Paging tom, paging tom maching question.

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ok so I have a older set of cast m/t vavle covers that have fins on them.   I would like to mill off the fins and the m/t logo,  The fins are all dinged up and basicly look like poop. ( http://cgi.ebay.com/ebaymotors/Pontiac-M-T-Aluminum-Valve-Covers-Mickey-Thompson-_W0QQcmdZViewItemQQitemZ140443155041QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories   same valve covers)  The fins are ~ 3/16" wide and about 3/8" deep.  I have no idea what kind of AL they are, only that they were cast some time in the 70s.

My question is, would it be better to use a end mill and take them off basicly 1 at a time, or a fly cutter and all at once?



I'm leaning towards the end mills as I'm not sure if a intermittent cut with a fly cutter is a good idea or not.  I'm not worried about the oil fill/breather  boss  as I've got other plans for it.   

[Badgersmilk]

Not Tom, but Certified Journeyman Machinist, and Engineer:  Take them off all at once and your likely to have stress fractures / cracks from the side load on the fins that will lead down into the base of the fin (part you want to keep).  Probably several of them.  Taking them off one at a time should be fine.  Have you considered brazing up the bad area's?  You can even do it with a propane torch and sticks they sell at average hardware stores.  Follow with some touch-up from a dremel tool, and WALLA! 

Just a thought.  

Those are sweet looking valve covers.  I'd hate to mill off what makes them unique.  I've seen guys braze up bad areas on them, paint the whole cover to match the car, then run a D/A sander over the top to polish up the top of the fins and M/T.  Looked GREAT IMO.

[tombogan03884]

BM gave about the same answer I would have, you could make a finish pass with the fly cutter to remove the EM tooling marks, but I would do the fins individually.
Welding cast AL can be a real SOB, but since there is no stress on the fins BM's idea of repairing them should work as well.

[Timothy]

Not a machinist by any standard but I was an auto mechanic.  The fins are there to dissipate heat from the valve train, they're not there for looks alone.  They also make an otherwise soft material more rigid.  

And Tom is absolutely right about welding aluminum, brazing may be your only choice and it's still not easy.  Badgersmilk has a good idea on painting and removing the paint on the fins.

Have fun...

[PegLeg45]

I had a set once, and from what I learned from years in the aluminum industry, the M//T's are basically high magnesium alloy aluminum, like the old 'mag rims' from the 70's era....basically a few steps up from "pot metal". If you chance machining the fins, whether you do it one at a time or all at once, there could likely be casting voids (thanks Tom, I remembered it this time) under the fins to deal with.

I would try to repair them 'as is' with a filler and then paint (or powder coat) them like BM said and polish the tops of the fins.

Brazing that stuff is tough, but there may be some types of epoxies out there with aluminum powder in it that would blend in pretty well, kind of like JB Weld, that can be filled and sanded (or bead blasted) like Bondo. Check with the Eastwood Company, they are the top supplier of restoration tools and items for that type of thing.

If you absolutely must mill them, you can still fill them and paint them.


http://www.eastwood.com/

http://www.alvinproducts.com/Products/Products.asp?id=1

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[Badgersmilk]

I'd b proud to have them on my engine...



Don't believe they made 'em for Fords though...

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those are actually very nice, these are a pos.

I mean if you didn't care what they look like, only that they function, they would be fine.


This is on a boat, with a exposed engine, they are by far the uglyest thing on the boat.

I mean shit they only made 16 of these motors that year.  a 64 421 HO is a very rare mill... Other then the crank, block and heads, nothing else is the same from a standard 421, which is very rare to start out with as it was a $$$$ option.  You don't even want to know how much the parts for this thing are,  The pistons, and vavles all had to be custom made.  When I say custom, I mean no one even had the specs for the pistons.  Ross had to have me ship them some old ones to start from scratch and build them.  The vavles started out and 3" diamter SS rods and were turned down.   

[tombogan03884]

I double checked with some guys at work who's work I respect. They agreed that if you take light cuts a Fly cutter should be OK and you definitely want to make your last clean up pass with the Fly or you will be able to see every tool pass on the part.
They both said"the fins are just cosmetic, that's why they are short and thick".
They also agreed with pegLeg that the cast Al isn't the best material to work  

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well I just got done striping them,  there are a ton of small cracks all over the place( not really that shocking)

so it looks like I need a new set of valve covers... sucks.