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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
While dismantling the engine for a general overhaul I noticed that at some time the PO changed some of the rocker arms as not all of them are the same type. The part that contacts the valve has a different curvature and some of them are touching the valve shell before reaching the valve. This is not ideal as the cotter pin holding the shell in place might dislodge.
Is this normal in these engines? I am attaching a picture below. You can see the difference between the 3rd and 4th ones from the left. Both of them are the exhaust valves. As a solution I swapped the 3rd rocker arm with the 2nd which is an inlet valve as the inlet valves have a higher valve contact point so the arm doesn't touch the shell on the inlet ones.
PS. The engine is an L98 TPI with cast iron heads 1987 350.
Also does anyone know where I can buy new nuts for the rocker arms. Looks like the PO used generic nuts on some of the rockers and anyway is always a good idea to change these. Already tried rockauto and hawks.
Different styles of rockers should make no difference as long as they're the same ratio. Once they're adjusted, the operation will still be the same. Geometry may be slightly off but on a street car, it wouldn't be much different than the average production engine.
If your local auto parts store doesn't carry rocker nuts, go to your GM dealer or go get some from your local auto wrecker..
If it were me, I would be replacing them. I belive you can get a stock GM 1.5 ratio set, with the nuts for like 80 bucks from summit. Figures i just threw a set of stockers out
Also does anyone know where I can buy new nuts for the rocker arms. Looks like the PO used generic nuts on some of the rockers and anyway is always a good idea to change these. Already tried rockauto and hawks.
Is it possible the PO put a few of the nuts on upside-down?
No The nuts that he used are normal flange nuts (not even lock nuts).
With the price that the stock rocker are from the likes of summit it is probably worth buying them rather than just the nuts. Might be tempted to get roller ones if there are any advantages on stock engine. What I am afraid from the stock ones is that all 16 of them will be like the ones I showed in the picture where their curve touching the valve is too curved resulting in the arm touching the case.
I went to search for some identification on my rocker arms and found 7 of them with numbers all different as follows :
VR2J01B3, VR2L21B1, VR222F90, VR3L11A3, VR307H90, VR205191, VR119F90
Still didn't try to search what they mean.
If I decide to change all the rockers should I go for 1.5 which is the stock ratio or 1.6? I read going to 1.6 might get some minor gains and shouldn't need further alterations. Not sure about ECM settings. Any views?
I've never looked at the differences too closely, but it looks like the rocker arm that's riding on the exhaust valve rotator is a self-aligning rocker arm...the others in your photo look like non-self-aligning rocker arms.
If this is the case, you need to determine which type of rocker arms you need to use.
If you replace the rockers with new, always use new ***** (pardon the expression).
Last edited by paulo57509; 01-03-2017 at 04:11 PM.
Have a look at the holes in the head where the pushrods go through. They'll either be large round holes, or they'll be flat on the front and back sides to guide the pushrod. If they aren't guiding the pushrods, the rockers need to be self aligning unless you want to have the heads machined for guide plates. Chances are pretty good that if it's the original engine, it had self aligning rockers originally.
Be careful about throwing parts in the valve train all willynilly. These engines have rotators on the exhaust valves. They can get in the way of aftermarket rockers. You can dump the rotators but since the valve spring pockets are machined differently to compensate for them, the springs have to be shimmed or the heads machined. Point being that regardless of what parts you use, you'll want to make sure they sit on the valve stem and not the retainers, and that they don't interfere anywhere in the range of motion.
Yep, you've got one head with guided pushrods and the other unguided. Not the first time a pair has been mismatched. I'd check the casting numbers to be sure the heads match. If they're different, I'd probably start looking for a matching head or pair of matching heads. If the casting numbers match, it wouldn't be too shocking to assume it could have left the factory that way. On the head with the round holes you need to run self aligning rockers, or have the heads machined for guide plates. On the other, if you run a self aligning rocker with guided pushrods you might run into binding, however if the casting numbers on the heads match, it's certainly possible that's how GM built it. A person could have the guided pushrod slots drilled round to match the other head, or have both machined for guide plates and run non-self aligning rockers, but I wouldn't want to make a suggestion either way.
Regardless what you do about the guided pushrods vs self aligning rockers, the rockers should only contact the valve stem.
The casting number are both the same (14102183). I am sure its an 8 not a 9 (I know the debate)
I would really appreciate an opinion. I am sure that even on the head with the round holes if I use SA Rocker Arms they will hit the retainer. Very slightly but they will hit it.
I agree on needing SA rockers. Possible that the tips of the valves were ground down on a prior? Rebuild. Also maybe the locks are not stock but are allowing retainer to be high on the valve. I tried guide plates on a car that needed SA rockers and broke 3 pushrods from them binding
I'd have to see the underside of your existing rockers to be sure, but from your photos all your rockers look to be self aligning. When you look at the tip of the rocker that sits on top of the valve stem, a self aligning rocker has two stamped in teeth that ride on either side of the valve stem. Here's a pic robbed from another thread on here...
In my experience, the valve stems don't protrude much at all from the retainers, especially on the exhaust valves with rotators. Aftermarket rockers often end up rubbing the retainers. I don't especially have a solution for you. I'd take a look at your rockers from the bottom side and look for the teeth as shown above. If they're all self aligning, and some clear, I'd probably try to find more like them to replace the ones that don't clear. If you've got non-self aligning rockers on the slotted head, I'd have the slots drilled round so self aligning rockers could be run on both heads. That said, I've seen enough slotted heads with self aligning rockers without damaged pushrods to believe it's probably not the end of the world to have both, but by the book it's certainly not optimal.
All of my rockers are self aligning. The problem is that some of them have a shallow tip and others have a deep tip causing the rocker to slightly touch the retainer of some of the exhaust valves. I can shuffle them around and put the shallow ones on exhaust valves and deep ones on the intake ones perhaps grinding a bit some of the rockers in places where it still touches the retainer but I would prefer getting a new set of rockers to have my mind at peace.
On the specs of the SA Rockers there is never mention of the depth of the tip. This is resulting in a blind decision.
Anyway thanks alot all for trying to help. I guess next step is to remove valves, measure stems to ensure they are all the same and hope for a good set of SA rockers when re-assembling. Will definately post what I bought and if it worked or not to help others.
When in doubt, go GM. 10089648 is a single rocker, ball, and nut. 12495490 is a full set of 16. These are current part numbers, might be slightly different than originals, but GM says they'll fit.
You are right. Probably GM is the safest route. Honestly was targeting to have at least grooved ball joints to improve lubrication but I won't risk it.
Tried to find the GM rockers on Rockauto but they don't have them. Getting them from Summit is too expensive in terms of postage. Are the ERK1868 similar to the stock GM ones? Any experiences? Rockauto have these.
Ended up ordering the GM ones from Summit as I couldn't risk getting a set like the wrong ones. Will let you know once I receive them if they fit right.
01-02-2017, 03:54 PM
Found some nuts on eBay though 
