Vortec L31 cylinder head
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==Valve spring retainers== | ==Valve spring retainers== | ||
| − | + | Either of these springs need to be installed using the correct retainer for a Vortec valve- Comp Cams p/n 787 (steel) or p/n 788 (titanium), NOT a retainer originally for the LSx engines; the LSx engines have 8mm metric valve stems. Also note the specs are with an installed height of 1.8". The image below shows the difference in installed height when using different retainers: | |
[[File:787-LEFT; 774-RIGHT (Gen III).gif|frame|left|300px|Retainer p/n 787 left; p/n 774 right]] | [[File:787-LEFT; 774-RIGHT (Gen III).gif|frame|left|300px|Retainer p/n 787 left; p/n 774 right]] | ||
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So what this means is three things: | So what this means is three things: | ||
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* Without resorting to welding up the holes to form slots to provide side to side alignment, Vortec heads cannot be used w/non self aligning rockers unless guide plates are used. Heads can use guide slots, OR guide plates, OR self aligning rockers, but only ONE of the three at any given time. | * Without resorting to welding up the holes to form slots to provide side to side alignment, Vortec heads cannot be used w/non self aligning rockers unless guide plates are used. Heads can use guide slots, OR guide plates, OR self aligning rockers, but only ONE of the three at any given time. | ||
| − | * If using 1.6 ratio rockers, there's a chance the Vortec's 7/16" hole will not be | + | * If using 1.6 ratio rockers, there's a chance the Vortec's 7/16" hole will not be large enough. A Lewis tool will not work, so instead, a drill bit larger than 7/16" can be used to open the pushrod holes up. Most often a 1/2” bit is used, but in any event use what ever size is needed to get the needed clearance. The push rod hole can also be lengthened with a grinding tool like a Dremel or die grinder. As a last resort this can be done using files. |
* If non self aligning rockers ARE used, they '''''must''''' be accompanied by some means of guiding the push rod. | * If non self aligning rockers ARE used, they '''''must''''' be accompanied by some means of guiding the push rod. | ||
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GM Performance Vortec small port Bowtie cast iron cylinder heads are machined for 2.00" intake valves and 1.55" exhaust valves and have bronze valve guides. Combustion chamber volume is 66cc nominal, deck surfaces are 0.450" thick, and port volumes are 185cc intake and 65cc exhaust. | GM Performance Vortec small port Bowtie cast iron cylinder heads are machined for 2.00" intake valves and 1.55" exhaust valves and have bronze valve guides. Combustion chamber volume is 66cc nominal, deck surfaces are 0.450" thick, and port volumes are 185cc intake and 65cc exhaust. | ||
| − | The valve cover rails are machined for both perimeter and '86-up centerbolt style valve covers. These heads are machined for 3/8" screw-in rocker arm studs, and have valve spring pockets machined for | + | The valve cover rails are machined for both perimeter and '86-up centerbolt style valve covers. These heads are machined for 3/8" screw-in rocker arm studs, and have valve spring pockets machined for larger than stock (1.25") SBC springs, and will accept up to 0.530" lift camshafts without modifications. They are identified with the Bowtie Emblem on the exterior of the head, below the exhaust flange, and the Vortec logo on top of the intake port area. They also feature the GM logo cast into the bottom of the intake ports. |
==Large port Vortec head p/n 25534445 (bare) and p/n 25534446 (assembled)== | ==Large port Vortec head p/n 25534445 (bare) and p/n 25534446 (assembled)== | ||
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