Vortec L31 cylinder head
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:Paul Shufelt | :Paul Shufelt | ||
:Chevy High Performance (Feb. 2001) | :Chevy High Performance (Feb. 2001) | ||
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| + | ==Valves== | ||
| + | Vortec heads come equipped with valves having a 30 degree back cut to help flow. Unlike previous SBC valves, Vortec valves have just one groove for the keepers instead of two grooves (one for the keepers, the other groove was for the oil control O-ring); Vortec heads use a positive-type valve stem oil seal and do not use the tin oil shield seen for years on SBC heads, nor do Vortec heads use exhaust valve rotators. | ||
==Valve springs== | ==Valve springs== | ||
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[[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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| + | The stock retainers can be reused with aftermarket springs if the OD is the same as the stock springs. In some cases, the retainer can be clearanced to give added lift clearance. This modification is sometimes referred to as the "ghetto grind". | ||
==Rocker arm studs== | ==Rocker arm studs== | ||
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==Exhaust valve seats== | ==Exhaust valve seats== | ||
| − | Not long after the L31 Vortec head was introduced, a writer for a car magazine | + | Not long after the L31 Vortec head was introduced, a writer for a car magazine stated that the 906 head was inferior to the 062 head because the exhaust flow was poor on the 906. Despite this idea being dispelled, it still surfaces now and then. Like is often the case, there's a grain of truth to this. On c/n 906 Vortec heads having the hardened exhaust seat insert (not all 906 heads used the insert), there can be a lip made by the seat where it's pressed into the head. If there's a lip it can be blended and smoothed to improve the flow using nothing more than a Dremel. And on the 906 heads having the insert, the seat was machined with a single angle instead of a three angle seat as seen on Vortec heads having the induction hardened exhaust seat. The wider seat was used to better transfer heat from the valve into the head/cooling system. |
| − | + | The 906 heads having the hardened inserts were preferred by some performance engine builders, mainly for marine applications. Later production 906 heads stopped using exhaust seat inserts and at some point, all Vortec head exhaust seats were induction hardened. | |
From GMPP: | From GMPP: | ||
| − | + | :The #906 casting head was available in two versions. One has an Inconel exhaust seat with a single angle grind, and the other has the conventional 3-angle grind on the exhausts as per the #062. The #906 with Inconel seat does not intrude into the exhaust port. It was used primarily on the HD and 1-ton truck applications where sustained towing of heavy loads & weight up inclines could cause eventual damage to a standard induction-hardened exhaust seat from excessive heat. | |
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|[[File:Hard insert seat vortec 906.jpg|thumb|300px|center|Casting number 906 Vortec head with hardened exhaust seat insert]] | |[[File:Hard insert seat vortec 906.jpg|thumb|300px|center|Casting number 906 Vortec head with hardened exhaust seat insert]] | ||
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