Wednesday, November 22, 2006

AV - Selling Junk to the Kiddies

> I came across a really nice rebuild kit for the Volkswagen that includes Big Bore cylinders that don't require any machining. Have any of you heard of this? <


It's junk; a package assembled for the 'Kiddie Trade' -- technologically naive youngsters who don't know anything about VW engines.

Such kits typically come with standard-size bearings. The odds of finding standard-size bearings on any air-cooled VW in need of an overhaul is about the same as for finding lips on a chicken. In fact, most of the schlock shops that offer such kits don't even carry the full range of bearings. That's because the of the remarkably wide range of possible bearing combinations available for the VW engine. Since the crankcase usually needs to be align-bored to return the saddles of the main-bearings to true circles, the mains may be as much as +1.5mm larger in OD, graduated in 0.25mm steps. That's seven sizes assuming you start with STD. (The factory only allowed two over-sizes but at the insistance of after-market rebuilders, famous for their $300 'overhauls', have provided the additional over-sizes. In the same vein, the crankshaft probably needs to be turned & polished -- and probably already has, since the youngest Type I air-cooled VW engine sold in the States has to be at least 25 years old. Here again, while the factory -- which used to overhaul its own engines (and offered the same warranty as for a new engine) allowed only one under-size, after-market bearing manufacturers offer under-size mains all the way down to -1.0mm. That's five ID's. Then you've got the thrust face on the #1, which you can get in up to three different combinations, plus STD. Seven OD's plus five ID's plus four Thrust Flanges gives you one hundred and forty possible main-bearing combinations for a used VW engine and we haven't even gotten to the rods. And the dingalings at Jaysie Whipme sell the kiddies a set of STD/STD bearings with their famous 'rebuild kits.'

The 87mm barrels are called 'slip-in' Big Bores because they fit the same spigot bores as the stock jugs. Trouble is, the over-boring results in a sealing surface that is so narrow it's impossible to maintain a reliable seal between the barrel and the cylinder.

Then they offer the kiddies a set of valve guides.

Have you any idea in the blue-eyed world how many mechanics are even qualified to replace VW guides? They are a shrink fit in the aluminum heads and the spec calls for a 500 degree differential.

To remove the old guides you core-drill them then heat the heads to 350 degrees and drive them out. If the bores will accept a new guide it is put to soak in a slurry of dry ice and 100% alcohol, which lowers the temp of the guides to about -120 F. then heat the heads to about 350 F and -- assuming you have the right tools & jigs -- drive the chilled new guides into the hot aluminum heads. But the schlock shops don't do that. They simply hit them with a chatter gun. That galls the bores as the guides come out and splits the guide-boss when the new guides go in; no big deal since their typical customer wouldn't recognize a good head if it walked up and pee'd on his leg.

But the best part of the joke is that the typical 'overhaul kit' costs more than buying the parts individually!

Such kits are enormously popular, of course. Which helps explain why a sturdy,well designed little engine acquired such a terrible reputation for reliability.


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