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Discussion Starter #1 (Edited)
For reference:

Dart 355cnc, 2.30 x 1.88, stock valve job, un-touched as received from customer.

right port, intake:
3.21 sq. in. throat
min. area 3.50 sq. in. @ pushrod (1.5" in)

left port, intake:
min area 3.74 sq. in. (2" in)

ex throat= 2.04 sq. in.

28" test, 4.50 bore

right / left / ex

.2 154.2 / 156.1 / 116.6
.3 223.2 / 226.2 / 163.3
.4 292.7 / 290.3 / 226.6
.5 337.8 / 333.5 / 265.6
.6 375.5 / 366.2 / 287.8
.7 401.5 / 383.2 / 302.2
.8 409.1 / 396.2 / 407.2
.9 417.1 / 407.2 / 321.3
1. 425.0 / 416.9 / 330.8
 

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Those are stronger then I thought they were. Thats a decent cylinder head for the $
 

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Discussion Starter #5
What do you think of the valve job? Whats the top cut like?
The valve job is decent. Top angle on these according to Dart is 32*. Like any out of the box head, there's quite a bit of clean up that can be done where the valve job transitions to the bowl but the cnc work isn't bad and the chambers are decent. Good swirl numbers for a conventional BB Chev. head.
I will say the ex ports are really "unhappy", even though they move some decent air.
 

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Discussion Starter #7
Decent head for the money?? They are the highest priced CNC head on the market!!!!!!!!!!!!!!!!!! However, they still are one of the best and respond well to the correct work.
LOL...Dart is pretty proud of their stuff...
I'm upgrading these to a 2.35 valve.
 

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I would think near 20cfm with bigger valve and the work that goes with making bigger valve prosper.As others stated valve job change on those heads helps.We always do those heads on 4.600 plus bore.I see Scott stated 4.500 so i be interested to see what a bigger valve does with that.
 

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Discussion Starter #14
Scott, that bench use a Flowcom or bench posted numbers? Or has it been recalibrated to 28"?
It's our SF600 with a Flowcom. I think it's on the conservative side given what I've seen as comparisons over the years. We haven't had it calibrated for some time.
 

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Discussion Starter #16
I would think near 20cfm with bigger valve and the work that goes with making bigger valve prosper.As others stated valve job change on those heads helps.We always do those heads on 4.600 plus bore.I see Scott stated 4.500 so i be interested to see what a bigger valve does with that.
I wish I had a 4.6 fixture. Engine is 4.53 bore and needs more valve area. I'm making the change more for the velocity profile than more flow, but I'm sure they'll pick up good since the valve is the restriction on these. I think I'm sticking with a 45* valve job.
 

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totally agree.. What have you seen for a gain with a bigger valve?
That's going to vary Chad, .. depends on the valve job profile used.

Aggressive VJ could make that head hit 450+ at higher lifts, .. I've had them over 460, .
but likely the best all around for on track is a good 50* profile with a 90-91% throat.

C
 

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I wish I had a 4.6 fixture. Engine is 4.53 bore and needs more valve area. I'm making the change more for the velocity profile than more flow, but I'm sure they'll pick up good since the valve is the restriction on these. I think I'm sticking with a 45* valve job.
Why do you think the valve is the restriction here when a good small block head could move more air than that through a smaller valve?
 

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the set darin did a few yrs ago went from .200 to .800.... 163, 240, 315, 370, 398, 415, 434..... that with a 2.35 valve
 
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