get to ABOUT 130 psi that might be when a sturdier rocker arm becomes practical. Again, just estimates.

The need to retrofit roller rockers and / or roller lifter-cam depends on the application & expectation. Every sbc & sbf RACE motor I know of has roller rockers ... they have a lotta spring pressure & lift resulting in steep angle and alotta side loading at valve tip. But they don't all have roller lifters-cam. Roller lifters are heavy and cannot run as high rpm as lighter flat tappets because with the added mass the roller lifter has added inertia and the roller lifter tends to float as the lobe accelerates & decelerates lifter. Note the Cup cars do not have roller lifters while both Busch & Craftsman motors do have roller lifters. Non-restrictor plate Cup motors turn more rpm (9K+) than either Busch or Craftsman motors ... largely due to Cup motors' lighter flat tappets permitting more revs.

As far as price goes ... I wrote "ABOUT" $150-$400 ... simply a guideline. I dunno, but there's probably some rr's of questionable origin on ebay for under $100 ... at the same time there's offset, shaft-mounted rr's made of titanium that'll set you back thousands. I co-own a late model asphalt circle track car & own a charger car ... both with sbc ... both with full roller rockers ... both with solid flat tappets. The rr's in our late model retail right at $400 ... my charger car's rr's are cheaper. Our competitors spend about the same as we do. Because I've always installed mine/ours, I dunno labor costs to install rr's ... it might cost a coupla hundred or you might find a guy to do it for fifty ... I dunno. Again, we have rr's in our race cars but I do NOT have rr's in my street-only 388 sbc vette.

Again, I don't claim 15% more power w/ rr's ... some suppliers claim it. IMHO, a C3 sbc street motor fitted with stamped rockers can be coaxed to make all the power & torque the rest of a typical C3 street car can reliably handle.
JACK:gap

 

[GerryLP]

Jack,


Are the restoration projects in which you are helping Confederate Air Force projects? The only project with which I have been involved is the restoration of an OH-13E Helicopter. This is an USAF version of the Bell-47 similar to the one shown in the opening credits of the M.A.S.H TV show. However, the restoration was only at a museum-level type of restoration. I was not allowed to restore it to flying status. Nevertheles, I had the oportunity to teardown the 6 Cyl. Horizontally Opposed Franklin engine and the entire airframe to its main sections including the removal of the cabin. What remains is to suspend it from its display location cealing. Historically speaking, its accurate.

 

[JohnZ]

John and Drags, I sense on your part and maybe others a dislike of vendors, and believe me, I understand very well your sentiments, and I could be misreading you all, but its almost as if you won't recognize that there were many times that high performance vendors drove the production decisions at the big corporations like GM and Ford. Sorry, I'll get off my soap box now...or was it shot-off????

Gerry, I understand where you're coming from - I don't have a dislike for vendors per se, just the way their marketing hype raises unrealistic expectations when they try to peddle "race parts" to people with ordinary street engines with ridiculous claims about the results. Many marketing types make their living simply lying to anyone who'll listen, and it'd take the FTC a million years to nail them all. A properly-developed engine is engineered as a "system" to serve a specific purpose, not a collection of catalog parts that "look good" in a 4-color brochure.

I spent 37 years in Engineering and Manufacturing with GM and Chrysler, lots of it in Powertrain development and engine manufacturing, and six years as the Viper Plant Manager (where we built our own V-10's from scratch) and as co-leader of Team Viper (the Viper race team), and I've been building both street and race engines myself as a hobby for about 40 years, so I'm as much of a power junkie as anyone else - here's how I relax:

 

[drags1998]

Hi John, I love what you do to relax. I assume it runs in S/Comp, A friend and I ran a 69 Camero/ 540 for years in S/C. What a kick!!! Anyone that says its easy to run 8.90 with a 00 lite has never tryed it. Good Luck!!!! Paul:cool

 

[GerryLP]

John,

That is an awesome therapy tool...:L...I can't wait until I am able to complete my race car. It began as a thought, and it's still in the planning stages, but at least I have the 1971 Camaro body and frame, a workable rear-end, a TH400, and a 402 small block that I am still trying to decide whether it be worth the time investment...I am beginning to appreciate time more than money these days.

 

[Jack]

Jack,


Are the restoration projects in which you are helping Confederate Air Force projects? The only project with which I have been involved is the restoration of an OH-13E Helicopter. This is an USAF version of the Bell-47 similar to the one shown in the opening credits of the M.A.S.H TV show. However, the restoration was only at a museum-level type of restoration. I was not allowed to restore it to flying status. Nevertheles, I had the oportunity to teardown the 6 Cyl. Horizontally Opposed Franklin engine and the entire airframe to its main sections including the removal of the cabin. What remains is to suspend it from its display location cealing. Historically speaking, its accurate.

CAF ... NO ... the warbirds I've worked on are in private hands in south carolina ... same goes for working cropduster (steerman w/ pratt) ... for example:

North American SNJ-5 Texan (similar to NA AT-6) w/ 600 hp, 9 cyl Pratt & Whitney radial (cruise@170mph, max@205mph). Origin: USA. Recently upgraded landing gear's hydraulic drum brakes w/ new hydraulic discs ... bent spar on landing instilled appreciation of non-grab brakes.

Nanchang CJ6-A (similar to Yak-18) w/ 285 hp, 9 cyl Huosai radial (cruise@180mph, max@230mph). Origin: Peoples Republic of China (mainland).

But I did visit a CAF wing's museum at Camarillo California ... very cool ... buncha great guys too.

A local pal has a homebuilt p-51 ... about 3/4 scale ... has an inline 6 motor from some kinda army trainer I think ... I think it's a Franklin but not sure.
JACK:gap

 

[onefast95vette]

I wouldn't even think 15% more power. Maybe 5% overall. The advantage is the durability. Most average cars don't run over 8000 rpm, so they don't need the added lift to offset the side lobing. I know I'm just a rookie, but I shift out of 1st at 6700, and out of second at 6400 and still run 10.8s. Just a thought.

Dan