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Guide Plates
Pontiac V8 Guide Plates
Keep the Pushrod Square — Guide Plates for Pontiac V8s
Guide plates hold the pushrods in line so a stud-mounted rocker stays square to the valve. On a Pontiac V8 they bolt under the rocker studs, and they are what makes a screw-in stud and hardened pushrod package work as a unit. Run a guide plate against a soft pushrod and the plate will cut through it.
Butler stocks flat 5/16" and 3/8" guide plates for factory cast iron heads, Edelbrock and Speedmaster heads, adjustable plates for early 326-389-421 castings, and the Fabcraft plates cut for 1962-63 Super Duty #980 and #127 heads. The 3/8" plates for Edelbrock and Speedmaster D-port and R-port heads are machined in Butler's own shop.
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More About Guide Plates
1. 5/16" or 3/8": Match the Pushrod
The slot width has to match the pushrod diameter. That is the first and simplest filter.
| 5/16" | the common size, and what most Pontiac pushrods are. Comp's 5/16" plates cover 1967 and later 350, 400, 428 and 455 cast iron heads, but note they will not work with a 1967 326. |
| 3/8" | Butler machines a 3/8" flat steel plate in-house for Edelbrock and Speedmaster D-port and R-port heads on 389, 400, 421, 428 and 455 engines, sold as a set of eight. This is the plate for a big-pushrod valvetrain. |
| Hardened pushrods required | a pushrod running in a guide plate has to be hardened for guide plate use. Butler's Comp stock replacement pushrods are sold hardened for exactly this reason. |
2. Your Head Casting Picks the Plate
These are not interchangeable across Pontiac head families, and the early castings are their own problem.
| 1967 and later cast iron | the 350, 400, 428 and 455 heads take the standard flat plates. Straightforward. |
| 326, 389 and 421 | the adjustable 5/16" plates exist for these engines, but read the fine print. You must convert to screw-in studs and mill the stud bosses on the heads. That is machine shop work, not a bolt-on. |
| Edelbrock and Speedmaster | Edelbrock's own 5/16" flat steel plate fits the Performer Pontiac head on 389 through 455. The Speedmaster-style 5/16" plate has both rocker stud holes slotted so it works on cast iron Pontiac and Edelbrock heads, and must be adjusted to the correct location when installed. |
| 1962-63 Super Duty | Fabcraft plates are cut specifically for the #980 and #127 Super Duty heads and are sold as a set of eight. Nothing else fits those castings. |
3. Installing Them
A guide plate that is bolted down in the wrong place is worse than no plate at all.
| Align before tightening | Butler's 3/8" plate is not cylinder specific and must be aligned before tightening. The same is true of the slotted plates. Set the pushrod in the slot, let it find center against the valve, then torque. |
| Check clearance | with a high lift cam and a long slot rocker, confirm the pushrod is not touching the side of the plate anywhere through the lift cycle. |
| What they do not fit | the Smith Brothers 7/16" dual taper pushrods cannot be used with guide plates. If your build calls for those, the heads need a different pushrod control solution. |
If you are running Edelbrock or Speedmaster heads and are not sure whether you need the 5/16" or the 3/8" plate, tell us which pushrods you are buying and we will match them.
Not sure what your Pontiac needs?
Call our tech team at 866-762-7527. Tell us your engine, heads, car, and power goal, and we will put the parts together as one combination that works.