Dave,
These are the "heat riser" openings that allow exhaust gases to circulate
under the plenum chamber. Heating the plenum improves gas/air mixing and
speeds warmup of the engine. If you are more interested in horsepower than
economy, you may want to use the intake manifold gasket with these openings
closed off. I use this type of gasket on my Tiger and have for the last
twenty years. Can't remember what it was like the other way, but I have no
objections to the way it works.
Bob
At 05:24 PM 10/15/98 -0700, Dave Binkley wrote:
>This is a little hard for me to explain, but here goes. I have the original
>intake manifold off and am in the middle of installing an Edelbrock F4B.
>Valve covers are off. Looking down at the cylinder heads it is pretty
>obvious that the forward and rear ports are for water. The four ports which
>mate up to the intake manifold for air/fuel are also obvious. What is the
>port in the middle for? This is the smaller one sandwhiched between the two
>middle intake manifold bolts.
>
>Here's why I ask. I have two intake gasket sets (both say they are for
>260/289/302). One gasket set has no hole where this middle port is. The
>other gasket set has a round hole where this middle (rectangular) port is.
>I'm guessing I need to use the set with the hole in the middle and probably
>need to cut the hole out to match the shape of the rectangular port.
>
>So, what's going on here?
>
>Thanks,
>
>Dave
>
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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