Setting Valve timing

Bump for Brian....

 

Your timing marks are: PM1-4| where the vertical line (ie: the |) is the factory TDC mark. If the long white line on the PP is your TDC mark, it's in line with the |.

The | mark location is stamped after the PM1-4 letters are stamped, it's exact location varies from engine to engine eg: PM1|-4, PM|1-4, and can be on top of any of the PM1-4 letters.

BTW, how are you measuring TDC? Long dial indicator? Piston Stop? Whistler? Something else?

There's a .PDF of the GT4 WSM online, Sorry, but I can't find my link to the site. I usually just search the Tech Q&A for things like 'WSM' or 'Shop Manual' and GT4.

However, if you've got CIS, then I'd start by checking the engine serial number stamping to see whether you've got an injected engine or a GT4 carb'd engine. Your best bet on the cams is to check out the numbers stamped on them to see if you can match them up with F* P/Ns. Hopefully you've still got the GT4 cams as the early carb'd cams gave the best power overall.

There are some pretty good descriptions of how to time the cams in both the Old FerrariChat, and also the current Tech Q&A. Again, search is your friend.

One of the members generated a .DOC file with a very thorough writeup, but the link is dead & I stupidly didn't keep a copy.

 

I found my flywheel marks were off 3*, and that little plate dont have enough slot to slip over to make it right. I ended up doing the mark on the PP too.

Because 30 years is a long time, many things could have taken place. For example, camshafts can be welded up and reground to a different profile. For this reason, it is best to run the motor around several times and check your cams duration and lift, and while your doing that, locate the center of lift.

Mark (M ke) was the first person I had heard to describe timing by lobe center, and after studying it further found it made far greater sense and is actually easier.

Now if you look at the euro timing, you can easily deduce where the lobe center should be located, and by watching your cam you can see where your at at where you want it to go. Just relise that there is only 4* difference in valve timing between the euro and the early US cars, and 15 HP. I dont believe all that power is attributal to the valve timing alone, but I dont know of any good dyno numbers of the various models that anyone else can say either. I just know my car ran like the dickens once I changed the belts and timed it to LC. I timed intake to 100* and exhaust to 90* LC. I might try 100 on the exhaust if I ever get Scotts adjustable belt sprockets installed.

 

Here's one of the longer & more detailed discussions. The best tips are towards the end of the thread:

http://ferrarichat.com/forum/showthread.php?t=94546

 

Brian -- I added some labels to describe Verell's words -- unfortunately, your photo shows the flywheel at about 1 deg BTDC (not TDC).

The paint marks on the clutch housing are typically added by the mechanic to be more easily seen (although the -3 ATDC one looks a little bit off, but might just be the photo angle).

You might have a "mixed" set of cams -- my notes have the lifts as:

Early carb 308 ('73-'77)
Intake = 8.949 mm
Exhaust = 8.323 mm

Late carb 308 ('78-'79)
Intake = 7.7 mm
Exhaust = 7.7 mm

(PS Although the '78-'79 carb 308 and later 2-valve injected 308 cams might have different F PNs, they have the same cam lobe profiles -- is that Mondial8 SPC you are referencing for euro or US-version Mondial8?)
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I magnified your picture. As I believed the first time, the bottom ~1/3 of your PM 1-4 letters is missing. Either they were stamped too close to the flywheel edge, or else the flywheel's been machined enough so they're cut off along the horiz line of the 4. I suspect over machining, so measure your flywheel's thickness at the earliest opportunity.

I agree with 91tr's interpretation that according to the flywheel marks the engine is at 1 degree before TDC. However, I'd trust my dial indicator.

BTW, that captive indicator shaft extension is a great idea. I've been borrowing a friend's long dial indicator extension whenever I'm doing timing.


Sorry about the bad links & missing pix, the Fchat hard drive crashed a couple of years ago, & the ISP's backup procedure was flawed. We're lucky we didn't loose everything posted prior to the event!

As for detailed procedures, there isn't one for several reasons:
a) Unlike Ford, GM, etc. Ferrari assumes that the techs were very experienced & factory trained, so didn't put them in the WSMs.
b) One member did write up a very good one, but it was on his web site & it went away sometime in the last year or so.
c) Prior to very recently, the most members used & trusted the cam cap & corresponding cam marks. Many still use them, as well as several pro. shops that I know of. (Let's NOT reopen that discussion here).


As to lobe center, the argument has been made that the lobe edge that lifts the valve gets significantly more wear than the trailing edge, and that this wear is uneven from lobe to lobe. Believe it's in the thread I posted the link to. It's going to come down to your call.

 

I have replaced and had reground many cams and have yet to see one wear there. The always wear at the point of most heat, stress, and friction, the toe of the lobe at max lift.

Timing at lobe centers? Thats absurd.

Solid lifter Ferrari cam specs are measured with .050 valve clearance going back to somewhere around the time of the switch from finger followers to roller followers on the 250's. Prior to that they were measured absolute.

 

Production date of June 1975 or earlier would mean a series 1 car.....different cams.

 

You were clear that based on your dial indicator meas'ts you believed TDC to be on "/".

All we were trying to say was that a) it's a 4, not a slash
b) The real flywheel mark was the vertical bar 1* later in rotation.

As I said, I'd trust carefully made dial ind. meas'ts more than the flywheel markings.

As for the cams causing problems with the CIS, It's unlikely. The only cams mentioned causing CIS problems have been the P6 grinds & similar very high lift grinds.

I'd set the cam timing for stock, button it up, see how it drives. If it drives fine, I'd spring for a dyno run with A/F data collection. The CIS is generally regarded as reducing power about 10%, so if it's within 10-15% of a carb'd car, I'd call it a day.

 

Sorry, I wasn't clear either -- I should have said that the relative alignment of the marks in your photo would "indicate" being at about 1 deg BTDC (even though you are physically at TDC). As Verell said, you should use your dial indicator measurement as the "true" indication of TDC and move the fixed reference mark piece to line up with the proper mark on the flywheel (when at TDC). IIRC, there are no alignment dowels in the flywheel to crankshaft connection so the slop in the flywheel bolt holes allows some angular movement -- since your marks seem "cut" (i.e., the flywheel was removed at one time) perhaps they weren't careful when reinstalling the flywheel.

With regard to the 308 CIS cams vs the late carbed 308 cams, I'm 95% sure that the lobe shape itself is the same. If you check the pages showing the distributors in those two SPCs you can note that the spline coupling piece/design that goes into the end of the cam is different so this would require different PNs (even if the cam lobe shape is the same) -- just a thought...

 

Lobe center is a calculation properly only used for an estimation when read by a tuner what a particular cam grind is designed for, the RPM range it is intended for. It is not the point of maximum lift, If it was it would be called the point of maximum lift. Lobe centers and the point of maximum lift may be the same but unless you are equipped with the proper equipment to figure that out you cannot tell and published cam specs almost never include that sort of information because it is considered useless. No car company, engine building company, or cam grinder suggests it use as a method for timing cams. The other problem is cam grinders try very hard to keep the valve at maxlift as long as possible so on many cams it can be impossible to measure with a dial indicator, it can cover too many crank degrees. In valve timing the most critical phase of operation is at overlap. That is exactly why Ferrari (and most knowledgeable engine builders) always say to measure exhaust closing and intake opening. On a solid lifter Ferrari motor you have 2 choices. One is to set the valve lash at .5mm and measure the opening of the intake valve. It should be adjusted to match the spec for the cam you have. Next measure the closing of exhaust in the same way. Choice 2 is to set valve lash at zero or holding the valve slightly open and turn the motor to see an intake valve lift of .5mm at opening spec. At that point the measured degrees at the crank should be made to agree with the cam spec. Then repeat for exhaust.

Thats Ferrari's way. They are a pretty smart bunch and have won a few races doing it that way.

I know there are all sorts here that will say I am full of it but just ask them how many F1 races their motors have won.

I am just up the road. If you still have problems give me a call because I am done here. I am just not going to get into the coming debate.

 

"If I understand this correctly then I think I could - understanding this is not how Ferrari says to do it - split the difference? If I know my valve clearance is .25mm couldn't I just measure .25mm of valve lift? If I can from .5 to zero (for a total of .5mm lift), or zero to .5 (for a total of .5mm lift) can I go from .25 to -.25 (for a total of .5mm lift)?"


You are on the right path, do not start to work around problems now. Reset the clearance to .5 and do it right the first time. Slop in dial indicators, setting the indicator stem at exactly 90 degrees so the is a direct push..... Too many variables that you can introduce to justify the time savings of not resetting 4 valves.
Get a can of brake cleaner and clean up the marks on the flywheel and the pointer. Clean is your friend as precission and repeatabilty is key to doing this properly. If needed remove the pointer and slot the mounting holes so it can be mounted exactly where needed. Your eyes will start to play games with you so paint the marks on the flywheel with a light colored paint and then scratch the paint exactly where the mark is. This will give you a "highlighted area with a fine line in the middle" and will aid in the setting process.
The piston has dwell at TDC so to set the TDC marks properly once and for all you need to check the the timing on the flywheel at 1mm before and 1 mm after TDC (or any measurement you want so long as it is the same before and after. I use one rotation of the indicator I am using on the job). Once they are the same, you have true TDC. I use a nautical map divider for checking this if you are using the flywheel rather than a degree wheel.
Remove your dial indicator from the plug hole and verify there is no carbon on the crown of the piston where the indicator is resting (remember, precission and repeatabilty). If there is any carbon, the thickness will change as the indicator stem rubs it away and give you fits while getting the pointer set.
You have invested enough time to this point where doing it anything but right would be a waste.
Keep going, I finally see a trend starting.

Dave

 

I do not want to step on any toes, and likewise dont want mine stepped on either. Camshafts and camshaft valve timing has and still is one of those "black art" things, and you could fill a small library with books on the subject and go blind reading it all and probably still not really know the subject that well.

But having said that, there are some things that are pretty well known. First of all, there is not very much gas flow past a moderately sized automotive valve until its opening up through .100". I use this size valve and opening as a reference because in the example of a tiny overhead valve model airplane engine its valves may only open .100" max. Second, most of the real gas flow occurs in the top 25% or so of valve opening.

At low engine speeds, especially at idle, it may be very important, critical even, for emissions quality to have the exhaust closing and intake opening at very precise moments. Its highley possible that moving those events even as much as a degree or two either direction could cause the engine to run "dirtier". But once the motor is spun up to driving speed, its the position of that top 25% or so of valve opening and the points that those events take place that will determine how much power the engine will produce, and where in the rev band that engine will produce its peak torque.

I have Mark Eberhart (M ke) to thank for getting me to study more heavily on the subject of lobe centers, and thier placement and effect on engine performance, as well as cylinder head flow. His work with supercharging his 308 QV has been well discussed and his performance numbers should be enough to at least listen to the man. Lobe centers, or more accurately, center of lift, is very critical and in any Camshaft discussion involving high performance engines, lobe centers and lobe seperation angles are heavily discussed. But you could never find the center of lift without first locating your opening and closing points. And for this you need a dial indicator and all the paraphenilia of tools that we are discussing. I did not make a point of claiming one would time an engine to lobe centers without knowing where its located. that WOULD be absurd.

Now on the one hand we have witness to Ferrari being a wonderful racing team and sports car builder that has won many thousands of victories at race tracks around the world for over 8 decades. On the other hand we have witness to some master in thier engine shop setting valve timing by whacking flywheels and cam pulleys with plastic hammers, and when called on his procedures innacuracies by a couple "students", the whole matter is swept under the rug. We have witness to engine blocks with cylinder misalignments, porous aluminum castings, crankshafts that were not exactly clocked, and camshafts that dont always clock exactly across thier length or even having the same lift from lobe to lobe. We even have witness to flywheel pointers that cant barely be modified enough to point at the flywheel at the correct indication. Mine was 3* off and so are a few other fellows that have taken the time to check for true TDC. And yet these "bastards" ran amazingly well and still managed to pass emissions.

Some of these cars are now over 30 years old, and only now is it coming to light that things have been this far off. Three degrees here, three degrees there, pins and pin hole slop here and there in the pulleys, and even camshaft index marks not all being exactly centered. I suppose this is heresy, finding fault with our beloved chariots of fire, perhaps I should be burned at the stake for pointing out my observations, or, like Galileo, denounce my findings and return to the days of blindness. But when I walk into the garage and find my two Ferrari's, all is forgiven. Enzo is not responsible for thier faults, he is only responsible for thier creation. Other men must take blame for these cars faults and inadequacies. Finding and correcting those faults wont be easy.

Its a Ferrari. As has been addressed, these are not mere means of transportation, unless your needing to be transported to Elysium. If none of that is worth the time and effort to massage Enzo's creation blessed to your momentary possession into its fullest form and ability, or to pay to have it done, sell it and let someone else master it. Timing the belts is not simple. Timing them as accurately as possible is even less so. And timing them to make the car run the way "You" want it to run will be the most difficult endevour. And that last endevour will pay you back in spades in both accomplishment, and joy.

 

Well said Art...

 

Yah BUT............. its another $16! GEZZZZ!

I am pleased that there is at least some thought towards doing some of this correctly and accurately. I can live with the debate on HOW to do it as long as it is done.

Dave