Rx7carl

When you street port the intake ports on a 4 port motor, what general guidelines do you use on how close you can go to the water jacket when you blend in the port. And any techniques to measure how close you are would be helpful. Looks like a pain to measure how close you are.

rotarygod

iTrader: (1)

It is very hard to describe without actually showing you. You want the transition from the port runners to the port opening to be as smooth as possible. I backcut the inside edge of the port opening to help with airflow from the runner. Alot of time gets spent here and it never shows up in pictures. I port mine a little bigger than the T-II porting templates. I use the old '70s 12A/13B porting templates on the T-II secondaries. They open the ports earlier than on the T-II templates. You can get a little larger but not enough to make it worth the risk of finding water. I have even gone so far as to add material to the back radius of the port to decrease the turn radius. Many things are common sense when you look at them and a few things are just acquired knowledge. The key is to not go too crazy and always remember that bigger isn't always better. Look at BDC's porting pictures. We both laughed because both of our porting styles are so incredibly close to each others and we have never taught each other anything.

Rx7carl

Good explanation. I think I understand. I only plan to open the runner where absolutely necessary. I understand the importance of velocity. But it looks like in order to get the transition to be gradual, mucho material must be removed to blend it to a nice soft radius and I fear hitting water!
Where can I see pics of BDC's stuff?

Thanks.

88IntegraLS

You can put your finger back behind the port in the water jacket opening above the runner tube and put your thumb in the bowl of the port and pinch to gauge wall thickness. The port in my sig is on an S4 NA plate with about 1/8 inch of metal between its upper bowl and the water jacket.

Rx7carl

Thats how I was gauging it yesterday LOL. Thanks!