Hi hoser,
According to my figures the static compression will be about 164 psi. The compression
ratio has been changed to 12.45:1 from 11.3:1. The indicated hp @ 7500 is 49.02 at the
crank (up from 43.9). The octane requirement is 91, minimum.
These figures are taken from the built in BMEP database within the computer program.
Actual power is most likely higher, especially since the engine is fitted with an
efficient tuned exhaust pipe and free flowing air cleaner and inlet port. The program puts
this modified engine at 108 BMEP psi. If that number is changed to 120 (pipe, carb, air
cleaner, porting) the power climbs to 54.3 @ 7500. It takes a real dynamometer test to
reveal the actual BMEP number. If you ever get a chance to put your Pilot on a chassis
dyno, do it. It's fast, painless and relatively inexpensive. I'd like to know what the
actual BMEP is. The number is good for engine modeling purposes.
The head was off by .005". It's a wonder that it sealed in the coolant.
Probe placement has such an impact upon the temperature indicated (if it's too close to
the piston it reads low, if it's too far from the piston it reads high). Not long ago I
jetted a Banshee and found it's peak at only 1050 degrees - it's probes were a little to
close to the piston. A plug chop verified it. If I tried to tune it for 1200 or 1250
degrees it would have melted down. Every engine is different. Your modified Pilot engine
will inherently create a little more heat due to the increased compression ratio. I
wouldn't be surprised if the EGT went up by 75 to 90 degrees from the recent
modifications. If you were running a little rich before, you may not have to do very much
jetting.
To verify the EGT readings, perform a plug chop. It's best to look at the plug very
carefully to determine the maximum exhaust temperature you can use. In some cases it may
be well over 1200 degrees or more. You need to find the maximum safe temperature you can
run. When the engine is under load and held at wide open throttle for about 1/4 to 1/2
mile, a new properly gapped plug will look light tan to light-medium gray on the
insulator. As always start with a larger jet than you will probably need and perform your
plug chop. When the first one is done, toss the plug and start with a fresh one after you
change the jet.
OK, I'm not going to install the old reeds on the freshly lapped reed cage. You can
install the new reeds on the modified cage when you get them. If you get a chance, radius
the edges of the new reeds using 600 grit wet/dry paper. The idea is to remove the sharp
edges - just at the edge though - be careful not to sand the sealing surface.
The roof angles of the transfer ports were flattened by
several degrees - (power band widening and boosting peak power). The boost port
was opened a bit in the area where it feeds only (mid range). The front
transfer ports were widened and their aim was brought back toward the rear wall
(mid range and top end). The exhaust port was opened to just under 70% of bore
width (top end). The compression ratio change (head work) adds power
everywhere, though it's probably noticed the most in the low to mid range.
Above the blue arrows are showing the areas where the ports were enlarged.
Above blue arrows show where the reed cage was modified.
Exhaust manifold was matched to the exhaust port on the cylinder and then polished.
Above the exhaust port was reshaped and polished.
