Yeah, it's neccessary.  It keeps the big rocks out of the oil pump.  The little ones will still get through so the big thing is to change your oil often.

I change the screen every couple of years and the rest of the time just change the oil.  The more often you pull the sump plate off, the more likely you are to develope leaks and strip out the studs.  No matter how long I've left a screen in, I've never changed one that was in any danger of stopping up.  If you don't keep clean oil in it, I suppose the screen could get caked with goo and crap from the oil and get baked by the heat of the engine.  You gott'a keep fresh, clean oil in it.

It seems strange in this day and time to say you need to change your oil every 2000 miles.  Back in "the day" that was the norm for all engines . . . the oil was just worn out and needed to be replaced.  Today's oil is much better and won't wear out near as fast.  Synthetic oils will last for thousands and thousands of miles and still have good lubricating properties.  But with an air-cooled type 1 engine, you don't have a filter.  The oil, no matter how much better than 1960's oil, will get just as dirty just as quick as it did back in the '60s.  When you consider that the air of today is much dirtier, you probably need to change your oil more often than you did back then.

Verl Taylor has nearly 300,000 miles on the bottom end of his 1967 1500 single port.  The top end has been rebuilt twice, but this engine is still running on the crank, cam, lifters and bearings that were installed on a German assembly line 37 or so years ago.  I talked to him about it once and asked him what his secret was.  He said he had run whatever type of oil he could get his hands on.  No particular brand, or even weight.  But, he said that he changed it all the time.  About every thousand miles when he was driving it every day.  He said a couple of times he had slacked and let it run 1500 miles between changes.  There are all kinds of experts out there with all kinds of advice on what oil to run and how often to change it.  Verl doesn't claim to be an expert, but he's the only person I've ever talked to that has run that many miles on a type 1 bottom end without splitting the case.  That's enough to convince me that no matter what type of oil you use, no matter what kind of driving you do, no matter what other factors are involved, the more often you change your oil, the longer your engine is going to last.

Keep the screen.  You never know when you're going to get a rock in your crankcase.  More importantly, keep clean oil in it.  To a point, dirty oil will go through the screen just as good as clean oil . . . but dirty oil doesn't lubricate as good as clean oil.

My experiance has been that the screen won't fall off even if the sump plate is loose or missing.  I usually try to "save" the screen and reuse it, but I can't remember ever getting one out without bending it up pretty bad.  The screens you get today don't really fit.  They have the right size and right number of holes, but they seem to be only in the general area of where they need to be.  So, don't worry too much about the screen falling off.  Now the drain plug . . . you want to make sure you use a new crush washer and get that sucker tight.  It will fall off.  My experiance with that has been that it will bounce harmlessly to the side of the road and won't hit the car behind you, but when you slow down you'll give the car behind you an oil bath!  Anthony can tell you about this first hand.   #-o

There are a few things you can do to really slow down the leaks from the sump area . . .

#1 -- Make sure the sump is flat.  Take a good flat sharping stone (the kind you can get at a flea market for a couple of bucks, they are about 2 or 3 inches wide and 8 inches long) and rub it around on the sealing surface of the sump plate in a circular motion.  You'll probably see it start to get shiny around all the holes first.  This is because the sump has most likely been overtightened and warped slightly at sometime in the past.  If it isn't perfectly flat it's gonn'a leak.  Keep polishing it till the whole surface is shiny.  Now it's flat.

#2 -- This one may be somewhat controversial.  Some people say not to use any type of sealer on the gaskets.  I use high temp. silicone . . . but instead of putting a bead around the sealing surfaces, before I pull everyting apart I take the gaskets and rub just a dab of the sealer into the paper . . . what I'm trying to do is "rubberize" the paper gasket.  The gaskets you get today are generally made of a cheap grade of paper that ends up making a pretty good wick.  All I try to do with the silicone is rub enough of it into the paper to keep it from wicking oil.

#3 -- Test fit the screen . . . If it won't slide over the bolts easily (and it won't . . . IF it does, please let me know where you got the screen!) slightly ream out the holes until it will slide into place without having to force it over the bolts.  This will help keep the screen flat.  The only problem now is it might fall off if you loose your sump plate . . . but then you'll have bigger problems to worry about than the screen, so don't sweat that too much.

#4 -- Use new copper washers under the CAP nuts.  No matter how well you get it sealed up between the bottom of the engine, the screen, and the sump plate, some oil is going to weap around the threads of the studs.  The washers crush when you use them and won't seall correcty if reused.  Even if they do oil will weap through the threads and drip off the bottom of the studs if you use regular nuts.  Cap nuts will stop this from happening.

#5 -- More isn't better when it comes to torque on the sump nuts.  The factory specification is just a FEW inch pounds.  I don't remember the setting off the top of my head . . .  maybe someone else can jump in here and give you the setting.  Anyway, I don't own a torque wrench capable of correctly measuring a torque that low, so I just use a 1/4" drive ratchet and place the head of the ratchet in my palm with an extension or deep well socket sticking out between my fingers and just give each bolt a good snug twist using just my wrist.  I'm probalby still getting them too tight.  If you use a 3/8 drive ratchet you WILL get them too tight.  If you use a 1/2" drive ratchet you will have to learn what a step stud is and how to install one (i.e. you will strip the stud out of the block).

#5 -- Use a new copper washer under the sump drain bolt and make sure it's tight.  This is a pretty good size bolt and is going into a steel sump plate . . . it can hanldle a little extra torque.  This one WILL fall out and take your oil with it if it's left loose.  Ask Anthony (about the what the oil will do if the bolt falls out, not about leaving the bolt loose).

If you have a later sump plate with no drain plug in the center, ditch it and get an older one with the plug.  VW did away with the plug to force you to have to remove and clean or replace the screen at every oil change.  I won't argue that they were probably right, it's probably best to remove the screen every time . . . but the extra work involved in getting the sump sealed up correctly every oil change is big deterent to me to change the oil.  I don't change mine often enough as it is.  If I had to deal with the sump plate every time, I'd end up putting it off way too long.  I'd rather sacrifice any gains I'd get from removing the screen and change my oil more often.  That's just my opinion.  Use your own judgement.

I'm using a filter and synthetic oil in my Beetle, so I gooped the gaskets up good, like Zen said, and got a sump plate with a drain bolt, and I don't ever intend to take the sucker off again.  I feel the same about the type IV engine.  As long as there's a filter to trap the little bits, the screen just keeps pieces of bearings, rods, case, from doing even more damage.  I imagine there will be other, really obiviously dramatic warning signs going down by the time the screen is filtering pieces of engine!  

Incidently, we don't use the screen in Vees or dragsters because of cavitation in engines seeing 6000+ RPM.  We put a filter on those engines, too.

As long as the sump plate is flat and the nuts are never over-torqued, the stock plate works fine.  I suppose a good billet plate would be less prone to warping than the stock stamped steel plate so it might be less prone to leaks.

I rub the high-temp silicone into the gasket material before I start.  By the time I assemble everything it's pretty much cured and doesn't stick to the metal parts.  I'm not trying to put a layer of flexible material on top of the gasket to create the seal.  If everything is clean and flat and tightened the correct amount the paper gaskets will seal it off just fine.  But over time oil soaks into the paper and it becomes a wick.  If you get the sump plate tight enough to stop the wicking, it warps the plate and then you have a REAL leak.  What I'm trying to do with the silicone is just close up the pores in the paper so it can't wick the oil from the sump to the outside of the engine.

Oh Yeah !    Volkswagen being frugal at heart counted every Mark. I think if they could have done away with the strainer and not cause a problem they would have done it. After all ,that strainer may have cost  VW 15 cents. Multiply that by a few million cars and you can see the money they could have saved. So I guess they thought it was important to install. Dang if I`m going to second guess them all the time.

In regards to the billet sump plate, another Vee racer put it to me best:  The factory plate may bend if it gets hit, but billet will shatter!