IAC Visits Andover
Posted: Sat Oct 11, 2008 8:22 pm
Part I:
Colin drove off into the darkness approximately 24 hours ago, so I've had some time to reflect on the Itinerant Air-Cooled session we shared.
The day started with Colin pointing out the prerequisites, namely my brake booster - laying in the driveway. I had taken the booster and master cylinder off to see if I could address the step-on-the-brakes-and-the-idle-goes-up issue I'd been having.
We went inside, got some coffee and started the session, reviewing my goals, going over the fundamentals of timing, dwell and the finer points of the design, care and feeding of hydraulic lifters. Colin corrected some invalid assumptions I had and proceeded to refine my understanding in other areas. The kitchen table session concluded with an overview of the PDSIT dual carb configuration on my bus with special attention paid to the central idle circuit.
With that, we went out to the garage to address the brakes. We replaced the round cross-section o-ring that sealed the master cylinder to the booster with the correct square-cut o-ring. We also used a thin layer of RTV on the booster as the mating surface had become pitted by rust. Once joined, Colin tested the assembled unit by playing it like some strange instrument right out of a Dr. Seuss story, determining that the booster was leaking along its perimeter where the two halves were joined. I put a rebuilt booster on the mental shopping list and we proceeded to install the unit as having brakes was deemed important.
Colin also took the opportunity to point out that my brake lever clevis pin was frozen solid with rust, brought out the PB Blaster and set things right with a thin smear of moly grease. We rolled the bus out in to the warm sunshine, bled the brakes and moved onto the valves.
I had done valve adjustments on solid-lifter VWs in the past (in fact my engine was a solid-lifter 1700 before having it rebuilt into a 2.0 with hydraulics), but I approached the hydraulic adjustment with a certain amount of trepidation. What if the lifters were air-bound? What was this magical "centering" of the lifters?
Colin reiterated the steps as outlined during our kitchen session, putting my concerns to rest and we proceeded to adjust the screws to 0 lash, then 1.5 turns in, watching to see that we were not pressing the valve stem inward. Given that this was the first valve adjustment after the rebuild (~300 miles ago), the NEXT adjustment was to be the baseline from which all future measurements were compared.
Next we moved on to the adjustment of the timing and found that we could not get the idle down to the correct level and the vacuum retard....wasn't. We pulled the distributor - and Colin observed that the distributor drive gear was a tooth or two off. It was at this point that Colin suggested for the first time that we should pull the gear and set it correctly. Understanding what you need to do if the washers slip, I quickly changed the subject :)
When the distributor checked out (advance plate movement was fine, vacuum can held from both the advance and retard sides), we popped it back in and Colin quickly deduced that it was the right-hand throttle link being too long causing the high idle.
I'll wrap this up tomorrow in Part II....
Colin drove off into the darkness approximately 24 hours ago, so I've had some time to reflect on the Itinerant Air-Cooled session we shared.
The day started with Colin pointing out the prerequisites, namely my brake booster - laying in the driveway. I had taken the booster and master cylinder off to see if I could address the step-on-the-brakes-and-the-idle-goes-up issue I'd been having.
We went inside, got some coffee and started the session, reviewing my goals, going over the fundamentals of timing, dwell and the finer points of the design, care and feeding of hydraulic lifters. Colin corrected some invalid assumptions I had and proceeded to refine my understanding in other areas. The kitchen table session concluded with an overview of the PDSIT dual carb configuration on my bus with special attention paid to the central idle circuit.
With that, we went out to the garage to address the brakes. We replaced the round cross-section o-ring that sealed the master cylinder to the booster with the correct square-cut o-ring. We also used a thin layer of RTV on the booster as the mating surface had become pitted by rust. Once joined, Colin tested the assembled unit by playing it like some strange instrument right out of a Dr. Seuss story, determining that the booster was leaking along its perimeter where the two halves were joined. I put a rebuilt booster on the mental shopping list and we proceeded to install the unit as having brakes was deemed important.
Colin also took the opportunity to point out that my brake lever clevis pin was frozen solid with rust, brought out the PB Blaster and set things right with a thin smear of moly grease. We rolled the bus out in to the warm sunshine, bled the brakes and moved onto the valves.
I had done valve adjustments on solid-lifter VWs in the past (in fact my engine was a solid-lifter 1700 before having it rebuilt into a 2.0 with hydraulics), but I approached the hydraulic adjustment with a certain amount of trepidation. What if the lifters were air-bound? What was this magical "centering" of the lifters?
Colin reiterated the steps as outlined during our kitchen session, putting my concerns to rest and we proceeded to adjust the screws to 0 lash, then 1.5 turns in, watching to see that we were not pressing the valve stem inward. Given that this was the first valve adjustment after the rebuild (~300 miles ago), the NEXT adjustment was to be the baseline from which all future measurements were compared.
Next we moved on to the adjustment of the timing and found that we could not get the idle down to the correct level and the vacuum retard....wasn't. We pulled the distributor - and Colin observed that the distributor drive gear was a tooth or two off. It was at this point that Colin suggested for the first time that we should pull the gear and set it correctly. Understanding what you need to do if the washers slip, I quickly changed the subject :)
When the distributor checked out (advance plate movement was fine, vacuum can held from both the advance and retard sides), we popped it back in and Colin quickly deduced that it was the right-hand throttle link being too long causing the high idle.
I'll wrap this up tomorrow in Part II....