L98 Valvetrain Upgrade
Thread Starter
Drifting
Joined: Aug 2002
Posts: 1,775
Likes: 125
From: Birmingham AL
L98 Valvetrain Upgrade
I've researched this topic and found few posts about the subject. I'm sure that plenty of L98 owners are facing the dilemma of leaking valve stem seals due to the age of these cars. For the 88-91 cars, moving the air conditioning bracket is a commitment and I'd like to upgrade to 1.6 full roller rocker arms while having the valve covers off. I am thinking that the Comp Cams 1.6 narrow body self aligning arms would be the right choice for me. I'll have the springs off individually while using compressed air in the cylinders to hold the valves. My reason for this work is the occasional puff of smoke indicating valve stem seal failure. I need help with creating a parts list. Which Felpro seals do I need and what springs do I need? Beehive, retainers, keepers? I'd like to make replacing the seals worthwhile with the upgrade. Thoughts? Heads are staying on the car. 1989 L98 ZF6
Race Director
Joined: Aug 2000
Posts: 11,470
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FWIW, MY 2-CENTS, AND NOT TRYING TO GET INTO A PI$$IN' CONTEST - not a big fan of stuffing rope or anything else in my spark plug holes, and pulling the springs with the cylinder at tdc to secure a dropped valve is a good idea. personally, if the heads are installed, I use the old, tried and true method - pressurize the cylinder (shop air around 125psi), and the simple lever arm spring compressor. done that many times over the last 50 years, and haven't dropped a valve yet (knock on wood!). finally, cover your head's oil drain holes with shop rags, and have a magnetic telescoping pick up tool handy. an extra set of hands is always helpful. 
Last edited by Joe C; Oct 24, 2016 at 10:48 AM.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Stuffing rope in the cylinder can be difficult, a lot of work and I read of 1 owner had the rope knot up and get stuck in there. What I'm saying is I never read someone happy after using the rope method. Yes, like alkim said use TDC for a precaution.
What you really need is to learn how to adjust your valves/lifters correctly. With a bad lifter pre-load the cam can and will eat itself. You have to know terms likezero lash and base circle not assume you know them and expect to get it right by chance.
Also what kind of rocker arms do you have now? Self-alining? My guess is your '89 L98 has guide plates and non-alining rocker arms. Why do you want to change over. IMHO guide plates are more reliable and you may have modify them a little by opening them up more for 1.6 rockers but that is easy to do and good experience for you.
Good luck and let us know how it works out for you.
What you really need is to learn how to adjust your valves/lifters correctly. With a bad lifter pre-load the cam can and will eat itself. You have to know terms likezero lash and base circle not assume you know them and expect to get it right by chance.
Also what kind of rocker arms do you have now? Self-alining? My guess is your '89 L98 has guide plates and non-alining rocker arms. Why do you want to change over. IMHO guide plates are more reliable and you may have modify them a little by opening them up more for 1.6 rockers but that is easy to do and good experience for you.
Good luck and let us know how it works out for you.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Also what kind of rocker arms do you have now? Self-alining? My guess is your '89 L98 has guide plates and non-alining rocker arms. Why do you want to change over. IMHO guide plates are more reliable and you may have modify them a little by opening them up more for 1.6 rockers but that is easy to do and good experience for you.
Good luck and let us know how it works out for you.
Good luck and let us know how it works out for you.
OP; The rockers you have in mind should work; you MAY need to break the oil drip tabs off the insides of the valve covers. If I were you, I'd reuse the springs, retainers and keepers. The L98 isn't a high revving engine and I don't think you'll float the valves at 4500 RPM.
Last edited by Tom400CFI; Oct 24, 2016 at 03:54 PM.
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Team Owner
Joined: Aug 2004
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From: Park City Utah
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Last edited by Tom400CFI; Oct 24, 2016 at 07:04 PM.
Drifting
Joined: Jul 2009
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From: Ashland PA
2021 C4 of the Year - Modified Finalist
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
In addition to the fact that they aren't hardened, the "guide" grooves are way too wide to effectively guide a push rod...and that is before they rapidly wear out.
Drifting
Joined: Dec 2012
Posts: 1,504
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From: Georgetown TX
Thanks for info. When I looked at them I did wonder why the plates were so wide and didn't seem to fit right. Now I know. Why did they have to use them, and why didn't they delete them If not needed?
Le Mans Master
Joined: Oct 2002
Posts: 7,098
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From: Las Vegas - Just stop perpetuating myths please.
I'm confused; what does that have to do w/this the OP's question? I guess when he's putting it back together?
L98's never came with guide plates. He's got self aligning rockers.
OP; The rockers you have in mind should work; you MAY need to break the oil drip tabs off the insides of the valve covers. If I were you, I'd reuse the springs, retainers and keepers. The L98 isn't a high revving engine and I don't think you'll float the valves at 4500 RPM.
L98's never came with guide plates. He's got self aligning rockers.
OP; The rockers you have in mind should work; you MAY need to break the oil drip tabs off the insides of the valve covers. If I were you, I'd reuse the springs, retainers and keepers. The L98 isn't a high revving engine and I don't think you'll float the valves at 4500 RPM.
Changing to 1.6 ratio rockers needs more clearance in the heads p-rod slots. The older generation small block heads needed the p-rod slot elongated. I don't have L98 heads and not sure if the p-rod slots are long/deep enough but this clearance needs to be checked on those whatever you call them plates. It ain't rocket science and the p-rod just needs to just slide through that plate or head slot w/o excessive drag. Yes even if the rockers are self-aligning you need to check the slot for enough clearance. Also the p-rods need to be hardened on that end. LT1 p-rods are hardened on the ends for this but not sure 'bout the L98. I believe there is a file test for hardness as a hardened p-rod are not scratched by dragging a file over it where non-hardend p-rods are easily scratched.
I don't know how you can just standby and read his request for help if you really understand what the valve train needs.
Thread Starter
Drifting
Joined: Aug 2002
Posts: 1,775
Likes: 125
From: Birmingham AL
thanks for the replies and discussion. From my research, the 87+ or centerbolt heads use self aligning rocker arms and have assembly aids that look like guide plates. The push rods are not hardened and the slots are too wide. It could be changed over but I haven't found a compelling reason to do the conversion. I am curious about the benefits of upsizing the rocker arm stud to 7/16" and if that is easy to do. Due the suds typically come out without a torch or breakage? Not something I want to get into with the heads on the car. Only the valve stem seals are bad, but I'd like to cheat a little with rocker arms if they will be off of the car. I have set valve lash before on a different motor and am familiar with the process. I just hate to go through all this work to only change the seals. The motor has 115k on it and I'd prefer new springs since they will be off momentarily, but which ones with the 1.6 RR?
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Listen! You need to think ahead here. Someone that doesn't know how to hold the valves up more likely has never adjusted the valves/lifters. Not informing him of possible consequences of bad adjustment is like just watching him walk over the cliff.
Changing to 1.6 ratio rockers needs more clearance in the heads p-rod slots. The older generation small block heads needed the p-rod slot elongated. I don't have L98 heads and not sure if the p-rod slots are long/deep enough but this clearance needs to be checked on those whatever you call them plates. It ain't rocket science and the p-rod just needs to just slide through that plate or head slot w/o excessive drag. Yes even if the rockers are self-aligning you need to check the slot for enough clearance. Also the p-rods need to be hardened on that end. LT1 p-rods are hardened on the ends for this but not sure 'bout the L98. I believe there is a file test for hardness as a hardened p-rod are not scratched by dragging a file over it where non-hardend p-rods are easily scratched.
I don't know how you can just standby and read his request for help if you really understand what the valve train needs.
Changing to 1.6 ratio rockers needs more clearance in the heads p-rod slots. The older generation small block heads needed the p-rod slot elongated. I don't have L98 heads and not sure if the p-rod slots are long/deep enough but this clearance needs to be checked on those whatever you call them plates. It ain't rocket science and the p-rod just needs to just slide through that plate or head slot w/o excessive drag. Yes even if the rockers are self-aligning you need to check the slot for enough clearance. Also the p-rods need to be hardened on that end. LT1 p-rods are hardened on the ends for this but not sure 'bout the L98. I believe there is a file test for hardness as a hardened p-rod are not scratched by dragging a file over it where non-hardend p-rods are easily scratched.
I don't know how you can just standby and read his request for help if you really understand what the valve train needs.
1. Who said he didn't know how to adjust valve train?? HE DIDN'T. That was quite the assumption that you've made. HE asked about springs, gaskets and rockers. He DIDN'T ask "how to set valve lash".
2. In spite of that, you plow ahead...misguided as you are.
A. '89 L98 heads don't have a "pushrod slot". They have a big HOLE for the pushrod that is way bigger than big enough for 1.6 rocker geometry changes.
B. Pushrods DON'T need to be hardened...b/c we're not using guide plates! We're using self aligning rockers, instead
C. LT1 pushrods are no different than L98 pushrods. Why are we talking about LT1 pushrods??
D. L98's DON'T have guide plates
E. They DO have self aligning rockers, so...
F. He's NOT "changing over"
OP is asking which Felpro seals what springs, retainers, keepers.
I don't know how you can just standby and read his request for help if you really understand what he asked in this thead.
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
I have, and many I know have, been successful with a rope.
I have, seen some valves dropped using air when the spring compressor tool bumps the valve.
Air seal broken and the seal cant hold the weight.
BTW you only use a foot or two of rope and press the piston against the valves.
Holds the stem positively firm when installing and seating the keepers.
My 0.02
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
Never say never Buckwheat.
I have, and many I know have, been successful with a rope.
I have, seen some valves dropped using air when the spring compressor tool bumps the valve.
Air seal broken and the seal cant hold the weight.
BTW you only use a foot or two of rope and press the piston against the valves.
Holds the stem positively firm when installing and seating the keepers.
My 0.02
I have, and many I know have, been successful with a rope.
I have, seen some valves dropped using air when the spring compressor tool bumps the valve.
Air seal broken and the seal cant hold the weight.
BTW you only use a foot or two of rope and press the piston against the valves.
Holds the stem positively firm when installing and seating the keepers.
My 0.02
me too; soft Dacron rope, piston at or near BDC, a foot or so into the cylinder, rotate crank by hand until piston forces rope up against the valves; simple, effective, cheap, and as nearly foolproof as anything I've ever done.
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
In my opinion, you don't need the larger rocker arm studs since you will not be running higher spring pressures nor a larger high lift cam. Bee hive springs use more pressure the higher the lift. if you use them, be sure and use the correct degree retainers. Easy way to know what rockers you have,look at the bottom of the arm where it rides on the valve stem. Self guided have two bumps there, one on each side of the contact point. Self guided are used on ALL vortec heads, have no idea about Vette heads or when Chevy switched. if you use 1.6 rockers on vortec, you have to drill out the pass thru point just a bit for clearance. Don't know about Alum Vette heads.Scorpion sales a set of decent roller rockers thru Summit for about 300 bucks. They can be had in self guided. You might just want to save bucks by just replacing the seals.
Last edited by ghoastrider1; Oct 25, 2016 at 08:10 AM.
