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Discussion Starter · #1 ·
What is the stock LS6 heads flow rated at, Intake and Exhaust? I am looking to get MTI 2e heads and wanted to see how much more the MTI's flow than stock.

Thanks.

:z:
 

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Cylinder vs. Valve Lift
Head /.200"/.300"/.350"/.400"/.450"/.500"/.550"/.600"

Stk.LS1/ 137 / 187 / 207 / 223 / 228 / 237 / 242 / 243
Stk.LS6/ 156 / 204 / 225 / 243 / 257 / 268 / 275 / 278
Ptd.LS1/ 164 / 217 / 234 / 253 / 270 / 284 / 296 / 305
Ptd.LS6/ 159 / 212 / 236 / 255 / 272 / 300 / 307 / 314

Head /.100"/.200"/.300"/.400"/.500"/.550"/.600"/.650"/.700"

Stk.LS7In/71 / 145 / 222 / 271 / 315 / 332 / 348 / 350 / 359
Stk.LS7Ex/60/ 120 / 159 / 192 / 207 / 214 / 219 / 270 / 272

* Bare head (no intake manifold)

** Ported LS1/LS6 heads have Manley 2.055" I / 1.60" E valves

*** LS7 = 2.200 Intake / 1.615 Exhaust Valves

**** all at 28" depression

Notice the ported LS1 outflows the ported LS6 below 0.300" Lift, but then the ported LS6 comes on at high Lift.

Ported E/I ratio should be around .80....ie. the Exhaust should flow 75% - 85% of Intake

Stock LS1 vs. Stock LS6 vs. Stock LS7 vs. C5R:

Chamber Volume cc = 66.67 / 64.45 / 70.00 / 30 - 38
Compression Ratio = 10.1:1 / 10.5:1 / 11.1:1 /12.5:1 - 14.5:1
Intake Port Vol. cc = 200 / 210 / 225* / 220*
Exhaust Port Vol. cc = 70 / 75 / 72* / 70*
Intake Valve Dia. in = 2.00 / 2.00 / 2.20 / 2.125
Exhaust Valve Dia. in = 1.55 / 1.55 / 1.615 / 1.625
Intake Port Angle deg. = 15 / 15 / 12 / 11

*LS7 & C5R cross sectional areas are similar but C5R has a shorter runner(s) due to the valve angle.

LS7 valve pockets are siamesed
 

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Discussion Starter · #3 ·
I may be missing something here but how many CFM on the intake runner and on the exhaust side for the stock LS6 head?
 

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DavidGP said:
I may be missing something here but how many CFM on the intake runner and on the exhaust side for the stock LS6 head?

Depends what valve lift you're at. Look at the table, it's in CFM:

Head /.200"/.300"/.350"/.400"/.450"/.500"/.550"/.600"
Stk.LS6/ 156 / 204 / 225 / 243 / 257 / 268 / 275 / 278

That's for the intake. Here's some exhaust numbers i found on google:

.200"/.300"/.400"/.500"/.600"
108 / 143 / 163 / 176 / 184

Hope that helps :guiness:
 

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The other thing to realize is that bare head flows are nice for comparison but actual intake CFM will almost always be lower with the intake manifold attatched. And the type of intake manifold makes a difference.

Conversely, while bare head exhaust flow may seem low, it will usually increase in actual conditions as scavaging will increase CFM if properly tuned. Scavaging can also increase intake flow depending on the cam overlap.
 

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Discussion Starter · #6 ·
Would upgrading to C5R heads be a good option. I saw them on GMPartsdirect for $1200?
 

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The C5R heads have a different shape port in a different location so you will also need a custom intake manifold.

The LS7 heads are similar but there hasn't been any confirmation yet that the intake ports are exactly the same as the C5R heads....so no one knows IF the new LS7 intake manifold would fit on the C5R head....but it might.
 
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