Milling Intake Manifolds FYI

[Don D]

"When you mill the heads {combustion chamber } the distance between the heads gets narrower,so you need to shorten your intake manifold so that it will line up to the intake ports in the head properly. Formula = example-milled .030- take .030 divide by .050 x .016 = .010 per side of manifold. You take a vernier caliper and measure across the intake for starters then you can 'lap' with 280-300 grit sandpaper on a flat surface to take off required amount. Take same amount off each side ! If intake manifold does not line up to intake port in head,you will have turbulence,not what you want."

[Admiral Akbar]

FWIW,

The about that typically need to be removed is.

one side chop = Head milled x sin(22.5 deg).

I don't use this formula as some manifolds are pretty loose to start.. I hand fit with a good mill file so that the angles match the heads then set up for a 0.005-10 clearance when the manifold is centered properly. I make sure the edges are deburred but not chamfered too much.

Max

[BVHOG]

Why not just mill the head to manifold mating surface the required amount at the time of milling the head gasket surface?

[garyajaz]

BVHOG
am not a machinest but doing the matching would be easier when heads installed because of angles and tollerances.

my stroker with plates needed a longer (S&S supplied) manafold.
once heads on and bolt slop accounted for, i could match things up...

this is on a ironhead with o-rings so i may be way off base.

on that old iron a guy can have bolts installed loose and move the head side to side a bunch.  only way to get angels right was assembled...

[FSG]

Below pic is from a Cadd setup I did quite some time ago. It's purpose was to determine the change in manifold mating surface as the heads were cut and thinner gaskets used.  In my shed intake manifolds are done by hand which is easy and often not required as most are sloppy for starters.  I'd not machine the head just for a manifold fit nor advise others to do so.  You can cut if off but you cant cut it back on.

[Don D]

FSG big cigar for ya, I agree.
Can you send me the DWG file? Just save a few minutes work.
I have AutoCad 2006 and 2008 and Inventor
TIA

[FSG]

Don, see attached, twas the same file, just exported to different formats.  I swore off Autocad when they lied to me about supporting Genaric Cadd Ver 6.1 many years ago and I've not touched their products since. 

I didn't put a lot of information into the file as it was for my own use, but you can see the crank centre, wristpin, head gasket, etc, etc.

[attachment removed after 60 days by system]

[FSG]

OT: but heres another cadd I did a few years ago.  It was to check the clutch plate separation and loss of separation when fitting the 18 deg ramps.  For those that don't know there were 15 deg ramps installed in some '90's models and weren't they a bitch.

[OKLARACIN]

belt sander

[mayor]

belt sander

my technique was similar....random orbit palm placed in a vise.   

[jrussell]

One thing I didn't expect to have trouble with was the top keeper of the pushrod tubes. Mine (all 4) needed to be shortened about 1mm when the heads were dropped to make 79cc.

My intake was loose enough to fit fine, but you could tell it was a tighter fit.