74u

iTrader: (9)

I just had some 821's milled to 58cc which took 0.065" off the deck. As predicted the intake bolts don't line-up. Is there any way to calculate how much I need to mill off the intake flange to get things lined back up?

To clarify, I plan to mill the aluminum intake surface of the head. Not the plastic intake manifold.

Just eyeballing it looks like the bolt holes are misaligned by about 30 - 40 thou on both sides...

I'm hoping to nail this on the first try because the machine shop isn't going to have time to keep knocking 0.010 off at a time.

A.R. Shale Targa

iTrader: (2)

there is a formula but a few of the shops I've worked at just did what you said and eye-balled it. Did you also change the gasket thickness ?? I'm assuming you used one when mocking it up correct ??
Since most people seem to be able to mill .030" and have the intake fit (barely); and since you went .065" I'd simply take .035" off the intake surface of the heads and call it good.

74u

iTrader: (9)

Yes...using a 0.040" thick head gasket.

With the heads bolted down on a compressed 0.040 gasket I set the intake on top as centered as I could. I took a long medical q-tip dipped in paint and ran it down the intake bolt holes to leave a mark on the heads.

I'm about 1/4 of a bolt hole off and the bolt measures 0.233 so I'm thinking I need to take around 55 - 60 off the flange. Measuring the width of the paint is about that same 55 - 60 thou.

Scary...cant put the material back if I miss my guess

A.R. Shale Targa

iTrader: (2)

That's why I only said .035 since too much and you're fucked.
because the intake flange is on an angle, just a small amount of missing material drops the intake a considerable amount. Back in the day I had to mill a BBC intake .050 after the 502 block was wacked .020" and the old *** 396 heads had been milled somewhere around .070". By doing the intake about half of the total deck/head material made it perfect.
Your .065" heads combined with the .011" thinner gasket equals .076"...it would suck if it needed .040" and you only went .035" but it would be far worse if you went .010"-.015" too much.......

dogsballs

Plastic manifold can flex a bit, you could make it fit without anything as plastic opening bigger than intake. Or roughly half of thickness removed

74u

iTrader: (9)

We ended up milling 0.060 off the intake flanges and got the ports to match up perfectly.

One bit of learning for me...milling the intake flange doesn't change bolt alignment. If you think about it milling the head gasket surface moves the intake bolt holes (on the head) closer to the center of the motor. No matter what you mill off that intake surface the bolt holes stay in the same place, and the bolt holes in the manifold stay the same distance apart. I learned the only way to fix the bolt alignment is to enlarge the bolt holes in the intake manifold.

Easily accomplished because the steel liners in push right out of the intake and make the hole about 30% bigger

CAMSTER

iTrader: (10)

That's rite times two here no need to mill intake it will bolt rite up, if need to enlarge bolt holes some people mill heads over .100 and never mill intake.

mOtOrHeAd MiKe

iTrader: (8)

It is amusing to think of the number of misaligned intakes installed on milled head/thin gasket builds. Was the bump in compression worth it?

74u

iTrader: (9)

That's debatable.

Here is what it cost...

One extra P to V check (another mock up)
Extra stress & worry getting everything fit
Two trips back & fourth to the machine shop
$250

Here is what it should gain...

About 25rwhp (increased from 10.1 to 11.3scr)
Reduced stress & worry that I'm "leaving power on the table"
Help tame the cam on the street - the most important thing to me

mOtOrHeAd MiKe

iTrader: (8)

LOL... sorry that was meant for the "slap it on and go crowd" who would just hog out the bolt holes and goop it with RTV to make it work.

You did it the right way.

Spidermonkey

You should be able to calculate it out using trig. The only information I would need to know the angle between the face of the head (that got machined already) and the face of the intake ports. Is it 90?

CAMSTER

iTrader: (10)

Anybody who mills the intake risk having to buy another one, when heads are milled nothing changes in terms of angle only the heads are lower (at same angle) at their base, only the intake runners tend to be slightly higher (by what?) maybe 0.060 at most, just a little grinding adjustment will take care of that, must of the times is not necessary.