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01-07-2007 09:48 PM #1
head flow
recently i just finished my vortec heads, but had some disappointing results with them.Car Craft did a test a while back with 355 and a LT4 Hotcam and a stock set of vortecs and made 420hp. then they took the heads and ported them out. I copied them exactly what they did to the vortecs and even added bigger valves on mine. there baseline was 228cfm intake @.500 and 152cfm exhaust@.500 after their porting they got 239cfm intake @.500 and 218cfm exhaust @ .500. then they bolted the heads on and ran another pull and got 460hp.
my baseline with bigger 2.02 vlave with no porting was 194cfm @ .550 and 163cfm exhaust @ .500. with 1.60 valve no porting.
I did my porting exactly to what they did, i blended the bowls in to 85 percent throat diameter.the valve guide bosses were narrowed, and the intake cross sectional area was opened to a .906 wide to a 1.100 wide. with a good gasket match with intake, exhaust ports. I brought my heads to a flow bench and heres my results with vortecs with 2.02 1.60 valves
intake Exhaust
.050 29 28
.100 65 58
.200 129 121
.300 180 169
.400 219 188
.500 224 201
.550 226 203
.600 227 204
these were supposebly flowed at 28 inches of h20. I want to know is the flow bench i used not accurate or is Car craft's numbers a bunch of bull****, has anyone ported a set of vortecs and flowed them in person or a stock set too?
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01-08-2007 07:49 AM #2
Originally Posted by vortec king
The bad news is your intake numbers are about like stock.
Due to casting "flash" and "core shift" there is alot of difference in production heads.
I.M.O.,the flow numbers will support 425 hp.
If you like n20 then these heads would work great.
If you are new to head porting don't be to up-set with yourself.
You can always sell the heads and start again.
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01-08-2007 02:51 PM #3
Originally Posted by erik erikson
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01-08-2007 03:27 PM #4
Originally Posted by vortec king
Most of the time out of the time from looking at my records I see with a 1.94/1.5 valve I see 215 to 220 at 28 inches of water and .500 lift.
Also keep in mind the valve design,valve job,combustion chamber work will effect these numbers also.
Yes, sometimes their numbers are a bit in-flated.
Even if you look at Scoggin Dickey parts catalog thet rate the L31 Vortec heads at 239/147, at .500 and 28" of H2O,that is a stock" out of the box "head .
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01-08-2007 07:19 PM #5
My book shows the same on stock heads ....239/147 @.500 .....but shows the exaust at 160 with pipe @ .500.
All the articles I have read show almost 20 cfm improvement from work to the valve ,with a special back cut, and seat work.But all the articles state keep away from the intake runner if unsure what to exactly do,because with a bigger valve you have to keep the high swirl going.......if not the flow will go down.Most of them say stay away from the short side radius if unsure as it will decrease flow from just opening this up full size on the vortecs.
Can you post some pics and do the valves have back cuts ,if so what are the angles on the back cut and are there 4 cuts or 3?Did they install massive hd seats for the bigger valves or cut down the existing seats ?Did they use oversized valves and hone the guides or install new guides?Whats the stem difference from stock valves to the new valves?Did you flow more than 1 runner on the intake?
I am with Erik those heads would love n2o or a some forced induction the way they are!!!Last edited by shawnlee28; 01-08-2007 at 07:38 PM.
Its gunna take longer than u thought and its gunna cost more too(plan ahead!)
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01-08-2007 09:41 PM #6
here is the pics of my vortecs, the heads have been cut out for 2.02/1.60 valves, I blended the bowls, narrowed the valve guide boss on intake and exhaust. I did not remove any material on the short turn radius, just remove slight ridege. the valves are ferrea stainless steel valves with back cuts on both intake and exhaust. The valve seats have a three angle valve job done on them, i don't remember the angles.
Yeah if we have to go changing lifters I am taking those comp cam lifters out.
New guy from Utah.