Pre Combat timing case mod (2015)

gripper · Apr 20, 2015

My 1970 Fastback that seized with the wet sumping valve issue is about to go back together. All the drilling mods to the timing cover tend to deal with the Combat engine and later. Many years ago (30+) I followed the top tips in the NOC technical handbook and did away with my camshaft breather and drilled a couple of 3/8 holes into the timing chest. I fitted a breather where the mag/started blanking plate was fitted. That plate has now been replaced with a XS reed valve. I notice that the drain hole from the timing chest is pretty high up and I guess the timing chest is swamped most of the time. I'm planning on drilling a 3mm hole in the bottom of the timing chest as shown on the Andover Norton website. Can anybody see a good reason not to do this. I wasn't planning on blocking the hole above and to the left of the oil pump.

pete.v · Apr 20, 2015

Well my thinking says that it is meant to be swamped to some extent. The higher(not high) standard drain and the crankshaft backing washer seem to promote this. Although there is a camp to evacuate the timing chest to gain what, I am not sure.

They say the cam chain and respective gears will be splashed adequately, whatever that is, but a sump that returns with efficiently will make me wonder why they designed to have the sump retain so much oil in the first place. They certainly could have dropped the drain hole location ages ago, but they didn't.

For me, I'm not taking the chance. There has been much discussion on other things relating to oil flow ideas that are proving to be way more a detriment than an asset, or simply put, more solutions to problems that don't exist.

The only true benefit I see for lowering the timing case to crankcase drain hole is when you change the oil, the oil in the timing case will drain without have to tip it on its side to get every drop out.

In addition, if, as you say, you are using the mag boss for reed valve breather, you want more openings, not less. So I might say that you have made your choice already.

We would like our crankcases to breath better, that,s all well and good, but we're not racers and we're not going to go dyno our motors to check the benefit or detriment of every hole we open of plug up.

For what it's worth, I run 2 reed breathers on my 72. An XS unit up from the old low breather on the crankcase going to the oil tank and the Grandpaul reed breather incorporated into the mag boss going to atmosphere. No big whoop. Breather easy.

comnoz · Apr 20, 2015

gripper said:
My 1970 Fastback that seized with the wet sumping valve issue is about to go back together. All the drilling mods to the timing cover tend to deal with the Combat engine and later. Many years ago (30+) I followed the top tips in the NOC technical handbook and did away with my camshaft breather and drilled a couple of 3/8 holes into the timing chest. I fitted a breather where the mag/started blanking plate was fitted. That plate has now been replaced with a XS reed valve. I notice that the drain hole from the timing chest is pretty high up and I guess the timing chest is swamped most of the time. I'm planning on drilling a 3mm hole in the bottom of the timing chest as shown on the Andover Norton website. Can anybody see a good reason not to do this. I wasn't planning on blocking the hole above and to the left of the oil pump.

I have not seen the hole recommended by NOC but for several years now I have been drilling a 1/4 inch hole to the lower left of the oil pump for timing chest drain.
The stock oil drain was designed when the engine was mounted vertically in the older chassis. When you tip the motor forward as in a Commando then the oil level is increased to a much higher level. That makes way too much oil being churned in the gears and getting hot. Jim

pete.v · Apr 20, 2015

Hey, Jim, I have got to ask, what is the temp difference of the oil with the standard hole vs the lower hole? 4 degrees maybe 7.2 degrees difference? You better test this out and get back to us.

When you tip the motor forward as in a Commando then the oil level is increased to a much higher level.

The canted difference does change the oil level slightly but I really do not think it's "much" higher. I recall checking this the last time this was brought up when I had a set of spare cases laying around. It's not that much different. And to set a precedence of "less oil is better then a little too much in the timing case" when there really is no research to substantiate this is not a good idea for so many new owners to grasp. Also, I have never had issue in this area.

I think the bigger issue is that so many, particularly 850's, use breathers from the old mag area. These changes may be OK for the very the few who can take advantage of and afford your breather, but as a "given" way to do things, is splitting hairs, impractical and the benefits are totally not worth the procedure for the rest of us who simply want to own and ride these fantastic machines without having to do some frankensteining to gain .05% in HP.

Sorry for the run on.

comnoz · Apr 20, 2015

pete.v said:
Hey, Jim, I have got to ask, what is the temp difference of the oil with the standard hole vs the lower hole? 4 degrees maybe 7.2 degrees difference? You better test this out and get back to us.

When you tip the motor forward as in a Commando then the oil level is increased to a much higher level.

Click to expand...

The canted difference does change the oil level slightly but I really do not think it's "much" higher. I recall checking this the last time this was brought up when I had a set of spare cases laying around. It's not that much different. And to set a precedence of "less oil is better then a little too much in the timing case" when there really is no research to substantiate this is not a good idea for so many new owners to grasp. Also, I have never had issue in this area.

I think the bigger issue is that so many, particularly 850's, use breathers from the old mag area. These changes may be OK for the very the few who can take advantage of and afford your breather, but as a "given" way to do things, is splitting hairs, impractical and the benefits are totally not worth the procedure for the rest of us who simply want to own and ride these fantastic machines without having to do some frankensteining to gain .05% gain in HP.

Sorry for the run on.

I have tested it with a pyrometer in the oil in the timing case. The temp difference in the oil temp was in the 20 degree area on the highway.
The level drops from well over the crank gear to 1/2 way up the crank gear. I also had a lexan cover over the large hole where most bikes have an ignition mounted. There was still plenty of oil flying around to keep everything well lubed. Jim

Danno · Apr 20, 2015

So the new 1/4" drain hole should be drilled level with the center of the crank gear? Do you by chance have a photo?

comnoz · Apr 20, 2015

Danno said:
So the new 1/4" drain hole should be drilled level with the center of the crank gear? Do you by chance have a photo?

Here is a picture showing the new drain hole. It is drilled parallel with the crank [IE no downward angle.]
Do not plug the upper holes unless you are using a crankcase reed breather -venting directly from the crankcase instead of the timing chest.

Here is the oil level in the timing chest with the stock "Atlas" drain hole in a Commando engine.

Here is the oil level with the new drain hole.

Snorton74 · Apr 20, 2015

pete.v said:
Well my thinking says that it is meant to be swamped to some extent. The higher(not high) standard drain and the crankshaft backing washer seem to promote this. Although there is a camp to evacuate the timing chest to gain what, I am not sure.

They say the cam chain and respective gears will be splashed adequately, whatever that is, but a sump that returns with efficiently will make me wonder why they designed to have the sump retain so much oil in the first place. They certainly could have dropped the drain hole location ages ago, but they didn't.

For me, I'm not taking the chance. There has been much discussion on other things relating to oil flow ideas that are proving to be way more a detriment than an asset, or simply put, more solutions to problems that don't exist.

The only true benefit I see for lowering the timing case to crankcase drain hole is when you change the oil, the oil in the timing case will drain without have to tip it on its side to get every drop out.

In addition, if, as you say, you are using the mag boss for reed valve breather, you want more openings, not less. So I might say that you have made your choice already.

We would like our crankcases to breath better, that,s all well and good, but we're not racers and we're not going to go dyno our motors to check the benefit or detriment of every hole we open of plug up.

For what it's worth, I run 2 reed breathers on my 72. An XS unit up from the old low breather on the crankcase going to the oil tank and the Grandpaul reed breather incorporated into the mag boss going to atmosphere. No big whoop. Breather easy.

Passive aggressive much Petey cakes? Thinkin and knowin are two different things. How long did this years New Years resolution last?

pete.v · Apr 21, 2015

Snorton74 said:
pete.v said:

Well my thinking says that it is meant to be swamped to some extent. The higher(not high) standard drain and the crankshaft backing washer seem to promote this. Although there is a camp to evacuate the timing chest to gain what, I am not sure.

They say the cam chain and respective gears will be splashed adequately, whatever that is, but a sump that returns with efficiently will make me wonder why they designed to have the sump retain so much oil in the first place. They certainly could have dropped the drain hole location ages ago, but they didn't.

For me, I'm not taking the chance. There has been much discussion on other things relating to oil flow ideas that are proving to be way more a detriment than an asset, or simply put, more solutions to problems that don't exist.

The only true benefit I see for lowering the timing case to crankcase drain hole is when you change the oil, the oil in the timing case will drain without have to tip it on its side to get every drop out.

In addition, if, as you say, you are using the mag boss for reed valve breather, you want more openings, not less. So I might say that you have made your choice already.

We would like our crankcases to breath better, that,s all well and good, but we're not racers and we're not going to go dyno our motors to check the benefit or detriment of every hole we open of plug up.

For what it's worth, I run 2 reed breathers on my 72. An XS unit up from the old low breather on the crankcase going to the oil tank and the Grandpaul reed breather incorporated into the mag boss going to atmosphere. No big whoop. Breather easy.

Click to expand...

Passive aggressive much Petey cakes? Thinkin and knowin are two different things. How long did this years New Years resolution last?

Defensive much Snorton74? No hidden agenda here. It's what I think and this is a forum. Google it.

pete.v · Apr 21, 2015

comnoz said:
[

I have tested it with a pyrometer in the oil in the timing case. The temp difference in the oil temp was in the 20 degree area on the highway.
The level drops from well over the crank gear to 1/2 way up the crank gear. I also had a lexan cover over the large hole where most bikes have an ignition mounted. There was still plenty of oil flying around to keep everything well lubed. Jim

So what I hear is that with this lower drain hole it will take even longer for my oil to warm up? And what about the timing side breather thing?

gripper · Apr 21, 2015

Thanks for the photos Jim, that's what I was thinking. With the higher level i.e. without the lower hole, I guess a lot of oil will end up being sprayed around close to my mag mounted breather and some will get through it. Pottering around at town traffic speeds the catch bottle on my XS breather stayed empty but at higher cruising speeds it would fill up. Out with my Black and Decker.

cjandme · Apr 21, 2015

comnoz said:
......Do not plug the upper holes unless you are using a crankcase reed breather -venting directly from the crankcase instead of the timing chest.....

Danno · Apr 21, 2015

comnoz said:
Danno said:

So the new 1/4" drain hole should be drilled level with the center of the crank gear? Do you by chance have a photo?

Click to expand...

Here is a picture showing the new drain hole. It is drilled parallel with the crank [IE no downward angle.]
Do not plug the upper holes unless you are using a crankcase reed breather -venting directly from the crankcase instead of the timing chest.

Here is the oil level in the timing chest with the stock "Atlas" drain hole in a Commando engine.

Here is the oil level with the new drain hole.

Thanks. Debate aside, that's good enough for me.

comnoz · Apr 21, 2015

pete.v said:
comnoz said:

[

I have tested it with a pyrometer in the oil in the timing case. The temp difference in the oil temp was in the 20 degree area on the highway.
The level drops from well over the crank gear to 1/2 way up the crank gear. I also had a lexan cover over the large hole where most bikes have an ignition mounted. There was still plenty of oil flying around to keep everything well lubed. Jim

Click to expand...

So what I hear is that with this lower drain hole it will take even longer for my oil to warm up? And what about the timing side breather thing?

There is a very small amount of oil going into the timing chest. The only supply is what returns from the intake side of the head and through the rear of the barrels. A very small dribble. It is already very hot when it arrives in the timing chest.

Lowering the oil drain hole did not make a noticeable difference in the temp of the oil in the tank. Jim

pete.v · Apr 21, 2015

Thanks for the level head and straight answers, Jim. I commend you for seeing through the crap and getting and staying to the point.

One more question, I can see being able drilling the lower hole with the motor on place by pressuring the case and greasing up a drill if I feel the need, but having a breather on the timing side, do you see it necessary to block the current upper drain hole or just let be?

comnoz · Apr 21, 2015

pete.v said:
Thanks for the level head and straight answers, Jim. I commend you for seeing through the crap and getting and staying to the point.

One more question, I can see being able drilling the lower hole with the motor on place by pressuring the case and greasing up a drill if I feel the need, but having a breather on the timing side, do you see it necessary to block the current upper drain hole or just let be?

With the breather on the timing case I would leave the upper holes open. Jim

pierodn · Dec 12, 2020

comnoz said:
Here is a picture showing the new drain hole. It is drilled parallel with the crank [IE no downward angle.]
Do not plug the upper holes unless you are using a crankcase reed breather -venting directly from the crankcase instead of the timing chest.

Here is the oil level in the timing chest with the stock "Atlas" drain hole in a Commando engine.

Here is the oil level with the new drain hole.

Sorry,
but a higher oil level in the timing doesnt need to lubrificate better the worm and intermediate gears and distribution chain?.
Thanks.
Piero

concours · Dec 12, 2020

pierodn said:
Sorry,
but a higher oil level in the timing doesnt need to lubrificate better the worm and intermediate gears and distribution chain?.
Thanks.
Piero

I read all this thread. Good stuff. But, I opted to keep my timing chain bathed in oil. Not detracting from any other views, just my lifelong fixing of junk habits.

dynodave · Dec 12, 2020

Of course the middle pix in jims photo's are of the super early 20M3 cases with the ATLAS only drain hole. The normal/later 20M3 cases have a casting core mod that allows the oil level to be lowered via a second lower drain hole that intersects into the higher drilled passage. Just sayin....The engineers were fixing the problems from just carrying over the entire atlas design.
You can see the second hole, though it is shown here on the 20M3S cases.

Time Warp · Dec 12, 2020

I elected to do a mid point drain.
This would put the new level somewhere below the 20M3S 750 / 850 revised location but higher than that mod where it is placed down near the lower oil pump stud.
It is now central (mill DRO) between the oil pump feed and return passages and passes through the lower portion of the (deep) hose pipe junction fastener hole below the factory thread coil insert.

The right hand side of the new hole corresponds with the bottom of the fastener hole.

Pre Combat timing case mod (2015)

gripper

pete.v

comnoz

pete.v

comnoz

Danno

comnoz

Snorton74

pete.v

pete.v

gripper

cjandme

Danno

comnoz

pete.v

comnoz

pierodn

concours

dynodave

Time Warp

.......back to the 70's.

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