[T2] [VB] Hot engine

[david raistrick]

is that 12.5 a/f at WOT under load (climbing)?

three things I'd try that go against convention:

go leaner.  add timing advance.  use a thinner oil.


lean out that 1/2 throttle to WOT a/f - I'd be shooting for 13.5 or so and
only richen it if needs it  (not having to mess with the insanity of jet
combos, I'd even try to push it further toward 14.2 for testing...).
I'm assuming you're shooting for more like 16:1 below 1/2 throttle?  or
haven't even gotten to the point of optimizing that area yet?


be aware of where your o2 sensors are and if they get good exhaust flow.
 (sometimes they're tucked into a corner that can be stale).   I've got the
same VS exhaust and have heard people complain about the location of the
bungs....I didn't notice anything significant when I compared vs the
tailpipe, but ymmv.

add some timing advance.  -start- at the fully 32 total advance (for an
upright.  t4's are a different monster), assuming a stock cam.    only back
it down if you're detonating.     (or maybe add more fuel...)



you've probably done at least the boiled-water test on the head temp
sensor+gauge to be sure it has a sane baseline?



> vanes are not installed

that one can be a biggie and could directly relate to your head cooling,
since the vanes direct the air to the right places.     I've never done
back to back comparisons, so I'm just recycling wisdom but still.



I'm going to talk about oil pressure and cooling a bit - but you dont
mention the oil temps under load, so maybe they're not high.   I suspect we
dont get a ton of oil cooling in the heads, but the splashing around the
valve stems may still do a lot.

that said - you might try switching to a thicker or thinner weight oil to
raise or lower the oil pressure (easier than trying to swap springs
around).

if your pressure is to high at speed and temp, you be opening the relief
bypass and skipping the cooler.   Depending on where your external is
plugged in and how it's thermostated (if it gets flow off the pump directly
with it's own bypass, instead of using the case bypass) that might explain
why you saw some relief adding the external.

The whole oil cooling system is designed around the idea of regulating oil
pressure, NOT cooling.   temp change is a side effect of the operation.

some excerpts from my notes:
..
connoly says:
"We recommend 10psi/1k RPM as the benchmark, without exceeding 45psi hot
pressure (which causes overheating)."

"The system works backward from what you think. High pressure will increase
temps, low pressures cool it off. What you need to look at
is the condition where you are on the highway at 70mph, what is the
pressure? With the system the way it's supposed to be, if it's
under 45psi the cooler will be operational. If the pressure is above this,
the high pressure is viewed as "cold oil" and the cooler
is bypassed. So too much pressure will actually cause the cooler to be
inactive.
..


might try switching to a thinner oil as a quick non-invasive check.  as
long as the light isn't triggering at idle (2psi), you're fine.   - but
adding a cheap oil pressure gauge to check your 1k/2k/3k/4k pressures might
be helpful.   try 10-30 or 5-30 or something if you're running 20-50 or
10-40.


I'm not that far off from you gearing wise - I'm turning 3700rpm at 65
(4.12+1.26 big nut with .82 4th, but on 27" tires), but pushing it with a
7.3:1 CR (6.9:1 dynamic CR) carbed single port 1600.   but I've never
instrumented the heads.

...david

>