Technical & General Discussion Area > Tech Torque Pre 1973

390 inlet manifold

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simo:
Hi Guys,
My '69 Mach1 is an S code with a 390 FE / C6 auto. The heads that are on it are from a Cobrajet motor but it's running a standard inlet manifold with a Holley 600 cfm carb. My question is would I benefit by swapping over to a Cobrajet inlet manifold or just leave it standard.
Many thanks
Simo

barnett468:

--- Quote from: simo on June 13, 2021, 12:41:12 pm ---Hi Guys,
My '69 Mach1 is an S code with a 390 FE / C6 auto. The heads that are on it are from a Cobrajet motor but it's running a standard inlet manifold with a Holley 600 cfm carb. My question is would I benefit by swapping over to a Cobrajet inlet manifold or just leave it standard.
Many thanks
Simo

--- End quote ---

Yes,

jiffy:
If this was in print/still available then it would be great reading and tell you what you need to know and WHY.

http://fepower.net/GFEIC.html

Suffice to say, like Barnett says - you'll get a power increase

Have a read of this - the section by Jay (he wrote the book above) tells you all you need to know

https://www.fordfe.com/new-to-fe-engines-questions-gt390-heads-vs-428-cj-t60504.html

an option for the intake is the PI intake - worth reading about them on CJ heads here:

https://www.fordfe.com/428cj-port-size-compared-to-390-heads-t3553.html


Bottom line - anything will be better than the 390 intake, and headers will perk it up even more. A CJ intake is effectively a MR intake so make sure the cam will support the revs that the top end will support.

simo:
Many thanks guys and those links were very informative.

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