Camshafts and the timing Game.

[mick taylor]

The subject of Camshafts timing.

1 facing the front of the engine do all engines turn running clock wise ?

2 As to the cam timing with a chain or a belt, as they stretch what goes on and how much degree could this make with being out of wack with the original spec ?
I have seen a Holden V8 that the slack in the timing chain must of been easy worked out too being like one tooth out, so what degrees would that be out ?

Some camshafts have dizzy gear on them that drive the dizzy that spin the other way to others I seen on TV with a Big Block Dodge to a Small block Valiant.

So what is going on with ones spark timing on a 5.0L EFI Holden V8 if you never touched it ? as the chain stretches the dizzy spark must retard ? you would not want it to creep forward on any engine.

I seen Valiant in 1975 claim you need not touch the dizzy for 50,000KM I think it was, but in that time I am sure the timing would be out of it's original point due to the chain stretch.

Modern day engines with veritable adv and retard setups on the camshafts get to a point that a light comes up warning you to change the belt. so all must be spot on in regards to everything until then.

I retarded my cam timing on a near stock 308 Holden by 4 deg just to see if I could get a bit more top end, but all it did was loose power every where, It did not have high compression, maybe 8.8:1 I would think as it had stock blue motor pistons, I would think that being retarded cam timing that this will lower the running compression a touch if anything.
Not to mention that -4 deg cam I would have to adv my spark by 4 deg as a rule.
I should of advanced the Cam timing by 4 deg would of been a better option and maybe got a bit more grunt.

Torana LH 308 cam timing is advanced by 5 deg over a HQ 308.
HQ 308 intake timing is 27-63, LH Torana 308 is 32-58

Now from the HJ 5.0L the cam is a pollution cam as it has more exhaust duration and a late exhaust close to add more heat to the exhaust to burn more fuel in the exhaust system I believe.
Intake 28-72 exhaust 78-30 is the HJ-X-Z
27-72 71-19 is the HQ
32-58 76-14 is the LH, is this called advanced or retard over the HQ ?

When we advance the spark we are sparking before the top dead centre.

But when we are advancing the cam ? I would think it is the other way round, so 20-60 straight up and if we retard it by 5 deg it would be 25-55 ? or is it 15-65. so an old chain will be retarding the cam timing no ? and retarding the spark timing point. so if your spark timing was 5 deg, now you will need 10 deg.

A mate once had his 308 rebuilt and the dude put the Cam timing out 2 teeth out, as he thought that Chev were the same number of links apart that he worked on, this engine was gutless as but would rev out real well.

[cs123]

So many questions.
A lot of you questions are actually well answered if you watch engine masters on motor trend.

They have done some shows on cam timing

[roKWiz]

I seem to remember the mid 70s Valiant's were first to offer electronic dissy's out of the big three. Holden was last with the blue motor I know the WB panel van I bought new in 82 was the first time I had an E dssy.

[jpd80]

Originally Posted by mick taylor

The subject of Camshafts timing.

1 facing the front of the engine do all engines turn running clock wise ?

2 As to the cam timing with a chain or a belt, as they stretch what goes on and how much degree could this make with being out of wack with the original spec ?
I have seen a Holden V8 that the slack in the timing chain must of been easy worked out too being like one tooth out, so what degrees would that be out ?

Some camshafts have dizzy gear on them that drive the dizzy that spin the other way to others I seen on TV with a Big Block Dodge to a Small block Valiant.

So what is going on with ones spark timing on a 5.0L EFI Holden V8 if you never touched it ? as the chain stretches the dizzy spark must retard ? you would not want it to creep forward on any engine.

I seen Valiant in 1975 claim you need not touch the dizzy for 50,000KM I think it was, but in that time I am sure the timing would be out of it's original point due to the chain stretch.

Modern day engines with veritable adv and retard setups on the camshafts get to a point that a light comes up warning you to change the belt. so all must be spot on in regards to everything until then.

I retarded my cam timing on a near stock 308 Holden by 4 deg just to see if I could get a bit more top end, but all it did was loose power every where, It did not have high compression, maybe 8.8:1 I would think as it had stock blue motor pistons, I would think that being retarded cam timing that this will lower the running compression a touch if anything.
Not to mention that -4 deg cam I would have to adv my spark by 4 deg as a rule.
I should of advanced the Cam timing by 4 deg would of been a better option and maybe got a bit more grunt.

Torana LH 308 cam timing is advanced by 5 deg over a HQ 308.
HQ 308 intake timing is 27-63, LH Torana 308 is 32-58

Now from the HJ 5.0L the cam is a pollution cam as it has more exhaust duration and a late exhaust close to add more heat to the exhaust to burn more fuel in the exhaust system I believe.
Intake 28-72 exhaust 78-30 is the HJ-X-Z
27-72 71-19 is the HQ
32-58 76-14 is the LH, is this called advanced or retard over the HQ ?

When we advance the spark we are sparking before the top dead centre.

But when we are advancing the cam ? I would think it is the other way round, so 20-60 straight up and if we retard it by 5 deg it would be 25-55 ? or is it 15-65. so an old chain will be retarding the cam timing no ? and retarding the spark timing point. so if your spark timing was 5 deg, now you will need 10 deg.

A mate once had his 308 rebuilt and the dude put the Cam timing out 2 teeth out, as he thought that Chev were the same number of links apart that he worked on, this engine was gutless as but would rev out real well.

I'll have a try at this..

Older engines often had timing chains and timing belts made down to a price that meant
they would stretch as they got older rather than catastrophic failure of the belt or chain.

The slop in a timing chain on a high mileage vehicle can be great, I've seen 20 degrees
and yes, this affects ignition timing when the distributor is driven by the camshaft
but the good news is this can be adjusted back to correct timing.

Where're the distributor turns clockwise or anticlockwise is dependant on whether the
distributor drive gear meshes on the right or left side of the camshaft.

In the early days of controlling exhaust emissions, it was common to delay the camshaft timing
between 4 to 6 degree of crankshaft rotation , this did two things:
- delayed inlet valve closing well after bottom dead centre when the piston was moving
back up the cylinder, reducing the amount of compressible mixture at lower engine speeds
and effectively lowering the compression of the engine.
- delayed exhaust valve closing after top dead centre when the inlet valve was already open
this combined with longer duration caused exhaust gas to dilute the fresh inlet mixture and
was a form of internal exhaust gas recirculation.


The Valiant distributor you speak of was an early form of electronic ignition that did away
with setting contact points every 10,000 miles, so yeah, you didn't have to touch the dizzy.

Those early timing chains stretch for sure but not much is noticeable this side of 140,000 km
so it only alters initial spark timing by small amounts until it really starts stretching or as
many people do, rebuild the engine with a good double row timing chain that doesn't stretch.

When looking at cam timings like 20/60 on the inlet,
the valve opens 20 degrees before top dead centre and closes at 60 degrees after bottom dead centre.
On the exhaust side,
a 60/20 cam opens 60 degrees before bottom dead centre and closes 20 degrees after top dead centre.

There's a lot of science way beyond this to get the best out of a camshaft for a given application
and there's a lot to consider when matching compression,cam, heads, headers and intake manifold.
When all of the above are matched, you get best power for your combination.

[ivorya]

powernation on youtube is another to look at.

Even if you go to their webpage, you can watch the previous seasons. Every make of engine is looked into. https://www.powernationtv.com/shows/engine-power

Different shows are there to watch as well. It is great viewing.

[Citroënbender]

Two motors that went CCW when viewed from the crank pulley end, were the Citroen units from early ‘50s (TA/ID/DS) through ‘70s (CX) and the Honda fours from the eighties and nineties.

A trap for novices is newer engines with short, hydraulically tensioned, link chains between cams in the head. If you wind the motor backwards by the crank pulley bolt, it’s quite easy for the secondary driven cam to become mis-timed.

[Tassie f100]

Doesn’t matter which side of the cam the distributor drives from,it still turns in the opposite direction to the cam.Crank turns clockwise,gear driven cam anti clockwise,distributor clockwise.Crank turning clockwise,chain or belt driven cam,clockwise,distributor anti clockwise. Depending on whether the engine is viewed from front or rear

[Citroënbender]

You’ve overlooked the motors with distributor coupled directly to the camshaft end. Mostly OHC, from those I’ve seen.

[Tassie f100]

Yeah there are probably others,but the only ones off the top of my head were the Camira and the early sidevalve V8 Fords.

[Citroënbender]

Peugeot (4, V6), Renault (4), Volvo (V6), I think possibly some of the Toyota fours too.

[mick taylor]

Originally Posted by jpd80

I'll have a try at this..

Older engines often had timing chains and timing belts made down to a price that meant
they would stretch as they got older rather than catastrophic failure of the belt or chain.

The slop in a timing chain on a high mileage vehicle can be great, I've seen 20 degrees
and yes, this affects ignition timing when the distributor is driven by the camshaft
but the good news is this can be adjusted back to correct timing.

Where're the distributor turns clockwise or anticlockwise is dependant on whether the
distributor drive gear meshes on the right or left side of the camshaft.

In the early days of controlling exhaust emissions, it was common to delay the camshaft timing
between 4 to 6 degree of crankshaft rotation , this did two things:
- delayed inlet valve closing well after bottom dead centre when the piston was moving
back up the cylinder, reducing the amount of compressible mixture at lower engine speeds
and effectively lowering the compression of the engine.
- delayed exhaust valve closing after top dead centre when the inlet valve was already open
this combined with longer duration caused exhaust gas to dilute the fresh inlet mixture and
was a form of internal exhaust gas recirculation.


The Valiant distributor you speak of was an early form of electronic ignition that did away
with setting contact points every 10,000 miles, so yeah, you didn't have to touch the dizzy.

Those early timing chains stretch for sure but not much is noticeable this side of 140,000 km
so it only alters initial spark timing by small amounts until it really starts stretching or as
many people do, rebuild the engine with a good double row timing chain that doesn't stretch.

When looking at cam timings like 20/60 on the inlet,
the valve opens 20 degrees before top dead centre and closes at 60 degrees after bottom dead centre.
On the exhaust side,
a 60/20 cam opens 60 degrees before bottom dead centre and closes 20 degrees after top dead centre.

There's a lot of science way beyond this to get the best out of a camshaft for a given application
and there's a lot to consider when matching compression,cam, heads, headers and intake manifold.
When all of the above are matched, you get best power for your combination.

I found talking to people out and about not everyone is on the same page.
I look at a engine as from the port side and the starboard side and the front is the number one cyl and on a V8 this can be on any side that is leading forward.

If we have a 20/60 cam intake and 60/20 exhaust say for example, as the chain stretches what can that timing become ? with 20 deg slop that would become a 0/80 intake and 40/40 exhaust ? as a stretched chain retards the cam timing. that would make the Spark timing if it was 6 deg by the book, become 26 deg, all tho we would not see that on the timing light and if we set it at 6 deg we are kidding ourselves and loosing even more power.

I would spark time my old cars by advancing till I got a ping and then drop back 2 deg and try again, if no ping I was fine with such regardless of what the book said.

When the ADR27A engines came out spark timing normally advanced to 12 deg from what was 6 deg before that law. because the cam is retarded.

With ADR27A the point of EGR was to lower the temperature in the combustion chamber so as to lower a deadly gas that they claim is bad for ones lungs. now a mate and some claims this makes more heat in the engine and I say that they are wrong because it lowers the combustion temp.
But if one increase the exhaust duration length like they did on the HJ-X-Z 5.0L Holden what that does is put more heat into the exhaust, so as to burn up more of spent fuel and when the VH 2.85L came out it needed an air pump and they pumped fresh air into the exhaust from the cyl head port into the exhaust manifold to burn off more spent fuel but when cat converters came about that was point of their job.

So then we seen with the VK 3.3L carby engine it got the air pump as well, the 3.3L got away with it in the VH, but the law got stricter ?

It's all very interesting all this ADR law when one looks into it all. back in 1976 I thought they were joking or mad. because the engine used more fuel and it lost power, not to mention they had to make bigger engines as well to pass the testing.
Funny tho the Holden HX V8 Automatics got EGR but Manuals did not, but the manuals were still gutless as the Auto's, but the XC V8's got EGR regardless, I wonder why.