I just tore my 12a bridgeport that I bought second hand. Anyways, it seems to me that the eyebrow starts lower than most I've seen. Is this ok and what would be the difference vs an eyebrow that starts higher? Also, I got a racing beat bridge template to compare as seen in the picks. Should I move the eyebrow up to match the racing beat or leave alone? Also, if I move the eyebrow up then my eyebrow would be very long- full length of the streetport. Is this ok and what would it effect? What should I do?

Racing Beat claims 115 degrees BTDC as their opening point. That is the outer edge of the bridge port that is uncovered first. So how far down it goes is of little interest. It would add a few degrees of overlap, but my guess is that it would be undetecable.



The upper end of the port is the closing line, and by the time the edge of the rotor is closing off the bridge port there is little flow going on there. The extra flow of the port is during the early opening portion of the cycle. Once the port has been flowing for some time and the rotor is advancing across the ports, most of the flow will be through the much better shape of the street port.



It isn't a "J" bridge port, so for the street, it looks pretty good. The finish on the iron looks real nice as well.



Lynn E. Hanover

Looks next to perfect!

You must look at a lot of FD bridge ports. That appears about normal or even a bit high. Most bridge ports I've seen extend down quite a bit more than that.



The difference is in when the port opens. Unless you've done any housing relief, it doesn't make as much of a difference as you'd think, since flow can't really start until well after TDC when the rotor starts pulling away from the "vertical" wall. If you start having nice reliefs on the housings, then it gets to be more of a side entry peripheral port and the lower edge becomes more critical, but there's still the problem with the rotor being in the way.



I wouldn't lose sleep over it or anything.

Thanks for the replies guys. I think I will open up the main port a little to match the RB template as in the second pic and leave the eyebrow alone.

Thanks, Sir. I just had all my irons lapped at Racing Beat. Going to rebuild this weekend. So you think the port is ok?

I would put a small radius all along the closing line, and polish it like chrome. But thats just me.



The port is fine. About 230 HP out of the box.





Lynn E. Hanover

I'm sorry, I'm a little new when it comes to porting. Can you show me what you mean by radius all along the closing line by pointing out? Do you mean bevel the closing edges? Sorry, I'm new to this. And what do you use to do you polishing?

Yes, bevel the edge of the closing line, but a bevel is a 45 degree angle. You want the "bevel to be round, as in a segment of a circle. Use a small file to round off the corner all along the line and a bit into the corners. Then sand smooth with 80 grit wet or dry paper (Silicone Carbide) wet with oil.



Then polish with a Dremel and a felt disc and carborundem paste. Comes in a stick from Sears. In typical ports the trailing end of the side seal is unsupported crossing the port opening and the polished radius geatly extends the life of the side seal.



Lynn E. Hanover



This picture is of a port I had just started and I have scribed the leading end track of the side seal

(on the bridge) and the trailing end scribe you will notice falls off of the iron and then comes back on near the top of the port. To the left is my see through rotor.

Thank you for the pics and your tips. I am going to port it out like you said and I'll post some pics. Thanks again.



Jarrett