Hey guys,
My head is at a machine shop for porting and machining for larger valves. Has anyone else here had they're head ported yet? If so, Do you know what #'s it was seeing on the flow bench before porting? I ask because he doesn't have a plate to put on the flow bench for the ecotec so he kinda has to guess. Thanks!

 

So how will he know if he did a good job?
Flow bench charts are just like dyno charts, the peak number is cool, but it's the area under the curve that matters to us peons who drive on the street.
Why doesn't he make a plate?
The cobalt is a great platform, lots sold so far, and a good value. I think they are here to stay in one form or another, so might as well suit-up...

 

The plates cost about $500 to order so it wont be beneficial to buy one for just my car. If I can get him stock flow #'s he can compare to see how accurate he is reading. He will be able to compare the final product to the flow #'s in the build book.

 

It's a crap shoot at best. Every flow bench reads different. It can give him an idea, but it sure isn't a real baseline.
500 isn't that bad, only have to do 5-10 charts to break even, or even just rent one from another shop?
Anyways, good luck, sounds like a cool project.
I'm doing the same myself, but the guy is flowing the heads, and sending with a chart.
I informed him I would be doing my own test also, he was cool with it.
You must be one of the first to do this I assume because nobody has piped up with numbers...????
Nice
Are you hitting the dyno after?

 

I would love to see some numbers for this I just had mine done this week(due to damage) went with the JBP valves etc. also!

 

You may wanna see if Patriot , JBP or Manta can help you with the flow#'s on the stock head and ported head . Patriot is working on a LSJ head , unless Im outdated all they have now is L61 casting . JBP has lots of head options and Manta deals with some of the GA cup cars and sell both built eco shortblocks and heads . They all should beable to give a stock # and a typical ballpark ported #

 

I would bet 220-250CFM is a reasonable number for an LSJ. +80CFM would be a really, really worked head I think.

Then again, I could be way off on the ^^^ numbers. Could be like 300CFM stock, but I doubt it.

 

^^^ Thanks alot guys, I will shoot patriot an email.

 

I think 220-250 is likely right. The fact that you guys see more boost than an rsx with the same supercharger tells me the heads likely don't flow as well.
Hopefully there is alot of room to hog-em out. I would say that 300 should be possible
with a talented porter.

 

extrude honed porting will be my method of choice

www.extrudehone.com

 

Looks like the GM Extrude Honed Manifold is well worth the price. They want $450-$550 to extrude hone a cast iron 4 cylinder exhaust manifold.

 

Be careful. That process has no control on where to port, only how much on the whole.
I'm telling you that an exaust manifold will do better with a new design...
Heads have shown improvement after a good cnc port, and use this as polish.

 

I suppose an interesting comparison would be the Olds Quad Four head. Basically the forerunner of the Ecotek. Sort of.
Anyway, stock they flow 260cfm on the intake side and 165cfm on the exh side at .400" of lift. A rather poor 61% I/E flow ratio.
I ported my own and got it up to 280/200.
The power difference was quite good.


As was mentioned, peak flow numbers tell little. Low and mid lift numbers are probably more important as the valve spends more time there than at full lift.
Modern head flow thinking dictates 75-80% E/I flow ratios. And I believe boosted engines would like even better exh flow.


I'm a little confused about the "plate" that you are talking about? Can you explain? Are you speaking of the bore fixture that the head gets mounted to? I guess if he can get an "after" reading, why can't he get a "before" reading as well.

Anyway, fun stuff. Better head flow (as long as it's quality flow) means more power.

Ron

 

The plate I'm refering to is a metal plate that attaches the head to the flowbench. He can get a before and after, but he's worried about accuracy.