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Old May 7, 2007 | 06:53 AM
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Default 408

Im picking up a 408ci shortblock and i would like to know if it will work with my ported ls1 stage 2 cylinder heads and ls6 intake, please all help needed...
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Old May 7, 2007 | 08:08 AM
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the heads will bolt up as the 400+ strokers use a LS block, usually the LS2 for aluminum. Others use a iron block which I dont remember the code but its not LS but the heads will bolt up. The real question is if they will flow enough?
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Old May 7, 2007 | 08:34 AM
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yes they will bolt up it being a 408 i would assume its an iron block (LQ4-9) thats fine. the LS6 intake will work fine also.

do you know any info about the setup....IE cam your using the compression the flow of the heads. in the end you could put a stock cam and heads on a 408 and they will work. may not produce the most power but would get you by till you could afford something else. good luck!!
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Old May 7, 2007 | 12:14 PM
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Default 408

the heads were ported by todd at T-Flow performance and the valve springs are good to .600 lift, and around 66cc's i dont have the flow #'s off hand but i also got a fairly aggressive cam..
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Old May 7, 2007 | 12:17 PM
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do you know the specs on the cam and you compression ratio.

it will work. EI it will run. MAX power relys on all the factors
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Old May 7, 2007 | 01:08 PM
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Originally Posted by playboy245
the heads were ported by todd at T-Flow performance and the valve springs are good to .600 lift, and around 66cc's i dont have the flow #'s off hand but i also got a fairly aggressive cam..
You need some dual springs good to .650 lift if you going to run a "fairly" aggressive cam in a 408. The cam in my 346 is "fairly" agressive at .6xx/.6xx so your 408 is going to be begging for more cam considering the cam you'll be running is going to be .580 or less lift. Just my opinion, but why not step up to a dual spring setup like comp 921's and get a cam with some lift above .600 and duration in the low to mid 240's and make some serious hp?
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Old May 7, 2007 | 06:01 PM
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i got the heads rebuilt and ported for almost dirt cheap and they came with single springs. if i do upgrade to dual springs will that throw off any of my specs for the heads or is it pretty much straightfoward??
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Old May 7, 2007 | 08:03 PM
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Default Single vs Dual springs

The main difference is open and closed seat pressure. It will not throw off any specs for the heads.

What cam are you planning to run?

Bob K.
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Old May 8, 2007 | 09:23 AM
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I have the grind number to the cam at my house when i get offf from work I will post it, it's a comp cam cam.

the flow numbers are
INTAKE EXHAUST
.100 72 63
.200 149 120
.300 205 155
.400 255 190
.500 287 214
.600 307 220
.625 310 228
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