Has anyone tried the Comp Cams magnum roller tipped rocker arms? They come in standard 1.5 ratio and 1.6 ratio. Would 1.6 ratio be overkill with the GM performance cam? Are roller rockers even worth the $120-$150 price?
first of all.... don't change rocker ratio when changing cams. you could break something. the cams are generally ground for "stock" rocker ratio.
As for are they worth it.... I doubt you'll ever see the diferance on anything but a full race setup. Altho if you are doing that kind of work, you should replace all the rockers, balls, nuts and studs. After this manny years, they are likely to have stress cracks in them.
If you do opt for higher ratio rockers then YOU ABSOLUTLY MUST replace the studs and have the heads Zyglo and MagnaFlux tested. The higher ratio will increase stud stress by a large amount. Any crack in the stud area is likely to come apart. The whole thing should be assembled by a race qualified mechanic. Between the cam and the high rate rockers, you could push the valves so far in that the piston smackes the hell out of them very easily.
I've seen a couple different articles that say roller tip rocker arms don't really roll like you think when it's under pressure of opening the valve and compressing the spring. Not really much better than stock, maybe a little stronger. You need to step up to the true roller fulcrum rocker arms before you'll notice any real power gains from the roller action (and less friction).
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07:30 PM
Eric Member
Posts: 916 From: Columbus, Ohio Registered: May 99
I wasn't sold on the roller rockers either, but I thought I'd throw the topic to some outsiders. Ogre, should I replace all the valve related components? I was planning on just getting a new camshaft/lifters, springs and retainers for my 3.2 rebuild. I don't want to cut any corners. I'd much rather spend a few dollars more now and have an engine that runs for another 140,000 miles. I already have someone good to do the headwork.
If you are going that far, replace the valves, rockers, balls, and nuts. If the studs are even questionable replace them to. It cost as much to test these parts as replace them.
I'm assuming that if you are going to this much effort that: You want to do it right. and/or You are going to race the car. In either case, it's not worth the hassle to save the old parts.
Roller lifters are stock in the late 4 cyls. after 86 I think. Roller lifters help both performance, and reduce wear to the cam. Between the sleeve bearings the cam rides in, and flat lifters, there is a trmendous amount of drag on the cam. This amount of drag is part of the reason the flat tappet 4 cyl's tend to chew up the cam gears. The roller setup turns far easier.
you also have to use a cam ground for rollers. Rollers follow the cam surface diferantly than flat ones. It's hard to explain, but it's important to remember.
If fact,,,, this would be a good thing to do to any 4cyls people are restoring that didn't come stock with the rollers. You would need the cam, roller lifters, and the pushrods. The rest I think is all the same.
GM performance has a roller cam too. It may be the same as the Crane cam. As far as I can tell, the roller cams are about twice the money. I wonder how much more power a roller camshaft would provide.
can't tell you,,,, I can tell you the 4 cyl GM config only gained around 4-6hp with all the changes from 86&87 combined. It would depend on the specific cam, and everything else you've done.
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08:06 PM
Eric Member
Posts: 916 From: Columbus, Ohio Registered: May 99
A mechanic was once telling me how solid lifters can make an engine rev higher but needs to be adjusted often. Crane also makes a set of solid lifters for the 2.8, any opinions on these?
As long as we're on the subjet of valvetrains, let me tell you of a problem I had after getting a valve job on my heads a few years ago. After I got my heads back from the machine shop, the valve stem height had changed because the seat was now deeper in the combustion chamber. This resulted in a less than optimal valvetrain geometry. The tips of the rockers are supposed to contact the surface of the valvestem exactly in the center and remain in the center throughtout the entire stroke. Now no matter how I adjusted the lash, the rocker tip wouldnt center. I needed longer pushrods to maintain correct geometry.
I ran a set of solid lifters in a Big Block 402 ONCE! Even with a stud girdle, I still had to adjust the valves too often. Even if regular lifters dont make as much power as solid, I like them more because of the fact that you dont have to adjust them so often. But I know other people who have run solid lifters forever and never had to re-adjust them. I aint that lucky, especially when you consider how hard that front valve cover is to get to, I will keep my hydraulic lifters(rollers in my "r" 4 cylinder).
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08:51 PM
lowCG Member
Posts: 1510 From: seattle,WA U.S.A. Registered: Jun 99
A "thrust control device" would be anything that would keep the cam from wandering back,and forth in it's bearing's.Usually there is a small,adjustable bolt put into the center of the timing cover,aluminum is good,plastic works too.The thrust is usually kept under 0.010 of an inch,varies per application(roller/standard)and is a good idea for any performance engine.
I've used solid lifters, They require Very presice adjustment to work right. Get a cleance to tight, and you can break things. To loose they clatter like hell. In a Fiero v6 otor, I would definatly stay hydraulic, Just to neven have to jerk apart half the motor again if nothing else.
Right now, the best type of cam and lifters are the hydraulic rollers. They are more expensive and if you have an older engine you must buy a "retro fit" roller cam kit which is even more expensive. But, they work nice and produce lots more power, partly by reduced friction and partly because the valves is opened faster, at the full open position longer, and the valves closed faster than regular cam and lifters. Because of extra stress, you must upgrade to better valve springs and use the high performance screw-in rocker studs.
I'm building a 350 V8 roller cam motor right now for my hotrod truck that should crank out close to 425 horsepower and still be streetable with a four speed manual transmission.
I used solid lifters (Z-28 mechanical cam and lifters) in a Chevy 327 once. It ran like crap until it hit 3,000 rpm and then it would sit you back and ran super strong all the way to red-line (would never float the valves at high rpm like hydraulic lifters will). You do have to adjust them every once and a while. In my opinion, solid lifters are just for racing.
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09:24 PM
lowCG Member
Posts: 1510 From: seattle,WA U.S.A. Registered: Jun 99
My old Mini Cooper had solid lifters and a lot of valve area for the size of the motor,don't know how high I revved it,but I had to adjust the valves at least once a week to keep it idling anywhere near smooth. Got it down to seven or eight minutes. Batboy,have you looked at any of the eighties,stock'vette roller profiles? Saw this neat '58 sedan delivery with a setup like that,worked very well with a newer Carter,perf dual plane.Not sure exactly which year,think it was around 300DEG,they changed alot.It gave a nearly flat,linear torque curve.
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10:41 PM
Nov 26th, 1999
fierosound Member
Posts: 15147 From: Calgary, Canada Registered: Nov 1999
The only roller cam I've seen available for the 2.8/3.1/3.4 V6 is the one from GM. Surely someone else has one, considering that Camaros had the same engines!!
Anyone know of any other manufacturer's of roller cams for these angines?
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01:42 PM
Nov 27th, 1999
HF6582 Member
Posts: 158 From: Bonne Terre, MO USA Registered: Mar 99
When I was rebuilding my 2.8 (before we knew about 3.4) I went with Crane 1:5 because we weren't sure about 1:6. The heads were completely done over and the roller tips have been fine even with the big Erson cam. Now we know that 1:6 roller tip will go fine with a bigger cam assuming that the heads have been completely gone over as they should when an engine is being rebuilt.
As for power I really couldn't say I know the basic difference. My 85 GT spun a bearing 2 weeks after I got it. I had never driven a GT as a daily driver before that. I am very happy with my performance though that was not the only mod my engine had. This is the first time I had heard of a roller lifter for the 2.8, I was told that there was not enough room for roller lifters.
Using solid lifters in a street driven Fiero is insane. Tearing down the upper and lower intake plemums as scheduled maintenance might be somebodies acceptable price for a little more power but to us mere mortals it might sound as much fun as eating glass.
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03:31 AM
PFF
System Bot
Nov 30th, 1999
pollock Member
Posts: 424 From: denton, texas, usa Registered: Sep 1999
The problem with the roller cam kit, as batboy touched on, is the fabrication requirement. Regular hydraulic lifters, as we all have, are free to spin in their bores. Their rotational position is irrelevant. Roller lifters, however, have a roller at the base which must be held parallel to the lobes on the cam. This is typically done with a stamped steel bracket of some description that fits in the lifter valley underneath the intake manifold. For example, such a kit is available for my Ford 289, bracket, lifters, cam, and all. To invent this on your own is not for the faint of heart.
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06:01 PM
Dec 1st, 1999
fierosound Member
Posts: 15147 From: Calgary, Canada Registered: Nov 1999
PN# 24504436 - Roller Rocker Arms - These roller rockers arms are used on late model V6/60 degree engines for improved performance.
PN# 17120070 Roller Tappet - These roller tappets are used on late model V6/60 degree engines for improved performance. (Must be used with late model cylinder blocks)
PN# 24505674 Camshaft "Roller Lifter Design" - This Gen III Roller Lifter design camshaft features 6000RPM operation (spring installed at 1.66") with a power peak at 5200RPM. It features a cast iron distributor drive gear for improved durability. (Requires fabrication to secure anti-rotation bars and installation of thrust control device.)
It appears "roller" parts are available from GM... if no-one else. Of course, nobody at GM knows what the cam's specs are...
The "late model cylinder blocks only" criterion is a real good indication of why a roller cam is not a viable alternative for the 2.8. I believe the application they are referring to here is for the FWD aluminum head motor.
Mike (Fiero info in user profile)
[This message has been edited by mwbackus (edited 12-01-1999).]
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07:59 PM
2FAST4U Member
Posts: 197 From: Denver,CO - USA Registered: Sep 1999
Crane, Lunati, Comp Cams, just about everybody list roller cams for the V-6. The main advantage for a roller cam for a street motor is that it allows the cam grinder greater latatude in the design of the cam. A roller can have more radical event timming ETC. whill still retaining some streetability. This is in addition to some small HP gains from a reduction in friction.
Roller rockers are a good idea for several reasons - reduced wieght, less friction, decreased valve stem wear, ETC. As for a 1.6:1 rocker - they are effective also but are most efective with a stock cam. You should always check valve to piston clearence when going to a higher ratio rocker. Check with cam manufacturer for use with a aftermerket cam.
After an exaustive search I have found that no cam manufacturer makes a Hydraulic roller for the Iron Duke 4. The ones listed are all solid lifter race grinds. So I bought a new roller and lifters from GM and Reed Cams in Georgia is regrinding it for me for more performance.
be forwarned - The cam and lifters from GM are expensive. over 200.00 for the cam and the dealer originally ask 46.00 apiece for the liftrers thats almost 400.00 for a set of lifters. I finally pissed and moaned enough that he lowered te price to 26.00 each
To help ensure that this forum remains the valuable research tool that it currently is, I always try to provide the most accurate information I can obtain. I have nearly all of the forementioned manufacturers catalogs available to me, and not one of them offers a roller cam for the 60 degree V6 173cu motor. If someone actually has information that contradicts my statement that there are NO roller cams made specifically for the 60 degree V6 173 cu. motor, please post some part numbers so that we may verify this and be enlightened.
I'll be happy to prove you wrong Mike. Check out the below URL to the official Crane Cams website. Oh my **gasp** they have a roller cam for 60 degree V6 2.8/3.1 engines. True, this is a racing mechanical roller cam that won't work on computer controlled engines, but nevertheless, it is a roller cam. I didn't bother looking anymore for others cams.
It is nice to know that they do indeed make "something" that will work, at least in a computerless system. A .625 lift is not what I had in mind when I asked the above question, but it will do. :-)
Check out the below URL to the official Crane Cams website. Oh my **gasp** they have a roller cam for 60 degree V6 2.8/3.1 engines. True, this is a racing mechanical roller cam that won't work on computer controlled engines, but nevertheless, it is a roller cam. I didn't bother looking anymore for others cams.
