Itinerant Air-Cooled

Ya'll,

I have had this Vanagon for a year or so now. It is camping season, and not having a bus to cruise finally got to me. Anyways, here is the run down. Last year, Colin and I did a quick diagnosis. and decided the engine had to come out to get a better idea. The engine would run, but there was some serious pre-ignition causing backfiring through intake manifold. Fast forward to a week ago. I pulled the engine, and started disassembly. When I took the heads off, I noticed they were stamped T.A.E? I still have not tracked down their origin. Every single other part on the engine was OG VW. I remembered Colin's many speeches about reuse the OG parts because the aftermarket stuff is crap, so that's what I did. I took the engine down to the short block, disassembled the heads, and found that 2 valves were so tight in their guides that there was no way they could open and close correctly, hold and adjustment, or let the lifters pump up correctly. We reamed out the guides ever so slightly to get a, "close to proper", clearance on the valve stems. I then lapped new stainless steel valves in, and cleaned up the rest of the engine and reassembled. The tin was the tightest fitting I have ever assembled. Nothing is missing, and It Is completely sealed. I reinstalled the engine today, and will start it up tomorrow. More to come. Here are some pics of the project in the meantime.

Scottie





OG Mahle Pistons and Cylinders.






This last pic is of the various rocker assemblies that were installed. I now have all matching, correct rocker assemblies in place.

Today was engine start day. It hit a few times, but no vroom. Battery was weak, and is charging now. I static timed it at 7.5 BTDC. I adjusted the hydraulic lifters on the stand before install. Before the rebuild, I had no problem turning the engine with a ratchet and socket on the fan hub. Now, this engine has so much compression its damn near impossible to turn by hand with the plugs in. Does anyone have a trick for turning the engine to adjust valves without taking the plugs out? Its a very tight fit on the rear of a vanagon with all the tin in place.

Scottie

Tight fit to get the plugs out? Or tight fit to get the wrench on the alternator nut? I don't like to use the fan hub nuts, and their torque is far more picky than the alternator nut. I don't remember if I could get to the alternator nut or not, now that I think about it. But you could chalk the front wheels, lift one rear wheel off the ground, put the car in 4th, and slowly spin the raised wheel to turn the crankshaft.

Or there might be a better way, but I'm not aware of it.

Congrats on finding the issues and getting everything buttoned up, by the way!

Robbie

The valve margin on your exhaust valves looks to be somewhat excessive.

Turning the engine by the fan hub nut isn't the best idea. I generally just grap the fan pulley by hand and turn it a little bit at a time, or use finger pressure on the alternator pulley fan. Socket on the alternator pulley works too, but there is less room to do that in a Vanagon with the fresh air scroll and boot in the way.

Tight fit to get wrench on the hub. I'll raise the rear wheels. Great idea, thanks.

Scottie

SlowLane wrote:The valve margin on your exhaust valves looks to be somewhat excessive.

Turning the engine by the fan hub nut isn't the best idea. I generally just grap the fan pulley by hand and turn it a little bit at a time, or use finger pressure on the alternator pulley fan. Socket on the alternator pulley works too, but there is less room to do that in a Vanagon with the fresh air scroll and boot in the way.

That's was my first set of heads I've did myself. Could you elaborate more on the excessive valve margin? I did the mineral spirit test in the intake and exhaust. They were sealed tight, no leaks.

Scottie

Compare the exhaust valve seat shiney area vs the intake seat shiney area. The exhaust seat contact area is too big and should be smaller like the intake seat. This is why when rebuilding heads they use several cutting tools to set up the correct margin size. 3 angle cut is the term you hear thrown about but its to keep the actual seat contact area a certain size for flow and heat control.
On the valve, there is the seat, which again is the part that contacts the head and is usually accompanied by a back cut. The margin is the small area between the seat and face of the valve aiming into the chamber. Use Prussian Blue to check your work and see if each valve is sealing and contact is correct.

You have also use a wirebrush to clean the combustion chambers? If you have now you should lap the cylinders into the heads to get a seal there. Again use valve lapping compound (fine) and rotate the cylinder back and forth into the head. Clean it and check your work with Prussian Blue. This is because you aren't going to use the head gaskets as VW tossed that from the rebuilding process.

energyturtle wrote: That's was my first set of heads I've did myself. Could you elaborate more on the excessive valve margin? I did the mineral spirit test in the intake and exhaust. They were sealed tight, no leaks.

Gotta Bentley for your Vanagon? Check pages 15.4 & 15.5 for a good pictorial explanation with acceptable ranges of valve margin (ie. the contact width between the valve and the seat faces).

SlowLane wrote:

energyturtle wrote: That's was my first set of heads I've did myself. Could you elaborate more on the excessive valve margin? I did the mineral spirit test in the intake and exhaust. They were sealed tight, no leaks.

Gotta Bentley for your Vanagon? Check pages 15.4 & 15.5 for a good pictorial explanation with acceptable ranges of valve margin (ie. the contact width between the valve and the seat faces).

No Vanagon Bentley. I do have the baywindow Bentley though, and the Wilson book. Thanks a ton. I'll study up tomorrow.

energyturtle wrote:

SlowLane wrote:

energyturtle wrote: That's was my first set of heads I've did myself. Could you elaborate more on the excessive valve margin? I did the mineral spirit test in the intake and exhaust. They were sealed tight, no leaks.

Gotta Bentley for your Vanagon? Check pages 15.4 & 15.5 for a good pictorial explanation with acceptable ranges of valve margin (ie. the contact width between the valve and the seat faces).

No Vanagon Bentley. I do have the baywindow Bentley though, and the Wilson book. Thanks a ton. I'll study up tomorrow.

I'm sure the Bay Window Bentley will have the same information. Still regretting giving away my copy when I sold my '71. The Bay Bentley was a delightfully concise piece of work compared to the massive hodge-podge of information that is the Vanagon Bentley.

"Margin" is actually the measurement of how much thickness exists at the edge of the valve face.
"Contact width" is contact width between the seat and the valve.
Exhaust contact width should be 2.5 to 3 mm, intakes really need to be less, like 2.2mm to avoid carbon pitting.
Colin

Amskeptic wrote:"Margin" is actually the measurement of how much thickness exists at the edge of the valve face.
"Contact width" is contact width between the seat and the valve.
Exhaust contact width should be 2.5 to 3 mm, intakes really need to be less, like 2.2mm to avoid carbon pitting.
Colin

Oops, that's what I get for acting like I knew what I was talking about. Revelation of hubris is always so humbling.

Anyhoo, just for what it's worth, the Vanagon Bentley specifies:
1.8-2.2 mm valve seat width (aka. contact width) for the intake valve
2.0-2.5 mm valve seat width for the exhaust valve

As I understand it, the exhaust contact width controls the rate of heat transfer from the exhaust valve to the valve seat (and thus the head itself). Too wide a contact causes the valve to run colder than designed, and I guess also causes higher head temperatures?

The engine itself runs well. 146-150 psi across the board. Here's my issue as of now. I had adjusted the AFM wiper only to compensate for the sick engine prior to the top end build. It will run, but has extremely poor throttle response (it takes more time to rev through the throttle range than it should). I reset the valves, gapped the points, static timed at 7.5 BTDC. Dwell is 44 at 3200 RPM. It will not rev past 3400 RPM? It will idle as soon as the engine starts, but after it holds throttle, it decelerates and stumbles to idle, then dies. I have also got a nasty intermittent backfire through the intake. It seems to be coming from the EGR block off? I blocked it off with the original gasket and a piece of a coke can. (Don't judge, its all I had:)! When I blocked it off, I disconnected the EGR pipe from its intake at the plenum, is this correct?

Scottie

energyturtle wrote:It seems to be coming from the EGR block off? I blocked it off with the original gasket and a piece of a coke can.

Did you sandwich the Coke can piece between the EGR valve body and the gasket? If so, the valve bobbin may have poked a hole in the thin aluminum. The bobbin sticks out from the mounting plane of the valve body.

If you just used a piece of Coke can for a blocking plate, well, that probably isn't going to work for very long, if at all.

I'm not sure about the EGR, but backfires mixed with low power just screams "mixed plug wire order."

Intake backfires typically occur when combustion occurs with the intake valve open, or the exhaust valve doesn't let the charge out before allowing the next cycle to start.

1-4-3-2?
Robbie