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Rd-Port Cylinder Heads
Pontiac V8 Rd-Port Cylinder Heads
Ram Air IV Pattern — Rd-Port Cylinder Heads for Pontiac V8s
Round port cylinder heads are the Ram Air IV answer. The exhaust flange follows the 1969-70 Ram Air IV pattern rather than the common D-port shape, and the larger 215cc intake and 175cc exhaust runners are what let a round port head keep feeding a big-inch Pontiac after a D-port has run out of air.
Butler carries Edelbrock Performer RPM round port heads complete in 72cc and 87cc, in Fast-Burn CNC chamber and original chamber versions, Speedmaster Ram Air aluminum castings bare or Butler Built, and Butler Built round port heads assembled on Edelbrock cores to your cam.
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More About Rd-Port Cylinder Heads
1. Round Port Means Round Port Headers
This is the one thing that catches people out, and it is worth settling before anything ships.
| The flange | Both chamber sizes use the Ram Air IV exhaust port flange. Standard D-port headers and stock-style manifolds will not bolt to it. |
| What you need | Round port headers, or Ram Air manifolds, plus round port exhaust gaskets. Budget for them in the same order as the heads. |
| What does not change | Stock valve cover and accessory bolt locations are retained, so the front of the engine and the covers you already own still fit. |
2. Fast-Burn CNC Chamber or the Original Chamber
Edelbrock lists the round port head in two chamber treatments at the same chamber volume, and Butler stocks both.
| Fast-Burn CNC chambers | The chamber is CNC machined rather than left as cast, which makes it consistent and precise cylinder to cylinder for improved flow and more efficient combustion. |
| Non Fast-Burn versions | The original Performer RPM round port chamber, still cataloged in both 72cc and 87cc, hydraulic flat tappet and hydraulic roller. |
| Butler Built chamber finish | On a Butler Built set you choose as-cast, hand-polished or CNC-machined chamber rather than taking what the box comes with. |
3. 72cc or 87cc
Round port comes in two chamber sizes, and they are aimed at different engines.
| 87cc | The street chamber. Edelbrock calls it ideal for 10:1 engines and rates it for excellent street performance on low octane fuel, and describes it as the street-legal, low compression version for 92 octane. |
| 72cc | Built for higher compression, racing-oriented combinations. |
| Neither one exactly | Butler can mill a casting to hit a target compression ratio. Tell us the number you want rather than picking a chamber and hoping. |
4. Edelbrock, Butler Built or Speedmaster
Three sources of a round port head on this page, and they are not interchangeable in price or in process.
| Edelbrock complete | Assembled by Edelbrock with 2.11" intake and 1.66" exhaust valves, manganese bronze guides, hardened steel guide plates and 7/16" rocker studs, in flat tappet and roller spring versions. |
| Butler Built on Edelbrock castings | Same core, all machine work done in the Butler head shop, then assembled with Ferrea valves, new guides and Comp springs, retainers and locks matched to your camshaft. Built to the same specification as the 61519 round port head, with the chamber finish, exhaust valve size and rocker slotting left as your call. |
| Speedmaster Ram Air castings | Offered as bare castings in 72cc and 87cc, and as Butler Built complete heads assembled on those Speedmaster cores. |
5. What Else Has to Line Up
A round port head changes more of the parts list than a D-port swap does.
| Spring package and cam | Flat tappet and hydraulic roller are separate part numbers. Supply the cam specs and Butler verifies the spring setup before the heads are assembled. |
| Exhaust valve size | Standard 1.66", with an upgrade to 1.77" available on Butler Built sets. |
| Rockers | Pushrod holes can be slotted for 1.65 ratio rockers while the heads are apart. |
| Later porting | These castings CNC port up to 340 cfm on round port, so an unported set now does not close the door on more flow later. |
Round port is the right call when the engine is big enough or spins high enough to want the extra runner volume, and when you are willing to buy the headers to go with it. If the car has D-port exhaust on it today, price the exhaust before you price the heads.
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.