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Old 08-17-2013, 05:10 PM
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Pocket porting Vortecs.Worth the time ???

Doing some odd & end things to engine & heads while it's apart for a rebuild.I have a somewhat pronounced ridge just below the valve seats.The ridge is pretty much all the way arond port,but,less noticeable on the floor section.Is it worth the time to clean up & blend this ridge on a set of 906 Vortecs?

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Old 08-17-2013, 05:28 PM
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I meant to post this in the "engine" forum.Sry,I didn't realize I was in the "basics" forum.Pleeze feel free to move it if necessary.
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Old 08-17-2013, 09:45 PM
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Porting and clean up is always a good thing,as long as the casting is up to the mods.The vortec is a very good small head with limitations.If you have the time and tools then go for it.
Fbird88 is one of the guys to talk to about home porting budget heads.
I think 245 ish is about all the CFM you will get on the intake side.The exhaust side is weak so ask fbird how far to go on that side of the heads?
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Old 08-17-2013, 10:35 PM
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Yep.I wuz hopin he would chime in.LOL. I don't wanna get in over my head,or,fool with the ports,but,I do wanna clean em up a little.That ridge & I can feel a slight lip around the chamber.Valves don't seem to be shrouded.
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Old 08-18-2013, 12:42 AM
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"Pocket port" Smoothing the V under the valves seat does not add much any flow. A few CFM. But it looks pretty.
To get a significant flow gain you need to work the WHOLE intake port.
But Do not completely grind out that V funnel under the valve. remember the valve is close to the seat more than it is way away from the seat, on a street cammed motor. Leave most of that V venturi under the seat
on a street motor. The venturi shape under the valve helps the air flow around the valve, when the valve is close to the seat at low lift. (Mild street cam)

A full race cammed engine is different. Then the valve is away from the valve seat .300+" for more of the time (cam duration) and you can afford to trade off low lift flow and quality for raw high lift flow gain, here on a race motor.
So it really depends on what you will be doing with the motor. Camshaft//rpm range.
Fully porting the intake and adding larger 2.02 or 2.05 valves increases flow and power.
No mystery here, larger port and valve='s more flow.

The exhaust side needs the full treatment and larger 1.60 valves help too.
When I "pocket ported" my old 062's with 1.94's flow went from 228 to 232cfm.
but Looks pretty.

Full nice port job but not a huge max ed out race "superstock" port and 2.02's 245-255cfm Nice power improvement over stock on more radical cammed builds. A nice "street strip head"
Like any as cast SBC port taller roof, streamline valve guide boss, open up pinch a bit helps flow.

Full max race port : for a high rpm race motor big duration and lift:

A full effort opened up max race port job flows more air with 2.05" valves but why not just start with a larger port volume head in the first place, for that... (buy a big port Bowtie Vortec- fastburn head and port that)

Measure the intake port CC volume on your 906's. The original Canadian made 062's '96 to 2000 were the best ports.

Some newer recent stuff is under CC sized and will need more porting fix up to make the same.

stock 1.94x 1.50 street motor home brewed port effort beyond just doing the bowls you can generally clean up the whole port. You don't need to reshape it , just clean up whats there and steamline a bit more. Let common sense prevail. For high rpm you can open up the pinch a bit.
You can get fairly aggressive porting on the exhaust side but don't make the port exit huge as all this does is agravate header gasket sealing.

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Old 08-18-2013, 08:05 AM
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I'll blend the ridge I was speaking of & clean the port up.Since this is a truck I'm more interested in low & mid range.Even @ a truck pull I'll be lucky if see over 4500 to 4800 rpm.I usually hit wheelhop,or,spinout befor any serious rpms.Depends a lot on the dirt & how well the track is prepared.Truck weighs over 5000 lbs,so,I won't be drag racing.I will make a few passes befor & after any major work just to see how it responds.Can't afford a dyno,so,my time slips should let me know. There is a slight lip I can feel around the edge of the chamber.If heads end up needing any decking,that should remove that.If not,i'll take it off.It feels sharp & very thin.An article I read stated that for 1 cfm of intake flow increase will give approx a 2 HP increase.Does that seem accurate to you?Thanks for the response.

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Old 08-18-2013, 05:58 PM
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I wish it was that easy. ( if you get 2HP per cfm @28" you did a great job {race motor) Yes you can smooth that sharp machined combustion chamber edge with a flat file by hand. No need to get carried away.

Why not fix the truck chassis?
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Old 08-18-2013, 06:32 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
I wish it was that easy. ( if you get 2HP per cfm @28" you did a great job {race motor) Yes you can smooth that sharp machined combustion chamber edge with a flat file by hand. No need to get carried away.

Why not fix the truck chassis?
I am planning some front suspension improvents.Gotta get this engine done & then beef up my transmission.I currently only compete for fun 5 to 6 times a year @ local smalltown pulls.Gonna try the mud drags also lateer on.It looks like fun !!!
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