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Old 10-12-2007, 02:04 PM   #1
Jpizzzle
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Default DIY PNP Heads?

I have an extra set of heads that are off and will be going on my hybrid as soon as my cams come in. My question, I know how to PNP things but do not have a flow bench. I don't really have the money to have someone do a PNP job as they are pretty pricey. Can i do this myself or has anyone else done this themselves? 2.5 block and 2.0 heads with a SZ55 turbo and some 274's. I would like to do a PNP but don't know if it is possible.

Thanks
Jon
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Old 10-12-2007, 02:21 PM   #2
MJU1983
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Like anything else, you get what you pay for...in this case free.
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Old 10-12-2007, 02:23 PM   #3
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Doing A PnP without a flow bench can certainly lead to different flow rates and speeds into each cylinder. You could probably gasket match the intake to the head without much of a problem but as for a serious PnP job, id want it flow tested to make sure all the runners are flowing the same.

Maybe look into extrudehone?

/Brox
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Old 10-12-2007, 04:44 PM   #4
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Quote:
Originally Posted by Broxma View Post

Maybe look into extrudehone?

/Brox
This looks to be inexpensive, but you also need to get a valve job after this is done, so depending on prices for a valve job (which is usually included in a good p&p job) you may just be better off getting p&p.
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Old 10-12-2007, 06:16 PM   #5
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What does a PNP job normally cost?
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Old 10-12-2007, 09:47 PM   #6
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You can make your own flow bench...
It will not be as accurate as a real one, but it gives repeatable numbers...

Look at this thread: Click Here
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Old 10-12-2007, 10:43 PM   #7
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In my belief, A mild DIY PNP is not going to do anything but improve things. Why? the stock cast head WAS NOT CLEANED UP AFTER CASTING. Therefore, a mild PNP is simply going to allow cleaner flow, NOT raddicaly alter flow. The next step is a gasket match. Again, probably not going to radically alter ****, since all 4 are going be adjusted the same. Finally, the third is the radical PNP which would not hurt to match air flow to......
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Old 10-13-2007, 12:33 AM   #8
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Quote:
Originally Posted by shvrdavid View Post
You can make your own flow bench...
It will not be as accurate as a real one, but it gives repeatable numbers...

Look at this thread: Click Here
Awesome, thanks for that lnik.
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Old 10-13-2007, 08:35 AM   #9
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I think that a bowl cleanup would not hurt things at all. The home made flow bench can be made pretty inexpensive if you want to start working with the ss radius and such and do a more thorough porting job. I looked into this myself. Barring that, cleaning up the flash in the combustion chamber will most likely not alter flow much if any and will help with the cylinder being less prone to det. Your heads will not really flow any more, but it will help with the ability to add more timing and boost and the engine being a bit less prone to detonation due to the fact that there will be less "hot spots" in the combustion chamber. Gasket matching as the above poster said will help a bit too
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Old 10-13-2007, 10:11 AM   #10
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You guys are high if you think you need a flowbench to port heads and make improvements. If I was looking to get some heads done and I had to choose between a guy with a flowbench and a guy who really knew what he was doing I'd go with the latter every time. I can make two different shape ports flow the same and make way different power. If you really want a tool to check your port work you need to use a dyno. I've used a flow bench to do esoteric stuff like filling ports in and completely reshaping them but for standard stuff it's just a waste of time. What the dyno says is 1000 times more important than static flow numbers.
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Old 10-13-2007, 10:33 AM   #11
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Quote:
Originally Posted by gumby647 View Post
You guys are high if you think you need a flowbench to port heads and make improvements.
This made me el oh el.
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Old 10-13-2007, 11:15 AM   #12
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This made me el oh el.
I don't get it.
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Old 10-13-2007, 11:16 AM   #13
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I think your high... I would use the guy that has lots of repeatable experience and has a flowbench. Thats the only way there will be a true flow match between the ports.. JMHO

Quote:
Originally Posted by gumby647 View Post
You guys are high if you think you need a flowbench to port heads and make improvements. If I was looking to get some heads done and I had to choose between a guy with a flowbench and a guy who really knew what he was doing I'd go with the latter every time. I can make two different shape ports flow the same and make way different power. If you really want a tool to check your port work you need to use a dyno. I've used a flow bench to do esoteric stuff like filling ports in and completely reshaping them but for standard stuff it's just a waste of time. What the dyno says is 1000 times more important than static flow numbers.
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Old 10-13-2007, 12:23 PM   #14
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Quote:
Originally Posted by gumby647 View Post
You guys are high if you think you need a flowbench to port heads and make improvements. If I was looking to get some heads done and I had to choose between a guy with a flowbench and a guy who really knew what he was doing I'd go with the latter every time. I can make two different shape ports flow the same and make way different power. If you really want a tool to check your port work you need to use a dyno. I've used a flow bench to do esoteric stuff like filling ports in and completely reshaping them but for standard stuff it's just a waste of time. What the dyno says is 1000 times more important than static flow numbers.
Ok....

I will agree that static flow numbers can be misleading to a point....

I fail to see how flowbench time is a waste of time...
No offense, but if it was a waste of time, someone did not know how to take advantage of the tools at hand...
I agree with you on the point that you can make two different shaped ports that flow similar numbers, but make different power because the flow changes the valve event cycles create...
But with a little creativity, heads can be flowed on a bench in a way which will reflect real world flow rates...
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Old 10-13-2007, 12:48 PM   #15
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Maybe I was too strong with "waste of time". What I mean is you can probably extract 90-95% of the potential of a set of heads without going to extreme measures. To get that last 5-10% usually requires that you junk a head or two in the process. Sometimes to find the limit you have to go past it.

For a DIY port job you are better off buying a cheap set of snap gauges and a caliper than building a flowbench. As I said before the dyno determines if a port job is good, not a flowbench.
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Old 10-13-2007, 01:01 PM   #16
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I will agree that just because it flows well on the bench doesn't mean it won't be a dog on the track...that is true.
The flowbench will also have been run by someone who doesn't know how to use the tool(s) infront of them.

Example:
A fun project in my IC engines class, for part of my minor, was we had little POS B&S "8hp" Animal engines. We were told to modify and tweak them (within cost reason) to make power. With just porting of the heads (lots of filling on mine) I had the highest hp and broadest tq curve despite not having the highest flow numbers. What was really sad was seeing how a lot of the engineering students couldn't understand why.
In the long run I made a 11.5hp (averaged over several runs) improvement using putty, some welding rod, die grinder and had to use the mill to put in my second spark plug.
Most of the power came from head work, both port and combustion chamber.
I guess the other team decided big flow numbers as apposed to having a nice velocity profile was more important.
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Old 10-14-2007, 06:34 AM   #17
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Times are changing, dry flow testing is no longer what you need to aim for, it now is a new world or wet flow, real world stuff....

http://www.superchevy.com/technical/...t_flow_testing

And then a CNC seat cutting machine, can make what ever shapes you can program in with a single tip edged tool, no multi angles anymore.


http://www.youtube.com/watch?v=ynRDk7fveB0

http://www.youtube.com/watch?v=hnCiSd_ZHio
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Old 10-14-2007, 08:31 AM   #18
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First off, I'm pretty sure you don't want to gasket match intake OR exhaust ports...

second... they sell that tool that sonicly lets you measure the thickness of wall so you don't grind too much... If I was going to get into porting I would definatly check that out.
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Old 10-31-2007, 01:46 PM   #19
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Quote:
Originally Posted by IllNastyImpreza View Post
First off, I'm pretty sure you don't want to gasket match intake OR exhaust ports...
Why's that? What would be preferrably done with them?
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