Aluminum valve cover fin milling question

I have a pair of sand cast aluminum valve covers that I'd like to get modified. I want to remove the center circle & 2 rectangle pad areas - so it's all fin.

Anyone ever do this or have it done?

Here is a pic of the valve cover

 

You'll probably need to recut each slot, if you don't the bottom radius may not match, and the freshly milled areawont match the sand cast pattern in the original slots

 

That's what I was thinking too. I have 3 of them. I'll get one modified to see if I like it or not.

 

that's what I would do... measure the distance of the fins and buy the corresponding ball end mill if you don't already have that one. mill it then sandblast them to get the surface finish the same

 

Set them up in a mill. May have to do some hand sanding on the edges and sand blast to match the texture. Might have to sand some of the existing casting, so when you blast everything the texture is the same.

 

I screw them to a piece of 3/4 plywood, then clamp the plywood to the mill, just easier than trying to clamp the valve cover. Chris

 

Great idea. Should be a straightforward job on a mill making a few p***es so long as you get it clamped down nice and square.
Hopefully you can achieve the desired look/finish without the part looking like it's a milled billet piece.

 

Because they are sand cast you will probably need to recut the whole slot to make it look uniform. The milled areas are going to look different not matter what you do. Not a big deal though. Mount it in the mill, get everything squared up, and take your time.

 

Can you see the boxes and circle from underneath? Check the thickness as there might be some shrinkage on those thick spots that might give you trouble.

 

Be sure to indicate the covers in from both far ends before you start cutting. If it's off by just a little over an inch, that will translate into alot over the length of the piece. Same with how level the piece is over it's length. Use power feed if you have it so the finnish is consistent. Otherwise It should be a simple job.

 

Really good call here...as long as you have enough material to take it...take a few .000s off of the current slits as well so you have a dead on match.

 

My poor man ways would have me using a radial arm saw with a metal blade and a sharp eye. Then hand filing and sanding, and possibly a media blast to blend it all in.

 

Tjet:
Machining is the easy part. Do you know what Porosity is ?
http://en.wikipedia.org/wiki/Casting_defect

This is when gas t****d in the moltem metal, it creates tiny to large gas bubles

The thicker part of the valve cover is where there maybe gas bubbles. The possible porosity, is no problem if you surface and paint them.

Silver/gray, Wrinkle paint on the sides and bottom of the fins does not always look bad.

Are they new cores before machining as there are no hold down bolt holes ?
If those are true sand castings there will gas bubbles!

Or sell them and buy what you want!

 

A lot of times the area underneath is pocketed and when you machine down to the cover level the area opens up or becomes paper thin and cracks.

 

This is a very good point. Can you see sunk spots around where the solid areas are on the back side. If so it will definitely be thin in those areas. The porosity possibility in the solid areas is very true too. Your not going to know it's there until you cut it though.

 

You can also use a router. I made some aluminum header adapters by tracing the exhaust gaskets to aluminum and then routing the holes and shape. Very easy to do. Aluminum machines as easy as wood with a router.

 

Another thing is that a special cutter needs to be made with a taper since all casting surfaces have a draft angle(to remove pattern from sand)any cutting from a standard cutter will be noticable.

 

You can also have it done on a CNC router table, that's how I did my gauge panel. Most sign shops have one now. A little time with a file and some 80 grit sandpaper and it will look great. Sandblast everything and polish the ribs and you're done.

 

with so many styles of valve covers available
unless you are doing it for the challenge
sell what you have and buy what you want
one mistake and you wasted time and probably a valve cover

 

Cutting them all the way then getting them blasted is a good idea. That way, when I get them polished, I can leave the area between the fins rough - or paint that area dark grey or flat black....I attached a rendering of it.

As for finding a set of all fin covers, pls let me know where I can find a pair. These are for a 425/455 Olds, & they are duplicates of original Sharp covers from the 60's...

http://www.nhra.com/blog/dragster-insider/2012/10/12/simply-terrifying/

 

Here is some work I did on a set of Mexican cast cover. They had big blocks where M/T should be. I ground a 1/4" mill bit to a 2degree tapper Just as Bruce sugested and mille the M/T in . I still need to do some hand filing with a curved jeulers file . I also tuned it up some with a small stone in a drimmle.
I also milled the solid name bar at he bottom to be just fins.
dwrfab Don Ross

 

Very nice work! That looks great.

 

Buy a end mill with the daft angle ground for mold release.

This style is what I use for all molds weither they are for metal casting/ polyester/thermo plastic.
As little as 0.5° Taper
,
http://www.mcmaster.com/#tapered-end-mills/=q1oek8