[footjoy]

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

[PAUL K]

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.

[footjoy]

Originally Posted by PAUL K

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

[PAUL K]

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.

[scott70]

Did you have the # 15 head cc'd? They are advertised at 87 but can easily be in the low 90's in reality.

[footjoy]

Originally Posted by scott70

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

[footjoy]

I just got the heads ccd and they unfortunately were 90 ccs

looking at .040 at least to get to 82ccs

This a street car. will heat be a problem for 40-50 thousands

Thanks

Greg

[shaker455]

How about just doing a head swap or maybe a set of E-heads?

[footjoy]

Originally Posted by shaker455

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

[shaker455]

You have a 400?

[footjoy]

Originally Posted by shaker455

You have a 400?

yes

[FrankieT/A]

Back to the OP's question...

If you mill more than .020 off the deck you should mill the intake surface as well. When you start getting past the .040 mark the deck on a Pontiac starts getting a thin and are prone to crack between cylinders. As for the 15's with small valves... I would bring the valves out to 2.11 and you will virtually have 64's minus a couple CC's, but still too big for a 400. Go to a 12, 13, 48 or even 62's( 62's having slightly larger chamber).

[Dragncar]

Originally Posted by FrankieT/A

Back to the OP's question...

If you mill more than .020 off the deck you should mill the intake surface as well. When you start getting past the .040 mark the deck on a Pontiac starts getting a thin and are prone to crack between cylinders. As for the 15's with small valves... I would bring the valves out to 2.11 and you will virtually have 64's minus a couple CC's, but still too big for a 400. Go to a 12, 13, 48 or even 62's( 62's having slightly larger chamber).

I have .060 milled heads, did not have to elongate bolt holes or mill any intake. Not prone to cracking. 64 heads work great on street 400s as do the 71 96 heads with a little milling. Its not hard to get 9-1 CR with those heads on a 400 and you don't really want anything much past 9.5 CR anyway. Big difference between a 13 and 48.
A 400 with 9-1 CR and iron heads is a great combo. 87ccs is not too big for that.

[footjoy]

Originally Posted by Dragncar

I have .060 milled heads, did not have to elongate bolt holes or mill any intake. Not prone to cracking. 64 heads work great on street 400s as do the 71 96 heads with a little milling. Its not hard to get 9-1 CR with those heads on a 400 and you don't really want anything much past 9.5 CR anyway. Big difference between a 13 and 48.
A 400 with 9-1 CR and iron heads is a great combo. 87ccs is not too big for that.

I need to mill .050 off of these #15 heads to get what I want 9.4:1. At what point do you know if you have to mill intake after assembly or after milling the head you take some kind of measurement. I saw The formula but I have read where guys say they didn't have to do anything.

Greg

[johnta1]

You probably need to trial fit the heads on the block with the intake to see how much to take off the intake side?

The block could have been decked also which would need to be accounted for.

The intake on the heads/block, the port alignment up/down would show how far off it is? Possibly the bolt hole alignment would be off.
(as Scott70 said basically)

[Dragncar]

Originally Posted by footjoy

I need to mill .050 off of these #15 heads to get what I want 9.4:1. At what point do you know if you have to mill intake after assembly or after milling the head you take some kind of measurement. I saw The formula but I have read where guys say they didn't have to do anything.

Greg

If you can mill them .020 and get 9.2 CR you will not notice the minuscule increase on power the .2 difference gets you. Its not worth milling off the extra. A plain ol 9-1 engine will do fine.
And you will not have to mill the intake, at .040 either.

[steve25]

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.

[footjoy]

Originally Posted by steve25

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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[Dragncar]

Originally Posted by footjoy

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.

[scott70]

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.