Best port shape?
10-22-2008, 10:23 PM
#1
Best port shape? Do the rectangular ports on the L92 and LS7 flow better than the cathedral style ports on the LS1s? I am talking about an aftermarket casting ported head. Just in the shape alone, is the rectangular port a better design when it comes to making power than the cathedral? Thanks.
10-26-2008, 06:27 AM
#6
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depends on the cubic inch and RPM you plan on shifting at.
The advantage of the L92 and LS7 head is that the pushrods are further apart and this allows a straiter shot and a larger cross section at the pushrod pinch. There is less of a velocity change at the PR pinch by doing this and these ports flow some real good #'s but you also have a pretty large runner volume and a large cross section at the pushrod pinch (minimum cross sectional area of intake port).
If you have enough cubes (408, etc) or spinning enough RPM with a smaller engine to make use of this, great, it is a better way to go.
If trying to use them on a small engine, the port ends up bing lazy and when the piston reaches BDC, there is no inertia still filling the cylinders with the big port where a smaller port would still pack a lil more in the cylinders.
A smaller engine will be better off with the LS1, LS6 style head and keeping the runner volume and push rod pinch cross section smaller.
Lloyd
The advantage of the L92 and LS7 head is that the pushrods are further apart and this allows a straiter shot and a larger cross section at the pushrod pinch. There is less of a velocity change at the PR pinch by doing this and these ports flow some real good #'s but you also have a pretty large runner volume and a large cross section at the pushrod pinch (minimum cross sectional area of intake port).
If you have enough cubes (408, etc) or spinning enough RPM with a smaller engine to make use of this, great, it is a better way to go.
If trying to use them on a small engine, the port ends up bing lazy and when the piston reaches BDC, there is no inertia still filling the cylinders with the big port where a smaller port would still pack a lil more in the cylinders.
A smaller engine will be better off with the LS1, LS6 style head and keeping the runner volume and push rod pinch cross section smaller.
Lloyd
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10-26-2008, 04:33 PM
#8
depends on the cubic inch and RPM you plan on shifting at.
The advantage of the L92 and LS7 head is that the pushrods are further apart and this allows a straiter shot and a larger cross section at the pushrod pinch. There is less of a velocity change at the PR pinch by doing this and these ports flow some real good #'s but you also have a pretty large runner volume and a large cross section at the pushrod pinch (minimum cross sectional area of intake port).
If you have enough cubes (408, etc) or spinning enough RPM with a smaller engine to make use of this, great, it is a better way to go.
If trying to use them on a small engine, the port ends up bing lazy and when the piston reaches BDC, there is no inertia still filling the cylinders with the big port where a smaller port would still pack a lil more in the cylinders.
A smaller engine will be better off with the LS1, LS6 style head and keeping the runner volume and push rod pinch cross section smaller.
Lloyd
The advantage of the L92 and LS7 head is that the pushrods are further apart and this allows a straiter shot and a larger cross section at the pushrod pinch. There is less of a velocity change at the PR pinch by doing this and these ports flow some real good #'s but you also have a pretty large runner volume and a large cross section at the pushrod pinch (minimum cross sectional area of intake port).
If you have enough cubes (408, etc) or spinning enough RPM with a smaller engine to make use of this, great, it is a better way to go.
If trying to use them on a small engine, the port ends up bing lazy and when the piston reaches BDC, there is no inertia still filling the cylinders with the big port where a smaller port would still pack a lil more in the cylinders.
A smaller engine will be better off with the LS1, LS6 style head and keeping the runner volume and push rod pinch cross section smaller.
Lloyd
