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Old 09-07-2008, 05:01 PM
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choosing right intake runner

hi, im getting ready to buy some dart iron eagle platinum series head for my 350 small block and didnt really know what size intake runners i should get. i thought maybe someone could give me a little help here.....

350 small block
bored 30 over with flat tops
camshaft specs duration 290 valve lift 447 cam lift 298
preformer intake manifold
700 holly
msd ignition

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Old 09-07-2008, 05:22 PM
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Intake runner size isn't the whole story. Two different manufacturers could make the same runner size and have vastly different flow figures based on flow bench testing.

For instance, one of the biggest surprises I found was the flow of the L31 GM Vortec heads. The intake runners are 170 cc's, but the flow at 0.400" valve lift is 227 cfm. ASTOUNDING!!

Check out these flow figures on different heads. Comparing them at 0.400" valve lift across the board will make more sense than trying to compare all lifts, which will only confuse you.
http://www.purplesagetradingpost.com...fo/heads1.html

Don't get sucked into buying the heads with the most flow either. It's way too easy to bolt the wrong head onto a 350 motor and have the motor be soggy on the bottom and mid-range.
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Old 09-07-2008, 08:18 PM
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Quote:
Originally Posted by First-Timer
hi, im getting ready to buy some dart iron eagle platinum series head for my 350 small block and didnt really know what size intake runners i should get. i thought maybe someone could give me a little help here.....

350 small block
bored 30 over with flat tops
camshaft specs duration 290 valve lift 447 cam lift 298
preformer intake manifold
700 holly
msd ignition
Your combo looks solid. For the street and your cam I'd go with the Sportsman 2's. Maybe drop back to a 650 carb.

Will you current choices *work*... yes.


techinspector1 is totally right about the runner size too. Lot's of numbers to wade through. Another number that gives a good indicator of a well flowed head is the 'Intake to Exhaust flow ratio' expressed with a percentage.
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Old 09-07-2008, 09:33 PM
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Generally speaking, for a street/strip engine, SBC or SBF,
cubes divided by 2 = runner volume

355 divided by 2 = 177 cc.

smaller size is better on the street, it helps keep the throttle response snappy

Hard to go wrong with aftermarket EngineQuest 180 cc Vortec iron heads.... cheap price too.
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Old 09-08-2008, 12:12 PM
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Sportsman II heads with their 200 cc intakes are too large for your setup. Go no larger than 180 for street driven car. Your looking at Dart? Call their tech dept. and be honest with them. They are excellent people and will give you straight advice.
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