Ignition Sprocket off by 3 teeth - OK?

[pmth95]

Just installed a new timing belt using markings from the old belt transferred to the new one. No interference while rotating engine. While double checking alignment of the Ignition sprocket per the manual, I see it is 3 teeth offset from the center line (see picture)

Option1: Ok to leave it as is, car ran before and according to@Sparky in this post, timing can be adjusted later to compensate for such an offset  

Option2: Might as well redo it correctly (even though i was hoping not to deal with the tensioner again). 
 

[910Esprit]

Dont worry about it, as long as the distributor has been timed correctly and the cams and crank marks have the correct alignment, it makes not a jot of difference....    

NB I'd personally redo it as I like things to be 'just so'

[Escape]

The position of the ignition sprocket isn't crucial, as long as you can get the timing spot on by moving the distributor. 3 teeth shouldn't be a problem, more could lead to issues with available space and the need to swap the plug leads. All doable, but it does complicate things, more chance of errors and harder to investigate if a problem develops later on. Unless you keep a good record, the next person working on the car will need to figure it out all over again. 😉  (I am often guilty of similar, but tend to keep my cars so only have my past self to blame if I get puzzled later on).

[Sparky]

Spookily topical!  I did one yesterday that was just one tooth retarded and couldn't be adjusted to spec as the vacuum capsule was in contact with the oil filter.  Neither could I rotate the distributor enough to move the leads clockwise to compensate.  All I could do was remove the belt and retime the aux sprocket.  I'm sure the distributor/vac capsule were correct, so I'm a bit confused as to why this happened.

So, to qualify my referenced post:  if the sprocket is retarded and you have a vacuum capsule, you might have trouble adjusting the ignition timing!

[pmth95]

I have a pertronix ignition and no vacuum capsule on the distributor, so rotation should not be an issue.
Was thinking of going with a 123 distributor in the future, I’ll check if the shape of the 123 has the potential for interference. 
 

4 hours ago, Escape said:

The position of the ignition sprocket isn't crucial, as long as you can get the timing spot on by moving the distributor. 3 teeth shouldn't be a problem, more could lead to issues with available space and the need to swap the plug leads. All doable, but it does complicate things, more chance of errors and harder to investigate if a problem develops later on. Unless you keep a good record, the next person working on the car will need to figure it out all over again. 😉  (I am often guilty of similar, but tend to keep my cars so only have my past self to blame if I get puzzled later on).

I guess i am the one trying to figure out what was done previously on the car. I’ll record it and decide when i do the next timing belt if i want to change it back to “normal”

[Geeman]

I recently fitted a 123 distributor bought from Barry Spencer in the US.  So far so good and easy too install.  Much more flexibility to rotate to a convenient position.  My 1984 US spec Turbo had the original distributor in, but as said when trying to re-time it after an engine out service to 10 degrees BTDC (per Barry's direction) I found the vacuum unit hit the oil filter before I got the 10 degrees.

One odd thing I found was with the cam marks aligned, and the front crank pulley aligned to TDC, the flywheel marks were about 2-3 degrees off.  Hmmm.  I went the front pulley marks as correct and compensated with my timing light on the flywheel.  So far so good.

 

 

[pmth95]

3 hours ago, Geeman said:

I recently fitted a 123 distributor bought from Barry Spencer in the US.  So far so good and easy too install.  Much more flexibility to rotate to a convenient position.  My 1984 US spec Turbo had the original distributor in, but as said when trying to re-time it after an engine out service to 10 degrees BTDC (per Barry's direction) I found the vacuum unit hit the oil filter before I got the 10 degrees.

One odd thing I found was with the cam marks aligned, and the front crank pulley aligned to TDC, the flywheel marks were about 2-3 degrees off.  Hmmm.  I went the front pulley marks as correct and compensated with my timing light on the flywheel.  So far so good.

 

 

It is my understanding that the flywheel marks are more accurate than the crankshaft marks, as the diameter of the flywheel is so much larger the precision is better. 

[DrieStone]

On 18/05/2023 at 08:19, Geeman said:

I recently fitted a 123 distributor bought from Barry Spencer in the US.

 

 

How difficult was this project? I'm close to getting my '83 on the road again, and I'd love to swap to a more modern distributor.

What's Barry's contact info?

[drdoom]

Pull up the Golden Gate Lotus Club website, I believe Barry has always advertised there.

[pmth95]

Car started right up today so i guess it was always off by three teeth. 

[DrieStone]

On 26/06/2023 at 11:44, drdoom said:

Pull up the Golden Gate Lotus Club website, I believe Barry has always advertised there.

I found his info an ordered a unit. He said that he's sold a bunch and he's waiting for more units to arrive.

Does this require removing the carbs to gain access, or can this be done (painfully) while the carbs are in place?

[Geeman]

On 03/07/2023 at 14:31, DrieStone said:

I found his info an ordered a unit. He said that he's sold a bunch and he's waiting for more units to arrive.

Does this require removing the carbs to gain access, or can this be done (painfully) while the carbs are in place?

I was able to swap it out without removing the carbs.  Mine is a US car and I also have the air pump and emission equipment removed which helps access.  I think I did remove the plenum cover though.

 

[EXCEL V8]

Sorry for the thread hijack - Gordon, do you have any photos of the air pump drive assembly?  The spindle that fits in the end of the cam and the oil seal/casting that goes with it.  I've been trying to find someone with this for a while now.

Thanks!

Pete 

[Geeman]

On 07/07/2023 at 16:45, EXCEL V8 said:

Sorry for the thread hijack - Gordon, do you have any photos of the air pump drive assembly?  The spindle that fits in the end of the cam and the oil seal/casting that goes with it.  I've been trying to find someone with this for a while now.

Thanks!

Pete 

Pete, I will have a rummage.  Give me a couple of days or so.  Do you have the parts manual? I believe its shows the different parts.

[EXCEL V8]

Thanks Gordon - I have only seen poorly-reproduced copies of the diagram on-line and written instructions on how to assemble.  The reason for asking is that I plan to use the same location for my cam position sensor, but when a threaded shaft is screwed into the end of the cam it is a long way off concentric.  I wondered how Lotus had overcome this or whether they just let it leak oil!! 😉

Pete

[Geeman]

37 minutes ago, EXCEL V8 said:

Thanks Gordon - I have only seen poorly-reproduced copies of the diagram on-line and written instructions on how to assemble.  The reason for asking is that I plan to use the same location for my cam position sensor, but when a threaded shaft is screwed into the end of the cam it is a long way off concentric.  I wondered how Lotus had overcome this or whether they just let it leak oil!! 😉

Pete

Pete here are some photos.  I’ll try and find the parts.  I’ll have them somewhere. 

[EXCEL V8]

Wow - thanks so much Gordon!  I wonder if the Lotus spindle is concentric or the oil seal is flexible enough to cope?  I measured 0.007" runout using a well-made shoulder bolt as a test piece - oil seals tend to like half of that.  My plan is to do the final finishing of my locating spindle on the lathe once it is screwed into place in the cam (cam centred in 4-jaw and fixed steady.  Lathe is just long enough!).

Thanks again and sorry for the thread hijack!

Pete

[snowrx]

Excel V8  The air pump drive flange has the piloted inside diameter and wide base, so it should run pretty concentric.

I have a turbo, so could not use that end for a cam sensor due to the heat from the turbine housing. I placed my VR sensor behind the exhaust cam pulley, with a M6 bolt in the pully as a trigger.

[EXCEL V8]

Thanks Tomas - I saw your neat conversion when researching the topic - nice work.  I'm committed to doing it the hard way though! 🙄.  It's the spindle that screws into the camshaft that doesn't run concentric.  If the hole in the air pump drive flange is a close fit on the spindle it won't run concentrically either - but I haven't had the chance to measure the actual Lotus parts (maybe Gordon would like to part with his unused air pump parts!!?  😉)

Pete

[Geeman]

1 hour ago, EXCEL V8 said:

Thanks Tomas - I saw your neat conversion when researching the topic - nice work.  I'm committed to doing it the hard way though! 🙄.  It's the spindle that screws into the camshaft that doesn't run concentric.  If the hole in the air pump drive flange is a close fit on the spindle it won't run concentrically either - but I haven't had the chance to measure the actual Lotus parts (maybe Gordon would like to part with his unused air pump parts!!?  😉)

Pete

Pete, no I wouldn’t 😬. But where are you located?  If in the US try Barry Spencer on the west coast.  He may have some spare ones.  Maybe even SJ in the U.K.  

[EXCEL V8]

I didn't expect for a moment that you would want to part with your spares Gordon - tongue-in-cheek comment by me 🙂.  I'm in the UK.

Pete

[snowrx]

My  parts are on the wrong side of the pond also, and would likely have the same tolerances. I did attempt a rear VR sensor off the (turned down) pully flange, but by the time I had heat shields around it it was just a bodge.

[drdoom]

Thomas your front of cam solution is very nicely done and I'll be emulating it on mine.

Cheers

[snowrx]

One could run it off the intake cam, which would keep the wiring away from the exhaust heat, but you'd want to keep the wiring away from the sparkplug electrical noise with a compact sensor or a 90 degree connector.  The rest is at https://www.lotustalk.com/threads/910-megasquirt.339834/#post-4494234

[DrieStone]

On 07/07/2023 at 09:59, Geeman said:

I was able to swap it out without removing the carbs.  Mine is a US car and I also have the air pump and emission equipment removed which helps access.  I think I did remove the plenum cover though.

 

I received my unit this week, and I'm going to try to install this weekend. Not sure if you remember, but Barry's note says to set it to 10° BTDC. I'm reading this as I should ignore the directions that say to set to to TDC and set the engine to 10° and rotate the distributor until I see the LED? I had Barry preprogram the unit, so it sounds like I just set the engine to 10°, set the LED, and I should be good to go.

I just want to make sure it's not something I do through the software (set the car to TDC and set an option in the software to 10°).