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New and more accessible timing marks

MC
Matt Colie
Fri, Jun 4, 2021 10:42 PM

When I was checking the timing I one day I thought to myself, “If every time of the thousands (no joke) that I have checked ignition timing on an
engine it was as hard as this, I would have found a better way.”  Well, when I start thinking about things, this can be dangerous.  I didn’t have
to look very far.  All I had to do was remember that most all the test engines I have had responsibility for over decades of career time in the test
laboratories had the timing marks on the flywheel.

Email guys, this is also posted on the photo site as a *.pdf ready for printing.

Gunsight timing                   By Matthew Colie 04 June 2021
New timing marks for Oldsmobile in GMC.

Anybody that has tried to check, or worse yet, set the timing in any GMC will see the value in this mod in just the next paragraph.  It is also
interesting to mention that my engine now has a scale such that even a single degree of the actual timing is very obvious.

My engine has a second set of timing marks that are visible through a hole in the bell housing.  This is easier to see and way easier to get to than
those on the damper.  There is also a reference mark in the edge of the rear for the block.  It takes very little effort to do this mod when the
engine is out, but I am sure it could be done with the engine and transmission in place..

The picture posted here, (sorry e mail guys I will post the document with the pictures site later) is indeed what you actually get to see. For those
that have not set timing, I have also included a picture (the best I could do) of the OE marks.  This was the best view I cold get with my camera and
those that have done this will admit that this is about as good as it gets.

Discussion of my mod for those that care.
Talk about convenience, it is also just about next to the distributor, so if adjustment is desired it is convenient to do.  I also put an adapter in
the cigar lighter (here after referred to as the DC mousehole) to get me the DC for the timing light.  This works, but it is less than ideal because
the engine hatch is in the way.  I did have a plan to add a power point that is more convenient, but that still has not happened.

Using a holesaw to make the window in the bell housing is simple.  The hardest part is getting the crank to 0° to make the marks.  When my engine was
on the work stand, this was real easy.  So, I made a bunch and made the reference on the back of the block casting as well.  Unfortunately, that first
set missed.  I had marked the top of the teeth and this was not very visible in the final assembly.  I just made new marks both paint and engraved on
the rear face of the teeth.

In Figure 2, the reference mark is hidden by the vacuum pot.

The real big gain here is the resolution here.  There are 144 teeth on the ring gear.  So, that is 2.5° per tooth.  Between 2 teeth is 1.25° That is
just a whole lot bigger and clearer than peering down though the belts and hoses at 1/4 inch = 4°.  The next huge gain is the fact that I was now
next to the distributor and could watch the mark move when I moved it and check that it stayed there.

The development story:

When I was checking the timing I one day I thought to myself, “If every time of the thousands (no joke) that I have checked ignition timing on an
engine it was as hard as this, I would have found a better way.”  Well, when I start thinking about things, this can be dangerous.  I didn’t have
to look very far.  All I had to do was remember that most all the test engines I have had responsibility for over decades of career time in the test
laboratories had the timing marks on the flywheel.

First, there is an important difference with both the majority of test engines and those installed in over the road vehicles.  That difference is
Flywheels with degree markings engraved.  Even the durability engines on waterbrakes still have them, and if they have a bell housing at all, it has a
window with a pointer.  So, this is not an original idea that I can take credit for, it is just a technology transfer that took way too long.

For those that might attempt this, it is way easier to move the crank when the spark plugs are removed.  The hole in the bell housing does not break
the flange at the margin.  I drilled that with the transmission bolted up and was able to capture the loose piece, but the engine was still out of the
coach.  The hole is 1-1/8 because that is a good size to have for running pipe.

I  first marked the teeth on the top but as soon as I bolted on the transmission, that mistake was obvious.  And when in the coach it was a bigger
problem.  That is when I went to the red paint.  This is the view you might have if you cut a big hole in the lift of the top step.

Two interesting notes: Figure 2 was taken  using the timing light flash as light.
The syringe is in that picture because I lost my golf tee.  There are two sets of clips on the power lead because I was trying out an HF adjustable
timing light.  No report on that today.

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

When I was checking the timing I one day I thought to myself, “If every time of the thousands (no joke) that I have checked ignition timing on an engine it was as hard as this, I would have found a better way.” Well, when I start thinking about things, this can be dangerous. I didn’t have to look very far. All I had to do was remember that most all the test engines I have had responsibility for over decades of career time in the test laboratories had the timing marks on the flywheel. Email guys, this is also posted on the photo site as a *.pdf ready for printing. Gunsight timing By Matthew Colie 04 June 2021 New timing marks for Oldsmobile in GMC. Anybody that has tried to check, or worse yet, set the timing in any GMC will see the value in this mod in just the next paragraph. It is also interesting to mention that my engine now has a scale such that even a single degree of the actual timing is very obvious. My engine has a second set of timing marks that are visible through a hole in the bell housing. This is easier to see and way easier to get to than those on the damper. There is also a reference mark in the edge of the rear for the block. It takes very little effort to do this mod when the engine is out, but I am sure it could be done with the engine and transmission in place.. The picture posted here, (sorry e mail guys I will post the document with the pictures site later) is indeed what you actually get to see. For those that have not set timing, I have also included a picture (the best I could do) of the OE marks. This was the best view I cold get with my camera and those that have done this will admit that this is about as good as it gets. Discussion of my mod for those that care. Talk about convenience, it is also just about next to the distributor, so if adjustment is desired it is convenient to do. I also put an adapter in the cigar lighter (here after referred to as the DC mousehole) to get me the DC for the timing light. This works, but it is less than ideal because the engine hatch is in the way. I did have a plan to add a power point that is more convenient, but that still has not happened. Using a holesaw to make the window in the bell housing is simple. The hardest part is getting the crank to 0° to make the marks. When my engine was on the work stand, this was real easy. So, I made a bunch and made the reference on the back of the block casting as well. Unfortunately, that first set missed. I had marked the top of the teeth and this was not very visible in the final assembly. I just made new marks both paint and engraved on the rear face of the teeth. In Figure 2, the reference mark is hidden by the vacuum pot. The real big gain here is the resolution here. There are 144 teeth on the ring gear. So, that is 2.5° per tooth. Between 2 teeth is 1.25° That is just a whole lot bigger and clearer than peering down though the belts and hoses at 1/4 inch = 4°. The next huge gain is the fact that I was now next to the distributor and could watch the mark move when I moved it and check that it stayed there. The development story: When I was checking the timing I one day I thought to myself, “If every time of the thousands (no joke) that I have checked ignition timing on an engine it was as hard as this, I would have found a better way.” Well, when I start thinking about things, this can be dangerous. I didn’t have to look very far. All I had to do was remember that most all the test engines I have had responsibility for over decades of career time in the test laboratories had the timing marks on the flywheel. First, there is an important difference with both the majority of test engines and those installed in over the road vehicles. That difference is Flywheels with degree markings engraved. Even the durability engines on waterbrakes still have them, and if they have a bell housing at all, it has a window with a pointer. So, this is not an original idea that I can take credit for, it is just a technology transfer that took way too long. For those that might attempt this, it is way easier to move the crank when the spark plugs are removed. The hole in the bell housing does not break the flange at the margin. I drilled that with the transmission bolted up and was able to capture the loose piece, but the engine was still out of the coach. The hole is 1-1/8 because that is a good size to have for running pipe. I first marked the teeth on the top but as soon as I bolted on the transmission, that mistake was obvious. And when in the coach it was a bigger problem. That is when I went to the red paint. This is the view you might have if you cut a big hole in the lift of the top step. Two interesting notes: Figure 2 was taken using the timing light flash as light. The syringe is in that picture because I lost my golf tee. There are two sets of clips on the power lead because I was trying out an HF adjustable timing light. No report on that today. -- Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms SE Michigan - Near DTW - Twixt A2 and Detroit
BH
Bruce Hislop
Sat, Jun 5, 2021 12:07 PM

Matt's link is an image so it can't be copied an pasted.  Here is a text link to the pdf that includes photos.

http://www.gmcmhphotos.com/photos/data/7363/Gunsight_timing.pdf

Even easier, at the moment it shows up as a recent posting when you enter the home page of gmcmhphotos.com

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

Matt's link is an image so it can't be copied an pasted. Here is a text link to the pdf that includes photos. http://www.gmcmhphotos.com/photos/data/7363/Gunsight_timing.pdf Even easier, at the moment it shows up as a recent posting when you enter the home page of gmcmhphotos.com -- Bruce Hislop ON Canada 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001 My Staff says I never listen to them, or something like that
R
RJW
Sat, Jun 5, 2021 12:27 PM

Matt Colie wrote on Fri, 04 June 2021 18:42

When I was checking the timing I one day I thought to myself, “If every time of the thousands (no joke) that I have checked ignition timing on
an engine it was as hard as this, I would have found a better way.”  Well, when I start thinking about things, this can be dangerous.  I didn’t
have to look very far.  All I had to do was remember that most all the test engines I have had responsibility for over decades of career time in the
test laboratories had the timing marks on the flywheel.

Email guys, this is also posted on the photo site as a *.pdf ready for printing.

http://www.gmcmhphotos.com/photos/gunsight-timing/p68233-gunsight-timing.html

This link will take you to the page that has the documents.  I could not get the other links to work.

Neat idea and something I will get around to doing someday.

--
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com

Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water
heaters.

Matt Colie wrote on Fri, 04 June 2021 18:42 > When I was checking the timing I one day I thought to myself, “If every time of the thousands (no joke) that I have checked ignition timing on > an engine it was as hard as this, I would have found a better way.” Well, when I start thinking about things, this can be dangerous. I didn’t > have to look very far. All I had to do was remember that most all the test engines I have had responsibility for over decades of career time in the > test laboratories had the timing marks on the flywheel. > > > > Email guys, this is also posted on the photo site as a *.pdf ready for printing. http://www.gmcmhphotos.com/photos/gunsight-timing/p68233-gunsight-timing.html This link will take you to the page that has the documents. I could not get the other links to work. Neat idea and something I will get around to doing someday. -- Richard 76 Palm Beach SE Michigan www.PalmBeachGMC.com Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
DS
Douglas Smith
Sat, Jun 5, 2021 11:56 PM

Matt,
Can I assume that the picture which includes the vacuum actuator on the distributor indicates the best location for the hole in the bellhousing? Or,
can the hole be located anywhere based on drilling ease/access if TDC on cylinder one is located accurately? Is there a distance from the mounting
flange (to catch the flywheel gear accurately) that is available or is it a guess? Is it safe to drill on an installed engine/bellhousing? What are
the consequences of losing the cutout disc from drilling (which clumsy/unlucky people {me} will do).

I ask this because timing has been a frustration for me for the 25 years I've owned my coach. Basically I've ignored it in the absence of problems.
That has meant that I've been, if you explore the margins, getting lousy mileage, experience a perfectly running engine (?), or flirting with disaster
with advanced timing, or some less than optimal blending of the three.

There are limited mods to stock which are universally accepted and generally not up for debate. The Pertronix lobe sensing unit (for my year GMC),
blocking the intake exhaust crossover, the flywheel timing for the Onan, and alloy wheels come to mind first. Everyone has their favorites based on
their willingness to pay or dig into the innards of their coach. I suspect your "Gunsight Timing" would easily join the list if the bar were lowered
just a bit for people like me who see a great idea but are a little intimidated by the process. Perhaps you have a friend out there with a coach "in
process" who could do the modification and document it for us rabble?
Doug

Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other

Matt, Can I assume that the picture which includes the vacuum actuator on the distributor indicates the best location for the hole in the bellhousing? Or, can the hole be located anywhere based on drilling ease/access if TDC on cylinder one is located accurately? Is there a distance from the mounting flange (to catch the flywheel gear accurately) that is available or is it a guess? Is it safe to drill on an installed engine/bellhousing? What are the consequences of losing the cutout disc from drilling (which clumsy/unlucky people {me} will do). I ask this because timing has been a frustration for me for the 25 years I've owned my coach. Basically I've ignored it in the absence of problems. That has meant that I've been, if you explore the margins, getting lousy mileage, experience a perfectly running engine (?), or flirting with disaster with advanced timing, or some less than optimal blending of the three. There are limited mods to stock which are universally accepted and generally not up for debate. The Pertronix lobe sensing unit (for my year GMC), blocking the intake exhaust crossover, the flywheel timing for the Onan, and alloy wheels come to mind first. Everyone has their favorites based on their willingness to pay or dig into the innards of their coach. I suspect your "Gunsight Timing" would easily join the list if the bar were lowered just a bit for people like me who see a great idea but are a little intimidated by the process. Perhaps you have a friend out there with a coach "in process" who could do the modification and document it for us rabble? Doug -- Douglas & Virginia Smith, dsmithy18 at gmail, Lincoln Nebraska, ’73 “Sequoia” since ‘95: "Wanabizo"; Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
MC
Matt Colie
Sun, Jun 6, 2021 3:12 AM

dsmithy wrote on Sat, 05 June 2021 19:56

Matt,
Can I assume that the picture which includes the vacuum actuator on the distributor indicates the best location for the hole in the bellhousing?
Or, can the hole be located anywhere based on drilling ease/access if TDC on cylinder one is located accurately? Is there a distance from the
mounting flange (to catch the flywheel gear accurately) that is available or is it a guess? Is it safe to drill on an installed engine/bellhousing?
What are the consequences of losing the cutout disc from drilling (which clumsy/unlucky people {me} will do).

I ask this because timing has been a frustration for me for the 25 years I've owned my coach. Basically I've ignored it in the absence of
problems. That has meant that I've been, if you explore the margins, getting lousy mileage, experience a perfectly running engine (?), or flirting
with disaster with advanced timing, or some less than optimal blending of the three.

There are limited mods to stock which are universally accepted and generally not up for debate. The Pertronix lobe sensing unit (for my year GMC),
blocking the intake exhaust crossover, the flywheel timing for the Onan, and alloy wheels come to mind first. Everyone has their favorites based on
their willingness to pay or dig into the innards of their coach. I suspect your "Gunsight Timing" would easily join the list if the bar were lowered
just a bit for people like me who see a great idea but are a little intimidated by the process. Perhaps you have a friend out there with a coach "in
process" who could do the modification and document it for us rabble?
Doug

Doug,

Timing has only been a frustration of mine for only 16 years..... (Chaumière came here in 2006.)
You have hit my favorite mods, but I have yet to afford the cost of alloy wheels.

The location of the hole in the bellhousing is completely arbitrary.  Make it where it works for you.  It only really needs to let you see teeth for
calibration. But do create a reference mark on the block casting.  And yes, I kind of wish I had located it differently than I did, but it works.  I
marked teeth and put the reference mark in the block while the engine was on a work stand.  I was also checking cam timing and lots of other things.

I would try to back it away from the bellhousing flange just because you don't need to weaken that area.  It cannot be a highly stressed area, but I
am sort of (OK - Really) paranoid.  Punch the hole, and if you loose the plug, pull the splash cover off the lower bell housing.  There was room for
me to get it out.  But I was also thinking I might have to walk it up to the starter hole.  There is nothing in there that can be hurt.  It you take
it slowly, you should be able to cut until it is just hanging on and break it back out of the hole.  I did, but the engine and transmission when in
the front frame yet to be installed.

That Pertronix 1181LS is just right up there with canned beer and colored sox in my book.  I have hated hanging by my toes to set timing all those 16
year and one major overhaul.  I'm about to put in a rebuild distributor with Dick Paterson parts.  I know I am going to appreciate it then.

Let me think about involving another.  I do have GM friends, but this might tax their sense of humor.

If you do have other questions, I here.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit

dsmithy wrote on Sat, 05 June 2021 19:56 > Matt, > Can I assume that the picture which includes the vacuum actuator on the distributor indicates the best location for the hole in the bellhousing? > Or, can the hole be located anywhere based on drilling ease/access if TDC on cylinder one is located accurately? Is there a distance from the > mounting flange (to catch the flywheel gear accurately) that is available or is it a guess? Is it safe to drill on an installed engine/bellhousing? > What are the consequences of losing the cutout disc from drilling (which clumsy/unlucky people {me} will do). > > I ask this because timing has been a frustration for me for the 25 years I've owned my coach. Basically I've ignored it in the absence of > problems. That has meant that I've been, if you explore the margins, getting lousy mileage, experience a perfectly running engine (?), or flirting > with disaster with advanced timing, or some less than optimal blending of the three. > > There are limited mods to stock which are universally accepted and generally not up for debate. The Pertronix lobe sensing unit (for my year GMC), > blocking the intake exhaust crossover, the flywheel timing for the Onan, and alloy wheels come to mind first. Everyone has their favorites based on > their willingness to pay or dig into the innards of their coach. I suspect your "Gunsight Timing" would easily join the list if the bar were lowered > just a bit for people like me who see a great idea but are a little intimidated by the process. Perhaps you have a friend out there with a coach "in > process" who could do the modification and document it for us rabble? > Doug Doug, Timing has only been a frustration of mine for only 16 years..... (Chaumière came here in 2006.) You have hit my favorite mods, but I have yet to afford the cost of alloy wheels. The location of the hole in the bellhousing is completely arbitrary. Make it where it works for you. It only really needs to let you see teeth for calibration. But do create a reference mark on the block casting. And yes, I kind of wish I had located it differently than I did, but it works. I marked teeth and put the reference mark in the block while the engine was on a work stand. I was also checking cam timing and lots of other things. I would try to back it away from the bellhousing flange just because you don't need to weaken that area. It cannot be a highly stressed area, but I am sort of (OK - Really) paranoid. Punch the hole, and if you loose the plug, pull the splash cover off the lower bell housing. There was room for me to get it out. But I was also thinking I might have to walk it up to the starter hole. There is nothing in there that can be hurt. It you take it slowly, you should be able to cut until it is just hanging on and break it back out of the hole. I did, but the engine and transmission when in the front frame yet to be installed. That Pertronix 1181LS is just right up there with canned beer and colored sox in my book. I have hated hanging by my toes to set timing all those 16 year and one major overhaul. I'm about to put in a rebuild distributor with Dick Paterson parts. I know I am going to appreciate it then. Let me think about involving another. I do have GM friends, but this might tax their sense of humor. If you do have other questions, I here. Matt -- Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms SE Michigan - Near DTW - Twixt A2 and Detroit
DS
Douglas Smith
Sun, Jun 6, 2021 4:21 AM

Colored socks…  Not so sure.
Sliced Bread…    For Sure.
Pertronix…          Best mod ever.
Gunshot Timing…  Best idea ever.

Did I ever tell you about the time the alternator belt threw my timing light into my face? Maybe over an adult beverage sometime.
D

On Jun 5, 2021, at 10:12 PM, Matt Colie matt7323tze@gmail.com wrote:

dsmithy wrote on Sat, 05 June 2021 19:56

Matt,
Can I assume that the picture which includes the vacuum actuator on the distributor indicates the best location for the hole in the bellhousing?
Or, can the hole be located anywhere based on drilling ease/access if TDC on cylinder one is located accurately? Is there a distance from the
mounting flange (to catch the flywheel gear accurately) that is available or is it a guess? Is it safe to drill on an installed engine/bellhousing?
What are the consequences of losing the cutout disc from drilling (which clumsy/unlucky people {me} will do).

I ask this because timing has been a frustration for me for the 25 years I've owned my coach. Basically I've ignored it in the absence of
problems. That has meant that I've been, if you explore the margins, getting lousy mileage, experience a perfectly running engine (?), or flirting
with disaster with advanced timing, or some less than optimal blending of the three.

There are limited mods to stock which are universally accepted and generally not up for debate. The Pertronix lobe sensing unit (for my year GMC),
blocking the intake exhaust crossover, the flywheel timing for the Onan, and alloy wheels come to mind first. Everyone has their favorites based on
their willingness to pay or dig into the innards of their coach. I suspect your "Gunsight Timing" would easily join the list if the bar were lowered
just a bit for people like me who see a great idea but are a little intimidated by the process. Perhaps you have a friend out there with a coach "in
process" who could do the modification and document it for us rabble?
Doug

Doug,

Timing has only been a frustration of mine for only 16 years..... (Chaumière came here in 2006.)
You have hit my favorite mods, but I have yet to afford the cost of alloy wheels.

The location of the hole in the bellhousing is completely arbitrary.  Make it where it works for you.  It only really needs to let you see teeth for
calibration. But do create a reference mark on the block casting.  And yes, I kind of wish I had located it differently than I did, but it works.  I
marked teeth and put the reference mark in the block while the engine was on a work stand.  I was also checking cam timing and lots of other things.

I would try to back it away from the bellhousing flange just because you don't need to weaken that area.  It cannot be a highly stressed area, but I
am sort of (OK - Really) paranoid.  Punch the hole, and if you loose the plug, pull the splash cover off the lower bell housing.  There was room for
me to get it out.  But I was also thinking I might have to walk it up to the starter hole.  There is nothing in there that can be hurt.  It you take
it slowly, you should be able to cut until it is just hanging on and break it back out of the hole.  I did, but the engine and transmission when in
the front frame yet to be installed.

That Pertronix 1181LS is just right up there with canned beer and colored sox in my book.  I have hated hanging by my toes to set timing all those 16
year and one major overhaul.  I'm about to put in a rebuild distributor with Dick Paterson parts.  I know I am going to appreciate it then.

Let me think about involving another.  I do have GM friends, but this might tax their sense of humor.

If you do have other questions, I here.

Matt

Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit


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Colored socks… Not so sure. Sliced Bread… For Sure. Pertronix… Best mod ever. Gunshot Timing… Best idea ever. Did I ever tell you about the time the alternator belt threw my timing light into my face? Maybe over an adult beverage sometime. D > On Jun 5, 2021, at 10:12 PM, Matt Colie <matt7323tze@gmail.com> wrote: > > dsmithy wrote on Sat, 05 June 2021 19:56 >> Matt, >> Can I assume that the picture which includes the vacuum actuator on the distributor indicates the best location for the hole in the bellhousing? >> Or, can the hole be located anywhere based on drilling ease/access if TDC on cylinder one is located accurately? Is there a distance from the >> mounting flange (to catch the flywheel gear accurately) that is available or is it a guess? Is it safe to drill on an installed engine/bellhousing? >> What are the consequences of losing the cutout disc from drilling (which clumsy/unlucky people {me} will do). >> >> I ask this because timing has been a frustration for me for the 25 years I've owned my coach. Basically I've ignored it in the absence of >> problems. That has meant that I've been, if you explore the margins, getting lousy mileage, experience a perfectly running engine (?), or flirting >> with disaster with advanced timing, or some less than optimal blending of the three. >> >> There are limited mods to stock which are universally accepted and generally not up for debate. The Pertronix lobe sensing unit (for my year GMC), >> blocking the intake exhaust crossover, the flywheel timing for the Onan, and alloy wheels come to mind first. Everyone has their favorites based on >> their willingness to pay or dig into the innards of their coach. I suspect your "Gunsight Timing" would easily join the list if the bar were lowered >> just a bit for people like me who see a great idea but are a little intimidated by the process. Perhaps you have a friend out there with a coach "in >> process" who could do the modification and document it for us rabble? >> Doug > > Doug, > > Timing has only been a frustration of mine for only 16 years..... (Chaumière came here in 2006.) > You have hit my favorite mods, but I have yet to afford the cost of alloy wheels. > > The location of the hole in the bellhousing is completely arbitrary. Make it where it works for you. It only really needs to let you see teeth for > calibration. But do create a reference mark on the block casting. And yes, I kind of wish I had located it differently than I did, but it works. I > marked teeth and put the reference mark in the block while the engine was on a work stand. I was also checking cam timing and lots of other things. > > > I would try to back it away from the bellhousing flange just because you don't need to weaken that area. It cannot be a highly stressed area, but I > am sort of (OK - Really) paranoid. Punch the hole, and if you loose the plug, pull the splash cover off the lower bell housing. There was room for > me to get it out. But I was also thinking I might have to walk it up to the starter hole. There is nothing in there that can be hurt. It you take > it slowly, you should be able to cut until it is just hanging on and break it back out of the hole. I did, but the engine and transmission when in > the front frame yet to be installed. > > That Pertronix 1181LS is just right up there with canned beer and colored sox in my book. I have hated hanging by my toes to set timing all those 16 > year and one major overhaul. I'm about to put in a rebuild distributor with Dick Paterson parts. I know I am going to appreciate it then. > > Let me think about involving another. I do have GM friends, but this might tax their sense of humor. > > If you do have other questions, I here. > > Matt > -- > Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES > Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms > SE Michigan - Near DTW - Twixt A2 and Detroit > _______________________________________________ > GMCnet mailing list > Unsubscribe or Change List Options: