1. Just a general question. How many more CFM's (air flow) should a pnped (port and polished) head flow over OEM (B series)?

Situation: I want to PnP a B series head. Portflow wants $900. A buddy of mine has a head already done up and wants to get rid of it for $500. The head has never been installed and was PnPed by PYR. So I would like to find out what the OEM flow rates are for a B seires and what what usual CFM flow rates are for a PnPed head. If this $500 is within that then I'll buy it.

2. What are the OEM flow rates of a B16A (JDM) head, B18C (JDM) and a PnPed head?

I realize there are probably variables affecting these numbers, meaning different type of ports, but I am looking for a rough estimate. Portflow claims a 20 CFM increase on their $900 portjob but that number is meaningless if I dont know what others produce (increased flow rates).

Thanks ahead of time.

Matt

 

bump

 

Well, theres the CFM pickup on the intake and the exhaust, they always arent the same numbers.

You have to look at how much lift the cfms are gained at also.

For example, my head was benchflowed and picked up about 15 cfm on the intake side picked up 25 on exhaust and that was considered a pretty decent "street port"

 

Also the rates will be different when using a 10" or 28" bench.

 

Too vague of a question, bro.
Certain factors to consider are the port size, the porter's capability to get equal flow in all the runners, the size and model of the flowbench, etc.

You shouldn't look at a flowbench number and say it's good or not. You should look at the before and after. That's all that matters.

It's like when someone dyno's their car and they make 160@ the wheels. Most would say that is shitty, but what if they were making 135 before?

Also, in a personal opinion I would say don't trust flowbench numbers. Even if you have the best flowing head in the world, if the cam, piston, timing and fuel combo doesn't work, you won't make the power. Figure out what works, and use that. Don't go by numbers. I've went against the grain forever, and in the process I have made some *very* respectable motors.

 

Thanks for all the advice. I have to agree with all of you. I don't have any knowledge of all the technical factors that go into building an all motor car; whatever it may be used for. I appreciate your feedback. I am just looking for a street port and 20-30 seems to be the acceptable gained flow rates. I've got alot to learn - HondaTech is great.


Matt

 

remember that a valve job is very important when u do the head. You pick alot of gains through a valve job, or even with aftermarket valves