[PontiacJim1959]

My questions are on the valve spring oil shields, not the oil deflectors.

This is a basic question, but specific to my heads. I rebuilt my 7K3 heads using the oil shields, along with Ferrea RA IV valves, bronze valve guides, and Viton seals.

Pontiac used them to keep splash oil off the valve stems and reduce oil consumption.

1.) I have read that when rebuilding the heads and installing the bronze valve guides along with the Viton valve seals fitted to the tops of the valve guides, that the tighter clearances of the valve-to-bronze valve guides, along with the better sealing qualities of the Viton seals, should not use the oil shields - not enough oil will reach the valve stems for lubrication and the valve could seize up. Fact or Fiction?

2.) Have read that removing the oil shields allows oil to flow over the valve springs to help in cooling them. But if I were to restrict the flow of oil to the rocker arms, via restrictors in the lifter bores or reduce oil flow through metered lifters, or metered pushrods, I would be limiting the amount of oil to the top end and certainly reduce any oil flowing over the valve springs to cool them. Fact or Fiction?

3.) What is a general limit to valve lift with the oil shields in place? My 7K3 heads were rebuilt using the longer Ferrea RA IV valves with the oil shields and my machinist/engine builder said the valve springs he installed would work to around .600" lift. I won't be going .600" lift, but may see .540".

4.) Is there any benefit to the stability (side movement/centering) of the valve springs by using the oil shields? The valve springs sit in their seat at the base, the valve springs fit over the valve guides, the spring retainer fits over the valve spring at top - all keeping the valve spring in place. But, the oil shield fits over the valve spring encasing them, and the spring retainer than fits/centers into the oil shield opening which would seem to add some stability to the valve spring. I realize a lot of engines do not use the oil shields and obviously have no issues, so this is more of a theoretical question in engineering design as Pontiac had their own reasons for doing things.

5.) I have seen, as have some of you, the oil shields break. What might be the cause? Bouncing of the valves at high RPM's with inadequate valve spring pressures - like adding a high lift cam over stock and then using the stock valve springs which didn't have enough spring pressure for the lift? Binding? High mileage wear?

So there you have it. Any thoughts or personal experiences?

[dataway]

Excellent questions ... looking forward to the answers.

[Kenth]

I have found Pontiac did not use the valve spring shields on any Ram Air engine due to the stronger valve springs for these engines because the shields would crack and end up in the oil pan
Instead Ram Air and H.O. engines did use positive intake valve stem seals and O-rings in all valve spring retainers, where std engines uses the oil shields and O-rings in the retainers.

[Cliff R]

No mention of using the factory retainers and factory type valves with an extra groove cut in them just below where the valve keeps sit. Both of those parts are needed to effectively use the "O" rings making the entire set-up nothing more than a large umbrella type valve seal. If all the parts aren't used oil runs down the valve stems and directly onto the tops of the valve guides so not very effective at oil control. Chevy small block engines used a similar set-up for decades before the use of positive seals became commonplace by the factory........Cliff

[mgarblik]

Here is my opinion to each question based on experience if I have any in each area. First, lets be clear on the purpose of the shields. The shields are 1 part of a 2 piece umbrella valve seal "system", used by GM, not just Pontiac. That being said, if you use a positive type valve seal that stays on the top of the guide, the little black o-ring and metal umbrella shield are not needed. I have seen the little black o-ring used without the shield, and it does absolutely nothing. Using the shield without the o- ring also would do little to nothing to keep oil out of the combustion chamber, especially on the intake.
Q1: I see no reason to use the shields with bronze guides that are almost always cut for positive seals. I like the positive seals. Older seal designs used teflon, solid white or black rubber with a white teflon insert. The solid white ones were a very tight fit on the valve stem and I could possibly see a dry situation or sticking valve being a possibility. I don't use those. The ones with the insert are soft enough I don't think they would cause an issue. Viton rubber seals I have seen are made by US seal and have a metal outer jacket, a blue viton seal molded in and a garter spring. I like this design and use them without shields. You have to have enough stem to guide clearance in any proper rebuild and it needs to be measured with a dial bore gauge to be really accurate . You can use a small hole gauge and a Mic, but it takes allot of practice. For Pontiacs, mild street performance, say 500 Hp or so, I like .0015" intake, .002" exhaust. Strictly stock engines, I might tighten those up .0002" Nitrous, turbo, Roots, big NA HP, open them up possibly as much as .0005" Remember when removing shields, you have to recheck installed height and shim for the removed shields.
Q2: Can't say for sure what shield removal does for spring oiling. With shield, oil hits shield and flows over the OD of the springs like an umbrella. With shields removed, oil flows all over the spring, OD, ID top to bottom. Millions and millions of springs operate fine with and without shields. Pontiac engines , IMO, way, way over oil the valve train. I can't see any situation where the valve train would be starved for oil, even restricting each lifter to as small as .030". With a .040-.050" restriction, the valve train is still flooded with oil The bearings need the extra oil at higher RPM's.
Q3: I do not know without measuring a specific set of heads.
Q4: The shields are designed to work as a valve seal, not a damper or locator. Now GM has used some sheet metal shields clamped to the spring as a damper, such as on a 3800 Buick V-6, but they are thicker and clamped to the bottom of the spring, not the top.
Q5: I have seen some of them break and even come off the spring. They are very brittle and generally don't get replaced, so they are 40-50 years old with millions and millions of cycles on them. Another good reason to leave them off. The ones I have bothered to look at are cracked. Could just be random metal fatigue. Don't have a good answer for that one. Obviously, being brittle if they contact anything solid, head surface from high lift, the rocker arm, guide top, anything like that, they are going to break.

Long answers, a little insight possibly.

[Lee]

I've seen several Pontiacs where the shields were installed with aftermarket springs. Later, when the valve covers are removed, there is shrapnel from the shields blowing apart.

Even though the shields may "fit" when the springs are static, the springs outside diameter pulses when in use, becoming larger than the static measurement. Even if the shields don't break, they are affecting the performance of the springs when they come in contact. There are probably some smaller diameter springs that will work o.k., but I'm not going to risk it.

No shields and modern guides & seals for any Pontiac I build.

[PontiacJim1959]

Some good responses and thoughts. The Ferrea stainless steel valves don't have the second groove for the o-ring seals.......so rethinking that part of it, oil will creep down the valve stem, but could still be inserted under the keepers. Not sure if any were used on my heads, never asked my engine guy.

Strong valve spring pressures used could crack the oil shields was a good answer. They are wedged between the retainer and spring coil, but like all things, I am sure there is some movement of the spring against the oil shield, if only minimal, and over time could wear the metal shield thin and crack/break, along with fatigue due to age.

Checking spring installed height after removal to ensure correct stack height was a good point. I had already thought of that as well, and knew to use a shim if required to maintain the correct spec for the spring height.

The aftermarket springs could indeed be slightly oversized and actually making contact within the oil shields. The up and down movement of the spring coils during opening and closing of the valve could cause wear and create a thin/weak point and have the shield crack/break. Make sense.

I am using a Crower solid cam with their solid lifters having the restricted oil holes to reduce oil flow to the rockers. Am aware of keeping oil in the bottom end, moreso with the 455 I am using, and one of the reason I went with these lifters as opposed to plugging the lifter oil supply holes with the restrictors.

All said, good replies that make sense, I believe I will be pulling the oil shields off in my application due in part to what I assume will be no factory o-ring seals due to non-factory valves, and the better Viton positive seals/bronze guides. I will check spring stack height and see if I need to shim. I think it also wise as a CYA measure to ensure they don't break due to age, fatigue, wear, or 12,000 RPM shifts. (Can you guess which part of the previous statement is BS?)

So if used at all, oil shields might be best for a factory low performance engine/rebuild or someone who never ever spins their GTO engine past 5,200 RPM's and when using the factory o-ring and umbrella seals - maybe.

[lust4speed]

I'll try and not repeat what has already been said above. The O-rings and metal shields are pretty much left over 1950's technology. Pontiac trusted the rubber umbrellas on the intake but realized that they would be quickly toast on the exhaust side. Can't remember too many stock Pontiacs that didn't start with a puff of oil with oil finding its way down the exhaust guide after sitting overnight. Also haven't pulled a stock umbrella off that wasn't hard as a rock and not doing a thing for oil control down the stem.

You need a controlled amount of oil making it's way past the seal into the guide area or it would be seize city. The Viton seal on both the intake and exhaust does a really great job of controlling the necessary oil flow without additional old-school parts.

And finally, restricting oil flow to the top end can have a negative effect. Heat from valve springs is carried off by oil flow and limited oil flow can shorten valve spring life. Probably no problem on stock setups, but high spring rates and longer travel puts additional stress on springs Pontiac didn't have in mind.