I'm just wondering how important it is to have the same flow rate in each intake & exhaust runner when hand porting your heads. I'm guessing that they will all be out by some unless you get them flow tested then make alterations from there?

Also, if you alter the shape or volume of the chambers, again, would they not need to be near identical?

Opinions please.

Robert

 

Usually if you work them over in the same areas and they're the same volume when you get done and the shapes all look the same, that's plenty close enough for a street motor.

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Here's how you measure the volume.

 

I've made crude templates out of old playing cards.

Once you get a port and runner to the shape and form that satisfies your hunger the best, get out the scissors and some old cards and cut templates that just fit inside the ports at various points and angles. One horizontal template at about 1/3 the way from the roof, one at about 1/3 the way from the floor, and a vertical template to check the height. You can flip the horizontal templates over to check the opposite or "mirrored" ports and runners. There is less lattitude on the exhuast side, but you can still get the templates close enough to insure a relatively consistent port shape and volume. Core shift may impede some of your efforts from head to head, but they should still be close. Any glaring oversights will be pretty obvious with the templates.

BTW - If you happen to get your hands on the Iraqi Ace of Spades, cut that up and stuff it in there instead of wasting a perfectly good playing card.

 

Templates are very helpful, a log time ago I purchased some head porting templates from Mopar Performance that really helped me get the shape right and all the ports the same on a set of small block heads for a 360, I had them flowed afterwards and they flowed what they were supposed too.

 

Does anyone have any pictures of how you made these templates? I cant quite picture exaclty how you are using them.

Thanks

Ben

 

Playing card, business cards, whatever, makes a good paper template. Once you have a card template from both axes (vertical and horizontal) and from both sides of the port, it's easy to cut sheet metal templates that are a little more permanent. Stamp the casting number in the templates and you'll have them forever.

 

Sounds good I think I will try that. From both sides you mean from both the vavle side and the intake/exhaust side right? I am going to start porting my sportsman II's soon(maybe tomorrow if I can get all the stuff I need).

By the way, who/what is DNR?

Ben

 

Yes, from both the intake flange side and the valve pocket. Once you get one shaped to your satisfaction (don't bother polishing before you're done grinding) make templates to guide you through the rest of the casting. It's a little harder from the exhaust side, but you'll get it in and out of there.

If you don't want to make steel templates, scan the card stock sample and save the graphic to print as many copies as you may need. (Isn't technology marvelous?)

Incidentally, DNR = Department of Natural Resources. It used to be a popular joke, but anyone in Wisconsin knows it's no longer a laughing matter. (Can you spell "R-e-v-o-l-u-t-i-o-n?" )

 

Thanks for the photo Vader.