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Old 10-27-2019, 07:31 AM
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Default How much does a #15 head have to Mill, before the intake has to be milled?

I have a stock 1970 #15 Head 87cc. Can I mill .050 off of it with out any problems?

if not how far can it go?

Thanks
Greg

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Old 10-27-2019, 08:41 AM
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Quite a few variables but generally you can mill .020 and not have to do anything. Milling it more and you usually have to grind some on the intake manifold bolt holes. Milling .050 might be okay with just grinding on the bolt holes. You can get an idea by mock assembling the heads without head gaskets (they're usually .040) and test fitting the intake manifold with its gaskets in place.

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Last edited by PAUL K; 10-27-2019 at 08:47 AM.
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Old 10-27-2019, 09:14 AM
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Originally Posted by PAUL K View Post
Quite a few variables but generally you can mill .020 and not have to do anything. Milling it more and you usually have to grind some on the intake manifold bolt holes. Milling .050 might be okay with just grinding on the bolt holes. You can get an idea by mock assembling the heads without head gaskets (they're usually .040) and test fitting the intake manifold with its gaskets in place.
Which is better opening up combustion chambers on a 75cc head or milling a 87cc head to get to get to 77cc?

Thanks
Greg

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Old 10-27-2019, 09:20 AM
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A 75 cc head might loose two cc just by performing a valve job. It would be easier to work with the 75 cc head.

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Old 10-27-2019, 09:39 AM
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Did you have the # 15 head cc'd? They are advertised at 87 but can easily be in the low 90's in reality.

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Old 10-27-2019, 11:18 AM
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Did you have the # 15 head cc'd? They are advertised at 87 but can easily be in the low 90's in reality.
I didn't get them cc'd. The only reason I even entertain the idea of using the 15s is they have 1,000 dollars worth of head work with screw in studs installed. And they probably don't have much value to anybody.

Greg

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Old 10-27-2019, 03:49 PM
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Default Just mill the intake side of the head an equal amount and you should be golden.

The 'vintage' (40-years-old) advice from HO Racing and Nunzi, back in the day, was to mill both the head/block surface AND the head/intake surface equal amounts.

If I recall their description correctly (without digging out the book), because the Pontiac block is a 90* block, simply removing the same amount on both surfaces keeps the distance between both intake mounting surfaces the same in relation to one another.

I've honestly only ever done this once, on a pair of 1971 455 big car heads (I think they were '66's), many years ago. We took off .060" on both sides and everything fit just fine.

Good luck!

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Old 10-27-2019, 06:03 PM
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did they get the 2.11" intake valve installed?

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1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.64 @ 87.3 mph on slippery street tires.Bad 2.25 60ft.Owned since 86'
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Old 10-27-2019, 06:12 PM
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How about just doing a head swap or maybe a set of E-heads?

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Old 10-27-2019, 07:15 PM
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How about just doing a head swap or maybe a set of E-heads?
That would probably be best. Although I live in KC and there isn't a lot heads out here in the middle.

Thanks

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Old 10-27-2019, 11:03 PM
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You have a 400?

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Old 10-27-2019, 11:04 PM
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You have a 400?
yes

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Old 10-28-2019, 09:15 AM
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did they get the 2.11" intake valve installed?


Small valves


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Old 10-28-2019, 09:50 AM
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As posted , to start with for a street motor you need to CC at least one chamber in each head to get a base line and after that for every .006" milled off the head you will remove 1 CC of chamber volume.

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Old 10-28-2019, 03:48 PM
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As posted , to start with for a street motor you need to CC at least one chamber in each head to get a base line and after that for every .006" milled off the head you will remove 1 CC of chamber volume.


Can .035 be taken off or more on a #15 head?


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Old 10-28-2019, 04:01 PM
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Quote:
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I didn't get them cc'd. The only reason I even entertain the idea of using the 15s is they have 1,000 dollars worth of head work with screw in studs installed. And they probably don't have much value to anybody.

Greg
Do you have a list of what was done to them? They may have already been milled some.

Stan

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Old 10-28-2019, 05:38 PM
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Quote:
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Can .035 be taken off or more on a #15 head?


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My 71 HO heads have had .060 milled off. I do not believe the intake (Warrior) was milled either.

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Old 10-28-2019, 08:35 PM
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you can always mill the heads ,install them on the block and then lay the intake on without gaskets. If the ports line up you know you need to mill the intake whatever the the thickness is of the intake gaskets.

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72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007
(cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD
1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.64 @ 87.3 mph on slippery street tires.Bad 2.25 60ft.Owned since 86'
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Old 10-29-2019, 01:01 PM
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Quote:
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you can always mill the heads ,install them on the block and then lay the intake on without gaskets. If the ports line up you know you need to mill the intake whatever the the thickness is of the intake gaskets.
This.

Also remember the stock 70 455 with 15s was only rated 10 hp less then the big valve 64s.

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Old 10-29-2019, 07:09 PM
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In reality I would think theres more than 10hp between the 2 heads. Maybe i guess with a really mild cam where the engine doesnt really care about the extra flow.

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72 lemans,455 e-head, UD 255/263 solid flat,3.73 gears,,,10" 4400 converter,, 6.68 at 101.8 mph,,1.44 60 ft.2007
(cam 271/278 roller)9"CC.4.11gear 6.41 at 106.32 mph 1.42 60 ft.(2009) SOLD,SOLD
1970 GTO 455 4 speed #matching,, 3.31 posi.Stock manifolds. # 64 heads.A factory mint tuquoise ,69' judge stripe car. 8.64 @ 87.3 mph on slippery street tires.Bad 2.25 60ft.Owned since 86'
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