I there a definitive method for setting the valve timing using a degree disc on my 365 GTC 4
I have read most of the books & it seems that I may as well just align the marks on the cams & the supports & leave it at that
Would the use of a degree disc be so much more accurate.
Regards
Ian Levy
UK
4 cam valve timing 365 GTC4
-
Dr. Ian Levy
- Posts: 179
- Joined: Mon Sep 09, 2002 1:16 pm
- Location: United Kingdom
- Contact:
Hi Ian,
On a V-12 engine, the cams span across 6 cylinders, and over time will twist slightly. Rewelding, and regrinding may correct some of the lobes, but checking the work, and the accuracy of the cam, with a timing wheel insures this. Francois takes pride in checking this with every engine rebuild and explains a lot of engine builders just follow the factory marks. The cams, chains, and gears are designed to be moved independent of the each other to get accurate timing, and checking to see what the front lobe is doing, compared to the back lobe, lets you find a good compromise for the best timing for all cylinders on that cam. I believe a stock 250 cam allows for 1/8 degree adjustment. This allows for pretty accurate timing for optimum performance. Think about it, if a Ferrari motor develops most of it's power at high revs, and valve timing is off by a few fractions of a degree, performance is affected dozens of times a second! Cleanliness builds durability, accuracy builds power!
When my engine went together, we used my original cams. Checking the cam timing to the factory marks showed some descrepancy between them and what was right, and me made the appropriate adjustment. It wasn't much, but it's nice to know I'm getting all the power I'm supposed to!
Tom
On a V-12 engine, the cams span across 6 cylinders, and over time will twist slightly. Rewelding, and regrinding may correct some of the lobes, but checking the work, and the accuracy of the cam, with a timing wheel insures this. Francois takes pride in checking this with every engine rebuild and explains a lot of engine builders just follow the factory marks. The cams, chains, and gears are designed to be moved independent of the each other to get accurate timing, and checking to see what the front lobe is doing, compared to the back lobe, lets you find a good compromise for the best timing for all cylinders on that cam. I believe a stock 250 cam allows for 1/8 degree adjustment. This allows for pretty accurate timing for optimum performance. Think about it, if a Ferrari motor develops most of it's power at high revs, and valve timing is off by a few fractions of a degree, performance is affected dozens of times a second! Cleanliness builds durability, accuracy builds power!
When my engine went together, we used my original cams. Checking the cam timing to the factory marks showed some descrepancy between them and what was right, and me made the appropriate adjustment. It wasn't much, but it's nice to know I'm getting all the power I'm supposed to!
Tom
late 2 cam timing
This post brings up a question that I have:
is the 'factory' valve timing on a late V12 4 Cam engines
(i.e. 365 GTC/4 and up)
optimized for performance
or a compromise to meet emission standards?
the 1979 Lotus Esprit (for example) DOHC 16V engine
is reported to have 2 'factory' valve timing settings
one for 'smogged' cars, and one for non-emission cars
(which are obtained by flipping the cam gears over
and using the alternate set of timing marks on that side)
this altered timing results in a significant
(if not downright considerable)
boost of output
If this is indeed the case with the V12s in question,
how can the optimal valve timing
for best performance be ascertained?
(other than dyno experiment$)
perhaps studying the valve timing on the earlier 4 cam V12
e.g. 'Daytona' engine may shed some light on this
(especially the competition derivatives)
the illustrious francois may have some insights, as well (tom?)
AKB
is the 'factory' valve timing on a late V12 4 Cam engines
(i.e. 365 GTC/4 and up)
optimized for performance
or a compromise to meet emission standards?
the 1979 Lotus Esprit (for example) DOHC 16V engine
is reported to have 2 'factory' valve timing settings
one for 'smogged' cars, and one for non-emission cars
(which are obtained by flipping the cam gears over
and using the alternate set of timing marks on that side)
this altered timing results in a significant
(if not downright considerable)
boost of output
If this is indeed the case with the V12s in question,
how can the optimal valve timing
for best performance be ascertained?
(other than dyno experiment$)
perhaps studying the valve timing on the earlier 4 cam V12
e.g. 'Daytona' engine may shed some light on this
(especially the competition derivatives)
the illustrious francois may have some insights, as well (tom?)
AKB
-
Dr. Ian Levy
- Posts: 179
- Joined: Mon Sep 09, 2002 1:16 pm
- Location: United Kingdom
- Contact:
GTC4 valve timing
In response to" [b]fest[/b] "my comment is that I am in the UK so the smog pump etc is not fitted to my car. I would have thought that optimium performance would mean minimum unaceeptable emissions for the better the combustion the less unburnt fuel & other noxious substances etc that would be avaiable for discharge into the atmosphere.
I still need a method to set the valve timing using a degree disc fitted to the flywheel. Any sugeestions
Regards
Ian L
I still need a method to set the valve timing using a degree disc fitted to the flywheel. Any sugeestions
Regards
Ian L
Ian,
The more I get to understand that valve timing issue, the more I wish I had played with a degree wheel when the engine was out of the car.
Fest –
Very interesting subject. I have heard that people have successfully retarded the intake cam a few degrees to achieve maximum torque at a higher RPM. = greater max HP and probably a higher top speed.
I have a book titled “the original Ferrari v12”. In it are specifications for cam timing for many of the 60s’ V12 engines. Comparing the numbers between the C4 and the Daytona, the Daytona has longer duration of both exhaust and intake (the lobes are “wider”). I did talk to Elgin Cams – a well know cam grinder in Red Wood City, who indicated that he has done several sets of cams for C4s and 400s. He referred to the lobes on the cams in the C4 as “puny” but adequate for a street car. As you probably know, the cams are hollow which means that they need to be straightened after extra material is added by welding. What this equates to is $$$ - but what else is new. My understanding is that the C4 was intended to meet smog requirements anywhere on the planet, and my perception is that all the cams are the same. My shop manual has one set of specification for C4 cam timing, which would “seem” to confirm that.
BUT – I have also heard/read that the European car has 20 more HP than the US version.
In looking at the manual, the European model has a single distributor verses the US dual.
The US version has an elaborate, throttle controlled retard mechanism the uses a second set of points to run the timing 10 degrees retarded for low throttle settings, but should provide similar timing once you step on it. – so, best I can tell, the performance should not be altered by ignition timing between US and European.
The carburetors are adjusted slightly different for US. The float is set at 6mm instead of 5mm, and the idle jet is slightly leaner. Because the idle jet is out of the picture for a performance run, one would think that if you bumped the float level. The performance should be equal except for the power required to drive the air pump??
I set my car up with the marks on the cams – as stated earlier, I wish I had taken the time to dial them in. (I could then also help Ian with the dial in procedure, assuming I would have learned it). I’m running 20 degrees of crankshaft advance in both distributors that is in full effect at 3300 RPM. I run 15 degrees initial crankshaft advance = 35 total degrees at 3300 RPM.
I have set the float level at 5 mm instead of 6. I have “ported” the stock (stainless steel – I know they are stainless because I had to weld up a crack) headers to match the exhaust ports in the heads. I have a London stainless exhaust system and the air pump was missing when I purchased the car. At 500 ft above sea level, according to my G Tech meter, and on regular gas, the car does 0 – 60 MPH in 6.3 seconds - That is a full second faster than many publications indicate – go figure
Other C4 observations -
- carb synchronizing makes a big difference in driving pleasure – I have found that mercury columns are the ticket here – purchase them in sets of 4 at a motorcycle shop.
- Running richer idle jets will yield better low end performance at the cost of gas mileage – (I now have 3 extra sets of idle jets - best purchase price for Weber parts is from Pierce manifolds in Gilroy CA) – the 65f9 are the most fun, but you pay at the pump and spark plug cleaning periodically will be necessary.
- Those foam rubber gaskets that run around the perimeter of the Air cleaner covers will significantly reduce the carburetor noise inside the car.
- There is a tendency for people to rest their luggage on the lip of the trunk (boot), which will bend the sheet metal. This in turn will open up the gap in the back of the trunk and allow the exhaust to leak in a make your belongings smell like exhaust.
- As the exhaust system cools off, water condenses in the exhaust system. This condensation mixes with the soot and when you drive off – these soot droplets will collect on the back of the car and make a mess – Only solution I have found is to let your car warm up for a long(er) time.
- JAF makes replacement bearing for the rear hubs at 1/5 the cost (thanks Ian)
Have fun
Aaron
The more I get to understand that valve timing issue, the more I wish I had played with a degree wheel when the engine was out of the car.
Fest –
Very interesting subject. I have heard that people have successfully retarded the intake cam a few degrees to achieve maximum torque at a higher RPM. = greater max HP and probably a higher top speed.
I have a book titled “the original Ferrari v12”. In it are specifications for cam timing for many of the 60s’ V12 engines. Comparing the numbers between the C4 and the Daytona, the Daytona has longer duration of both exhaust and intake (the lobes are “wider”). I did talk to Elgin Cams – a well know cam grinder in Red Wood City, who indicated that he has done several sets of cams for C4s and 400s. He referred to the lobes on the cams in the C4 as “puny” but adequate for a street car. As you probably know, the cams are hollow which means that they need to be straightened after extra material is added by welding. What this equates to is $$$ - but what else is new. My understanding is that the C4 was intended to meet smog requirements anywhere on the planet, and my perception is that all the cams are the same. My shop manual has one set of specification for C4 cam timing, which would “seem” to confirm that.
BUT – I have also heard/read that the European car has 20 more HP than the US version.
In looking at the manual, the European model has a single distributor verses the US dual.
The US version has an elaborate, throttle controlled retard mechanism the uses a second set of points to run the timing 10 degrees retarded for low throttle settings, but should provide similar timing once you step on it. – so, best I can tell, the performance should not be altered by ignition timing between US and European.
The carburetors are adjusted slightly different for US. The float is set at 6mm instead of 5mm, and the idle jet is slightly leaner. Because the idle jet is out of the picture for a performance run, one would think that if you bumped the float level. The performance should be equal except for the power required to drive the air pump??
I set my car up with the marks on the cams – as stated earlier, I wish I had taken the time to dial them in. (I could then also help Ian with the dial in procedure, assuming I would have learned it). I’m running 20 degrees of crankshaft advance in both distributors that is in full effect at 3300 RPM. I run 15 degrees initial crankshaft advance = 35 total degrees at 3300 RPM.
I have set the float level at 5 mm instead of 6. I have “ported” the stock (stainless steel – I know they are stainless because I had to weld up a crack) headers to match the exhaust ports in the heads. I have a London stainless exhaust system and the air pump was missing when I purchased the car. At 500 ft above sea level, according to my G Tech meter, and on regular gas, the car does 0 – 60 MPH in 6.3 seconds - That is a full second faster than many publications indicate – go figure
Other C4 observations -
- carb synchronizing makes a big difference in driving pleasure – I have found that mercury columns are the ticket here – purchase them in sets of 4 at a motorcycle shop.
- Running richer idle jets will yield better low end performance at the cost of gas mileage – (I now have 3 extra sets of idle jets - best purchase price for Weber parts is from Pierce manifolds in Gilroy CA) – the 65f9 are the most fun, but you pay at the pump and spark plug cleaning periodically will be necessary.
- Those foam rubber gaskets that run around the perimeter of the Air cleaner covers will significantly reduce the carburetor noise inside the car.
- There is a tendency for people to rest their luggage on the lip of the trunk (boot), which will bend the sheet metal. This in turn will open up the gap in the back of the trunk and allow the exhaust to leak in a make your belongings smell like exhaust.
- As the exhaust system cools off, water condenses in the exhaust system. This condensation mixes with the soot and when you drive off – these soot droplets will collect on the back of the car and make a mess – Only solution I have found is to let your car warm up for a long(er) time.
- JAF makes replacement bearing for the rear hubs at 1/5 the cost (thanks Ian)
Have fun
Aaron
I have a 400iA
which is rated at 315 hp
vs a rating of 340 hp for the 400
this drop in HP may not be attributable
to induction (injection vs carburation) alone...
as both engines have the same compression ratio, etc
the timing and or cams may have something to do with this
i plan to investigate this phenomenon
starting with the published valve timing specs
i can also compare cam shaft part numbers
perhaps that will shed some light
a custom grind would undoubtedly yield gains
but perhaps an earlier cam with some tweaking of the timing
may yield some improvement as well
my car is not fitted with a 'smog' pump either
nor cats, etc (as it is a Euro model)
but none the less
there are specific references in the factory workshop manual
regarding tuning for emissions e.g. HCO levels
which would lead me to believe that the car is tuned to meet emissions specs
at the expense of some performance
Dr Levy-
as for your comment regarding 'optimal' tuning,
from my experience (here in the emission control laden' US)
although one would think that the optimal tuning (for performance)
would be the most efficient and therefore the 'cleanest'
is in actuality not the case: sadly
the state of tune required to produce the least emissions
is not the state of tune that yields the best performance
we gearheads in the states have been fighting this battle
since those grim days of the early 70's
as for your question regarding verifying valve timing
'hot rodders' have been using 'degree wheels'
for many years to dial in the cam timing
I am sure one is still available
try a place like http://www.summitracing.com
you should be able to adapt it to the 4 cam v12
without too much difficulty
I believe the method is to attach the degree wheel
to the CAM shaft
not the crank shaft
AKB
which is rated at 315 hp
vs a rating of 340 hp for the 400
this drop in HP may not be attributable
to induction (injection vs carburation) alone...
as both engines have the same compression ratio, etc
the timing and or cams may have something to do with this
i plan to investigate this phenomenon
starting with the published valve timing specs
i can also compare cam shaft part numbers
perhaps that will shed some light
a custom grind would undoubtedly yield gains
but perhaps an earlier cam with some tweaking of the timing
may yield some improvement as well
my car is not fitted with a 'smog' pump either
nor cats, etc (as it is a Euro model)
but none the less
there are specific references in the factory workshop manual
regarding tuning for emissions e.g. HCO levels
which would lead me to believe that the car is tuned to meet emissions specs
at the expense of some performance
Dr Levy-
as for your comment regarding 'optimal' tuning,
from my experience (here in the emission control laden' US)
although one would think that the optimal tuning (for performance)
would be the most efficient and therefore the 'cleanest'
is in actuality not the case: sadly
the state of tune required to produce the least emissions
is not the state of tune that yields the best performance
we gearheads in the states have been fighting this battle
since those grim days of the early 70's
as for your question regarding verifying valve timing
'hot rodders' have been using 'degree wheels'
for many years to dial in the cam timing
I am sure one is still available
try a place like http://www.summitracing.com
you should be able to adapt it to the 4 cam v12
without too much difficulty
I believe the method is to attach the degree wheel
to the CAM shaft
not the crank shaft
AKB
AKB,
The constant is the flywheel and piston postition, the variable is the cam position and the actual placement of the lobe due to twist and regrind, so I would imagine the degree wheel is mounted on the flywheel, and the lift of the valve is measured in accordance to the position of the piston. Adjustments are made in the chains that operate the cams.
As far as performance is concerned in older designed engines, running slightly rich is good, but bad for emissions. The early smog engines were stop gap measures to meet emissions standards, so they weren't really designed from the start with emissions in mind, so they're a compromise between good performing engines, and smog legal engines.
Tom
The constant is the flywheel and piston postition, the variable is the cam position and the actual placement of the lobe due to twist and regrind, so I would imagine the degree wheel is mounted on the flywheel, and the lift of the valve is measured in accordance to the position of the piston. Adjustments are made in the chains that operate the cams.
As far as performance is concerned in older designed engines, running slightly rich is good, but bad for emissions. The early smog engines were stop gap measures to meet emissions standards, so they weren't really designed from the start with emissions in mind, so they're a compromise between good performing engines, and smog legal engines.
Tom
tom-
I was always under the impression that the duration of a cam
was in degrees of CAM rotation not CRANK rotation
is this correct?
if it is cam rotation, then is that not what is checked
with a degree wheel (at least on a 1 cam car)
or am I just plain lost here?
I do understand that it is the relationship between the piston (position)
and the valve (opening and closing) that constitutes valve timing
but
how do you check the exact angle
(in respect to the camshaft)
at which the valves open and close
if the degree wheel is not on the cam
(especially if the cam has twisted)
I am aware of the method of using feeler gages to tell
when the valve is opening / closing
but is there a more accurate way?
AKB
I was always under the impression that the duration of a cam
was in degrees of CAM rotation not CRANK rotation
is this correct?
if it is cam rotation, then is that not what is checked
with a degree wheel (at least on a 1 cam car)
or am I just plain lost here?
I do understand that it is the relationship between the piston (position)
and the valve (opening and closing) that constitutes valve timing
but
how do you check the exact angle
(in respect to the camshaft)
at which the valves open and close
if the degree wheel is not on the cam
(especially if the cam has twisted)
I am aware of the method of using feeler gages to tell
when the valve is opening / closing
but is there a more accurate way?
AKB
-
Dr. Ian Levy
- Posts: 179
- Joined: Mon Sep 09, 2002 1:16 pm
- Location: United Kingdom
- Contact:
GTC 4 Valve timing
Hello
The degree wheel that I have from Ferrari is about 11.5 inches diameter
It is the exact same diameter as the flywheel so it defintely goes on there
The manual refer to a disc as a goniometer & instructs that you fit it to the crankshaft.
It also details various degree measurement :43 degrees before TDC as the beginning of intake valve opening & 38 degrees after BDC as intake valve fully closed. A total of 261 degrees of crankshft rotataion. All measured with valve clearance at 0.5mm
My problem is how to determine exactly when the valve is beginning to open & the first point when it is fully closed
Any suggestions
Regards
Ian L
The degree wheel that I have from Ferrari is about 11.5 inches diameter
It is the exact same diameter as the flywheel so it defintely goes on there
The manual refer to a disc as a goniometer & instructs that you fit it to the crankshaft.
It also details various degree measurement :43 degrees before TDC as the beginning of intake valve opening & 38 degrees after BDC as intake valve fully closed. A total of 261 degrees of crankshft rotataion. All measured with valve clearance at 0.5mm
My problem is how to determine exactly when the valve is beginning to open & the first point when it is fully closed
Any suggestions
Regards
Ian L
as discussed I believe that one can use a feeler gage
to determine when the valve is just beginning to open
i.e. decrease of clearance (to 0) as lobe comes closer to contact
conversely, one can determine when the valve
has just closed, when clearance can again be detected
as for the dial indicator
does one measure movement of the valve itself?
(or in this case the cup / spacer)
that would be a sure fire way to determine
exactly when the valve first starts to open (move)
and also when it is fully closed (stops)
if so I can see tom's point...
it may be tricky to get the indicator to read on the edge of the cup
especailly with the cam/lobe right in the way
probably a fixture can be devised
(most likely if it can be done, francois has done it)
to determine when the valve is just beginning to open
i.e. decrease of clearance (to 0) as lobe comes closer to contact
conversely, one can determine when the valve
has just closed, when clearance can again be detected
as for the dial indicator
does one measure movement of the valve itself?
(or in this case the cup / spacer)
that would be a sure fire way to determine
exactly when the valve first starts to open (move)
and also when it is fully closed (stops)
if so I can see tom's point...
it may be tricky to get the indicator to read on the edge of the cup
especailly with the cam/lobe right in the way
probably a fixture can be devised
(most likely if it can be done, francois has done it)
Valve timing ...
Degree wheel definitely is attached to the crankshaft ... no matter how many cams your have or valve train complication.
Valve open duration is also measured from the cranshaft as it is the degree of crank rotation that the valve stays open.
I know with Ducati motorbikes, that you measure the valve timing at 1mm of valve lift (thus the valve is open by exactly 1mm). This process eliminates the inaccuracies around the valve clearances. If you think about this if your valve clearances are too large the valves will actually be opening slightly later than they should.
If Ferraris measure them with the valves closed, you need to make sure that the valves are closing perfectly (ie. there is nothing inhibiting this, grit on a valve seat holding a valve open) and that the valve clearances are spot on.
In most engines (not sure about Ferraris) you then set the camshaft timing by using number one cylinder as the reference. After all there is nothing that you can do if the camshaft has been twisted ... other than compromising the timing on all cylinders (that would be a serious mathematical problem ... :) ), OR getting the camshaft reground (preferred method).
The other thing that many (most ?) engine builders do is set the cam timing to the middle or centre of the open and closing times. Why? because the duration is a factor of your cam grind and thus if your cam has more duration than it should and you set it to open exactly as per the specs ... your valve will stay open passed the closing point by a larger margin than if you equalised the differences around the opening and closing times. To explain better: Say the standard duration was 40 degrees but your cam has 42 degrees. I would set it to open 1 degrees before it should and 1 degrees after it should. Otherwise the valve would close a whole 2 degrees later than it should. Naturally the figures I have used have been exaggerated ... Also most performance cams (ie. cams that have a special grind to deliberately increase duration) will come with cam timing information.
I would also make sure that you rotate the engine in the correct direction only and never rotate backwards ... as this will alter valve timing due to cam chain tensioning.
Have fun.
Pete
Valve open duration is also measured from the cranshaft as it is the degree of crank rotation that the valve stays open.
I know with Ducati motorbikes, that you measure the valve timing at 1mm of valve lift (thus the valve is open by exactly 1mm). This process eliminates the inaccuracies around the valve clearances. If you think about this if your valve clearances are too large the valves will actually be opening slightly later than they should.
If Ferraris measure them with the valves closed, you need to make sure that the valves are closing perfectly (ie. there is nothing inhibiting this, grit on a valve seat holding a valve open) and that the valve clearances are spot on.
In most engines (not sure about Ferraris) you then set the camshaft timing by using number one cylinder as the reference. After all there is nothing that you can do if the camshaft has been twisted ... other than compromising the timing on all cylinders (that would be a serious mathematical problem ... :) ), OR getting the camshaft reground (preferred method).
The other thing that many (most ?) engine builders do is set the cam timing to the middle or centre of the open and closing times. Why? because the duration is a factor of your cam grind and thus if your cam has more duration than it should and you set it to open exactly as per the specs ... your valve will stay open passed the closing point by a larger margin than if you equalised the differences around the opening and closing times. To explain better: Say the standard duration was 40 degrees but your cam has 42 degrees. I would set it to open 1 degrees before it should and 1 degrees after it should. Otherwise the valve would close a whole 2 degrees later than it should. Naturally the figures I have used have been exaggerated ... Also most performance cams (ie. cams that have a special grind to deliberately increase duration) will come with cam timing information.
I would also make sure that you rotate the engine in the correct direction only and never rotate backwards ... as this will alter valve timing due to cam chain tensioning.
Have fun.
Pete