Ok, you can see from my subject line I'm questioning my cam timing.
Here's the set up; valves clearance checked and adjusted on #1 cylinder, naturaly at the proper TDC, verified by the rotor position. Both valves were pretty good at .006 and .008 but I readjusted them anyway after inspecting the adjusting screws, which were in good shape.
The cam timing mark on the right bank was off about a lines width from the mark on the bearing cap. The left bank marks were spot on. I then went through the same procedure on cylinder #12. I then went back to cylinder #1 at TDC and turned it through the power and exhaust stroke to see when the inlet valve would open, unfortunatly it doesn't start to open until well past the AA-27 degree mark on the flywheel, instead it doesn't open until about 15-17 degrees before TDC. I then went back to #12 and I got about the same reading, showing the intake valve opening about 10 degrees late according to the specs and the AA-27 mark on the flywheel.
keep in mind I'm not using a degree wheel (yet) just using a calibrated eye on the flywheel marks.
Since the both cam timing marks (at least the left bank) are pretty close, does this indicate that my cam has a about a 10 degree twist between the sprocket and the inlet lobe? Doesn't 10 degrees seem like alot? Is there another way to cross check? I guess I could check the rear most lobes to see where they fall to confirm a twist?
--T
cam timing off?
Re: cam timing off?
I know I'm talking to myself but here's some more info:
I checked cylinders #6 and #7 and surprisingly they too showed the same late inlet opening as #1 and #12, about 18 degrees BTDC instead of the 27 degree BTDC per spec. When I say "late" I mean later than spec, not later than TDC. I also double checked all my valve clearances to make sure they were not causing a false ovbservation.
If my observations are correct then they tell me that my cams are not twisted between the front and rear lobes but since the cam timing marks line up pretty good with the bearing cap mark then one could conclude that there is a twist between the sprocket mount flange and the first set of lobes.
I guess this makes it easier if need to re-time the cams because I wouldn't need to compromise front to back.
Am I getting ahead of myself? Is there away to cross check? could I have the wrong cams? or could there really be a local 10 degree twist between the sprocket and first set of lobes? I'd like to be certain before I take the plunge and move those cams.
--T
I checked cylinders #6 and #7 and surprisingly they too showed the same late inlet opening as #1 and #12, about 18 degrees BTDC instead of the 27 degree BTDC per spec. When I say "late" I mean later than spec, not later than TDC. I also double checked all my valve clearances to make sure they were not causing a false ovbservation.
If my observations are correct then they tell me that my cams are not twisted between the front and rear lobes but since the cam timing marks line up pretty good with the bearing cap mark then one could conclude that there is a twist between the sprocket mount flange and the first set of lobes.
I guess this makes it easier if need to re-time the cams because I wouldn't need to compromise front to back.
Am I getting ahead of myself? Is there away to cross check? could I have the wrong cams? or could there really be a local 10 degree twist between the sprocket and first set of lobes? I'd like to be certain before I take the plunge and move those cams.
--T
Re: cam timing off?
Hi Tom,
Valve timing is something that Francois is teaching me slowly as I build my experience with setting cams up, so there are some ideas for you to consider before I ask Francois for his advice.
You say:
How did the car run before? What leads you to believe the cams are timed incorrectly? The discrepancy between the two cams can be attributed to chain stretch. There are all sorts of wacky set ups, but I'm just making sure you're reading the marks right and I'm understanding too!
Tom
Valve timing is something that Francois is teaching me slowly as I build my experience with setting cams up, so there are some ideas for you to consider before I ask Francois for his advice.
You say:
When you say "doesn't start to open until well past the AA-27 degree mark" This is measured with 0 degree lash? Valve lash clearance changes when the engine heats up, so we set them with clearance so there is none when the engine is up to temp. I can review with Francois when I see him, but I think there is something here when he times in a cam.I then went back to cylinder #1 at TDC and turned it through the power and exhaust stroke to see when the inlet valve would open, unfortunatly it doesn't start to open until well past the AA-27 degree mark on the flywheel, instead it doesn't open until about 15-17 degrees before TDC. I then went back to #12 and I got about the same reading, showing the intake valve opening about 10 degrees late according to the specs and the AA-27 mark on the flywheel.
How did the car run before? What leads you to believe the cams are timed incorrectly? The discrepancy between the two cams can be attributed to chain stretch. There are all sorts of wacky set ups, but I'm just making sure you're reading the marks right and I'm understanding too!
Tom
'63 330 America #5053
Re: cam timing off?
Aha! My thinking didn't account for the reduction of lash when the engine was warm! My observations were done with the standard gaps on a cold engine.
The car ran quite well before all this, it had good power and torque with very little smoke. Nothing lead me to believe a mis-timed cam but I've been slowly servicing and base lining things since the only clues I've had about the cars service history are ones of neglect so when I'm done I can wring the car out with more confidence.
Thanks Tom, I'll check the timing with zero lash and report back.
--Tom
The car ran quite well before all this, it had good power and torque with very little smoke. Nothing lead me to believe a mis-timed cam but I've been slowly servicing and base lining things since the only clues I've had about the cars service history are ones of neglect so when I'm done I can wring the car out with more confidence.
Thanks Tom, I'll check the timing with zero lash and report back.
--Tom
Re: cam timing off?
Hi Tom,
I'm reading a good book "One Doctor," by B Reilly, that talks about parallelisms between auto mechanics and physicians. If this is true I can take away two things doctors often say, one of them being "do no harm" and the second, "if you hear hoof beats, think horses, not zebras!"
Good luck!
Tom
I'm reading a good book "One Doctor," by B Reilly, that talks about parallelisms between auto mechanics and physicians. If this is true I can take away two things doctors often say, one of them being "do no harm" and the second, "if you hear hoof beats, think horses, not zebras!"
Good luck!
Tom
'63 330 America #5053
Re: cam timing off?
Nice post Tom, and well understood.
Ok, I checked the valve timing with zero lash, of course I needed to watch the intake opening with a dial indicator instead of by feel, it was much better...only appearing to be off by about 4 or 5 degrees. Since the car was running well, I've decided to leave the cams where they are for now, but at least I have an approximate base line that they may have a twist.
My cam rollers and adjusting screws look good but I did see that the axial play of the rockers on the shaft is considerably out of spec with about .010-.012 of total slop side to side. Should I worry about this or stay off the slippery slope? I'm not trying make everything perfect, just making sure that no disasters are on the horizon, so all in all things look pretty good up here.
Is there anything else I should check before finishing up the valve adjustment and putting the covers back on? I think I read somewhere that checking the chain tensioner is easier with the covers off.
--Tom in SoCal
Ok, I checked the valve timing with zero lash, of course I needed to watch the intake opening with a dial indicator instead of by feel, it was much better...only appearing to be off by about 4 or 5 degrees. Since the car was running well, I've decided to leave the cams where they are for now, but at least I have an approximate base line that they may have a twist.
My cam rollers and adjusting screws look good but I did see that the axial play of the rockers on the shaft is considerably out of spec with about .010-.012 of total slop side to side. Should I worry about this or stay off the slippery slope? I'm not trying make everything perfect, just making sure that no disasters are on the horizon, so all in all things look pretty good up here.
Is there anything else I should check before finishing up the valve adjustment and putting the covers back on? I think I read somewhere that checking the chain tensioner is easier with the covers off.
--Tom in SoCal
Re: cam timing off?
Hi Tom,
Have you taken a look at the tops of the valves when you took the adjusters out? Although there is not much you can do about wear on the top of the valve, you can at least take a note to see if there is any damage. You can also see if the axial play in the rockers is affecting the way the adjuster contacts the valve stem.
Chain tension is a good thing to check. You can see the deflection of the chain with the chain covers off down inside the timing chain case. The spring inside the tensioner should give you the correct tension, but make sure the clamp bolt isn't binding things up.
Tom
Have you taken a look at the tops of the valves when you took the adjusters out? Although there is not much you can do about wear on the top of the valve, you can at least take a note to see if there is any damage. You can also see if the axial play in the rockers is affecting the way the adjuster contacts the valve stem.
Chain tension is a good thing to check. You can see the deflection of the chain with the chain covers off down inside the timing chain case. The spring inside the tensioner should give you the correct tension, but make sure the clamp bolt isn't binding things up.
Tom
'63 330 America #5053
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Steve Meltzer
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Re: cam timing off?
I won't be contributing anything to the discussion about the technicalities of cam timing, but I've often thought the parallels between medicine and auto mechanics were quite striking. In addition to the maxims quipped by Tom, I'd add: 1) "it's difficult to make a healthy patient better" (ie: your cam timing, even if not obsessively perfect, maybe as good as one can make it and is probably fine). Tho' maybe not applicable here, when I was a med student, a highly respected cardiovascular surgeon used to say, "I maybe wrong, but I'm never in doubt". steve
steve meltzer,
"I've spent all of my money on wine, a beautiful woman, and stunning cars. Then, squandered the rest."
"I've spent all of my money on wine, a beautiful woman, and stunning cars. Then, squandered the rest."
Re: cam timing off?
Hi Steve,
Thanks for your thoughts. You might work on one make and model, but your machine is much more complicated!
Tom
Thanks for your thoughts. You might work on one make and model, but your machine is much more complicated!
Tom
'63 330 America #5053
Re: cam timing off?
The valve ends are slightly worn-in and shiny but nothing I would call damage. I don't think the axial play of the rocker(s) is having much affect on the stem clearances. The Max. for axial play is about .008" and I've got about .012" I'm thinking that this condition is not particularly threatening so I'll just record it and leave it for now.tyang wrote:Hi Tom,
Have you taken a look at the tops of the valves when you took the adjusters out? Although there is not much you can do about wear on the top of the valve, you can at least take a note to see if there is any damage. You can also see if the axial play in the rockers is affecting the way the adjuster contacts the valve stem.
Chain tension is a good thing to check. You can see the deflection of the chain with the chain covers off down inside the timing chain case. The spring inside the tensioner should give you the correct tension, but make sure the clamp bolt isn't binding things up.
Tom
I'll be sure to check out the chain tensioner, Is this a good time to inspect the distributors? Is there any thing else I should check while I have her blouse unbuttoned?
--Tom M.
Re: cam timing off?
Hi Tom M.
Since you're doing a valve adjustment, this is usually a part of a "major tune up" at our shop, which would include ignition check. Check point gap, phase and check for smooth advance on a distributor machine. See if there is play in the bearings, check timing on both banks when you put them back in. Put a drop of oil on the felt wiper inside the distributor. With the distributors out, it's a good time to get some white paint and mark AF10 and full advance marks. I sometimes use two different color paints for the two sets of marks. If you have a variable timing light, mark PM 1/6 and 7/!2 and let the timing light move the mark.
clean the distributor cap and rotor contact points, did I forget anything?
Tom
Since you're doing a valve adjustment, this is usually a part of a "major tune up" at our shop, which would include ignition check. Check point gap, phase and check for smooth advance on a distributor machine. See if there is play in the bearings, check timing on both banks when you put them back in. Put a drop of oil on the felt wiper inside the distributor. With the distributors out, it's a good time to get some white paint and mark AF10 and full advance marks. I sometimes use two different color paints for the two sets of marks. If you have a variable timing light, mark PM 1/6 and 7/!2 and let the timing light move the mark.
clean the distributor cap and rotor contact points, did I forget anything?
Tom
'63 330 America #5053
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Steve Meltzer
- Posts: 987
- Joined: Mon Sep 06, 2004 10:31 am
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Re: cam timing off?
Last summer, when I had the cam covers off and was drivin' poor Dyke Ridgley crazy, he suggested I re-torque the heads, which. I checked and slightly tightened the chain tensioner and replaced all of the bronze bushings and their pins.
Tom, maybe it's because I've been practicing medicine for awhile now, but I think it's vastly easier than repairing these cars, by far. (shhhhh...don't the AMA I said so!) steve
Tom, maybe it's because I've been practicing medicine for awhile now, but I think it's vastly easier than repairing these cars, by far. (shhhhh...don't the AMA I said so!) steve
steve meltzer,
"I've spent all of my money on wine, a beautiful woman, and stunning cars. Then, squandered the rest."
"I've spent all of my money on wine, a beautiful woman, and stunning cars. Then, squandered the rest."
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Colin Angell
- Posts: 49
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- Location: Worcestershire, England
- Contact:
Re: cam timing off?
Hi Tom
Which engine do you have? The marks on the cam shafts seem only to be a guide for initial engine assembly and exact cam timing should be carried out as you have described, by rotating the engine to discover exactly when the valves open (or close). I find it easier to feel when the rollers lock up, but I know others do it the other way round. I hate to challenge Tom's wisdom, which is why I asked which engine you have, but normal procedure, on 365 engines at least, is to increase valve clearance on number 1 & 12 to set the timing, not to close it up. I think that has something to do with allowing for the shape of the ramp on the cam lobes, but can't properly remember without looking it up. Obviously the gap needs to be re-set to normal clearance after timing.
It is really quite surprising how well these engines will run within a wide range of cam timings, so you may have a pleasant surprise awaiting you when you get it spot on! I guess that you will know how to adjust the cams, so I won't try to teach my granny to suck eggs, but I'm sure you will find plenty of help if you need it.
Good Luck
Colin
Which engine do you have? The marks on the cam shafts seem only to be a guide for initial engine assembly and exact cam timing should be carried out as you have described, by rotating the engine to discover exactly when the valves open (or close). I find it easier to feel when the rollers lock up, but I know others do it the other way round. I hate to challenge Tom's wisdom, which is why I asked which engine you have, but normal procedure, on 365 engines at least, is to increase valve clearance on number 1 & 12 to set the timing, not to close it up. I think that has something to do with allowing for the shape of the ramp on the cam lobes, but can't properly remember without looking it up. Obviously the gap needs to be re-set to normal clearance after timing.
It is really quite surprising how well these engines will run within a wide range of cam timings, so you may have a pleasant surprise awaiting you when you get it spot on! I guess that you will know how to adjust the cams, so I won't try to teach my granny to suck eggs, but I'm sure you will find plenty of help if you need it.
Good Luck
Colin
Re: cam timing off?
Hi Colin,Colin Angell wrote:Hi Tom
Which engine do you have? The marks on the cam shafts seem only to be a guide for initial engine assembly and exact cam timing should be carried out as you have described, by rotating the engine to discover exactly when the valves open (or close). I find it easier to feel when the rollers lock up, but I know others do it the other way round. I hate to challenge Tom's wisdom, which is why I asked which engine you have, but normal procedure, on 365 engines at least, is to increase valve clearance on number 1 & 12 to set the timing, not to close it up. I think that has something to do with allowing for the shape of the ramp on the cam lobes, but can't properly remember without looking it up. Obviously the gap needs to be re-set to normal clearance after timing.
It is really quite surprising how well these engines will run within a wide range of cam timings, so you may have a pleasant surprise awaiting you when you get it spot on! I guess that you will know how to adjust the cams, so I won't try to teach my granny to suck eggs, but I'm sure you will find plenty of help if you need it.
Good Luck
Colin
No wisdom here. As I said,I'm still learning how to do it when we set up a freshly built engine. It seems with more lash, how would you feel when the roller contacts the cam? I'm going to have to look how a Ferrari workshop manual explains it!
Tom
Tom
'63 330 America #5053
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Colin Angell
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Re: cam timing off?
Hi Tom
I gather that this May be a 330 engine and having done some homework I have learned that up to the 365 engine the cam timing is carried out using normal rocker clearance, so having already set yours you should now be ready to time the cams. Please check this information, because i have also seen some conflicting info that the valve clearance should be set to 0.5mm for your engine and I am sure that you can find out for certain by looking at a manual for your car.
Set number one at TDC and then rotate the engine in the normal direction (I usually engage 5 the gear and roll the car forward) until you see the cam start to move to open the inlet valve of no1. Now stop and go very gently. If you get hold of the roller you will feel that it is free to turn, but as soon as it touches the cam it will lock up. That is the exact point at which the valve will begin to open and it should correspond with the AA Mark on the flywheel.
It is really too crude to rely on rolling the car forward when you get close to the point of contact and I use a socket spanner on the crank pulley to very carefully pull the engine round. Remember that you must only allow for forward motion and that if you let the engine fall back you will have to back up a short way and start again. You will have no way of calculating any backlash, so everything must be done by rotating the engine forward.
As I said earlier I know that some people prefer to keep going through the valve opening cycle and reach the point when the valve properly seats. Shut, when the roller once again becomes free to rotate, but it doesn't work for me.
It sounds as though your engine has the cams retarded by about 10 degrees, which could be because of chain stretch and you will benefit from getting back in time. What you have to do is to fix the cam in position, disconnect it from the crank and then move the crankshaft in relation to the cam and then connect them back up. It may sound complicated, but it is not particularly difficult and definitely pays dividends.
With the cam in the right position and no1 inlet valve just about to open lock the engine in place with chocks under the wheels and the handbrake on. Then remove or at least loosen the centre rocker assembly and slide a thin strip of paper underneath it and then relighted the hold down nuts. That will lock the camshaft in position. Then disconnect the cam sprocket which is held on with 5 short bolts and and a single cover plate. Now the crank and cam are disconnected and you should lever the crankshaft round until you get AA in the correct position when the crank and cam should be perfectly aligned. You will however not be able to get the bolts back in to fix the sprocket back onto the camshafts and now for the tricky bit.
Moving the sprocket by seven teeth of the chain in the direction of engine rotation will advance the timing by 4 degrees so to advance your timing by ten degrees becomes awkward because there is in theory only adjustment in 4 degree increments, giving plus or minus 2 degrees of error. In practice there is normally enough slop in the fit of the bolts to overcome that and it is possible to get very close to a perfect fit. I would suggest that you try rotating the sprocket through 14 teeth and then trying to line up the bolt holes. If they are a long way off try another 7. The action is a bit awkward as you need to pull the sprocket forward, holding the chain up and then lifting it up over the sprocket teeth and counting in your multiples of seven as the sprocket is rotated. When you have it all in line and the bolts refitted the crank and camshaft of 1-6 bank should be in time. Now remove the strip of paper from under the rocker assembly so that the engine is free to turn and torque it down properly.
Repeat for the other cam shaft.
The first time you try this it will probably take a full day and a bit of head scratching, but if you get into the habit of doing it at every major service it can be carried out quite swiftly.
Apologies for the marathon post and good luck
Colin
I gather that this May be a 330 engine and having done some homework I have learned that up to the 365 engine the cam timing is carried out using normal rocker clearance, so having already set yours you should now be ready to time the cams. Please check this information, because i have also seen some conflicting info that the valve clearance should be set to 0.5mm for your engine and I am sure that you can find out for certain by looking at a manual for your car.
Set number one at TDC and then rotate the engine in the normal direction (I usually engage 5 the gear and roll the car forward) until you see the cam start to move to open the inlet valve of no1. Now stop and go very gently. If you get hold of the roller you will feel that it is free to turn, but as soon as it touches the cam it will lock up. That is the exact point at which the valve will begin to open and it should correspond with the AA Mark on the flywheel.
It is really too crude to rely on rolling the car forward when you get close to the point of contact and I use a socket spanner on the crank pulley to very carefully pull the engine round. Remember that you must only allow for forward motion and that if you let the engine fall back you will have to back up a short way and start again. You will have no way of calculating any backlash, so everything must be done by rotating the engine forward.
As I said earlier I know that some people prefer to keep going through the valve opening cycle and reach the point when the valve properly seats. Shut, when the roller once again becomes free to rotate, but it doesn't work for me.
It sounds as though your engine has the cams retarded by about 10 degrees, which could be because of chain stretch and you will benefit from getting back in time. What you have to do is to fix the cam in position, disconnect it from the crank and then move the crankshaft in relation to the cam and then connect them back up. It may sound complicated, but it is not particularly difficult and definitely pays dividends.
With the cam in the right position and no1 inlet valve just about to open lock the engine in place with chocks under the wheels and the handbrake on. Then remove or at least loosen the centre rocker assembly and slide a thin strip of paper underneath it and then relighted the hold down nuts. That will lock the camshaft in position. Then disconnect the cam sprocket which is held on with 5 short bolts and and a single cover plate. Now the crank and cam are disconnected and you should lever the crankshaft round until you get AA in the correct position when the crank and cam should be perfectly aligned. You will however not be able to get the bolts back in to fix the sprocket back onto the camshafts and now for the tricky bit.
Moving the sprocket by seven teeth of the chain in the direction of engine rotation will advance the timing by 4 degrees so to advance your timing by ten degrees becomes awkward because there is in theory only adjustment in 4 degree increments, giving plus or minus 2 degrees of error. In practice there is normally enough slop in the fit of the bolts to overcome that and it is possible to get very close to a perfect fit. I would suggest that you try rotating the sprocket through 14 teeth and then trying to line up the bolt holes. If they are a long way off try another 7. The action is a bit awkward as you need to pull the sprocket forward, holding the chain up and then lifting it up over the sprocket teeth and counting in your multiples of seven as the sprocket is rotated. When you have it all in line and the bolts refitted the crank and camshaft of 1-6 bank should be in time. Now remove the strip of paper from under the rocker assembly so that the engine is free to turn and torque it down properly.
Repeat for the other cam shaft.
The first time you try this it will probably take a full day and a bit of head scratching, but if you get into the habit of doing it at every major service it can be carried out quite swiftly.
Apologies for the marathon post and good luck
Colin