Surface for milled heads

[KIRCHNER]

iS there any particular finish prefered on a surfaced head? i know factory finish is dead smooth but worked heads always have some kind of machine marks depending on the mill used and or operator. is there a maxium allowable roughness/imperfections for sealing?

[Umassot50]

iS there any particular finish prefered on a surfaced head? i know factory finish is dead smooth but worked heads always have some kind of machine marks depending on the mill used and or operator. is there a maxium allowable roughness/imperfections for sealing?

I machine a lot of two stroke heads. Usually in a lathe and they come out very flat and smooth. I also flat hone heads and cylinders with Emery paper and a granite surface plate. As for a maximum allowable roughness I can't say. You would have to be able to accurately measure roughness. Besides visually that's sort of hard to do. If I had to speculate I'd say better than 100 Ra surface finish would be desired. I work at an aerospace shop so I deal with this stuff regularly. It takes a really screwed up cutter or really out of wack speeds and feeds to exceed 100-125 Ra.

[H2OPERF]

Felpro gaskets recommends 50RA minimum for aluminum heads, lapping on a granite block w/320 will get way below that number Should be around 10-20RA

[KIRCHNER]

IM only asking about this is because my heads were shaved and 6cc removed ,used same gauge to test and psi is lower @120 not 150? changed nothing runs good. gauge checks out ok i also took notes. whats goin on???? i heard a little texture helps grip on a head gasket. all 6 read the same.

[Merc 2.5]

Wow. So let me get this right. You shaved 6cc, roughly 40thou?and compression went down? Gasket or o ring? Was this a diff set of heads or heads off motor? Compression b4 and after?

[KIRCHNER]

60 THOU to be exact. same heads, compression before 130 using victor gaskets 1.2mm was 38cc now 33. did em twice! im baffled. something stuck in gauge hose? not 33,32.

[FMP]

Open the carbs throttle body, kidding!

[KIRCHNER]

Open the carbs throttle body, kidding!ILL try anything gauge isnt holding pressure as its pumping tryed it today.

[FMP]

So much psi now, bursted it !:D

[Onetime]

Different head Gasket thickness.

[HEAVYBULLET]

On what motor ?

[Chaz]

Open the carbs throttle body, kidding!

Frankie ... that was actually funny :p

I was gonna say ... summers tween this .... :eek: ... >

https://tse3.mm.bing.net/th?id=OIP.XRGuUhyU5KyxWDHVQXzNYAHaDU&pid=Api&P=0&w=423&h=190 (http://r.search.aol.com/_ylt=AwrEy1ojIIxb.0gA9eZjCWVH;_ylu=X3oDMTIzaWQzaGt0BHNlYwNzcgRzbGsDaW1nBG9pZAM3OGU5MjQ1MjFlZWI0ODUzN zYwNmFhMjEwNzM0NTQ0MwRncG9zAzM5BGl0A2Jpbmc-/RV=2/RE=1535938723/RO=11/RU=https%3a%2f%2fcitizen-femme.com%2fwp-content%2fuploads%2f2016%2f05%2fsalar-de-uyuni-bolivia-salt-flat.jpg/RK=0/RS=g45tnNI8lAqVl2K6Z8IRNvxtjas-)

an dis ... >

https://tse3.mm.bing.net/th?id=OIP.tpahSsfS8drtUQn52WbwHgHaGV&pid=Api&P=0&w=206&h=177 (http://r.search.aol.com/_ylt=AwrEzdKmIYxb_U4AHpZjCWVH;_ylu=X3oDMTIyMmI5b2QxBHNlYwNzcgRzbGsDaW1nBG9pZAM2MjQ0ODBhMGRkMmYzZjMxM zJiMGNmNTcwZjk1NmNhZQRncG9zAzEEaXQDYmluZw--/RV=2/RE=1535939110/RO=11/RU=http%3a%2f%2fwww.xinamarie.com%2fmosaic%2fimages%2fB_KG11.jpg/RK=0/RS=NNshesiUXsnGHLABH.ZYIMoq0G4-) Something that most dont know , or talk about is that the angles on the bit's that cut so nicely and radiuses that expell the chips going across a flat surface , do a tearable job ( dragging @ the wrong angle ) on the trailing side . It sukks only having one milling machine . Some things call for everything being 90* square . For surfacing you have to put .00025 to .0005 "helicopter blade" into the cutter.
Yes , the cut will be "hollow" a "half a thousandths" from the outside edge to the center with a single cutter pass . But keep in mind this is nothing ... conpaired to the " four , five , six , thousandths I have seen those smooooth stock "BENT" heads .

https://i.imgur.com/c4hDFR7l.jpg

CNC guys are all about speed , multiple passes with smaller cutters . Not really what i like to see . The first thing everybody does is run their finger across the overlap lines . some you can feel ... NFG , others you can't ..
It really comes down to using the right tool for the right job . taking your time and doing it right .

https://i.imgur.com/uAZQNJKl.jpg

[FMP]

Overlap line, been staring at one wondering should I drag it over fine cloth paper and a flat surface or leave it? Almost undetectable but.... spray bomb pass or recut... likely cut.

Found this resourceful guy making good use of his tools.
https://m.youtube.com/watch?v=ooG2ZI6Wdys:thumbsup:

[KIRCHNER]

2.4 220

[rock]

Found this resourceful guy making good use of his tools.
https://m.youtube.com/watch?v=ooG2ZI6Wdys:thumbsup:

Sure hope the head came out better than the wood they are designed to cut does. I have always used the "hollow grind" method then flattened them with emory cloth on a flat surface. Works for me.

Rock

[FMP]

He's up and running strong so I guess it did the job.

Flatten, applies to decking as well. Watched a builder(old pro) weight a block then slide it on the cloth flat surface, even strokes. Front half as well .