Author Topic: OHC 4 stroke datsun engine timing questions  (Read 2018 times)

Offline theeoracle

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OHC 4 stroke datsun engine timing questions
« on: February 12, 2019, 06:06:20 AM »
I'm having trouble trying to figure out how to time an engine i'm designing in CAD and will build. There's not much room inside the valve cover and front cover. My original thought was to use an MXL belt and pulleys but they won't work with the shaft diameter and overall OD the pulleys would be. My though right now is to use sprockets and a chain. I'm wondering is there a small low profile chain tensioner that anyone has made before. Any and all suggestions will help.

Offline Allen Smithee

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Re: OHC 4 stroke datsun engine timing questions
« Reply #1 on: February 12, 2019, 10:23:59 AM »
Depends how complex you want the result to be - you could use a geared solution using two or three intermediate idler dears to keep the gear diameters down as in this wide-angle V engine:



Or alternatively use bevel gears and a vertical drive shaft like a rolls royce merlin:



AS
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Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #2 on: February 12, 2019, 04:16:28 PM »
preferably something simple but I guess i'll have to use gears for it being such a small area. There is a company in japan who created a gear driven system for a Datsun engine. I'll have to take some inspiration from that.

I'm not sure where I can get gears that would work though. The crank diameter is .5 and the timing needs to be 2:1.
I have access to 3/4/5 axis CNC machines. So I might have to make custom gears that would fit over the .5 crank shaft?

Also i'm going to have to have each gear adjustable to get rid of backlash?

Offline Longboy

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Re: OHC 4 stroke datsun engine timing questions
« Reply #3 on: February 12, 2019, 04:20:47 PM »
Reducing the crankshaft diameters beyond the main bearing at the point where the MXL cogs go may work in your design. Without any reference numbers provided here nor the scale size, an example of a crank nose at .625 in. can be turned down to .312 in. to accommodate a 60/30 tooth cog set. The cog flange diameters are about 1.7 in and .95 in. for the example's cam drive case clearance needs. The alternative is a CAD rework of the cam drive area.

I just see now your post with the .5in crank diameter.
Wadda you mean, "It don't run"???

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #4 on: February 12, 2019, 04:48:02 PM »
So I think I can make the 60/30 pulleys work if I make the end crank diameter .375, once I bore the id some. So to attach the lower pulley I could just machine a flat in the crank and have a setscrew in the pulley like in the pic?

Also tensioning the belt is a little tricky because it has to go around the water pump passages in the front cover. I'm thinking one idler at the inspection cover in the head and a tensioner closer to the crank?
« Last Edit: February 12, 2019, 04:51:44 PM by theeoracle »

Offline Longboy

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Re: OHC 4 stroke datsun engine timing questions
« Reply #5 on: February 12, 2019, 06:13:27 PM »
So I think I can make the 60/30 pulleys work if I make the end crank diameter .375, once I bore the id some. So to attach the lower pulley I could just machine a flat in the crank and have a setscrew in the pulley like in the pic?

Also tensioning the belt is a little tricky because it has to go around the water pump passages in the front cover. I'm thinking one idler at the inspection cover in the head and a tensioner closer to the crank?


The hub dia. of a 30T cog is about .550in. You will be catching about 4 threads of a #6 set screw with a .375 in. overbore. Dual setscrews with a flat seat on the crank "may" be enough. A solution to inadequate hub diameter is to make a collar to press fit / epoxy around the existing hub and re drill for a longer setscrew and more thread area.  You can pre- drill the collar to line up with the hub setscrew holes and drill the next thread size up.

Your water pump box is an issue working a belt around by idlers. You would need to be dead nuts on the belt tooth count too.  What I would think about, looking at your photo, is eliminate the water pump box section under the cam drive cog for an external cam drive set-up with idlers on engine mounted brackets to give you more lead way as well as a sprocket guard bolted to the engine or as part of the valve cover.  :ThumbsUp:
 
Wadda you mean, "It don't run"???

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #6 on: February 12, 2019, 06:19:23 PM »
I think I might even be able to use a 42/21 pulley if I bore the 21 pulley out to .375. That leaves .047" of wall thickness, I think that will be enough, what do you think?

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #7 on: February 12, 2019, 06:37:05 PM »
So I think I can make the 60/30 pulleys work if I make the end crank diameter .375, once I bore the id some. So to attach the lower pulley I could just machine a flat in the crank and have a setscrew in the pulley like in the pic?

Also tensioning the belt is a little tricky because it has to go around the water pump passages in the front cover. I'm thinking one idler at the inspection cover in the head and a tensioner closer to the crank?


The hub dia. of a 30T cog is about .550in. You will be catching about 4 threads of a #6 set screw with a .375 in. overbore. Dual setscrews with a flat seat on the crank "may" be enough. A solution to inadequate hub diameter is to make a collar to press fit / epoxy around the existing hub and re drill for a longer setscrew and more thread area.  You can pre- drill the collar to line up with the hub setscrew holes and drill the next thread size up.

Your water pump box is an issue working a belt around by idlers. You would need to be dead nuts on the belt tooth count too.  What I would think about, looking at your photo, is eliminate the water pump box section under the cam drive cog for an external cam drive set-up with idlers on engine mounted brackets to give you more lead way as well as a sprocket guard bolted to the engine or as part of the valve cover.  :ThumbsUp:

In an ideal world yes I would have the timing drive outside of the valve cover and front cover but then it won't look much like a datsun engine.

Offline Longboy

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Re: OHC 4 stroke datsun engine timing questions
« Reply #8 on: February 12, 2019, 07:00:36 PM »
If you are determined to an authentic recreation, then that decision is made for you!  Which Nissan engine are you modeling and how did they drive the cam?
Wadda you mean, "It don't run"???

Offline Longboy

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Re: OHC 4 stroke datsun engine timing questions
« Reply #9 on: February 12, 2019, 07:15:55 PM »
I think I might even be able to use a 42/21 pulley if I bore the 21 pulley out to .375. That leaves .047" of wall thickness, I think that will be enough, what do you think?

If the wall thickness refers to the cog hub on the crankshaft....you are now down to less than two threads.
Wadda you mean, "It don't run"???

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #10 on: February 13, 2019, 05:26:15 PM »
If you are determined to an authentic recreation, then that decision is made for you!  Which Nissan engine are you modeling and how did they drive the cam?

I think I might even be able to use a 42/21 pulley if I bore the 21 pulley out to .375. That leaves .047" of wall thickness, I think that will be enough, what do you think?

If the wall thickness refers to the cog hub on the crankshaft....you are now down to less than two threads.

I'm making an L16, used in a bunch of different Datsuns from pretty much 68-79. I have one in pieces in my garage so i've just been using that as a guide. I'm probably one of the youngest people on here at 22 so I'm just figuring out what needs to get done and how I can do it as I model. This is my first engine project ever so any pointes would be cool.

and for the lower pulley this is how I image it could work. There's .165 for the threads to hold onto.

Offline Admiral_dk

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Re: OHC 4 stroke datsun engine timing questions
« Reply #11 on: February 13, 2019, 07:03:44 PM »
A very big project as a first  :o  but then again you won't be the first - neither to succeed nor fail as a first .... though that said, it is usual better starting with an easier design and then go gradually more and more difficult.

I still wish you the best and hope you will continue no matter the result.

Per

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #12 on: February 13, 2019, 07:55:37 PM »
thank you

These are the pieces i've made so far.


Offline Admiral_dk

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Re: OHC 4 stroke datsun engine timing questions
« Reply #13 on: February 13, 2019, 10:04:04 PM »
They look great  :cheers:

Let me guess - you have access to a nice CNC mill ...  :thinking:  - don't get me wrong, as this still requires creating a good tool path in order to avoid some not very nice mishaps (if you haven't got a clue about those, you don't know CNC yet  ;) ).

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #14 on: February 14, 2019, 05:22:27 AM »
They look great  :cheers:

Let me guess - you have access to a nice CNC mill ...  :thinking:  - don't get me wrong, as this still requires creating a good tool path in order to avoid some not very nice mishaps (if you haven't got a clue about those, you don't know CNC yet  ;) ).

yup I work in a CNC job shop. I started about 3 months ago from knowing nothing about machining. we got five 3 axis haas mills and just got a 5 axis haas 3 weeks ago.

Offline Longboy

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Re: OHC 4 stroke datsun engine timing questions
« Reply #15 on: February 14, 2019, 06:43:39 AM »



[/quote]

I'm making an L16, used in a bunch of different Datsuns from pretty much 68-79............... This is my first engine project ever so any pointes would be cool.

and for the lower pulley this is how I image it could work. There's .165 for the threads to hold onto.
[/quote]

I see it now with the large hub behind the flange. On the water pump box.......maybe you could extend that rectangle shape out to the right some ( in photo) or just enlarge it for more internal room setting up the belt pulleys and still be true to the original engine external looks.

Most of the modelers here with years behind them are going say start out with a simpler, newbie project engine. CNC can make the transition from simple to complex quicker. Hands on, human experience....not so fast. Continue your work if comfortable, your Datsun engine can be set aside if needed for another day as you get more time behind you.
Wadda you mean, "It don't run"???

Offline Bluechip

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Re: OHC 4 stroke datsun engine timing questions
« Reply #16 on: February 14, 2019, 08:35:41 AM »
Quote should be from theeoracle ...


I'm making an L16, used in a bunch of different Datsuns from pretty much 68-79...............


One of those powered my 1972 510 Estate ( wagon ? )

After the vagaries of the rubbishy Ford Cortina 1600E that preceded it the reliability of the Datsun was a revelation.

Fond memories ... Except it came with white-wall cross-ply tyres .... Soon dumped them before they dumped me ...  :)

Don't help you to model the engine though.  :thinking:

Dave

« Last Edit: February 14, 2019, 08:38:58 AM by Bluechip »

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #17 on: February 15, 2019, 04:23:26 PM »




I'm making an L16, used in a bunch of different Datsuns from pretty much 68-79............... This is my first engine project ever so any pointes would be cool.

and for the lower pulley this is how I image it could work. There's .165 for the threads to hold onto.
[/quote]

I see it now with the large hub behind the flange. On the water pump box.......maybe you could extend that rectangle shape out to the right some ( in photo) or just enlarge it for more internal room setting up the belt pulleys and still be true to the original engine external looks.

Most of the modelers here with years behind them are going say start out with a simpler, newbie project engine. CNC can make the transition from simple to complex quicker. Hands on, human experience....not so fast. Continue your work if comfortable, your Datsun engine can be set aside if needed for another day as you get more time behind you.
[/quote]

I do have a question regarding the oiling system though. Do you think I need through crank oiling like in a real car or do you think having the crank splash in oil is enough? The crank will have bronze oil bearings. Also for the camshaft oiling I plan on using a spray bar and a low pressure pump that I will make. Do you think that would work with 8 outlets for each cam?

Offline Admiral_dk

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Re: OHC 4 stroke datsun engine timing questions
« Reply #18 on: February 15, 2019, 08:39:37 PM »
Lubrication is always a good question and not always an easy one to answer as there are several factors involved.
The size of the workload is one of the biggest factors, so let's start here. :

How big is the engine - bore, stroke and compression (the last can usually be answered with the CAD program you're using) ?
How big will the load be ? - RPM ?
What kind of fuel will you be using ?

Cylinders / pistons can usually get plenty of oil from the fuel with 1-2% oil in it and splash lubrication is in most cases plenty in this area. Con rods again, can often get away with plash lubrication and all ball bearing are very happy with an oil mist (actually preferred). Camshafts and crankshaft bearings vary, as plain bearing often require pressure to work, but that is again VERY load dependent. The cams themselves are happy with splash lube.

OS model latest FS series four-stroke aero engines are only lubricated from a bit of oil in the fuel and a genially  simple system of channels that uses the unavoidable higher pressure in the crankcase + the fact that some of the oil in the fuel ends up there, to move that oil through the crank bearings to the camshaft. From there it goes through the pushrod tubes to the cylinder head where it lubes the valves etc. and goes back to the inlet through a very small hole, get sucked back in and the hole thing repeats  :praise2:

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #19 on: February 16, 2019, 05:10:24 AM »
Lubrication is always a good question and not always an easy one to answer as there are several factors involved.
The size of the workload is one of the biggest factors, so let's start here. :

How big is the engine - bore, stroke and compression (the last can usually be answered with the CAD program you're using) ?
How big will the load be ? - RPM ?
What kind of fuel will you be using ?

Cylinders / pistons can usually get plenty of oil from the fuel with 1-2% oil in it and splash lubrication is in most cases plenty in this area. Con rods again, can often get away with plash lubrication and all ball bearing are very happy with an oil mist (actually preferred). Camshafts and crankshaft bearings vary, as plain bearing often require pressure to work, but that is again VERY load dependent. The cams themselves are happy with splash lube.

OS model latest FS series four-stroke aero engines are only lubricated from a bit of oil in the fuel and a genially  simple system of channels that uses the unavoidable higher pressure in the crankcase + the fact that some of the oil in the fuel ends up there, to move that oil through the crank bearings to the camshaft. From there it goes through the pushrod tubes to the cylinder head where it lubes the valves etc. and goes back to the inlet through a very small hole, get sucked back in and the hole thing repeats  :praise2:

So for now there is no intended use other than to run it on a stand.
The bore is .96 and stroke is .96. The conrods will have bronze oil bearings on them, same with the mains. As for the camshaft it will look the same as in the picture. Some Datsun L series engines used a spray bar for the camshaft. I will try that on my valvetrain. I guess my question is if I use a spray bar and drill 8 holes for each lobe and the oil comes from the center of the tube will I get even flow throughout the whole tube? or do I need to drill progressively larger holes further out.

Offline Roger B

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Re: OHC 4 stroke datsun engine timing questions
« Reply #20 on: February 16, 2019, 07:36:57 AM »
For short runs off load on a stand on a stand splash lubrication should be fine for the bottom end. You will need something for the OHC. This could be as simple as remove the rocker cover and give the cams and drive gears a squirt from an oil can before you start.
Best regards

Roger

Offline Admiral_dk

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Re: OHC 4 stroke datsun engine timing questions
« Reply #21 on: February 16, 2019, 11:50:46 AM »
That amount of CC's is enough to warrant pressure oiling of the mains if it is loaded for sure or sustained runs …. but Roger might be right about just a plash in all the right places before a run - I hope some of the builders of bigger 4, 6 & 8 cylinder engines here will chime in, though I'm sure that they all have presure oiling. This should be possible in an engine of this size and to an extent required for a scale model.

The next part of your question - yes all oil lines / galleries have a certain internal diameter and a much smaller outlet at each oiling point in order to keep the presure in the system + make sure all places get what they need. On full size engines you will often find jets like the ones in an old carb in the oil lines (except that you can't change them). The jets over the cams create a spray pattern as it both cools and lubes better than a constant flow of oil there - in performance engines.

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #22 on: February 16, 2019, 04:49:35 PM »
That amount of CC's is enough to warrant pressure oiling of the mains if it is loaded for sure or sustained runs …. but Roger might be right about just a plash in all the right places before a run - I hope some of the builders of bigger 4, 6 & 8 cylinder engines here will chime in, though I'm sure that they all have presure oiling. This should be possible in an engine of this size and to an extent required for a scale model.

The next part of your question - yes all oil lines / galleries have a certain internal diameter and a much smaller outlet at each oiling point in order to keep the presure in the system + make sure all places get what they need. On full size engines you will often find jets like the ones in an old carb in the oil lines (except that you can't change them). The jets over the cams create a spray pattern as it both cools and lubes better than a constant flow of oil there - in performance engines.

If I really need pressured oil going to the mains, would I also need the rods to be pressured? How would I go about doing this. I know conley uses his hole popper EDM. I could probably find someone who has one.

Offline Admiral_dk

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Re: OHC 4 stroke datsun engine timing questions
« Reply #23 on: February 17, 2019, 10:41:43 PM »
You "only" need to drill a small hole from the main bearing to the throw in the crank in order to lube the big-end of the con-rod as the small end never is pressure lubricated.

There are several engines here on site where you can see it done with pictures and accompanying text.

George Britnell comes to mind as one of the masters here, but he is absolutely not the only one - have a look under Engines - your own design.

Offline theeoracle

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Re: OHC 4 stroke datsun engine timing questions
« Reply #24 on: February 18, 2019, 02:45:31 AM »
You "only" need to drill a small hole from the main bearing to the throw in the crank in order to lube the big-end of the con-rod as the small end never is pressure lubricated.

There are several engines here on site where you can see it done with pictures and accompanying text.

George Britnell comes to mind as one of the masters here, but he is absolutely not the only one - have a look under Engines - your own design.

cool thanks

I finished the water pump today.
I am super happy with the way it turned out.
<a href="http://www.youtube.com/watch?v=HGlv9gJG6h0" target="_blank">http://www.youtube.com/watch?v=HGlv9gJG6h0</a>
<a href="http://www.youtube.com/watch?v=F18DgD9Nd5Q" target="_blank">http://www.youtube.com/watch?v=F18DgD9Nd5Q</a>

Offline Jack3m

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Re: OHC 4 stroke datsun engine timing questions
« Reply #25 on: March 20, 2019, 07:54:25 PM »
I used to work on the L16 professionally in the day.  The tensioning was done by oil pressure pushing out a shoe type device that ran against the chain.  Frankly it has been so long I really don't remember exactly how we timed it, but it was adjustable, one of 3 choices on the cam gear.  Had some dots that had to line up on chain and pulley as I remember also.  If you did not know what you were doing it really was a mess.

I see with the water pump pully you are not going full scale, so maybe it doesn't matter to you.  Still a cool project.
Jack of all trades, master of none