Vortec L31 cylinder head
(→Upgrading and compatibility) |
(→Using an early style intake on an aftermarket Vortec-type head) |
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===Using an early style intake on an aftermarket Vortec-type head=== | ===Using an early style intake on an aftermarket Vortec-type head=== | ||
| − | Vortec heads use an intake manifold having 8 instead of 12 bolts. Also, Vortec intake ports are taller than earlier SBC heads; there's not enough metal above the port (except on "raised port" aftermarket intakes) to allow the head and intake port to match up. That means earlier 12 bolt intakes will not match up to the Vortec bolt pattern or ports. | + | Vortec heads (also applicable to the 4.3L 90 degree V6) use an intake manifold having 8 instead of 12 bolts. Also, Vortec intake ports are taller than earlier SBC heads; there's not enough metal above the port (except on "raised port" aftermarket intakes) to allow the head and intake port to match up. That means earlier 12 bolt intakes will not match up to the Vortec bolt pattern or ports. |
Many aftermarket Vortec style heads (including Bow Tie Vortec heads) feature dual bolt patterns allowing the use of the early 12-bolt intakes. This has a very limited use. | Many aftermarket Vortec style heads (including Bow Tie Vortec heads) feature dual bolt patterns allowing the use of the early 12-bolt intakes. This has a very limited use. | ||
| − | Commonly available 12 bolt SBC dual plane intakes do not have enough metal above the port to be ported to match the Vortec port, w/o having a vacuum leak or razor thin sealing surfaces above the ports. An early intake would need at least 0.325" of material above the intake port opening to have any chance of sealing, and that doesn't take the difference in the port width/location into account. Because of the height of the Vortec intake port, only the single plane 'raised port' race intakes have enough height to actually match up to the Vortec head intake port- but even then the ports may be too wide or have other fitment issues. | + | Commonly available 12 bolt SBC dual plane intakes do not have enough metal above the port to be ported to match the Vortec port, w/o having a vacuum leak or razor thin sealing surfaces above the ports. An early intake would need at least 0.325" of material above the intake port opening to have any chance of sealing, and that doesn't take the difference in the port width/location into account. (This practice of welding intake manifold ports is common with the turbocharged 4.3L used with the GMC Syclone and Typhoon where the OEM intake manifold does not cover the ports when the heads are redrilled for the 4.3L bolt pattern.) Because of the height of the Vortec intake port, only the single plane 'raised port' race intakes have enough height to actually match up to the Vortec head intake port- but even then the ports may be too wide or have other fitment issues. |
Because of these differences, a Vortec-specific intake should be used. | Because of these differences, a Vortec-specific intake should be used. | ||
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