'89 rocker arms

[thirdtimevetteowner]

Can anyone tell me if '89 L98 aluminum head rockers are the self-aligning type, or do they have push rod guide plates and screw in studs? Also, can the valve springs support the extra compression of 1.6 rockers w/out coil bind? Thanks.

Rich K.

 

[redc4corvette]

Should have screw in studs ,the rockers I think need to be self aligning .
If the springs are weak they will scuff the under side of the rocker where the push rod is.

 

[thirdtimevetteowner]

Thanks red, but if they have screw in studs, wouldn't they then also have push rod guide plates, negating the need for self-aligning rockers? And I don't quite understand what you mean about them "scuffing" the rockers. They would have to be extremely weak to cause that particular problem, no? The car only has 41k on it, but then again it is 16 yrs old so metal fatigue could come into play. I suppose I may as well just pull a cover off, and have a look.

 

[redc4corvette]

Most chevy alum heads come with self aligning rockers.
No guide plates.
But I think all alum heads have screw in studs mine do on my 94.
My L98 has the cast iron heads and it has none of the above.
The push rods just rattle around inside the head pushrod pocket and no plates.
My 94 I installed roller rockers and with the weak springs the under side of the rocker tip at high revs was scuffing bad .
I had to install the comp cam bee hive springs to make more spring tention on the rocker.
Now I rev to 6500 with out a problem .
The one draw back with the bee hive LS1 spring is no dampner and if you lose a valve the chances are it will go through the piston.
For the extra rpm I took that chance 2 years down and still ok.

 

[thirdtimevetteowner]

Thanks again redc4,
I can't quite understand Chevy's logic in using screw-in studs w/out guide plates, other than simply a matter of $, meaning it would cost less to use slotted stamped rockers than it would to use the guide plates too, especially in a non-high performance application such as the L98 engine. But now I am wondering if I could use aftermarket guide plates and roller rockers, such as Comp Cams Magnums or Pro Magnums (w/an appropiately longer stud naturally). Anyone can chime in here to help me and redc4 figure this thing out, please, but then again it is 4:30 A.M. Time sure flies surfing and searching for data and such.

 

[redc4corvette]

It's only 12:00 here.
If they save a buck that adds up to thousands a year.
I know the L98 is a truck motor and just has a roller cam in it and that is all that is special about it.
I have had my L98 covers a few times and the studs for the rockers are only 3/8
My AFR's are 7/16 and i have the Pro mg on it .
I tried to use them on my L98 but the studs on the Iron head are to small .

 

[m nordin]

They do have guide plates but they were only for engine assembly purpose since they are not hardened. You can use self aliging RR´s an skip the guide plates (or just cut the tabs on the stock ones) or do it the "old way". Check for any clearance issues on RR and centre bolt valve covers, think you need narrow body RR´s

MN

 

[Jack]

Even with typical OE spring pressures, Aluminum heads NEED screw in studs whereas pressed studs are usually adequate for Iron. Crane, Comp and others make a roller rocker that is self-aligning (sometimes called a "rail" design) and do not need a guide plate. That same type RR is what comes in some of the GMPP hot cam kits. Whether 3/8" or 7/16" studs ... stud holes in head are 7/16" ... might seem silly but that's the way it is. Although some later heads have a metric thread in hole ... dunno which years/models. Stamped long-slot self-aligning rockers are available with special coatings that improves their sliding on PR tip, valve tip and at ball-fulcrum ... ask www.howardscams.com
JACK:gap

-edit- some studs are 3/8 on top, others 7/16 ... all but a few later heads have 7/16" holes (in error, I had typed 3/8 holes).

 

[thirdtimevetteowner]

A few questions MN - How do roller cam motors supply oil to the rockers, just by splash and the drippers inside? Would 1.6 ratios cause a problem with spring coil bind?
And why couldn't hardened guide plates be used w/non-self-aligning, roller fulcrum rockers? Comp Cams makes roller-tip, self-aligning ones, but they are the ball pivot type, which are not nearly as efficient as the fulcrum type. And it seems as though I am stuck w/the stock valve covers because of accessory clearance problems, so it also seems like the roller-tip, self-aligning type are the best case scenario. Oh well.
Thanks to you and redc4 for your thoughts w/my dilema.

 

[thirdtimevetteowner]

Sorry Jack, didn't see your post until I wrote the last one. That helps some. I'll check out the howardscams site and maybe get a resolution to what should have been a fairly easy fix. My intentions are to use 1.6 rockers, a K & N air filter, throttle body air foil, and Hooker Super Comps until later, at which point I tear it down and swap heads for some high flowing ones, and maybe an Edelbrock RPM Pro-Flow, or Holley Stealth Ram MPI (or maybe a Weiand huffer, which is actually cheaper).

 

[m nordin]

thirdtimevetteowner: Do you mean it is some difference in how the oil is feed to the rockers in a roller cam engine? Oil path is the same, through the lifter and pushrod up to the rocker.

By writing the "old way" I was refering to hardened guide plates and non railed rockers, that is what I do.

BR

MN

 

[thirdtimevetteowner]

MN, Thanks for enlightening me on the oil to the rockers subject. I did not know hydraulic roller lifters supplied oil just the same as flat tappet hydraulic ones. That makes my decision on buying roller rockers much easier. The only thing left is knowing if the L98 springs will accomodate 1.6 rockers or not, and if they will fit under the original valve covers. Someone mentioned that the drippers may interfere with the longer rockers. Can you answer that, as well? And by the way, just why are the drippers there in the first place? Also can Iuse the same push rods?

Rich K.

 

[AdvancedAutoCC]

MN, Thanks for enlightening me on the oil to the rockers subject. I did not know hydraulic roller lifters supplied oil just the same as flat tappet hydraulic ones. That makes my decision on buying roller rockers much easier. The only thing left is knowing if the L98 springs will accomodate 1.6 rockers or not, and if they will fit under the original valve covers. Someone mentioned that the drippers may interfere with the longer rockers. Can you answer that, as well? And by the way, just why are the drippers there in the first place? Also can Iuse the same push rods?

Rich K.

Rich,
#1, yes. #2 yes, but with work.(see #3) #3 yes..they hit, you must grind them off! They were put there to lube the stock stamped rocker arms. #4, you can use the same pushrods.
If you don't want to mutilate your valvecovers underneath, or just don't want the hassle of grinding, use some standard stamped steel valvecovers from a Z28 or the chrome equivalent made by Spectre Industries (what I did).

Good luck!

 

[Vettelt193]

I agree with above, the drip tabs need to be taken off, they will get in the way.

You are best off with self aligning rockers, unless you have some killer deal on regular full rollers. the installation is simple, and you don't need extra parts.

What else do you have done on your car to go with 1.6 rockers? The L98 has such a bottle-neck on the intake, 1.6's may not be worth the hassle, considering that you will probably need new springs as well. Most of your power increase on the L98 (and even LT1's) really comes from the roller fulcrum / less friction, unless you have a more modified engine.

I had a mixed set on my LT1; 1.6 intake, 1.5 exhaust. I liked that setup better than the full 1.6's, and with the exhaust being the typical area that has spring problems, I used stock springs. The mixed set frees up the intake a bit, while not killing your torque down low.

If I had an L98, I would throw 1.5's in it and concentrate on the intake work... or better yet, just spend the money i was going to spend on rockers on intake work.... your net gains will be better $ for $.

 

[Jack]

Oiling ... as said ... flat tappet or roller, solid or hydraulic ... in each of the 4 types, pressurized oil feeds into side of lifter body and comes out of its cup ... directly into hollow pushrod ... up the pr to the RA cup. Stamped RA have a hole in cup and oil is squirted all about and onto valve covers too ... some drips off the drippers & back onto the RA, spring etc. Roller rockers have various locations as to where the oil comes out ... varies between RRA manufacturers and amongst each RRA mfg's models. I've heard that Crane makes the Hot Cam RRA for GM ... that they fit under stock centerbolt covers ... but that's not gospel. The coated stamped RA will do a really fine job ... & they'll fit under stock covers ... that's gospel. You'll need minimum 0.050" gap between coil ... less than that you'll have coil bind when it heats up & expands and stuff WILL break. Put a 1.6 rocker on BOTH an intake and an exhaust, adjust the 2 rockers, then roll motor through and measure the widest coil gap on each valve when each valve is FULLY OPEN ... if 0.050" or more you're good to go. Another is to measure your max valve lift as it is now ... and what is the gap now. Divide the valve lift by 1.5 and then multiply it by 1.6. Subtract the theoretical 1.6 VL from the actual 1.5 VL. Then subtract that difference from the widest coil gap you have now. Do this on both an intake and an exhaust. Again, if the result is 0.050" or more, you're OK ... any less and you'll need to go back to square 1 ... as in change springs. If you're gonna be doing this stuff, invest in a cheap dial indicator and magnetic base ... and a set of feeler gages.
JACK:gap