Larry:
Cooler air has greater density compared to hotter air. Therefor, with
cooler air, you get a greater charge of air (which includes a greater =
oxygen
content) into the engine during the intake stroke resulting in greater =
power
output.
Paul Bartz
From: Larry & Kaye Kepple [mailto:kepple]
Sent: Tuesday, May 11, 1999 2:43 PM
Subject: GMC: Air Cleaner Experience
My experience with my air cleaner may help some of you guys. I have a =
73 GMC
26'. I was getting poor gas mileage and so I got my carb. rebuilt by
Cinnabar. Didn't really change the power or gas mileage, which usually =
was
about 6 to 6 =BD mpg (but I am glad I had it done to minimize possible =
damage
to exhaust manifold gaskets). So then I had it power tuned (timed =
while
driving with full throttle). During the testing I thought I noticed a
considerable improvement. Of course the air cleaner was off during the
power tune. But when I tried it out with the air cleaner back on the
performance was lousy. My rig had an HEI conversion by the previous =
owner
and they had removed and reshaped a small part of the air cleaner =
cannister
to make room for the bigger HEI distributor. They had done a nice job =
but
the ignition wires were crammed next to the distributor and the wires =
were
old. So I thought the ignition might be getting shorted on the =
cannister.
So I installed a set of high temperature wires but this didn't help =
either.
I changed the air cleaner recently and hadn't driven much so I was sure =
that
wasn't the problem. At this point I was sure this thing was simply =
starving
for air. I have a hill that I performance test on. With the air =
cleaner
and cannister installed I could only go up the hill at 52 to 57 MPH, =
but
with the cannister removed or with the cover off I would go up the hill =
at a
respectable 63 MPH.
I discussed the problem with Wes Caughlin at Cinnabar and he suggested =
I get
a junk yard air cleaner from a Toronado or Cadillac with HEI ignition. =
A
local mechanic wanted to try an after market air cleaner but I would =
lose
the thermostatically controlled inlet and Wes convinced me that sooner =
or
later I would be in cold weather conditions where it would be needed. =
The
local mechanic also mentioned I could drill holes in the sides of the
cannister as a compromise solution. I talked to Jim Bounds too. =
Mentioned I
was going to maybe cut holes and he thought it was worth a try. So I
drilled ten 5/16" holes on the side of the cannister generally opposite =
the
intake and on the side that was truncated by the distributor. Then I =
tried
it on the hill. However I could immediately tell it wasn't working and =
I
only went 52 MPH up the hill. But then I remembered I had screwed the =
wing
nut on the cannister cover tighter than normal. That's when it finally
occurred to me that the air restriction was caused by inadequate air =
space
between the air cleaner and the carb. throat.
Some previous owner had sort of flattened the cover and the tighter I
twisted the wing nut the worse it ran. However I only had about =BD"
clearance from the wing nut stud to the bottom of the plywood floor =
panel (
this rig was #29 to be built). So rather than mess with my cannister =
which
now had a bunch of holes in it I went to the junk yards and finally =
found
one from a 79 Toronado with a 403 (mines a 455) but it seemed to fit =
and had
same intake dimensions. But now the plywood cover wouldn't close. But =
I
respectfully decided not to simply bend the cover down as had been done
before. Instead I routed about 5/8" from the plywood cover just above =
the
air cleaner..
When I tested it on the hill I got 60 MPH, still 3 MPH below what I =
could
get without the cannister (or cover) but at least I felt this was =
probably
normal. But I wasn't satisfied. I had read where some of you were =
thinking
about adding a dryer hose to the intake to get some ram air effect. I =
also
read where cooler air rather than engine air could be a power =
advantage. So
I made an intake extension out to the grill using 4" thin walled =
aluminum
dryer pipe. I started with a 4 x 3 reducer then three sectional
(adjustable) elbows and finally a 15" straight length which got me to =
the
grill. I covered the end with =BC" hardware cloth (wire). All sections =
of
pipe and fittings are secured with two pop rivets. The routing was =
along the
outside of the vertical frame support brackets (bars) and then back to =
the
side of the radiator just above the air compressor about 6". Really =
doesn't
look too funky. I supported at radiator and near air cleaner intake. =
Also I
made a pipe clamp to attach to air cleaner intake that is easily =
removeable.
Then I tried the hill again. It went 62 MPH in repeated trials. One =
MPH
below the record without an air cleaner. I tried it several times =
again the
next day with slightly different results, both with and without the ram =
air
tube and with the air cleaner removed.
Results are as follows:
Air cleaner cover removed 63-63.5MPH (direct flow to carb. with no air
filtration at all)
Air cleaner and cover in place 60-63 MPH (standard configuration)
Air cleaner in place plus extended intake to grill 62-63 MPH
I can't really be sure the intake extension is helping. Maybe just a =
teeny
bit. I did notice that even with the new cannister I could still =
decrease
performance about 1MPH just by screwing down the wing nut an extra 1 & =
=BD
turns. I believe the available area just above the carb. intake is =
very
critical. In any case I think this problem is behind me.
Hopefully my gas mileage will improve. I will let you know.
If you have any doubts about your air cleaner cover restricting air I
suggest you make a comparison test with the cover temporarily removed =
on a
nice clean road. Its too soon to say whether the intake extension is a =
good
deal but I am glad I added it. If anybody out there could explain the
benefits of the cooler outside air to the engine I would appreciate =
hearing
about it. Is it simply because there is more oxygen molecules in =
cooler
air? At highway speeds the intake air at the grill may not be that =
much
lower than at the front of the engine where air cleaner normal intake =
is. I
might check the temperature difference if someone can tell me something
specific about the cooler temp.benefits.
Cooler air has greater density compared to hotter air. Therefor, with
cooler air, you get a greater charge of air (which includes a greater =
oxygen
content) into the engine during the intake stroke resulting in greater =
power
output.
Paul Bartz
From: Larry & Kaye Kepple [mailto:kepple]
Sent: Tuesday, May 11, 1999 2:43 PM
Subject: GMC: Air Cleaner Experience
My experience with my air cleaner may help some of you guys. I have a =
73 GMC
26'. I was getting poor gas mileage and so I got my carb. rebuilt by
Cinnabar. Didn't really change the power or gas mileage, which usually =
was
about 6 to 6 =BD mpg (but I am glad I had it done to minimize possible =
damage
to exhaust manifold gaskets). So then I had it power tuned (timed =
while
driving with full throttle). During the testing I thought I noticed a
considerable improvement. Of course the air cleaner was off during the
power tune. But when I tried it out with the air cleaner back on the
performance was lousy. My rig had an HEI conversion by the previous =
owner
and they had removed and reshaped a small part of the air cleaner =
cannister
to make room for the bigger HEI distributor. They had done a nice job =
but
the ignition wires were crammed next to the distributor and the wires =
were
old. So I thought the ignition might be getting shorted on the =
cannister.
So I installed a set of high temperature wires but this didn't help =
either.
I changed the air cleaner recently and hadn't driven much so I was sure =
that
wasn't the problem. At this point I was sure this thing was simply =
starving
for air. I have a hill that I performance test on. With the air =
cleaner
and cannister installed I could only go up the hill at 52 to 57 MPH, =
but
with the cannister removed or with the cover off I would go up the hill =
at a
respectable 63 MPH.
I discussed the problem with Wes Caughlin at Cinnabar and he suggested =
I get
a junk yard air cleaner from a Toronado or Cadillac with HEI ignition. =
A
local mechanic wanted to try an after market air cleaner but I would =
lose
the thermostatically controlled inlet and Wes convinced me that sooner =
or
later I would be in cold weather conditions where it would be needed. =
The
local mechanic also mentioned I could drill holes in the sides of the
cannister as a compromise solution. I talked to Jim Bounds too. =
Mentioned I
was going to maybe cut holes and he thought it was worth a try. So I
drilled ten 5/16" holes on the side of the cannister generally opposite =
the
intake and on the side that was truncated by the distributor. Then I =
tried
it on the hill. However I could immediately tell it wasn't working and =
I
only went 52 MPH up the hill. But then I remembered I had screwed the =
wing
nut on the cannister cover tighter than normal. That's when it finally
occurred to me that the air restriction was caused by inadequate air =
space
between the air cleaner and the carb. throat.
Some previous owner had sort of flattened the cover and the tighter I
twisted the wing nut the worse it ran. However I only had about =BD"
clearance from the wing nut stud to the bottom of the plywood floor =
panel (
this rig was #29 to be built). So rather than mess with my cannister =
which
now had a bunch of holes in it I went to the junk yards and finally =
found
one from a 79 Toronado with a 403 (mines a 455) but it seemed to fit =
and had
same intake dimensions. But now the plywood cover wouldn't close. But =
I
respectfully decided not to simply bend the cover down as had been done
before. Instead I routed about 5/8" from the plywood cover just above =
the
air cleaner..
When I tested it on the hill I got 60 MPH, still 3 MPH below what I =
could
get without the cannister (or cover) but at least I felt this was =
probably
normal. But I wasn't satisfied. I had read where some of you were =
thinking
about adding a dryer hose to the intake to get some ram air effect. I =
also
read where cooler air rather than engine air could be a power =
advantage. So
I made an intake extension out to the grill using 4" thin walled =
aluminum
dryer pipe. I started with a 4 x 3 reducer then three sectional
(adjustable) elbows and finally a 15" straight length which got me to =
the
grill. I covered the end with =BC" hardware cloth (wire). All sections =
of
pipe and fittings are secured with two pop rivets. The routing was =
along the
outside of the vertical frame support brackets (bars) and then back to =
the
side of the radiator just above the air compressor about 6". Really =
doesn't
look too funky. I supported at radiator and near air cleaner intake. =
Also I
made a pipe clamp to attach to air cleaner intake that is easily =
removeable.
Then I tried the hill again. It went 62 MPH in repeated trials. One =
MPH
below the record without an air cleaner. I tried it several times =
again the
next day with slightly different results, both with and without the ram =
air
tube and with the air cleaner removed.
Results are as follows:
Air cleaner cover removed 63-63.5MPH (direct flow to carb. with no air
filtration at all)
Air cleaner and cover in place 60-63 MPH (standard configuration)
Air cleaner in place plus extended intake to grill 62-63 MPH
I can't really be sure the intake extension is helping. Maybe just a =
teeny
bit. I did notice that even with the new cannister I could still =
decrease
performance about 1MPH just by screwing down the wing nut an extra 1 & =
=BD
turns. I believe the available area just above the carb. intake is =
very
critical. In any case I think this problem is behind me.
Hopefully my gas mileage will improve. I will let you know.
If you have any doubts about your air cleaner cover restricting air I
suggest you make a comparison test with the cover temporarily removed =
on a
nice clean road. Its too soon to say whether the intake extension is a =
good
deal but I am glad I added it. If anybody out there could explain the
benefits of the cooler outside air to the engine I would appreciate =
hearing
about it. Is it simply because there is more oxygen molecules in =
cooler
air? At highway speeds the intake air at the grill may not be that =
much
lower than at the front of the engine where air cleaner normal intake =
is. I
might check the temperature difference if someone can tell me something
specific about the cooler temp.benefits.
