naphtali5725

what is the main purpose of blocking the crossover ports in the heads?
is this really necessary for a daily driver engine, and if so, why?
and can you just weld up the crossover port on the intake and mill it flat so it seals it? or is it a must to fill it up with aluminum etc.?

kind regards

joe_padavano

There are two reasons. First, eliminating the hot air passage under the carb allows for a denser intake mixture. Second, the ports in the heads disrupt flow, hurting ultimate power. Simply plugging the crossover in the intake fixes the first, but not the second, which is why people fill the port prior to porting the heads. None of this is necessary or even particularly desirable for a stock or mild daily driver since the heat is there to assist with cold engine performance.

naphtali5725

Thanks as always Joe! So in my application, i'll just leave it all stock...
Kind regards

67 Cutlass Freak

The main purpose is to keep the hot exhaust gasses away from your intake manifold which helps to have a cooler fuel air charge. This will give you better performance.

Absolutely not. In fact if you drive your Olds in the cold winter months, I would not recomend it.

Yes you can. In fact someone sells aluminum plugs that you can custom shape and drive into the intake. I have not used them, but others have said over time they can come loose and rattle around. You could melt down some aluminum and pour it into the intake, then grind off the excess. Most of the guys that get serious about porting the OE cast heads will fill the heat riser on the heads with molton alluminum, then reshape the port. This works best for getting the exhaust out ASAP. here's some photos to give you an idea what's involved. It's pretty easy-




If you are running headers you could also weld up the exhaust dividers on the center two ports. This helps some for performance as well. If your just looking for a bit more performance but want to keep all the driveability, the biggest gains can be had by unshrouding the valve with a good bowl blend and a quality 3 angle valve job. Here's some articles if you wanted to read about porting-
http://www.mondellotwister.com/articles.html