Milling heads

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October 4th, 2018, 10:17 PM

redbaron442455

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Milling heads

Does anyone know what is the most that can be milled off a set of 68 455 big valve C heads?
I'm hoping to be able to bring it down to 70cc currently 85cc.

thanks,

October 6th, 2018, 06:41 AM

OLDSter Ralph

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I believe .005" per cc. 15 cc X .005" = .075" material removal.

October 6th, 2018, 08:31 AM

Charlie Jones

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If you have your heads milled that much , make sure the machinist mills the proper amount off the intake ports .
Otherwise your intake manifold isn't going to fit .

October 6th, 2018, 01:36 PM

redbaron442455

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great thanks guys!
just curious whats the most you have ever heard of being safely milled off olds heads?

October 6th, 2018, 02:41 PM

Qwik71442

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Quote:

Originally Posted by redbaron442455

great thanks guys!
just curious whats the most you have ever heard of being safely milled off olds heads?

FWIW-I have personally gone from 81 to 84cc’s on several sets of C’s down to 72cc with no issues.

Last edited by Qwik71442; October 6th, 2018 at 02:47 PM.

January 2nd, 2019, 08:12 PM

73aussie455

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Quote:

Originally Posted by Qwik71442

FWIW-I have personally gone from 81 to 84cc’s on several sets of C’s down to 72cc with no issues.

Couple of quick questions here please,
Were you using the stock hydraulic flat lifters in that engine?
Did you have to buy shortened push rods with that much milled off the heads? or did the stock length ones cope ok?

How much needs to be milled off the intake if you mill .012" - .015" off the heads? is there a formula to work this out?
Do you mill the intake side of the heads or the intake manifold flange?

I'm going to do just as the OP has suggested, so I'm keen for any info, thanks.