Well, just what the title asks..I am considering buying a set of them, but which ones should I spend money on? Are the full rockers worth their price? Do I also need to buy any new studs or bolts to use either of them? Do the full rocker ones come with everything needed to install them on the heads?
Can I pick up a set cheaper elsewhere? What do I need to look for? SBC, any particual stud size?
How much performance can be gained by going with 1.6 rollers? Are they going to change my gas milage any? I would think, since there is less resistance, they would actually help gas milage, but I don't know.
------------------ Original Blue 87GT 5spd. Modified 2.8L V6 Centerforce Dual Friction, H4 Blue headlights, Cleared Taillights, Mr. Mikes Leather, MoMo Carbon Fiber Steering Wheel, Lowered 1.5", Konig Verdict 17" Rims, Power everything, Speed Hut Gauges, Short Shifter, Ported Manifolds.
IP: Logged
11:41 PM
PFF
System Bot
Oct 24th, 2004
4mulaFire Member
Posts: 399 From: North Platte, NE Registered: Mar 2003
well... don't know if this will help too much BUT...
I'm currently in the process of upgrading my setup to incorporate the full roller rockers. I have a lumpy cam in the package, and a bunch of other stuff, but the important bit is that the 1.6:1 ratio will increase valve lift a little to a lot (depending on cam). The decreased resistance is good, definitely, but the really good bit is in the increased lift. More lift, more air/fuel.
If you grab a new cam as well, it can only get better. But by themselves I personally would consider it a worthy upgrade.
I was told (and I never take salesmen seriously) that the full roller is better than the roller tip by 5-10% in power. I'm unsure as to the validity of this, doubt it, but decreased resistance is good. It may be inconsequential, (is that spelled right?) but think: the engine has 12 of those things going up and down several times a second each, and that can add up to a lot of friction. AND HEAT! Don't forget the heat. Or your oil changes. Trust me.
Hope this helped. -Steve
IP: Logged
01:17 AM
Scott-Wa Member
Posts: 5392 From: Tacoma, WA, USA Registered: Mar 2002
If you look at what friction your attempting to reduce, it's doubtful that roller rockers or just roller tipped rockers really produce measurable performance increases in HP. If might reduce friction a fractional amount... and I've got full roller rockers on two engines of mine (a 289 ford street/strip engine pushing about 520hp on the bottle and a 429 Thunderjet that's been heavily modified). The gains I'd expect is in stiffness, accuracy, and hopefully reduced reciprocating mass along with possibly increased longevity... but in the real world where it's $$$ designing parts and advertising selling them, I don't really believe anything I don't see backed up by real world numbers.
With increased ratio, you are stressing valvetrain components more than stock in an attempt to open the valve further without a cam change. This modification can make a tiny bit of extra power, have no effect, or lose a bit of power. No way to really know until you do back to back testing like real race engine builders when you are second guessing the engineers that designed the vehicle.
I've seen race engines that had different ratios between cylinders along with intake/exhaust because they were doing enough to see where the modifications helped. Buying a set cause it sounds like it might make more power isn't a real good reason when your talking about a potential of less than 5hp between the factory and best for application aftermarket rocker.
Don't let me talk you out of it though.. they sure are pretty with valve cover off and it sounds good benchracing :-)
By increasing ratio I have read that you also increase the duration.Also rollers will give you more rpm support up top.But unless you replace the springs it may not be as beneficial as if you do.
IP: Logged
09:09 AM
4mulaFire Member
Posts: 399 From: North Platte, NE Registered: Mar 2003
Ah I see now...Looks like $300 or so dollars for full rollers sounds like a bit of a waste for no more power then I'm planning to do. Looks like I can spend it more productivly elsewhere on the car. I don't plan on having this engine for more then another year or so, so its no big deal. I do have a lumpier then stock cam however, new lifters, and fairly new (still stock) valve springs. I think I will however pass up on the new rocker arms right now. Thanks for the information!
IP: Logged
10:59 AM
Scott-Wa Member
Posts: 5392 From: Tacoma, WA, USA Registered: Mar 2002
By increasing ratio I have read that you also increase the duration.Also rollers will give you more rpm support up top.But unless you replace the springs it may not be as beneficial as if you do.
It increases lift, not duration. the ratio is the multiplier that you use on the cam lift to come up with valve lift... eg. .100 lift at cam times 1.5 rocker ratio is .150 in lift at valve. At 1.6 ratio it's .160 in lift at valve. Depending on actual flow characteristics of head that can help or hinder. You could actually end up with more valve shrouding at max lift if the valve gets to close to cylinder wall and ruin swirl/disturb flow pattern. If the extra lift from ratio combined with a high lift cam makes the area under lift larger than the port volume that can also lead to no flow increase. Just some things to consider... it's all stuff manufactures and racers with high budgets and flow benches/engine dynos take into consideration.
In a basically stock street engine you are increasing area under lift a bit with a small increase in max lift, so might see a bit of torque increase. It doesn't effect duration at all since .000 lift time 1.5 or 1.6 still comes out to .000 lift. The big gains come from cam changes that agressively open the valve faster so that you get more area under lift. Roller cams are best for this since they can slam the valve open so much faster than a hydraulic that a much lower duration roller cam can outflow a hydraulic cam for same application.
It's science... it's voodoo... it's fun to play with. There is software out there that tries to simulate a lot of the variables, but it still comes down to matching everything as a package for what you really want to do with the car.
IP: Logged
04:22 PM
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
Originally posted by Scott-Wa: With increased ratio, you are stressing valvetrain components more than stock in an attempt to open the valve further without a cam change. This modification can make a tiny bit of extra power, have no effect, or lose a bit of power. No way to really know until you do back to back testing like real race engine builders when you are second guessing the engineers that designed the vehicle.
Scott-Wa makes a good point. The valve rockers are levers. If you increase the ratio (valve side vs pushrod side), you decrease the camshaft's mechanical advantage vs the valve. In other words, you increase the drag on the valvetrain. This causes more friction in the valvetrain parts (possibly reducing longevity). And since the camshaft is mechanically linked to the crankshaft, it also increases the drag on the crank, i.e. sapping power from the engine. The power increase from the increased valve lift may or may not overcome the power loss from the increased drag. Only the dyno will tell.
Also, keep in mind that the stock 2.8 valvetrain can only accomodate a gross valve lift (total lift measured at the valve) of 0.420". Anything more will cause the valve springs to bind. You can estimate the gross valve lift with any cam/rocker combo by multiplying the cam lobe height by the rocker ratio. If that estimate is 0.410" or greater (just to be safe), then you'll need to find some aftermarket valve springs that will accomodate more lift.
Does that help?
(edit for correction)
[This message has been edited by Blacktree (edited 10-24-2004).]
4mulaFire said: Do I also need to buy any new studs or bolts to use either of them? Do the full rocker ones come with everything needed to install them on the heads?
The full roller rockers on WCF's website look like small-block V8 rockers. They most likely use 3/8" studs. I noticed that WCF also sells adapter studs for them. If you don't want to drill/tap your heads for 3/8" studs, then you'll need those adaptors. I'm not sure if the adaptors are included with the rockers (probably not). But if you drop an email to WCF, they can answer that question.
This is just my opinion, but for the price of those full roller rockers with adaptor studs, you could buy a new cam and a set of roller-tip rockers, and probably have money left over. You'll probably get a better performance increase too, depending on the cam specs.
[This message has been edited by Blacktree (edited 10-26-2004).]
IP: Logged
05:24 PM
4mulaFire Member
Posts: 399 From: North Platte, NE Registered: Mar 2003
Trust me.
