GWB: Top End Refresh

ARCHIVE- GWB Top End Refresh

• Don
• Mon 18th June 2007, 8:12 am

In the beginning...

After the last breakdown, I decided it was time to do a top-end refresh. Goals were:

• Remove heads to fix stripped studs


• Hone cylinders


• Re-ring pistons


• Inspect heads and case for cracks and such

So the decision at this point was whether or not to drop the engine. I decided to leave it in the bus.

I pulled off the carbs and intakes, fan shroud, and tinwork. Dropped the exhaust system and removed the bumper (for ease of accessing the muffler bolts).

Heads

Pulling the heads was a breeze! The only hiccup was the right head had to go down out of the engine compartment instead of up. Big deal.

For this project I picked up a cheapo craptastic 120v 70a arc welder for $80 from Pep Boys. The idea was to weld nuts to the snapped studs to get them out. After much fumbling and one garage fire (!) I got the job done:

(The holes are from trying to drill it out... The steel those studs are made from is HARD!)

I pulled they cylinders off next. Checked for out-of-round (no issue there) and honed them. Then I got one of my new 94mm 2.0 piston rings. Put it inside the cylinder to check gap... It overlapped! Huh?

2.0 Rings by Cofap

A quick micrometer check showed I have 93mm 1800 pistons and cylinders, not 94`s.

Work came to a screeching halt.

I ordered a set of 93mm 1800 rings and got them a couple days later. Work resumed the next weekend.

Inbetween here somewhere I decided to paint my pushrod tubes. Not for looks (nobody but me will see `em), but because I want to easily see and trace any oil leaks I develop. I soaked them in parts dip 12 hours, rinsed them, then hit them with a wire wheel. There was some surface rust on them that needed to be cleaned off.

I then primered them with white Rustoleum, and painted them the next day with white Rustoleum Professional. Not as smooth or shiny as other paints, but the "professional" line has proven itself to me as a tough paint for rattle can...

A few surprises awaited me during the head inspection.

First, one of the heads had a slightly sunk valve and a welded crack:

It seems to me that the sunk valve MAY be from the repair, and the seat is just a bit lower than it should be. If so that`s great. But I`ll be watching that valve closely...

The other surprise was a head gasket:

I`ve no idea just how that happened. It`s like the gasket was sucked into the combustion chamber. A couple mm`s of the gasket are missing, presumably shot out the exhaust long ago.

Pistons and Cylinders

I decided to do away with head gaskets altogether. As has been discussed ad nauseum, the VW factory instructed its dealers and rebuilders to NOT use a head gasket, instead lapping the cylinders to the heads and using shims at the bottoms of the cylinders. So I did the same.

Nice thing about the Victor Reinz gasket sets, is they come with both head gaskets and barrel shims. So I could be prepared regardless of my decision.

I cleaned up the cylinders, checked of out of round (less than .2mm at the biggest difference... looks good to me), honed them to remove the glaze present in the cylinders, lapped them to the heads, and set them aside.

The piston rings were all chrome rings, shiny and in excellent condition. The gaps were even well within specs. However, one ring was snapped: The #4 bottom compression ring. I have no idea how that ring could just break, but it happens to be on the same cylinder as the sucked in headgasket. So all bets are off there...

Using the broken pieces of the old ring and a soft brass wire brush, I cleaned out the piston grooves. Only that one piston had anything in the groves to speak of and needed use of the ring. The rest just needed some light brushing and carb cleaner.

Installing the new rings was kind of a PITA with the pistons still attached to the rods, and the engine still in the bus. Took an extra 2-3 minutes per piston in this condition. So again, no big deal. I forced oil into the ring grooves and smeared it around the pistons, especially on the skirts. Did the same to the cylinders, and using a steel band style ring compressor got the cylinders over the pistons. Smooth as silk, once I realized I should wipe the oil off the compressor BEFORE putting the ViceGrips on it... heh.

I got the heads back on and cross-torqued them. This involves torquing opposite studs. Example: forward center bottom stud on the right, forward center bottom stud on the left. Rear corner top stud on the right, rear corner top stud on the left. The theory is that it reduces strain on the case and helps the studs stay torqued. The heads will be retorqued again when I`m ready to begin reassembly of the valve train. This is a week later, so the heads, cylinders, and case should have had a good chance to settle. This should avoid the necessity of retorquing the heads a few hundred miles down the road.

In the meantime, I pulled the top of the right hand carb off. The symptoms of my last breakdown were fuel starvation, but fuel is flowing smoothly from the tank, through the filter, and out of the fuel pump. So the problem MUST be in the carbs.

Here`s what I found:

Obviously, I`ll be tearing the left carb down as well, just to make sure those chunks of rubber aren`t in both carbs.

Jets (per markings):

Right Carb

• x127.5


• 140

This is where I`m at today, January 20, 2006. Tomorrow I get to see if I can`t finish...