Hiya all
Can you please give me your advice on the static ignition timing, spark plug type (and grade) and gap that you would recommend for my sprint motor?
The rough motor spec is:
Gas flowed head
Standard valves
STR091 cam & vernier
Weber 45s
Tubular exhaust manifold
16lb flywheel weight
Electronic ignition
Vacum advance removed from distributor and mechanical advance recalibrated to motor spec.
I've always preferred NGK - but any advice welcome.
Cheers
Shaun
Spark Plugs and Ignition Timing?
-
Hans ten Broeke
To start with, there are at least 3 types of distributors with 7, 9 and 11 degrees of advantage, so without knowing what you have an advise cant be giving.
We use 7 ' units to get a descent advantage at idle and lower reves, because of the multi throttle setup 45 or 48 Weber you end up with a slow burning mixture at almost closed throttle positions.
We run also max 31' at max advantage, what give a good top end, so the idle setting is 16 17 degrees. (the advantage is a bit over 7' for the distributor)
We had measurable better results over the NGK plugs with the Denso Iridium 0.4mm plugs with a small U groove.
Hope this is not confusing you to much, but setting up a ignition is more than just changing the plugs.
By the way, Magnecor make superior cables, important!
--
Hans ten Broeke
De Hoge Esch 49
7783 CBÂ Â Gramsbergen NL
STOC #2830
'92 green topST
'93 red usaST (ex #221) (2005)
'73 CB 750 Candy Glory Gold
'71 Jamathi 50TT -restoration project, but proud to have one-
'78 Maico 370 Enduro Red
'95 CB Sevenfifty Red
'96 SZR 660 Super Mono Orange
'96 CB 70 Dax Red (2000)
and too many cages to mention...
We use 7 ' units to get a descent advantage at idle and lower reves, because of the multi throttle setup 45 or 48 Weber you end up with a slow burning mixture at almost closed throttle positions.
We run also max 31' at max advantage, what give a good top end, so the idle setting is 16 17 degrees. (the advantage is a bit over 7' for the distributor)
We had measurable better results over the NGK plugs with the Denso Iridium 0.4mm plugs with a small U groove.
Hope this is not confusing you to much, but setting up a ignition is more than just changing the plugs.
By the way, Magnecor make superior cables, important!
--
Hans ten Broeke
De Hoge Esch 49
7783 CBÂ Â Gramsbergen NL
STOC #2830
'92 green topST
'93 red usaST (ex #221) (2005)
'73 CB 750 Candy Glory Gold
'71 Jamathi 50TT -restoration project, but proud to have one-
'78 Maico 370 Enduro Red
'95 CB Sevenfifty Red
'96 SZR 660 Super Mono Orange
'96 CB 70 Dax Red (2000)
and too many cages to mention...
-
shauniedawn
Thank you both for your replies.
I'm happy to send you a pic of my manifold Neil - but as the motor is going in a TR7 I don't think you'd be interested?
...as for your very technical answer Hans - yes you have confused me a little! However, I do understand what you are saying to a degree (pun intended!!) - in that you need the full info on the distributor to be able to advise correctly. However, I think you are telling me that static timing of around 17 or 17 degrees BTDC could be a starting point.
If I've got this wrong please let me know.
Thanks again
Shaun
I'm happy to send you a pic of my manifold Neil - but as the motor is going in a TR7 I don't think you'd be interested?
...as for your very technical answer Hans - yes you have confused me a little! However, I do understand what you are saying to a degree (pun intended!!) - in that you need the full info on the distributor to be able to advise correctly. However, I think you are telling me that static timing of around 17 or 17 degrees BTDC could be a starting point.
If I've got this wrong please let me know.
Thanks again
Shaun
-
shauniedawn
-
Hans ten Broeke
With a 7 degree distributor the static is 16 17 degrees, because a 7 degrees distributor (the number 7 is stamped on the plate below the so called ground plate) will bring 2 x 7 = 14 degrees advance.
We found out on our dyno that 31' engine advance give the max power.
So 31 - 14 give 17Â Â The engine starts and idles at this 17 and the distributor bob wights and springs allow it to advance 7' x 2 (this 2 is because the distributor is rotating with 1/2 the rpm of the crank, 4 stroke you remember) to the max off 31'
Again this 31' proved to be ideal for our engines running (till now) flat top pistons, with crowned pistons it could be more because there is more in the way of the flame front.
For people who did a lot of experience in 2 valve engines with mostly the spark plug on the side of the combustion chamber 31' degrees max advance douse look not enough, but the main factor for this mild advance figure is the fact that in this 4 valve head the spark plug is in the middle what give a relatively short flame front.
I know people will tell now that more advance give more bottom grund, but that is mostly only because they use a distributor with a to long advance curve, for example the 11' distributor will make  22' engine degrees, now still having the max on 31' will bring the idle on 9'  (31' - 22'  = 9') not enough for a Weber setup.
Now simply giving more idle advantage will bring more power in the lower revs, but the danger is far to much advantage in the higher revs.
If you go with this 11' distributor from 9' to 16' at idle will let you end ad the max revs to 38' what is far to much and can be dangerous for you engine.
I don't have the plus by hand right now but we run an equivalent of heat range 7.
These plugs do last very long also, what could be an isu on a road car. Â
--
Hans ten Broeke
De Hoge Esch 49
7783 CBÂ Â Gramsbergen NL
STOC #2830
'92 green topST
'93 red usaST (ex #221) (2005)
'73 CB 750 Candy Glory Gold
'71 Jamathi 50TT -restoration project, but proud to have one-
'78 Maico 370 Enduro Red
'95 CB Sevenfifty Red
'96 SZR 660 Super Mono Orange
'96 CB 70 Dax Red (2000)
and too many cages to mention...
We found out on our dyno that 31' engine advance give the max power.
So 31 - 14 give 17Â Â The engine starts and idles at this 17 and the distributor bob wights and springs allow it to advance 7' x 2 (this 2 is because the distributor is rotating with 1/2 the rpm of the crank, 4 stroke you remember) to the max off 31'
Again this 31' proved to be ideal for our engines running (till now) flat top pistons, with crowned pistons it could be more because there is more in the way of the flame front.
For people who did a lot of experience in 2 valve engines with mostly the spark plug on the side of the combustion chamber 31' degrees max advance douse look not enough, but the main factor for this mild advance figure is the fact that in this 4 valve head the spark plug is in the middle what give a relatively short flame front.
I know people will tell now that more advance give more bottom grund, but that is mostly only because they use a distributor with a to long advance curve, for example the 11' distributor will make  22' engine degrees, now still having the max on 31' will bring the idle on 9'  (31' - 22'  = 9') not enough for a Weber setup.
Now simply giving more idle advantage will bring more power in the lower revs, but the danger is far to much advantage in the higher revs.
If you go with this 11' distributor from 9' to 16' at idle will let you end ad the max revs to 38' what is far to much and can be dangerous for you engine.
I don't have the plus by hand right now but we run an equivalent of heat range 7.
These plugs do last very long also, what could be an isu on a road car. Â
--
Hans ten Broeke
De Hoge Esch 49
7783 CBÂ Â Gramsbergen NL
STOC #2830
'92 green topST
'93 red usaST (ex #221) (2005)
'73 CB 750 Candy Glory Gold
'71 Jamathi 50TT -restoration project, but proud to have one-
'78 Maico 370 Enduro Red
'95 CB Sevenfifty Red
'96 SZR 660 Super Mono Orange
'96 CB 70 Dax Red (2000)
and too many cages to mention...
cheers anyway.-
shauniedawn
-
shauniedawn
-
speedracer
-
Hans ten Broeke
To start with: Happy New Year to all of you
As mentioned before, The Dutch Denso importer (technical representatives) where involved in a test cession on our dyno some years ago.
My question on them was if this, by that time new car type of plugs (already standard in several fast Japanese bikes) was available with the typical conical seat, as used in our sprint heads.
They where available, (some France cars do use the same conical seat in 14mm) in a few heat ranges.
The guys promised to send a few sets to try in our racing cars.
On the dyno in a back to back test, we could see a little more smooth power curve at the top reves.
My explanation is that the 0.4mm point just could produce a better spark at this difficult circumstances, single coil in combination with a distributor, (more modern systems not allowed by the regulations, time period you know)
The way the plugs are made, look, very good plating ext, including the V groove convinced me.
Next to that most of my bikes did have NGK plugs, with good results, we sell many standard NGK plugs in the shop, and use them in the regular customer cars, my normal road sprint even has standard NGK, but when it comes to real power and every single bit counts, we have very good results with the Denso Iridium plugs, so the small price difference against the NGK iridium plugs is for us not worthy to go and try , test them also.
Actual the first set of plugs are still in the racing engines and perform excellent. I can ensure you not changing these plugs with new ones till now has nothing to do with finance, I want to find the edge.
Of course they are checked very regularly, till now they don't foul, and the tip is still very sharp, square.
Hans
As mentioned before, The Dutch Denso importer (technical representatives) where involved in a test cession on our dyno some years ago.
My question on them was if this, by that time new car type of plugs (already standard in several fast Japanese bikes) was available with the typical conical seat, as used in our sprint heads.
They where available, (some France cars do use the same conical seat in 14mm) in a few heat ranges.
The guys promised to send a few sets to try in our racing cars.
On the dyno in a back to back test, we could see a little more smooth power curve at the top reves.
My explanation is that the 0.4mm point just could produce a better spark at this difficult circumstances, single coil in combination with a distributor, (more modern systems not allowed by the regulations, time period you know)
The way the plugs are made, look, very good plating ext, including the V groove convinced me.
Next to that most of my bikes did have NGK plugs, with good results, we sell many standard NGK plugs in the shop, and use them in the regular customer cars, my normal road sprint even has standard NGK, but when it comes to real power and every single bit counts, we have very good results with the Denso Iridium plugs, so the small price difference against the NGK iridium plugs is for us not worthy to go and try , test them also.
Actual the first set of plugs are still in the racing engines and perform excellent. I can ensure you not changing these plugs with new ones till now has nothing to do with finance, I want to find the edge.
Of course they are checked very regularly, till now they don't foul, and the tip is still very sharp, square.
Hans
-
Eric
Re: Spark Plugs and Ignition Timing?
Hi Hans,
I read with great interest your explanations about ignition timing. This weekend I played a bit with my Sprint and found that with an advance with 18-20° set at 1000 rpm with my strobe light, the car ran best especially over 3500 rpm until 5000. With only 10° advance the car did not really want to run over 3500 rpm. I did not try more as you remember perhaps I repaired the cylinder head last November and got some shims from you. I find it particular difficult so set the timing with the strobe as the centrifugal advance works already at 1000rpm. I have the intention to try to set the timing at 31° at 4000rpm and look what it will be at idle. My car is standard with a mildly uprated road cam. From your say I noticed that the 10° static as explained in the Haynes manual is far from perfect and at first it should determined what distributor one has, and then calculate the advance timing.
Thanks for all help, Eric
I read with great interest your explanations about ignition timing. This weekend I played a bit with my Sprint and found that with an advance with 18-20° set at 1000 rpm with my strobe light, the car ran best especially over 3500 rpm until 5000. With only 10° advance the car did not really want to run over 3500 rpm. I did not try more as you remember perhaps I repaired the cylinder head last November and got some shims from you. I find it particular difficult so set the timing with the strobe as the centrifugal advance works already at 1000rpm. I have the intention to try to set the timing at 31° at 4000rpm and look what it will be at idle. My car is standard with a mildly uprated road cam. From your say I noticed that the 10° static as explained in the Haynes manual is far from perfect and at first it should determined what distributor one has, and then calculate the advance timing.
Thanks for all help, Eric