When you get your head ported and polished are you supposed to lose low end torque?

 

people say you loose torque or hp...

a port doens't mean you loose torque or hp... it's ported to see how much more flow you get with the whole rotation of the camshaft.. if you gain everywhere on the rotation you gain power everywhere.. if you loose on the low ramp you can loose torque, if you loose at high lift, then you could loose alot.. basically when you flow a head, you only mesure to see an increase/decrease at a certain lift.. having a head that flows more when the lobe is open the most is the key part, but if you fail to recognize that the flow is also important when the valve is starting to open and close, and not just when the valve is fully open is the key.

that's why something proven is important so you don't loose that power elsewhere but gain soley up on top.

 

Loss of low end torque has to do with air velocity and swirl. WHen you increase the ports for better flow it icrease the air that can get in your combustion chamber. However at low RPM, air enters the chamber at lower velocity due to the reduced restriction, this is bad for low end tourque. When air velocity is low it does not tend to mix with the fuel good. American v8's have a lot of low-end torque not only due to displacement but because of the restrictive 2 valve heads. As RPM rise the pistons sucks in air more frequently thus creating higher air velocity, and due to the improvement in flow the motor will make more power in the higher rpm band. It also depends on the port job, a moderate street port/polish will have mild improvements at almost any rpm, but a more serious port/polish will improve high end at the cost of low end tourque. If your geting a p/p tell the shop your setup and they will open up the ports to fit your application best.