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Old July 19th 2018, 14:23
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owdlvr owdlvr is offline
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Join Date: Sep 2008
Location: Canada - West Coast
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Went down to Victoria BC for the VW show in mid-june. Hilariously, the Rally Bug won best late model beetle, even thought I hadn't really cleaned it. I only entered for the parking with group, but I'll take it!

The Rally Bug thanked me by dropping a valve seat on the way home. Sitting at a traffic light idling, and all of a sudden the valve train started making horrific noises. I pulled into the gas station next to the light, popped the 1/2 valve cover and found #2 intake with about 1/4" of play. Presumably I dropped the valve seat, and hadn't yet broken off the valve head...I mean, I would anticipate that a valve head makes a lot more noise! Truck and trailer were 2.5 hours away, so basically 8 hours round trip to get the truck and trailer, come back for the car and get home. Well, the head is garbage right? Readjusted the valve, considered the likely possibility of grenading the motor before getting home, and then decided to go for it! The last thing I did was to select a VERY rich tune, and lock out the tune so it wasn't reading the O2 sensor, just running off the map. It was rich enough to burn the eyes of my buddy behind me as we drove :P

After getting home at 8:30pm, I drained the oil and pulled the motor. Valve seat confirmed, don't know if I did any piston damage. Carnage photos tomorrow night once I pull the motor apart.

The next day...



Sadly, the piston got the kiss of death from the valve seat. That's my last set of forged German Mahle pistons. I have a new set of pistons and cylinders on the shelf, but they are cast units. Sad Panda. The new heads will be CNC ported and shaped, as my usual head guy who hand did this set isn't available in 2018. Since I will need to spec the combustion chamber size, I installed a new piston and cylinder and measured it all up. The cylinders are a slightly different length than my old ones, and the cylinder heads will be slightly different as well...so I'll have to do all new pushrods and valvetrain geometry on the rebuild.

If your valve train ever makes horrible noises, and you decide "I can limp it 2.5hrs home from Victoria", be sure you're making an educated decision. I knew the moment the seat dropped the head was garbage and the piston was likely done too, and so I figured it was worth the risk. Not sure if you can see the aluminum melted all around the valve seat from combustion gases escaping up the intake. It's in the parts washer tonight...will be clearer when clean.



Unfortunately my end play (crank movement forward and back) was out of spec. It wasn't a shim problem, the thrust bearing has pounded out the case .005". So tonight I tore the whole motor down to a bare case so it can head to the machine shop. That's a two and half hour job with cleaning 50% of the components, and measuring everything before disassembly so I know what's in spec and what needs to be replaced. It'll get new main bearings, new cam bearings and maybe new lifters...but everything else is in spec. I'm super, super tempted to switch to an aluminum case (vs magnesium)...but the $900usd is NOT in the budget. My engine building friend says they run hotter as well, so we'll repair the magnesium case.

New heads, new intakes, and new pushrods all ordered from CB Performance. Of course I CNC ported and matched everything, so it should be a little quicker out of the box once it's back together :P heh heh. You can't blow up parts and NOT upgrade!?!

-Dave
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'71 Type 1 - Rally Project
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'73 Type 1 - Proper Germanlook project
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