There's no factual evidence that deep sumps cool the oil any better than stock. They were designed for drag racing to reduce the friction of the crank turning in an oil bath by dropping the oil below the crank circumference.
Read what Bob Hoover says about deep sumps. You've never heard of Bob Hoover? It's worth an hour or so of your time. http://bobhooversblog.blogspot.co.uk/2006/
"Deep Sump
Is it a good idea to put one of those larger oil-sump deals on your bus? It sounds like a really good idea, but is there some technical reasons that it would be harmful?
I've never seen a deep sump that didn't leak, apparently because the sump-plate studs -- even when replaced with longer units -- were never meant to carry such a load.
Reduced ground clearance, while never a problem on the drag strip, can cost you an engine in daily driving. I've seen several crankcases with chunks knocked out of them as a result of hitting something with the attached (and quickly detached) deep sump. I've also seen a couple of engines lost when the oil pick-up extension came adrift, started sucking air.
With a filled deep-sump, the oil takes forever to warm-up. And of course you have to keep the thing filled if you want your dip-stick to work
Drag-racing, we ran the engine with the minimum of oil, pouring in fresh for each run. It never showed up on the dip-stick because the dip-stick does not extend into the deep sump.
We used to call these things the 'Poor Man's Dry Sump'. Getting the liquid oil out of the crankcase gave us extra rpm, always important when you're trying to catch a clock. For roundy-round, rallys and road courses, we had a better results -- and less expense -- using a windage tray and fabricating extenders for the push-rod tubes. Running at speed, we thought the deeper sump would keep the oil from pooling-up out in the head... and maybe it did, for a few seconds. Fact is, running at speed the extra capacity of the deep sump doesn't mean squat -- we just ended up with an extra quart of oil in the outside head. Live and learn
I thought the added surface area of the deeply finned (and properly fabricated sumps, such as the one Gene Berg made) would result in cooler oil temps. It didn't. The oil took longer to come up to normal operating temperature but once there, it was about as hot as before. Apparently the oil cooler is about twenty times as effective at cooling the oil as any form of sump --- you'd need about five times the surface area of the typical deep-sump before you saw an appreciable drop in your engine's oil temp. There's bound to be some variation here. I'm talking about using a deep-sump in California. Veedubers in Finland probably swear by the things
All of the guys who claimed miraculously low oil temps after bolting on a deep-sump usually had chromed valve covers, chromed push-rod tubes, no thermostat and so on -- they were already running near the red-line before they bolted the thing on -- and most of their claims were based on only a few minutes of run-time -- the extra oil hadn't even warmed up yet.
Deep sumps are suicide off-pavement... or on-pavement for that matter, if you have to negotiate the occasional rough alley or railroad track.
Deep sumps tend to get in the way when you need to drop your engine, forcing you to raise the vehicle higher (bugs) to clear the rear apron and to use a different scooter (buses).
Finally, most of the deep sumps I've seen were very poorly made, the exception being the ones Gene Berg used to sell (I've not seen his most recent offering but I understand it's aluminum. It used to be magnesium and beautifully made, too.) The deep sumps sold locally are bubble-packed crap, cast in Taiwan and have casting inclusions and lots of CASTING SAND RESIDUE. (Someone on the Type2 List... [Thom?] ran into this problem.) It would be suicide to bolt such a thing on an engine.
The bottom line? Deep sumps first appeared on the drag strip. Kiddies bolt them on because they can and because they look kewl and because all the tits & ass VW magazines say it's the thing to do. I ran them on the strip but found them impractical on the road, sought other -- more effective -- solutions.
Your engine, your decision.
Want to increase your oil capacity? Add a full-flow oil filtration system. The big FRAM PH-8A canister holds nearly a quart of oil, the hoses about half a pint.
-Bob Hoover
-1995"
