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Hot cams and advanced ignition

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I agree with Roger. After everything we have talked about the fact is that Lutz's engine runs great. The timing can't be that far from a correct setting for that engine. The problem is that the indicated measurement is off. In my opinion now the problem is in the electrical/electronic measuring.
 
From Lutz' original post: "...When I checked the ignition timing of my AH 3000 BJ8 with a strobe light I found it was set at 45° BTDC at idle and about 65° at about 4500 rpm. Nevertheless the car is performing excellant!..."

The timing is 30 deg off. If there are 12 teeth on the distributor drive gear (#112 above) then it's one tooth off; if 24 teeth, then two teeth off.

All this advocacy of not fixing it makes it sound like this is a big risky job. Doesn't it make sense to fix it so the car can be properly timed with the pulley marks?
 
The timing is NOT 30 deg off!!!

It wouldn't run if it were. The measurement is off.
 
Look at the facts given by Lutz.

The car runs perfectly.
His strobe shows that ignition occurs 45deg BTDC.
He has double-checked that his TDC point is accurate
All 6 plugs fire at 45 deg BTDC No.1 according to his strobe.

Distributor drive gear? If it were really timed 30 deg out it wouldn't run. Camshafts? Hooey.

The timings represented by Lutz and his strobe cannot be right. They make no sense, and Lutz agrees with that.
 
I totally agree that there must be something wrong with the electrical/electronic measuring because the car wouldn't run with 45° in idle, never ever. But let's wait and see what the guys from Bosch will find tomorrow. I'll let you know.
 
steveg said:
From Lutz' original post: "...When I checked the ignition timing of my AH 3000 BJ8 with a strobe light I found it was set at 45° BTDC at idle and about 65° at about 4500 rpm. Nevertheless the car is performing excellant!..."

The timing is 30 deg off. If there are 12 teeth on the distributor drive gear (#112 above) then it's one tooth off; if 24 teeth, then two teeth off.

All this advocacy of not fixing it makes it sound like this is a big risky job. Doesn't it make sense to fix it so the car can be properly timed with the pulley marks?
Click to expand...

Steve, wouldn't you say that it makes no differance whether I relocate the distributor drive gear one or two teeth or just turn the dizzy about 15° (equals 30° for the crankshaft)? Since I can turn my distributor 360° if I wanted, I can set the dizzy by turning to every positon as I could by relocating the drive gear.

By the way have a look at the following article published by Moss Motors:
https://www.mossmotors.com/forum/forums/thread/10572.aspx

There you can see that you are basically free to set the position of the dizzy to any place you want as long as the distributor is not interfering with the engine block.
 
Last edited:
Back from Bosch! Here is what they found:

To recap:
  1. First of all I found with a strobe light the ignition timing to be set at 45° at idle and 65° at about 4500 rpm.
  2. I then replaced the old no resistance igniton wires with new no resistance wires and measured 30° at idle, but still not 15° (may be due to electrical interferences)
  3. Next thing I did was to replace #1 sparkplug wire with a resistance wire --> but no difference!

Bosch measured 23.9° BTDC! They use a computer system which a strobe light with advance control is attached to.

IMG_5895.jpg

So, my strobe light ist about 6° off!

But what about 23.9°? They confirmed, that the enginge is running very well with this timing. When I told them, that the engine has a hot cam, they said that this might be the reason for this kind of advanced setting. A hot cam may sometimes afford an advanced setting up to 10° more than recommended by the factory. It depends on the engine. Since they do not have expreriences anymore with Healey engines, they cannot say that this definitaley applies to the BJ8 engine. But they also confirmed that it is more important to set the ignition at high rpm and therefore in accordance with the AH 3000 workshop manual it should never exceed 38°.
They also said, that the engine with its hot cam might perfom better at high rpm if they would set the timing closer to 15° but it then might run very poor at low rpm.
Since I rather prefer cross country trips at low speeds than to go for races I decided to leave the engine at 24° at idle an about 38° at 4500 rpm.

That's it!

Thank you all for your help and patience!
 
Final report:

Two days ago I bought an old Bosch strobe light from the 70ies, which is not connected inductively but in between the distributor cap and the plug wire, so there is only a little chance that interferences have any influences on the measurements of the ignition timing. The Bosch strobe showed the same results like the measurements documented by Bosch last week: 24° BTDC at idle, while the new inductively working strobe light still shows 30°.

Then I changed the no resitance sparg plug wires with High Performance HT Ignition Lead Cable - Low Resistance Red Silicol with 350 ohm per foot resistance.

The Bosch strobe was still at 24°, but the new inductive strobe changed from 30° to 24° BTDC. So the non resistance spark plugwires were responsible for the faulty indication of the inductive strobe light.

Anyway it is definitely true that my BJ8 with its 298° camshaft has to be set to 24° BTDC at idle to run the engine perfectly.

Lutz
 
Ok Lutz, sounds pretty good but lets go a little deeper here unless my next points have already been covered and I just forgot.
24* BTDC is pretty high for a base setting but I do believe an engine can run with it. The dominant parameter then is where does the total timing end up. I've tuned alot of engines in my day and have built a few hot rodded engines as well but they are V8 engines. I have also tuned, MG, Healey, Triumph and other LBCs. None of the engines I have worked on do well past 38* BTDC max advance. But I know of a few that reach into the low 40s. Typcally 35* BTDC is good without worry of detonation.
So if your timing is reading 24* BTDC at idle, is the vacuum line connected between the distributor and the intake manifold. If the vacuum line is connected then you can be reading what the vacuum advance is adding to your base distributor setting. Typically vacuum advance units will add between 8 and 12 degrees of advance. Without a vacuum line connected to the distributor you would set your initial distributor advance at about 12*. So you see where your full advance comes from, 12 vac, 12 base setting, and about 10 or 12 centrifugal = 34 to 36 degrees total which usually comes all in around 2500 rpms. So what is your total advance in degrees at around 3000rpms and does this include the vacuum canister hooked up? Thanks. Having said all of this, i was just thinking of a crane electronic module that I had in my Vette engine for awhile. With that electronic module in the distributor and the original vacuum advance canister hooked up the engine would break up at 4500 rpms consistently. It seems that the crane module was putting in to much advance to early and the vac unit just compounded the problem. The crane unit was adjustable but I never did get back to evaluating what I could do with it, i just disconnected the vacuum canister and ran it that way. Without the vac unit hooked up the engine easily pulled to more than 6000 rpms. But with my high rear ratio that was already more than 130 mph and I didn't need anymore.
 
I'm going from memory in the '70's but I recall having a problem with timing my Healey and it would run great at idle but not the 15 degrees per spec. It was a lot higher and I sorta recall going into the timing gear gears where it was off or the dizzy and backing it down a tooth or two. This problem almost sounds like the timing light clip is on another plug wire other than the #1 plug wire. I'd first check that the spark plug wires are connected to the correct holes in the dizzy cap. I also recall that if the dizzy is 180 out of its normal setting you still can time the engine but you need to clip the timing light to #6 plugwire.
 
Patrick67BJ8 said:
I'm going from memory in the '70's but I recall having a problem with timing my Healey and it would run great at idle but not the 15 degrees per spec. It was a lot higher and I sorta recall going into the timing gear gears where it was off or the dizzy and backing it down a tooth or two. This problem almost sounds like the timing light clip is on another plug wire other than the #1 plug wire. I'd first check that the spark plug wires are connected to the correct holes in the dizzy cap. I also recall that if the dizzy is 180 out of its normal setting you still can time the engine but you need to clip the timing light to #6 plugwire.
Click to expand...

Hi Patrick,

I'm sorry, but your questiosn had already been answered either in this thread or may be in another one published by me: [FONT=&quot]https://www.britishcarforum.com/bcf/showthread.php?107119-Ignition-timing-with-Pertronix-Ignitor-and-strobe-light.

Lutz[/FONT]
 
Hi Vette,

vette said:
Ok Lutz, sounds pretty good but lets go a little deeper here unless my next points have already been covered and I just forgot.
24* BTDC is pretty high for a base setting but I do believe an engine can run with it. The dominant parameter then is where does the total timing end up. I've tuned alot of engines in my day and have built a few hot rodded engines as well but they are V8 engines. I have also tuned, MG, Healey, Triumph and other LBCs. None of the engines I have worked on do well past 38* BTDC max advance. But I know of a few that reach into the low 40s. Typcally 35* BTDC is good without worry of detonation.
Click to expand...

The total timing is at 38° at 4000 rpm and higher.


So if your timing is reading 24* BTDC at idle, is the vacuum line connected between the distributor and the intake manifold. If the vacuum line is connected then you can be reading what the vacuum advance is adding to your base distributor setting. Typically vacuum advance units will add between 8 and 12 degrees of advance. Without a vacuum line connected to the distributor you would set your initial distributor advance at about 12*. So you see where your full advance comes from, 12 vac, 12 base setting, and about 10 or 12 centrifugal = 34 to 36 degrees total which usually comes all in around 2500 rpms. So what is your total advance in degrees at around 3000rpms and does this include the vacuum canister hooked up? Thanks.
Click to expand...

I do not have a vacuum advance system with my Mallory Distributor.

Lutz
 
If your total timing is at 38* then I would say that is good. If your base setting is at 24* then your built in distributor curve is obviously from 24 to 38. after everything we have gone thru on this thread that's a big improvement and I think there have been multiple issues. I have never found a street cam that needed 24* base setting. No matter how radical the "street cam" was. So I still think there is some improvement that can be made and i believe it is in the curve of the distributor's timing. Just a note of historical trivia, Smokie Yunick, a promenant race engine builder of the 1950's & 60s here in the States, built winning engines by locking the timing of the engine at full advance at whatever the engine seemed to like most. i've never personally seen an engine like that running and can't imagine what is was like at idle but it must have worked well enough to get it down a race track.
 
Works for light aircraft piston engines. Mag timing is fixed, usually between 20-25deg; but, of course, they operate in a fairly narrow RPM range (600-2700).
 
38 degrees seems very advanced. I'm not aware of any Healey race cars over here that run that advanced. FYI my car has a 300 degree rally cam, triple Webers and 11:1 compression and is only running 31 degrees of advance. However, if your car works thats great. Do you never experience any 'pinking' under load?
 
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