Differences

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--- engine_details:heads [2020/03/30 18:09] – created ben
+++ engine_details:heads [2020/04/14 16:50] (current) – ben
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 ====== Heads ======
+===== Supercharged vs Naturally-Aspirated heads =====
+The most significant differences in OEM heads is the difference between naturally-aspirated (L36/L26) heads and supercharged (L67/L32) heads.
+Supercharged heads have injector ports located in the intake runners inside the head itself. However, naturally-aspirated heads have no injector ports in the heads because they are located in the intake manifold for these heads.\\
+Because of this difference both will have different valve covers as well to make room for the injectors.
+L67 heads could be used in conjunction with the L36 intake manifold to allow the use of an extra set of injectors for a very high end build if necessary. This would be difficult to tune with the OEM PCM though.
+===== Casting Differences =====
+==== Series 3 heads ====
+Series 3 and series 2 heads have some small differences, the most noteable is the difference in valve sizes.
+Series 3 heads use a 1.83" diameter intake valve where Series 2 heads use a 1.80" intake valve.
+Aside from that most other differences are not noticeable. Some people have said that the castings are cleaner on series 3 heads, however others have said there is no difference.
+==== Differences in Series 2 heads ====
+There was a change in the casting used in the series 2 heads sometime around 1997/1998. Eariler heads are known for having a tendency to crack in the combustion chamber. Later heads seem to have resolved these issues though.
+Earlier L36 castings were labeled "2261" and later castings were labeled "4781"
+This image shows a cutaway of the early 2261 castings:
+{{https://www.gmforum.com/attachments/performance-brainstorming-tuning-96/52284d1501314485-sliced-2261-early-l36-castings-4781-castings-next-sliced2261casting2.jpg?nolink&|Name:  sliced2261casting2.jpg
+Views: 154
+Size:  87.3 KB}}
+This image shows a cutaway of the later 4781 castings:
+{{https://www.gmforum.com/attachments/performance-brainstorming-tuning-96/52285d1501314485-sliced-2261-early-l36-castings-4781-castings-next-3800ports06.jpg?nolink&|Name:  3800ports06.jpg
+Views: 139
+Size:  55.7 KB}}
+{{https://www.gmforum.com/attachments/performance-brainstorming-tuning-96/52294d1501314495-sliced-2261-early-l36-castings-4781-castings-next-3800ports03.jpg?nolink&|Name:  3800ports03.jpg
+Views: 210
+Size:  48.8 KB}}
+===== Resources: =====
+[[https://www.gmforum.com/performance-brainstorming-tuning-96/sliced-2261-early-l36-castings-4781-castings-next-253593/page2/|https://www.gmforum.com/performance-brainstorming-tuning-96/sliced-2261-early-l36-castings-4781-castings-next-253593/page2/]]