Do I need to use guide plates

The preface to that statement: "I go with guide plates when high lifts and stiff springs get involved, That's usually accompanied with high rpms- at that point roller rockers start to make good sense along with hardened pushrods...". Doesn't apply to my configuration.

 

I think Richfox is right. I think I remember that the factory slots would bind with a high lift cam. They are not "long" enough

 

That's what I'd say----

 

With a mild cam this in my opinion is the best answer. The one thing I might add is drill and pin the studs if you don't go with screw in studs. You drill into the side of the stud with a 1/8" bit and drive a roll pin in to keep the pressed in stud from pulling out.

 

Yes to the two above posts.

And just to add a bit more info, adding guide plates will NOT rectify this issue. The reason they are slotted is that the top of the pushrod moves towards and away from the centerline of the engine as they move up and down. This motion is due to the rocker rotation around it's pivot point. For that matter, the bottom of the pushrod moves slightly as well, due to the lifter movement. The slots need to be lengthened appropriately to accommodate this movement of the pushrod, since the guide plates do not have any effect on the pushrod's relationship to the slots. Note that higher ratio rockers (SBC 1.6 for example) put the pushrod closer to the center of rotation of the rocker, and can also affect the pushrod clearance at the slot in the head. It will lessen the possibility of binding when valve is open, but may when valve is closed.

 

If i was installing guide plates, i would bore out the slots as they are redundant and stand a very good chance of causing a bind.

 

As 31Vicky mentioned, the guide plates serve two purposes. They keep things lined up, but also move the support closer to the rocker, so with high lift cams you don't have the extra pushrod length unsupported. I've seen several SBC engines bend pushrods between the head and the rocker when they bend.
Self aligning stock ball rockers are as the name says, self aligning, so the design is keeping them lined up, if they are properly adjusted. If a roller rocker has much play in the pushrod opening it will allow the roller tip to work off center against the valve stem, and eventually round off the edge of the valve stem and the roller tip.

 

RichFox your statement is true for the most part other than it is mandatory to drill out the push rod hole in the head if you install guide plates.

 

I wouldn't go so far as "mandatory", but opening up the slots is very easy to do and highly recommended, especially if the heads are off the motor. The OP said he's building a "short block" which normally means no heads, but sounds like he'll be able to do this with heads on the bench.

If someone were adding roller rockers with the heads are still on, I'd be inclined to just check the clearance very carefully on every pushrod. If they decide to do it with the heads on, take every precaution to capture all the cast iron debris resulting from whatever method is used to open up the slots.

Some will disagree, just my opinion, and what I'd do under the cir***stances.......

 

A lot of good answers here; but many of them are not addressing my specific question... does my configuration require guide plates. Many are overlooking the fact that I'm running a fairly mild cam, ~.450 lift, with stock valve springs.

 

If your heads have the slot and your rocker arm alignment is good you do not need them.
I would never run guide plates and the slots together you are just asking for trouble IMO.

 

Again they are most likely fine but still don't ***ume anything, make sure and check the alignment when they are ***embled. The push rod length is an important factor too, make sure and check it for contact on the valve tip.

 

re: danritz
"A lot of good answers here; but many of them are not addressing my specific question... does my configuration require guide plates. Many are overlooking the fact that I'm running a fairly mild cam, ~.450 lift, with stock valve springs."

short answer: NO

 

I was finally able to spend some time in the shop over the last few days. I installed and adjusted the pushrods and rocker arms. I'm happy to report that all looks good. There is virtually no side play - the narrow slots in the heads keep the pushrods well under control, and the push rods keep the rockers lined up really well. There's plenty of leeway in the slots in the other direction as the pushrod/rocker work their way through the cycle. The rollers are centered on the valve stems, and look good all the way through the cycle. There's no coil bind. Happy ending.

A sincere "thank you" to all who took time to help me out on this; I really appreciate your ***istance.

Filing away in my book o' knowledge for future reference...

There are 3 types of pushrod guide systems:

1. The heads are slotted where the pushrods p*** thru and the narrow slot is the guide. This style of head/slots was used for decades in Chevy engines. Works well with low-to-medium lift cams, and non-high-pressure valve springs. Hardened pushrods, the ones required when using guide plates, are not required; virtually all quality pushrods are made of hardened material.

2. When adding guide plates the slot in the head is opened up and the guide plate does the job. This would involve machining the slots much wider to prevent interference between the slot and the guide plates, which could destroy the pushrods. Must use specially hardened push rods compatible with guide plates.

3. The self aligning rocker, which requires the slot in the head to be opened up just like when using guide plates. If your heads still have the slot type guide system then you'll use standard style rockers.

Only one of the above should be utilized; if the heads have the narrow slots, and guide plates are to be used, the slots should be machined to a much larger opening, as noted in #2, above.

Generally speaking, guide plates are probably required for cams with ~.500 and greater lift, and high spring pressures. With a low-medium-lift cam, the slotted heads provide more than adequate push rod guidance.

Some of the posted responses ran contrary to some of the above; none-the-less, this is an overall summary of the consensus of postings, here and elsewhere.

Again, thank you.

Dan