Valve Cover

jps635 · Post by **jps635** » Wed Sep 03, 2014 8:32 am

For those of you who have black valve covers with the bmw logo and stripes accentuated in aluminium, what did you use to clean off the black - sand paper on a block or a fine file?

Do the aluminium highlights get clear coated?

Thanks Chris

m6dave · Post by **m6dave** » Wed Sep 03, 2014 11:07 am

I prepped the raised sections first, start with a file then use wet and dry paper wet on a hard block. Next I used a calico wheel with bees wax to polish them up then wash with prepsol to get rid of the wax. If you are going to paint it put the paint on then clean it off the raised section immediately with a rag dampened with thinners on a flat board. I powder coated mine and masked the raised sections with high temp masking tape. This might work with the paint too. I stuck 50 mm wide tape over the whole area then trimmed it with a stanley knife to just leave it on the high spots. It is very fiddly but delivers a great result.

jps635 · Post by **jps635** » Thu Sep 04, 2014 5:44 am

Thanks. I'm getting mine powder coated and they suggested exactly what you did, masking the raised bits with high temp tape, but seems awfully fiddly. Thought it would be easier to just file or sand off after powder coating the whole thing,

m6dave · Post by **m6dave** » Thu Sep 04, 2014 10:07 am

Hi Chris
Do what they said it looks perfect. If you want to save some money polish the raised sections before you take it to the powder coaters. If you don't mind I would be interested to know how much they charge for this service. The cost of the powder is not much but it would take about 4 hours to do.

Alpinacsi · Post by **Alpinacsi** » Thu Sep 04, 2014 11:56 am

For 30 years I have been finishing first and then sanding the raised surfaces. You can also take a razor blade and skim cut the surfaces and then use the blade to scrape followed by sanding to the desired level.

Many ways to do this and each has its pros and cons. With the method I use: you have to be careful not to chip the edges if you are scraping before the sanding. With masking: you have to be careful that you do not have tape lines as powder coating can get heavy in places and the high temp tape used for powdercoat masking is difficult to work with. Also you can not mask the roundel and text.

I do not polish the raised areas because I do not clear coat after it is done. The alum will oxidize and look like any of the other alum parts under the hood. No sense in polishing unless you plan to clear coat as it will be difficult to continue the polishing once it is installed.

orlando · Post by **orlando** » Sun Sep 07, 2014 8:07 am

I got mine sandblasted, powder coated, then sanded the lettering, the lines and the roundel, then polish them and finally clear coated the whole cover.

See before and after pictures below.

jps635 · Post by **jps635** » Mon Sep 08, 2014 7:50 am

If you don't mind I would be interested to know how much they charge for this service.

Hi Dave. $120 for the powder coating.

I asked them to do the masking but they said, umh no, we'll clean it, give it back with the tape and once masked up powder coat.

ron · Post by **ron** » Mon Sep 08, 2014 5:18 pm

orlando wrote:I got mine sandblasted, powder coated, then sanded the lettering, the lines and the roundel, then polish them and finally clear coated the whole cover.

See before and after pictures below.

Definitely cheaper than buying mine and paying for a courier! Looks good.

orlando · Post by **orlando** » Mon Sep 08, 2014 10:24 pm

Thanks Ron. I am very happy with the end result. It wasn't cheap though!

dwcains · Post by **dwcains** » Thu Sep 25, 2014 7:16 am

I just got mine powdercoated:

The raised areas were lightly sanded/polished after the cover was media blasted. After the powder was sprayed on, it was gently/carefully brushed off the raised areas, before the cover was baked. The result looks perfect, with sharp edges between the coated and uncoated areas, and a very even wrinkle finish. Cost was $75 at a Tampa, FL shop.

jps635 · Post by **jps635** » Thu Sep 25, 2014 7:57 am

Looks superb.

Brucey · Post by **Brucey** » Thu Sep 25, 2014 9:51 am

That does look good. Those edges are much sharper than I would have expected to see, I'm sure that my casting isn't as good as that.

One concern I have is just how durable powdercoat is on this part.

With the stock injection system, the (80-87 style) AFM sits on the rocker box and rubs away at it in use.

Has anyone got one that is a few years old that has seen a lot of use?

cheers

ron · Post by **ron** » Thu Sep 25, 2014 11:23 am

Brucey wrote:Has anyone got one that is a few years old that has seen a lot of use?

When done 6 1/2years ago.

Taken 5 minutes ago. The bare alloy stripes etc. could do with a polish.

Brucey · Post by **Brucey** » Thu Sep 25, 2014 12:02 pm

still looks nice, but that is the 87-89 version with the AFM that bolts on to the rocker cover, isn't it? I don't think there is anything set to fret and rub against that cover, is there?

BTW it seems that even the slightest winter use hereabouts speckles the engine bay with a mist of salty water; I've had to remove my first Sparco strut brace for some serious polishing, because it was starting to suffer pitting corrosion! It seems that all kinds of polished and painted finishes under my bonnet suffer terribly unless they are lathered in waxoyl or similar.

cheers

sansouci · Post by **sansouci** » Thu Sep 25, 2014 2:52 pm

Ron,
Looks great. But how do you clean the raised sections without getting the residual wax/polish in the wrinkles?
Is the powder coating "scrubable" with a soft brush?
--Ken

ron · Post by **ron** » Thu Sep 25, 2014 3:01 pm

sansouci wrote:Is the powder coating "scrubbable" with a soft brush?

It cleans off with "white spirit" or similar.

sansouci · Post by **sansouci** » Thu Sep 25, 2014 3:03 pm

I think we call that Turpentine over here. Good 'ol paint thinner.....

scottb · Post by **scottb** » Sat Sep 27, 2014 12:46 pm

When I did a set of covers for my Jensen Interceptor, I painted everything, then used a razor blade held @90 degrees to scrape the paint off... took a while and a lot of razors but looked nice

dwcains · Post by **dwcains** » Tue Sep 30, 2014 12:06 pm

Brucey wrote:That does look good. Those edges are much sharper than I would have expected to see, I'm sure that my casting isn't as good as that.

One concern I have is just how durable powdercoat is on this part.

With the stock injection system, the (80-87 style) AFM sits on the rocker box and rubs away at it in use.

Has anyone got one that is a few years old that has seen a lot of use?

cheers

The raised areas were machine sanded after media blasting, but before the powder was applied. Not really sure how sharp the edges were initially. I grabbed this cover at a pick-and-pull junk yard and will swap it with the one on my car. That one looks pretty good, and I was planning to take it to the same powder coat guy and then sell it. Don't need a spare.

I think if the mounts for the AFM are in proper repair, there shouldn't really be any contact between the AFM and the valve cover. There was a very slight wear mark on the junk yard cover, but it was just a small shiny are, and didn't really remove any metal to speak of. I'll check for clearance when I mount the nice one on my car, and shim/adjust as needed.

Brucey · Post by **Brucey** » Tue Sep 30, 2014 1:42 pm

dwcains wrote: I think if the mounts for the AFM are in proper repair, there shouldn't really be any contact between the AFM and the valve cover. There was a very slight wear mark on the junk yard cover, but it was just a small shiny are, and didn't really remove any metal to speak of. I'll check for clearance when I mount the nice one on my car, and shim/adjust as needed.

On the underside of the AFM /airbox mounting bracket (all Motronic M30s to 6/87) there are two rubber bungs. These rubber bungs carry a good portion of the weight of the AFM/ airbox assy and they bear against the rocker cover. There are always marks from this rubbing; I can't see how it could be entirely avoided. Although there is a rubber cone mount under the airbox too, this often (if your engine mounts are good and not old and collapsed) doesn't take much weight. I've seen cars without the lower rubber mount and they had the same rub marks on the rocker box as those with it. I've seen cars without the two rubber bungs and this leaves the airbox resting on the ignition lead trim, which pretty soon bends and/or fails under the load.

Any weight not borne there must be taken by the induction boot or the rubber mountings to the right of the airbox; the former isn't capable (and will split if you try) and the latter is in the wrong place.

Remember that the engine twists from side to side when it is under load; I guess this is a bit worse on manual cars than auto ones.

The post 6/87 M30 engined cars don't have the same issue here; the AFM is bolted to the rocker cover and the airbox is bolted to the bodywork, and there is a flexible joint between them, rather than between the AFM and the throttle body.

cheers