[T2] Power loss in 4th

[jules]

If the bus is mechanically sound this issue is either environmental or
behavioral.

Oil temp/pressure won't give you a good reading on head temps - they are
good for trending the overall engine temp but you're clearly overheating at
your heads (as evident from the stretching valves/sinking seat) - the heads
can heat up to dangerous temps before that increase is reflected in higher
oil temps.

If you're trying to drive up hills in 4th under 3000 RPM you're lugging
your engine - and that will cause overheating, doubt you'll find much
argument there. Also the 1600sp is a small engine for a heavy bus. How fast
are you driving on those long highway runs? Maybe you just need to slow
down a bit - drag increases pretty rapidly after 55mph - and that little
engine is working really hard in 4th going up the hill with all that wind
resistance, etc... power loss can be a symptom of overheated engine...
anyway, that's all I have to offer on the subject based on personal
experiences. Couldn't hurt to try changing behavior a bit and see what
happens...

i can say without a doubt that the [permanant] damage i've personally done
to aircooled engines was by my own behavior which caused resulting
mechanical failure -  not by pure mechanical failures alone. If you're
overheating at your heads and continue to drive in the same manner without
changing _something_ you _will_ eventually drop one of those valves into
the #3 combustion chamber... sorry not trying to be negative - just trying
to alert you of impending failure (ask me how I know) so that you may
change course before it's too late

jules
'75, '78 westies
troy NY


On Tue, Oct 13, 2015 at 5:10 PM, Avocado Tom Tarka <avocadotom at gmail.com>
wrote:

> Jules,
>
> Have read all the docs you cite.  Engine is otherwise well tuned, carb
> adjusted per Bentley, starts easily, timing and dwell to spec.  Cooling tin
> is all in place.
>
> Agree in theory on the 009 but there's also evidence that operation above
> 3200 RPM has diminishing returns in terms of the engine fan speed not
> offsetting the additional heat generated by the engine - at least in terms
> of long highway runs. See Eric and Barb's extensive writing on the topic,
> as well as the research that Clara on the vintage bus list has done.
>
> I've been tracking engine temperature closely through oil temps and (by
> proxy) pressure.  Temp is good around town but creeps up on long highway
> runs, particularly on grades. I suspect that fuel starvation is impacting
> engine temperature, it's just a matter of figuring out the cause.
>
> Thanks for taking the time to respond.
>
> Cheers,
>    Tom
>
> ----
>  "We are MoTown. We are professionals. We're here to get the job done."
>
> On Oct 13, 2015, at 4:30 PM, jules <jules.herr at gmail.com> wrote:
>
> Tightening valves are certainly a sign of overheating. Usually it's the
> exhaust - not the intake - but not a good sign either way.
>
> Back when I had a 1600 powered bus, after rebuilding it once by the side
> of the road in nowhere nebraska, I'd try to never let my rpms drop below
> 3000, especially under load - and especially with the 009 - which doesn't
> give the the extra 'kick' of the added few degrees of vacuum advance you'd
> get (and really need) under load. The engine is cutting out at 2500? you
> know how the old joke goes right... Don't let it drop to 2500.
>
> sounds like you've got a multitude of issues. overheating almost certainly
> is one. Some of it's cause may be mechanically derived. Does the engine die
> at idle, too? Some may be remediable by changing driving habits.
>
> from the type2 library:
> http://type2.com/library/cooling/coolsami.htm
>
> more general resources:
> http://www.vw-resource.com/overheating.html#keep
>
>
> Start dropping below 3000 under load with the 009 - downshift.
>
> and
>
> Making sure you've got all the cooling parts in place NEVER hurts. Look
> for obstruction to the cooling airflow (blocking the cool air intake in the
> front of the doghouse. Check for vacuum leaks. Check the float and needle
> valve. Adjust your behavior as necessary.
>
> good luck
> jules
> '75, '78 westies
> troy ny
>
>
>
>
> On Tue, Oct 13, 2015 at 3:16 PM, Avocado Tom Tarka <avocadotom at gmail.com>
> wrote:
>
>> Jules,
>>
>> I'm starting at 3300 rpm and losing power and therefore RPMs. The engine
>> starts cutting out around ~2500, which is about where I'd be shifting
>> anyway, as it corresponds to roughly 3900 in 3rd (coming from 4th), or 4100
>> in 2nd.
>>
>> The valves were adjusted that morning. Both #3 valves were tight, perhaps
>> unsurprisingly.  That's been the trend for the last 2 or 3 adjustments, and
>> I've been checking them frequently.
>>
>> Woot!
>>    Tom
>>
>> ----
>>  "We are MoTown. We are professionals. We're here to get the job done."
>>
>> On Oct 13, 2015, at 12:47 PM, jules <jules.herr at gmail.com> wrote:
>>
>>
>>
>> On Mon, Oct 12, 2015 at 1:24 PM, Avocado Tom Tarka <avocadotom at gmail.com>
>> wrote:
>>
>>> Hi volks,
>>> - only happens when going uphill, particularly with steep grades
>>> - happens primarily in 4th but may just be RPM related: it seems to
>>> occur below ~2500 rpm (just noticed it in 3rd)
>>>
>>
>> sounds like you're lugging the engine. 4th gear 2500 rpm UPhill in 4th in
>> a 1600 sp? Sounds like a recipe for engine overheating to me. You've got to
>> keep the RPMs up to keep the fan moving - especially critical under load
>> (going uphill in 4th).
>>
>> When is the last time you adjusted the valves? Are they getting tighter
>> in time or looser? Valve that are constantly getting tighter at each
>> adjustment are an indicator of overheating at the head.
>>
>>
>>> - hear ticking sound from carb after stopping to cool down (like a
>>> wind-up kitchen timer ticks)
>>
>> - watched fuel getting sucked through pre-carb filter after stopping to
>>> cool down
>>>
>>
>> sounds to me like the needle valve in the carb isn't closing fully -
>> could be the float has a leak and is taking on fuel, or the valve itself
>> needs cleaning/replacement.  An Easy way to check - after a long run - stop
>> engine - disconnect or clamp off fuel supply to the carb. wait 15 minutes,
>> open the carb and see if it's full or drained down. (always have fire
>> suppression means available when working with fuel system ESPECIALLY near a
>> hot engine)
>>
>>
>>
>>> Bus also seems to be trending towards overheating when the power loss
>>> occurs. Not sure if that's related.
>>>
>>>
>> Well sure, if you're running uphill in 4th at 2500 RPM then you're
>> creating the overheating situation - that's probably directly related to
>> your power issues.  Try running those uphills in 3rd at around 4000 rpm
>> instead.
>>
>>
>> Good luck~
>> jules
>> '75 '78 westies
>> troy ny
>>
>>
>