Corellian Corvette

Here's one I've never seen posted and have been wondering for a long time.

I understand that changing the ratio of the rocker arms can somewhat have the same effect as a cam, not as dramatic, but some improvement.

I have a '73 L48 that is running *really* well right now in terms of reliabilty, but is a bit low on power. Since I currently don't have any leaks/drips/vaccum problems, etc., I'm really not inclined to go tearing things apart to add a cam.

Is there any advantage to getting a new set of rockers on a basically stock but strong-running engine? (I have a lars-tuned distributer, true duals with 2.5 in pipes and Dynomax Turbo mufflers, new carb, performer manifold, and no emmisions stuff. Car purrs like a kitten at idle and barks with the throttle. Bark is worse than it's bite.)

What kind of performance increase would I see?

Is there a set of rockers that I could get that will allow me to run the stock valve covers. I recently got a really nice set of polished L-82 covers and would like to continue using them.

Thanks!!!

Mac

I asked the same question a while back over on the Factory Correct Resto forum. Give me a few minutes to search out the thread. The answers were fasinating!!

Got it: http://forums.corvetteforum.com/zerothread?id=197410


[Modified by Mac, 8:52 PM 1/31/2002]

flynhi

Most of the info I have read over the years concluded that the main benefit was better manufacturing tolerances so that all ratios were a true 1.52 or 1.6 vs a range from 1.42 to 1.55.
Tests I've read didn't see much difference in HP or oil temp.

fwayne

Roller rockers aren't the way to increase power. They supposedly will reduce oil temperature, but the increase in power due to a slight improvement in actual lift ratio will be very modest. Rockers that will probably fit your application with no mods are Crane part number 11750. Call Crane's tech line to confirm (386-258-6174).

73 LS-4

If you look at most of the tests on full roller rockers, they increase power most of the time way up the band, below 3k rpm your only going to gain about 4 horse get it about 5.5k and you may see 8, the higher you spin it the normally the more gain, of course the engine has to be able to make power high enough to take advantage of this as well. I put a set of the Gold Race on my BB, and really didn't gain much out of them except maybe a tiny bit at higher rpm that I could tell, I actually seemed to gain more power out of recurving the distributor to tell you the truth. A set deffinitly won't hurt power any, but gain vs cost they aren't real beneficial unless your spinning a lot of RPM. A set of 1.52's with the roller tips might be a good compromise in that you can keep your stock valve covers and get an accurate ratio without a lot of cost.

:cheers:
Pat Kunz

Corellian Corvette

Thanks guys. Please keep the suggestions coming.

Based on reading the other link (thans Mac!), and the feedback here, this is what I've figured so far (man I love this place!):

a. Not a lot of HP to be gained from rockers only, and according to dyno tests by Car Craft, 1.6 rockers actually lost power.
b. Some efficency to be gained on the high end, will help reduce some friction and keep oil cooler.
c. There may be some improvements just based on the fact that original lifter tolerances were questionable.

So, sounds like there is some improvement but not a lot.

Looking at the comp cams site, I think the model number 1412-16 is the one for my car. Here's the link if someone wants to see them:

http://www.compcams.com/information/...gnumRoller.asp

Summit has this set of the Magnum 1.52 roller lifters for $135. Apparently these will fit under my stock valve cover. My lifters in there now are probably original, so basically I need to decide if it's worth $135 to improve some old lifters with better made, more efficient versions and I *may* pickup some modest HP.

I don't want to go to 1.6 because I don't feel like grinding away the heads. All that will come if I ever decide to do an engine build up.

Right now I'm leaning towards it just for the fact that I may have the original lifters in there.

Again, please keep 'em coming.

Corellian Corvette

FYI - THis month's issue of VETTE magazine has an article about using Roller Rockers on the vette.

fwayne

I can't remember what magazine it was, but I recently read an article - maybe the same one - about replacing stock with 1.6:1 rockers resulting in a power loss. The higher ratio did not cause the power loss, rather power dropped because the pushrods were coming into contact with the head. Increasing rocker ratio should always increase power. How much, depends.

bb69

I work for a company that supplies rocker arms to the OEM's. The main benefit to roller rockers is not the roller tip; it's the bearing that the rocker pivots on. The benefit is a huge reduction in friction, which translates to longer valvetrain life, less noise, and less heat. The roller tip is usually found on aluminum rockers because aluminum wouldn't last being in contact with the valve. Another benefit the better rockers have is stiffness. If your rocker is bending, that means the valve is not opening all the way. The main disadvantage to many roller rockers, is higher mass. In a pushrod valvetrain, mass is by far the largest factor in determining redline.

Basically, roller rockers are not going to give you huge improvements in HP, but they are a better solution, hence, the reason the OEM's are all using them.

Corellian Corvette

Thanks guys. Obviously one concern that I have is that, since I don't know the history of the car, it is entirely possible that I have the original rocker arms, so the minimal cost of the roller tip set guarantess that at least I know that I have the correct ratio.

fwane - you're right. I re-read the article and that was in fact the case.

The big issue for me is that I want to retain the stock covers. The guy at Comp Cams wasn't sure that the full roller rocker setup would fit under the stock covers (issue with the nut on top that holds the rocker). He said that it really depends on what's there and it works for some people and not others.

Has anyone been able to use full Roller Rockers under Aluminum L82 valve covers?

fwayne

I used Erson roller rockers on heads with L82 valve covers. I had to install a spacer between the head and the valve cover for clearance.

And remember, it's not the roller tip that your buying (it doesn't actually roll when it moves across the valve stem - it slides) it's the roller trunion.

Corellian Corvette

Interesting. Where do you get the spacers?

The rockers that I'm getting only have roller tips -- the trunion part is the same as the current ones on there. There is a link to them above.

Ganey

Roller rockers has come up many times.
In the beginning of the SB Chevy design some thought roller rockers would add hp. Chevy agreed to change the design to roller rockers if any hp was added. Despite the efforts of some including Smokey Yunick, no hp was gained.
The power increase is due to the increase of rocker ratio as stock measure about 1.47 so even 1.52 is an increase. 1.6 were made for tuning.

Full rollers are needed for about 6500+ rpm to prevent galling of the ball pivot & when spring pressures are high. There is a way to gain a little power w/ full roller rockers.

All you need is the roller tip which fit under the L-82 Al. valve covers. Double gaskets are not needed.

:cool:

fwayne

Oh. Oops, never mind. And forget about any benefits other than improved, consistent ratio - no friction reduction with these rocker arms.

I probably got my spacers at a local Super Shops, but this was years ago. I have no idea where to find them today. A quick search on a couple of parts sites came up with nothing.