Q1_Aircraft: Onan 22 HP modification info??

Looking at the Onan, I am surprised that efforts were not made to clean
up the induction system, particularly the manifold setup. Yechh!
I'm going to watch for a '60' as a reasonable upgrade, but trick out
(meaning clean up) the '48'.
Seems to me..REAL bottom line on a Q-1 is to start honoring the whole
concept by building light...squeegeeing with feeling, as it were...and
carrying the feeling through all phases of the process....no avionic
stacks...no ...um...SECOND 1/2 VW...etc et al.
Hmmmm...guess I'll have to start from scratch.......as the only actual
way to achieve the above, given that most all new builders leave too
much resin in their layups...

Nick L.



> I agree, the Q1 in it's original form is the winner, but it is also true
> that the original 20 HP Onan was kind of on the low end when it comes to
> HP, even though it was not too bad, and have the best flying record so
> far.
>

Yes, the induction system on the Onan was designed by a drunk plumber, and can
be fixed up pretty good, with some extensive porting. Onan does not really
suffer from small ports, but from sharp bends, and obstructions, that does not
promote good flow and will do obvious turbulence in both the intake and exhaust
ports, so you don't really need to emphasize the size of the bore, but instead
emphasize the way things will flow in the ports. Standard issue Onan
ports....they're terrible.

In order to make a really nice induction system, you need to get hold of
mandrel bent pipes.

With mandrel bend means, pipes that are not bent in a pipe bender, but have
been manufactured with an inside mandrel, making the inside diameter, consistent
through out the bend.(Gotta be, or know a good TIG welder also)

I have never done this on an Onan, but I am also thinking about longer intake
maifold, as this would be more a tuned manifold rather than the short bar that
are now sitting on top.

The manifold would by necessity then go around and end on the underside of the
engine.

My thinking here is that this would be an inherently safer engine, as all
'real' aircraft engines have their carb on the bottom.

Reason for that is, a carb can flood, because of a thousand reasons, stuck
needle, broken fuel hose, stuck float,, you name it, and the gasoline flood will
then, with a top located carb, flood and drench a hot engine.

With a carb on the bottom, you will get longer runners , and I am pretty sure
that this will enhance performance, a bit, as there is a mass pushing on,
towards the intake valve, and that mass doesn't stop pushing just because the
valve closes. It have inertia , and with the right length you will get an extra
push when the intake valve opens.

It will for sure put the carb in a safer spot, and you can do an aluminum box
around it, with a drain straight from the box, to outside. Whataya think of
that?

A trick of the trade, here, while you are porting up and cleaning up the Onan.

Take off the head, and take out the valves, and observe something here that
will get you another 1/4 hp (with a little bit of luck) .

When the heads are off, you can se the aluminum casting, and any metal
inserts, like the liner to the bore in the cylinder. Ok check out where the
steel ends and the aluminum starts when you are going towards the valves. Notice
a flat area, that goes towards the hardened valveseats, but then notice how
recessed the valve seats are.

You can grind off aluminum, by making two 'troffs' or ditches ( very shallow)
from the valve seats to the cylinder lining, by taking off the aluminum that
will be in a straight line from the top of where the valve metal insert is, to
the top of the cylinder liner.

You will get two, wide ,shallow, 'dog ear' looking ditches, one from each
valve pointing toward the cylinder in that way, and you will in that way clear a
better path for the charge to either excavate or fill the cylinders. Take off
the head and have a look at what I mean. That operation will increase the
headvolume a little bit, but when everything is done, do a very conservative
head shave.

Another way of getting a bit more oomp out of this thing is to thermal coat
the top of the pistons.

When it comes to the valves, you will increase the breathing by , grinding the
valves against the valve seats using the normal process, grinding compound and a
stick with a suction cup, , and then look where the surface track is on the
valve. Now, if you can imagine on the side of that valve, make a perfect part
of a circle, starting from the track, where the valve hits the seat, going
around until it ends on top of the valve face. That will get more breath into
the Onan also.

I have done that with many engines, and it is easy, you put the valve and
tighten it down in a drill chuck,(with some leather inbetween) Preferably a hand
drill, as you can maneuver it much better , and spin it, while you are using a
metal file. (You might want to practice first on a scrap valve, unil you will
get the hang of it, it is easy, you'll get it quick)

It's the small things that adds up.

Oh I forgot something, an old mechanics trick, when you have grinded the seats
down to it's last and finest grinding compound, clean it all up, and use motor
oil, and do it agin. You will get a mirror surface.

While you are doing the valves , you can undercut the valve from the point of
the track, where the valve is seated, to the stem, so you will get one straight
line. That will also make for better flow.

Its the small things that adds up.

The very best result in getting the 48 Cu Incher breath better is to do a cam
job though. But if you do the porting, and the valves as you say, the cam job
will benefit even more.

I am pretty sure that some of us will get the Onan out of the ordinary
category of -'Oh well I guess I haaaave to use the Onan'....into something that
will be a really joyful engine, and I hope you will do good with yours.

Whataya mean no second 1/2 VW???

I am planning to put one on the tip of each wing ....and the tail,... and have
a 6 engine aircraft.

I've got rolls and rolls of bailing wire, no problem.

Roger




Leonard Nick < Nical@... > wrote:
Looking at the Onan, I am surprised that efforts were not made to
clean
up the induction system, particularly the manifold setup. Yechh!
I'm going to watch for a '60' as a reasonable upgrade, but trick out
(meaning clean up) the '48'.
Seems to me..REAL bottom line on a Q-1 is to start honoring the whole
concept by building light...squeegeeing with feeling, as it were...and
carrying the feeling through all phases of the process....no avionic
stacks...no ...um...SECOND 1/2 VW...etc et al.
Hmmmm...guess I'll have to start from scratch.......as the only actual
way to achieve the above, given that most all new builders leave too
much resin in their layups...

Nick L.

> I agree, the Q1 in it's original form is the winner, but it is also true
> that the original 20 HP Onan was kind of on the low end when it comes to
> HP, even though it was not too bad, and have the best flying record so
> far.
>





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Very interesting stuff. Tuned intake manifolds are a natural so long as
you pick the right RPM range.. happily I have a nice TIG machine as part
of my shop that might be of use here .
Having the carb below is de rigeur insofar as I am concerned; running
the manifolds aft and down, then vee'ing together is pretty simple
stuff. Did that to a 18 HP B&amp;S engine once for a part 103 project.
Worked a treat.
I look forward to peeling the 48 apart with an eye to cleaning it all
up. A cam regrind is essential. There are some pretty neat coating tech
that can be added here. One interesting is polishing and then teflonning
(sp)the crank throws!! The drag racer types apparently can see the diff
on the dyno.
It is all about oil sling....


> Yes, the induction system on the Onan was designed by a drunk plumber, and
> can be fixed up pretty good, with some extensive porting. Onan does not
> really suffer from small ports, but from sharp bends, and obstructions,
> that does not promote good flow and will do obvious turbulence in both the
> intake and exhaust ports, so you don't really need to emphasize the size
> of the bore, but instead emphasize the way things will flow in the ports.
> Standard issue Onan ports....they're terrible.
>
> In order to make a really nice induction system, you need to get hold of
> mandrel bent pipes.

Agreed. In the diameters we are phosphoring about, ss exhaust stock
units from Aircraft Spruce aren't an option....but SOMEONE out there
knows exactly the source...hmmm??????
>
>
>
> With a carb on the bottom, you will get longer runners , and I am pretty
> sure that this will enhance performance, a bit, as there is a mass
> pushing on, towards the intake valve, and that mass doesn't stop pushing
> just because the valve closes. It have inertia , and with the right
> length you will get an extra push when the intake valve opens.
>
> It will for sure put the carb in a safer spot, and you can do an
> aluminum box around it, with a drain straight from the box, to outside.
> Whataya think of that?
>
> A trick of the trade, here, while you are porting up and cleaning up the
> Onan.
>
> Take off the head, and take out the valves, and observe something here
> that will get you another 1/4 hp (with a little bit of luck) .
>
> When the heads are off, you can se the aluminum casting, and any metal
> inserts, like the liner to the bore in the cylinder. Ok check out where
> the steel ends and the aluminum starts when you are going towards the
> valves. Notice a flat area, that goes towards the hardened valveseats,
> but then notice how recessed the valve seats are.
>
> You can grind off aluminum, by making two 'troffs' or ditches ( very
> shallow) from the valve seats to the cylinder lining, by taking off the
> aluminum that will be in a straight line from the top of where the
> valve metal insert is, to the top of the cylinder liner.
>
> You will get two, wide ,shallow, 'dog ear' looking ditches, one from
> each valve pointing toward the cylinder in that way, and you will in
> that way clear a better path for the charge to either excavate or fill
> the cylinders. Take off the head and have a look at what I mean. That
> operation will increase the headvolume a little bit, but when everything
> is done, do a very conservative head shave.
>

This sounds a little like 'Singh Grooving'...an interesting idea whom a
Mr. Climes has posted about.

> Another way of getting a bit more oomp out of this thing is to thermal
> coat the top of the pistons.
This implies mixture control....
>
> When it comes to the valves, you will increase the breathing by ,
> grinding the valves against the valve seats using the normal process,
> grinding compound and a stick with a suction cup, , and then look where
> the surface track is on the valve. Now, if you can imagine on the side
> of that valve, make a perfect part of a circle, starting from the track,
> where the valve hits the seat, going around until it ends on top of the
> valve face. That will get more breath into the Onan also.
>
> I have done that with many engines, and it is easy, you put the valve
> and tighten it down in a drill chuck,(with some leather inbetween)
> Preferably a hand drill, as you can maneuver it much better , and spin
> it, while you are using a metal file. (You might want to practice first
> on a scrap valve, unil you will get the hang of it, it is easy, you'll
> get it quick)
> Sounds like we are talking about '3 angling' the valves...not as
elegant as a continuous arc, but...
> It's the small things that adds up.
Amen....but in order for that to happen, the big stuff has to be fairly
close to start with.

>
> Oh I forgot something, an old mechanics trick, when you have grinded the
> seats down to it's last and finest grinding compound, clean it all up,
> and use motor oil, and do it agin. You will get a mirror surface.

Wow! THAT is neat....I wanna grind a valve just to watch that happen.
>
> While you are doing the valves , you can undercut the valve from the
> point of the track, where the valve is seated, to the stem, so you will
> get one straight line. That will also make for better flow.
Are you referring to the area that transitions from the stem to the
contact point at the seat??
>
> Its the small things that adds up.
>
> The very best result in getting the 48 Cu Incher breath better is to do
> a cam job though. But if you do the porting, and the valves as you say,
> the cam job will benefit even more.
>
> I am pretty sure that some of us will get the Onan out of the ordinary
> category of -'Oh well I guess I haaaave to use the Onan'....into
> something that will be a really joyful engine, and I hope you will do
> good with yours.
This is a case of 1 or two people doing the homework, as as usual the
group tends to wait until the trail has been cut, marked, street lights
installed, service businesses in place etc etc.
>
> Whataya mean no second 1/2 VW???
>
You don't unnerstand, Roger, whassamatta wid you: Put the 1/2 VWs
vertically on each canard tip ( takes care of the job of lift), install
a weedeater engine and generator fwd of the firewall, run a flexible
shaft back to the tailcone prop and you are all set. Plenty of extra
power for the Garmin 496 (?? whatever) comm stack , cabin heater ( for
those high altitude XCs) and of course flatscreen TV to reduce some of
the boredom of extended time aloft. Trans continental is fine and all,
but probably rather tedious at 150 mph...
It's all SO simple...so simple...

Silk purses from sow's ears, anyone?? (sorry, another layer of the
discussion...)

Nick L.
>
>
>
>
>
>


Nick Leonard

' Merely the vain choice between unsatisfied desire and the languor of ennui'

L.N,

Reading your answer there are no doubt that you're the man to do this.

About the 3 angle job, and the radius, no I think you misunderstood me about
what goes where.

The seat will need a 3 angle job, but the valve, will have the radius.

As per the rest of it...youv'e got it, you seem to be a man with experience
and you have a very good 'motorhead' , so as times goes by, you will probably be
the one that will be in the lead in the 'Onan Revival Misson'.

So you have alrady done a B&amp;S with an underneath carb....

Got a Q for you, this i a theory I am working on, but I just want to run it by
you to see if there is more angles to it.

Ok, her it goes, let me give you some background first, so we're talking about
the same thing.

The pulses that will feed an engine in a tuned intake or exhaust needs to be
pretty long in order to feed a low RPM application.

The pulses themselves is not the air as it moves, but shockpulses, that moves
much quicker. See it like this, fill a hose with ping pong balls, and let them
roll trough, that would be the air, but if you knock on the last one, there will
be another pulse that will be more instant trough the whole train of ping pong
balls, that's the one that will transport energy around, and if tuned
exactly,push an extra amount of charge into the engine.

Having longer intakes will help in that regards, but the distance between the
intake valve and behind the Onan, and down to where the carb is, is pretty short
after all.

What do you think of this, I have never seen or heard about it but I am
thinking that this just might be a way to get a system that is pretty closely
tuned.

Imagine that instead of a Y you put a T there, let the carb feed into the
system in a 90 deg angle, (I know, I just said 90 deg angle, but here is where I
have an incling that you may get back some poop), and in that way you will get a
pulse that will travel the whole lengh of the intake system. The intake valve
closes, and air,that have inertia,will amass behind the intake valve, creating a
highpressure area, and from there, the shockwave will bounce back, in the intake
system, go back, and underneath the engine, and as it has a 'T' connection, at
that spot, a straight shot into the other intake pipe, and the shockwave will
travel into that pipe. around the engine and up to the other cyliners intake
valve ( that hopefully will open just about that time).

The idea would be to use one cylinders pulse to feed the opposing cylinders
intake stroke.

The reason I am thinking that this may work is that the pulse is traveling
with the speed of sound, and that is a bit more than 300 Meters/sec, the speed
the Onan will have is in the 2600 to 3600 RPM ranges, and as one work stroke is
generated on the Onan each revolution, you will also then get a pulse every
revolution, and that seems to be coincident with the pulse lengh at these RPM's.
you need about a meter, a touch more than three feet between each intake valve.

Question is, will there be poop enough in the pulse if there is a hole in the
middle for the carb, will it be like a fluite, and the pulse will end there, or
will it travel straight into the opposing sides intake pipe?

I have made no experiments with this, this is just a thing in the head, and I
want to run it by you to see if there is something obvious that I have
overlooked, in theory I have a feeling it will work, and this is an application
that will only be good in an opposed, two cylinder fourstroke, so I guess that
the field experience out there,is very limited.


As for added engines, naa, get a grip, bailing wire is the way to go, and
helium in the wings to make it fly. A captured black hole with a coil around it,
( bailing wire, will do that too) will provide all the electricity you need for
the weedeater engine that runs the generator that runs a plug in coffe brewer
that steams a turbine that powers a generator that makes the world go around.
In that way you dont need to fly, you can sit still and make the world move
instead, pure relativity. Piece of cake.

Roger





Very interesting stuff. Tuned intake manifolds are a natural so long
as
you pick the right RPM range.. happily I have a nice TIG machine as part
of my shop that might be of use here .
Having the carb below is de rigeur insofar as I am concerned; running
the manifolds aft and down, then vee'ing together is pretty simple
stuff. Did that to a 18 HP B&amp;S engine once for a part 103 project.
Worked a treat.
I look forward to peeling the 48 apart with an eye to cleaning it all
up. A cam regrind is essential. There are some pretty neat coating tech
that can be added here. One interesting is polishing and then teflonning
(sp)the crank throws!! The drag racer types apparently can see the diff
on the dyno.
It is all about oil sling....

> Yes, the induction system on the Onan was designed by a drunk plumber, and
> can be fixed up pretty good, with some extensive porting. Onan does not
> really suffer from small ports, but from sharp bends, and obstructions,
> that does not promote good flow and will do obvious turbulence in both the
> intake and exhaust ports, so you don't really need to emphasize the size
> of the bore, but instead emphasize the way things will flow in the ports.
> Standard issue Onan ports....they're terrible.
>
> In order to make a really nice induction system, you need to get hold of
> mandrel bent pipes.

Agreed. In the diameters we are phosphoring about, ss exhaust stock
units from Aircraft Spruce aren't an option....but SOMEONE out there
knows exactly the source...hmmm??????
>
>
>
> With a carb on the bottom, you will get longer runners , and I am pretty
> sure that this will enhance performance, a bit, as there is a mass
> pushing on, towards the intake valve, and that mass doesn't stop pushing
> just because the valve closes. It have inertia , and with the right
> length you will get an extra push when the intake valve opens.
>
> It will for sure put the carb in a safer spot, and you can do an
> aluminum box around it, with a drain straight from the box, to outside.
> Whataya think of that?
>
> A trick of the trade, here, while you are porting up and cleaning up the
> Onan.
>
> Take off the head, and take out the valves, and observe something here
> that will get you another 1/4 hp (with a little bit of luck) .
>
> When the heads are off, you can se the aluminum casting, and any metal
> inserts, like the liner to the bore in the cylinder. Ok check out where
> the steel ends and the aluminum starts when you are going towards the
> valves. Notice a flat area, that goes towards the hardened valveseats,
> but then notice how recessed the valve seats are.
>
> You can grind off aluminum, by making two 'troffs' or ditches ( very
> shallow) from the valve seats to the cylinder lining, by taking off the
> aluminum that will be in a straight line from the top of where the
> valve metal insert is, to the top of the cylinder liner.
>
> You will get two, wide ,shallow, 'dog ear' looking ditches, one from
> each valve pointing toward the cylinder in that way, and you will in
> that way clear a better path for the charge to either excavate or fill
> the cylinders. Take off the head and have a look at what I mean. That
> operation will increase the headvolume a little bit, but when everything
> is done, do a very conservative head shave.
>

This sounds a little like 'Singh Grooving'...an interesting idea whom a
Mr. Climes has posted about.

> Another way of getting a bit more oomp out of this thing is to thermal
> coat the top of the pistons.
This implies mixture control....
>
> When it comes to the valves, you will increase the breathing by ,
> grinding the valves against the valve seats using the normal process,
> grinding compound and a stick with a suction cup, , and then look where
> the surface track is on the valve. Now, if you can imagine on the side
> of that valve, make a perfect part of a circle, starting from the track,
> where the valve hits the seat, going around until it ends on top of the
> valve face. That will get more breath into the Onan also.
>
> I have done that with many engines, and it is easy, you put the valve
> and tighten it down in a drill chuck,(with some leather inbetween)
> Preferably a hand drill, as you can maneuver it much better , and spin
> it, while you are using a metal file. (You might want to practice first
> on a scrap valve, unil you will get the hang of it, it is easy, you'll
> get it quick)
> Sounds like we are talking about '3 angling' the valves...not as
elegant as a continuous arc, but...
> It's the small things that adds up.
Amen....but in order for that to happen, the big stuff has to be fairly
close to start with.

>
> Oh I forgot something, an old mechanics trick, when you have grinded the
> seats down to it's last and finest grinding compound, clean it all up,
> and use motor oil, and do it agin. You will get a mirror surface.

Wow! THAT is neat....I wanna grind a valve just to watch that happen.
>
> While you are doing the valves , you can undercut the valve from the
> point of the track, where the valve is seated, to the stem, so you will
> get one straight line. That will also make for better flow.
Are you referring to the area that transitions from the stem to the
contact point at the seat??
>
> Its the small things that adds up.
>
> The very best result in getting the 48 Cu Incher breath better is to do
> a cam job though. But if you do the porting, and the valves as you say,
> the cam job will benefit even more.
>
> I am pretty sure that some of us will get the Onan out of the ordinary
> category of -'Oh well I guess I haaaave to use the Onan'....into
> something that will be a really joyful engine, and I hope you will do
> good with yours.
This is a case of 1 or two people doing the homework, as as usual the
group tends to wait until the trail has been cut, marked, street lights
installed, service businesses in place etc etc.
>
> Whataya mean no second 1/2 VW???
>
You don't unnerstand, Roger, whassamatta wid you: Put the 1/2 VWs
vertically on each canard tip ( takes care of the job of lift), install
a weedeater engine and generator fwd of the firewall, run a flexible
shaft back to the tailcone prop and you are all set. Plenty of extra
power for the Garmin 496 (?? whatever) comm stack , cabin heater ( for
those high altitude XCs) and of course flatscreen TV to reduce some of
the boredom of extended time aloft. Trans continental is fine and all,
but probably rather tedious at 150 mph...
It's all SO simple...so simple...

Silk purses from sow's ears, anyone?? (sorry, another layer of the
discussion...)

Nick L.
>
>
>
>
>
>

Nick Leonard

' Merely the vain choice between unsatisfied desire and the languor of ennui'





__________________________________________________
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Tired of spam? Yahoo! Mail has the best spam protection around
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[Non-text portions of this message have been removed]

>
> The seat will need a 3 angle job, but the valve, will have the radius.
> Yes, OK...got it. Makes sense now.
>
>
> So you have alrady done a B&amp;S with an underneath carb....
> yup. Worked just fine. I have a fairbanks morse mag running direct off
the crank for ign power. simple and effective.
>
Interesting induction pipe timing idea. But with flow through tubes,
consider a...say...3' radius bend in a tube. At increasing flowrates
that bend will behave more and more like a restriction in cross section.
Consequently, it will cause the engine to start behaving asthmatically
(sp). Not good.
If you put a carb on a Tee, at some (early) point the flow rate will
decay because of the above. The sharper the tee, the lower the
flowrate before wheeze
Seems to me that on a Quickie application, the most critical period is
full power climb. Say 3300 RPM (?) -whatever. If a chap did his
lengths and radii to work at this high flowrate, then backing off for
cruise would at least not starve the engine...even if the standing
wave was no longer quite right......
On the B&amp;S conversion, I Veed the tubes about 4' above the carb mount,
using as little angle as possible; making up the lineup to the ports in
a largish radius to clear the cylinders. We got full rated RPM and flew
the project at max gross a few times. Climb was...um...lousy but the
engine never missed a beat. Had the engine made, say, 25 HP we'd have
kept developing it, but starting with 18 that would have destroyed any
reliability....
>
> As for added engines, naa, get a grip, bailing wire is the way to go,
> and helium in the wings to make it fly. A captured black hole with a
> coil around it, ( bailing wire, will do that too) will provide all the
> electricity you need for the weedeater engine that runs the generator
> that runs a plug in coffe brewer that steams a turbine that powers a
> generator that makes the world go around. In that way you dont need to
> fly, you can sit still and make the world move instead, pure relativity.
> Piece of cake.
>
> Dang! Why didn't I think of that??? All this conjecture is fun &amp;
soforth...but in the end, we all reach for the spare Mr. Fusion most
of us have lying around the garage someplace. Unless of course you have
a Black Hole Garbage Can in the corner, at which time regret cleaning
the garage on a constant basis...Packrats know universal truths that
nagging wives ignore...

NAL
>
>
>
>
>
> Very interesting stuff. Tuned intake manifolds are a natural so
> long as
> you pick the right RPM range.. happily I have a nice TIG machine as part
> of my shop that might be of use here .
> Having the carb below is de rigeur insofar as I am concerned; running
> the manifolds aft and down, then vee'ing together is pretty simple
> stuff. Did that to a 18 HP B&amp;S engine once for a part 103 project.
> Worked a treat.
> I look forward to peeling the 48 apart with an eye to cleaning it all
> up. A cam regrind is essential. There are some pretty neat coating tech
> that can be added here. One interesting is polishing and then teflonning
> (sp)the crank throws!! The drag racer types apparently can see the diff
> on the dyno.
> It is all about oil sling....
>
>> Yes, the induction system on the Onan was designed by a drunk plumber,
>> and
>> can be fixed up pretty good, with some extensive porting. Onan does not
>> really suffer from small ports, but from sharp bends, and obstructions,
>> that does not promote good flow and will do obvious turbulence in both
>> the
>> intake and exhaust ports, so you don't really need to emphasize the size
>> of the bore, but instead emphasize the way things will flow in the
>> ports.
>> Standard issue Onan ports....they're terrible.
>>
>> In order to make a really nice induction system, you need to get hold of
>> mandrel bent pipes.
>
> Agreed. In the diameters we are phosphoring about, ss exhaust stock
> units from Aircraft Spruce aren't an option....but SOMEONE out there
> knows exactly the source...hmmm??????
>>
>>
>>
>> With a carb on the bottom, you will get longer runners , and I am pretty
>> sure that this will enhance performance, a bit, as there is a mass
>> pushing on, towards the intake valve, and that mass doesn't stop pushing
>> just because the valve closes. It have inertia , and with the right
>> length you will get an extra push when the intake valve opens.
>>
>> It will for sure put the carb in a safer spot, and you can do an
>> aluminum box around it, with a drain straight from the box, to outside.
>> Whataya think of that?
>>
>> A trick of the trade, here, while you are porting up and cleaning up the
>> Onan.
>>
>> Take off the head, and take out the valves, and observe something here
>> that will get you another 1/4 hp (with a little bit of luck) .
>>
>> When the heads are off, you can se the aluminum casting, and any metal
>> inserts, like the liner to the bore in the cylinder. Ok check out where
>> the steel ends and the aluminum starts when you are going towards the
>> valves. Notice a flat area, that goes towards the hardened valveseats,
>> but then notice how recessed the valve seats are.
>>
>> You can grind off aluminum, by making two 'troffs' or ditches ( very
>> shallow) from the valve seats to the cylinder lining, by taking off the
>> aluminum that will be in a straight line from the top of where the
>> valve metal insert is, to the top of the cylinder liner.
>>
>> You will get two, wide ,shallow, 'dog ear' looking ditches, one from
>> each valve pointing toward the cylinder in that way, and you will in
>> that way clear a better path for the charge to either excavate or fill
>> the cylinders. Take off the head and have a look at what I mean. That
>> operation will increase the headvolume a little bit, but when everything
>> is done, do a very conservative head shave.
>>
>
> This sounds a little like 'Singh Grooving'...an interesting idea whom a
> Mr. Climes has posted about.
>
>> Another way of getting a bit more oomp out of this thing is to thermal
>> coat the top of the pistons.
> This implies mixture control....
>>
>> When it comes to the valves, you will increase the breathing by ,
>> grinding the valves against the valve seats using the normal process,
>> grinding compound and a stick with a suction cup, , and then look where
>> the surface track is on the valve. Now, if you can imagine on the side
>> of that valve, make a perfect part of a circle, starting from the track,
>> where the valve hits the seat, going around until it ends on top of the
>> valve face. That will get more breath into the Onan also.
>>
>> I have done that with many engines, and it is easy, you put the valve
>> and tighten it down in a drill chuck,(with some leather inbetween)
>> Preferably a hand drill, as you can maneuver it much better , and spin
>> it, while you are using a metal file. (You might want to practice first
>> on a scrap valve, unil you will get the hang of it, it is easy, you'll
>> get it quick)
>> Sounds like we are talking about '3 angling' the valves...not as
> elegant as a continuous arc, but...
>> It's the small things that adds up.
> Amen....but in order for that to happen, the big stuff has to be fairly
> close to start with.
>
>>
>> Oh I forgot something, an old mechanics trick, when you have grinded the
>> seats down to it's last and finest grinding compound, clean it all up,
>> and use motor oil, and do it agin. You will get a mirror surface.
>
> Wow! THAT is neat....I wanna grind a valve just to watch that happen.
>>
>> While you are doing the valves , you can undercut the valve from the
>> point of the track, where the valve is seated, to the stem, so you will
>> get one straight line. That will also make for better flow.
> Are you referring to the area that transitions from the stem to the
> contact point at the seat??
>>
>> Its the small things that adds up.
>>
>> The very best result in getting the 48 Cu Incher breath better is to do
>> a cam job though. But if you do the porting, and the valves as you say,
>> the cam job will benefit even more.
>>
>> I am pretty sure that some of us will get the Onan out of the ordinary
>> category of -'Oh well I guess I haaaave to use the Onan'....into
>> something that will be a really joyful engine, and I hope you will do
>> good with yours.
> This is a case of 1 or two people doing the homework, as as usual the
> group tends to wait until the trail has been cut, marked, street lights
> installed, service businesses in place etc etc.
>>
>> Whataya mean no second 1/2 VW???
>>
> You don't unnerstand, Roger, whassamatta wid you: Put the 1/2 VWs
> vertically on each canard tip ( takes care of the job of lift), install
> a weedeater engine and generator fwd of the firewall, run a flexible
> shaft back to the tailcone prop and you are all set. Plenty of extra
> power for the Garmin 496 (?? whatever) comm stack , cabin heater ( for
> those high altitude XCs) and of course flatscreen TV to reduce some of
> the boredom of extended time aloft. Trans continental is fine and all,
> but probably rather tedious at 150 mph...
> It's all SO simple...so simple...
>
> Silk purses from sow's ears, anyone?? (sorry, another layer of the
> discussion...)
>
> Nick L.
>>
>>
>>
>>
>>
>>
>
> Nick Leonard
>
> ' Merely the vain choice between unsatisfied desire and the languor of
> ennui'
>
>
>
>
>
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>


Nick Leonard

' Merely the vain choice between unsatisfied desire and the langour of ennui'