exhaust port work

[Kenny_Kline]

Spent about an hour on 1 runner today. Just ported it close enough so I can go in there with a sandpaper roll and clean/smooth everything out then polish. Have 3 more runners left to port before that though. Outside black line represents gasket. The exhaust flows up the runner so porting the upper part is critical to almost match the gasket line. Porting the lower part of the runner isnt as important as the flow of exhaust doesnt ride this wall has hard as the other but opening up overall space for exhaust gases to pass because of over sized valves. ALso, took down the divided alot to help everything smooth itself as it exits. Here is a ported runner to a stock runner compared side by side to give you an idea how much material actually got taken out. Work still in progress but I am hoping by Sunday, the head will be done that way I can get this thing torqued on.

 

[bazeng]

Great job mate!
looks good!

 

Don't make the divider so sharp. It tends to break off with the high amount of heat.

 

[prove_it]

+1 you should never take the divider out on the exhaust. You'll be ok just try to balance the rest of the ports.
Also try not to take so much off the bottom of the port. The air doesn't flow as much there and removing it will affect the exhaust pulses. You want a small step from the head to manifold so air has a harder time going back into the port.
Otherwise it's looking real good, shiny is fast.

 

[curtis]

Steps cause turbulence don't do it, there's a reason for the term gasket match and before you ask I ported my first dsm head back in the early 90's. Since then have probably done over 25 of them. No I don't have a flow bench or numbers. But know people who do and some of them hold some really sweet records. a) Chris's head on Mikes evo that pushed past 200 more than a few times, his ass built his own flow bench and b) Marcus my buddy in town that holds the record for the best flowing cnc'd brodex head ever made and his heads have been on the fastest Mustangs in the country for many years, records like stock compression 302 n/a that made over 600 on motor, fastest pro 5.0, true street and pro outlaw and his personal car made 2600hp with a 108mm turbo. Guess what they all gasket match there sh*t.

 

[BadVr4]

focus more on the bowls on the head. thats where you will pick up most of your power

 

A header is always bigger than the port hence you have steps. Ehaust is alway turbulent, by having steps you are trying to prevent reversion. I have a flow bench and removing material from the bottom of the port hurts it. By all means gasket match the intake side. Bowl work makes the most difference on the flow bench. What really matters is how it works on the car. The idea that bigger is better is flat out wrong when it comes to head porting. Port shape dictates power.

 

[Kenny_Kline]

I have over sized valves and had the seats cut to match then blended the bowl to match the seat. That lip is gone.

I only took a little out of the bottom of the exhaust port. I took alot out of the top and alot out of the side. I took some off the divider. I am in the middle of polishing the head and will get pics up over the weekend.

The intake side has been port matched