What I’d like to do is remove the fins on my valve covers to make them smooth like older model Jags. Is there enough “meat” in the covers to allow this without rendering them too thin and/or too weak/prone to warpage? If it -can- be done; what’s the best method? I don’t have a milling machine…
Without the use of a milling machine its going to be hard labour. There should be enough meat as the thinnest part will be in the valleys.
One way would be to drill series of holes in the ribs to remove as much ally as possible and then hand file the remainder, I’m a retired toolmaker that used to do a bit of filling in my younger days and this would be a huge job then woundn’t contenance it today 
Why not just source a set of smooth covers?
You could do the rough removal with a belt sander and some 36 grit belts. I use my HF belt sander and sanding belts frequently to work on steel and aluminum items. I’d advise doing it outside just because you don’t want that aluminum dust coating everything in the garage.
Yes, I did it to an XJ engine in a cheap D replica I was selling. Looked OK and waay cheaper than smooth covers. However, prepare for one or two blow holes. Give them to a small machine shop for a cheap milling job and save your arms and shoulders for getting the black finish off the sides.
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Without a milling machine it will probably be a challenge to get them to the same shape. It will also be some hard graft.
Check if the black comes off with paint remover first… getting it out of the fillets and radii that are around the filler and stud holes will be a PITA if you have to do it mechanically.
Clamp them to a stiff bit of hardwood to make them easier to hold and do the rough removal with a belt sander and coarse grit (until the ribs are almost gone). Then change to a longboard with a bit of felt backing.
Sounds like a good idea , may be a problem with the thickness of the alloy around the holes , as you can see in the pic , if you take the fins down so they are smooth , looks like the thickness will be around half , and I know smooth cam covers do suffer with cracks around the holes , maybe that’s why Jaguar put the fins on , have not come across a ribbed cam cover with cracks around the holes , I may be wrong .
I don’t thick the polished ribbed cam cover looks too bad
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They look good.Thanks for posting.
I intend to do the same this weekend. Still may paint the valleys however.
@PeterCrespin: …a cheap D Type replica you say?
Yeah, shook hands on my second Realm hours before I found someone to build a ‘real’ one. So I just smartened it up and flipped it. That was around 2010 and it will be finished next year!
Thanks, I was afraid that the metal might end up too thin. Mine don’t even have the cast-in “Jaguar” detail, just a flat spot for a poorly applied decal.
It would be a shame to erase a cast name set. Have at it for the cheapskate ones. Metal is plenty thick if you stop when ribs are gone and you are gentle with the nuts.
Yeah, I don’t think I’d have even considered doing it to a nice set. the look of the finned/black units is so “70’s’” it’s actually painful. It probably looked the bee’s knees in '74 but it’s terribly dated now IMHO. I’d rather have them overall black crinkle finish with the fins. Even worse when all the emissions equipment was intact. Almost unrecognizable as a Jag engine!
That’s the reason Dad swapped out the purdy shiny ones, for the more durable ribbed ones.
Good advice; be gentle with your nuts.
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On the XJ6 3.4 Engine I put in my MK2 , the cam covers did not have Jaguar on them , and the oil filler cap was not a nice alloy one , I fitted cam covers off a 240 , re-painted them !
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I know of two sets I could score but the price is a bit scary! Both are part of entire parts cars!
That is beautiful!!!
Everything has been so far! Motivated to just clean my stock stuff up now!
Your spend hours getting them to look just right , so your pleased with them !!
Then a very low price set of smooth cam covers will come along , sods law 
lol