question about setting valve clearances

andrew · Post by **andrew** » Fri Sep 22, 2006 7:33 pm

I’ve been wrestling with valve adjustment today, and have a rather specific question for someone in the know. Sorry this is so long, but I hope to be clear.

I have been using as guides both the Roush & Apen (R&A) and Bishop (B) books, which at first glance appear pretty helpful. Yet, they appear to contradict one another in a meaningful way, as it turns out, so I’m seeking another expert view.

To begin adjusting, R&A (pages 25-26) say to crank the engine to PM1/6 (TDC for cylinders 1 and 6) on the flywheel. They claim that cylinders 1 and 6 are *both* closed at that point and can *both* be adjusted. From there, they simply say to turn the engine over while you “observe the position of the cam lobe on the next cylinder to be checked…[and] rotate the engine until the lobe is pointing away from the rocker arm” (p. 26). In this manner you can adjust your way through the firing order [1-7-5-11-3-9-6-12-2-8-4-10].

B (pages 102-103) says to crank the engine to PM1/6 *and* be certain that the arrows on the cam bearing caps (one each bank, clearly visible) align with the index marks on the cam (one each bank also, which on my car appear to have been inscribed not by the factory but by some mechanic). In his words, B says that “at TDC the cam lobes are pointed downward and outward. This is the correct position for adjusting the clearances. Thus, with the engine at PM1/6 and the cam indexes all aligned, cylinder number 1…is ready for adjustment” (pp. 102-103).

After cylinder 1, B recommends rotating the engine 60 degrees through the rotation and setting each valve in the firing order. This is straightforward enough and is nicely facilitated by the corresponding marks on the flywheel, which he doesn’t mention [in order: PM1/6 then PM7/12, PM2/5, PM8/11, PM3/4, & PM9/10; 2 full rotations, paying attention to the odd number in the pair first, then even numbers; by the way, mine actually read: “PM1/6” then “PM7/12” then “2/5” then just a scribed line representing 8/11 then “3/4” than another scribed line representing 9/10].

So, you’re probably wondering what could possibly be the problem, right? Sounds pretty simple, especially with the convenient flywheel marks.

Well, first off, R&A don’t mention aligning the index marks on the cam bearing caps with the index marks on the cam (in fact, they don't mention these marks at all). At PM1/6 these marks will be aligned nicely and then, after one more rotation of the flywheel, they will not be anywhere in sight. Consequently, it would appear that PM1/6 is not enough, you have to attend to the index marks as well -- this appears to be an important difference between R&A and B. Fair enough, though: I simply figured this was an important omission on the part of R&A and all would be well after beginning at PM1/6 with the index marks all aligned as B said.

So, I proceeded, following R&A’s advice and setting valves in pairs of cylinders at a time (see above: R&A say that 1 & 6 can be set at the same time, 7&12, etc. etc.). Thus, I did this as I went through the firing order, with the logic that it would save time and I could always confirm when I got to cylinder #6 in the firing order that it was indeed correct. However, when I came to #6 it was not correct (no gap), nor were any of the remaining ones (12,2,8,4,10). Again, not a big deal: I concluded that R&A were mistaken and went through the remainder of the firing order, setting diligently as I went.

Finally, my questions:

1. Are R&A really wrong? Why, as they say, does it appear that you cannot/should not set valves on paired cylinders at the same time? Is there something else going on here (i.e., user error)? Did I misunderstand something?

2. Recall that R&A say to “rotate the engine until the lobe is pointing *away* from the rocker arm” to set #1. B says that to adjust #1 “the cam lobes are pointed downward and outward” (presumably this means outward/away from the arm). Yet, on my car, with the engine at PM1/6 and the cam indexes all aligned, the cam lobes for #1 are tucked *under* their respective rocker arms, not pointing *away* from them (at 5 and 7 o'clock in both cases). As you go through the firing order, #7’s lobes then point away from the arm, #5’s are next tucked under their arms, etc. etc.; they alternate through the order.

The question: Does it matter that #1 appears to be "backward" from what both R&A and B say – this sounds silly (TDC is TDC, right?), but it actually matters later when B, on page 106, talks about checking valve timing (which I did next, see discussion of checking CS16, etc.)? If you’re still with me, the real fear is that it appears that the mechanic-made index marks on the cam might in fact be 180 degrees off…I would feel a tad better if it looked like a factory mark. Put another way, if the PM1/6 mark is aligned, and if the cam lobes are at 5 and 7 o'clock (and thus valves are closed/at TDC) and you begin setting #1 and proceed through the firing order, does it matter if the cam indexes are aligned or not? Does it matter if the lobes are pointing away from the rocker arms or tucked under them? My instinct says no (again TDC is TDC), but the discrepancy and the ensuing discussion in B on page 106 that indicates/requires that the lobe should point away from the arm to check timing has me worrying a bit...

I really appreciate any perspective on this, thanks.

TOMKIZER · Post by **TOMKIZER** » Fri Sep 22, 2006 8:24 pm

Andrew, I think I followed your description but you have to remember that, for each cylinder, there are two revolutions per "cycle", one revolution for the intake and compression strokes and one for the power and exhaust strokes. Therefore, TDC is TDC but there are two TDC's for each cylinder per cycle. What you want for each cylinder that you adjust is the TDC that occurs between the compression stroke and the power stroke for that cylinder. It is the one where both valves are closed. The other TDC for that cylinder is between exhaust and intake. In fact, at that point both valves are open (it's called overlap and the exhaust valve is still closing while the intake valve is beginning to open). All you really have to do is put the F/Wheel on PM 1/6 and look to see if the lobes are pointed away from their respective rollers on cylinder 1. If not, look at cylinder 6. One of the two cylinders will be at TDC comp/power and the other cylinder will be at TDC exh/int. On the cylinder at TDC comp/power, there should be some lash in the rocker arms that you can feel if you wiggle it (unless your valve clearances are completely gone, in which case, you should have exhaust or intake backfire during running). The rocker arms on the other cylinder should be part of the way up or down the cam lobe ramps and the valves should be partly open. In any case, you will find that those rocker arms are as stiff as it can be and there will be no clearances. Adjust the lash on the cylinder whose cam lobes are pointed away from their respective rocker arm rollers. If it was cylinder # 1, then proceed to cylinder # 7 by rotating the engine counter clockwise 60 degrees to PM 7/12. If it was #6, then proceed to cylinder #12. It really doesn't matter which bank you start with so long as each 60 degrees, you adjust the correct cylinder. Once you've found the right cylinder to start with, follow the firing order, 60 degrees at a time. YOU CANNOT ADJUST PAIRED CYLINDERS ON THE SAME REVOLUTION.
Confusing, isn't it.
Good Luck.
Tom Kizer

andrew · Post by **andrew** » Fri Sep 22, 2006 9:09 pm

Thanks for the speedy response, Tom.

Ok, first I think we have established--as you say and as I verified--that R&A are wrong in claiming that you can/should set valves on paired cylinders at the same time (i.e., 1&6, 7&12, etc.). If nothing else, this should benefit everyone here who reads R&A to know...

Next, I understand TDC as it occurs twice: at the conclusion of the intake/compression stroke (between compression and power) and at the conclusion of the power/exhaust stroke (between exhaust and intake). Thanks for the clarification on "overlap."

To clarify further, you're saying that when TDC at the conclusion of the compression stroke occurs (that is, TDC between compression and power strokes) the cam lobes will be pointed *away* from the rocker arms? Indeed, that was my understanding and what gave me pause...when the flywheel is at PM1/6 and the arrows on the cam bearing caps align with the index marks on the cam, my cam lobes are *tucked under* their respective rocker arms. This would indicate that I'm at TDC after exhaust stroke, right? If that's the case, the conclusion to reach is that the index marks on my cam are 180 degrees off. Sound right?

Finally, though, I'm still not clear on one thing you say. You note that one should "Adjust the lash on the cylinder whose cam lobes are pointed away from their respective rocker arm rollers. If it was cylinder # 1, then [after adjusting #1] proceed to cylinder #7 by rotating the engine counter clockwise 60 degrees to PM 7/12." That, of course, makes good sense and was the procedure I followed (just that I began with the lobes tucked under rather than facing away). BUT, if you start with #1 (with cam lobes facing away from the rocker arm), and rotate 60 degrees to #7, the cam lobes will now be TUCKED UNDER their respective rocker arms (rather than facing away from them). So, if you advance by 60 degrees through the firing order, you will alternate between cam lobes *facing away* from the rocker arm on one cylinder with cam lobes *tucked under* the rocker arm on the next cylinder. Yet, by what you said, I understood the correct way to be to adjust the valve lash *only* when the cam lobes faced away from the arms. Thoughts?

mcmichael · Post by **mcmichael** » Fri Sep 22, 2006 11:02 pm

Andrew-

Tom Kizer pretty much says it, except you want to turn the engine CLOCKWISE to the next cylinder in the firing order. As viewed from in front of the car, looking at the front of the engine. Though of course, when I refer to the “right bank” or “left bank”, that’s when you’re sitting in the driver’s seat. Hey, it gets worse!

OK, back to your original questions. No. 1 – is R&A wrong? Well, what got printed in the book is wrong. I have both books, they are written by gentlemen who have many multiples times the knowledge I will ever posses, and both of them have a lot of valuable information. But, typos and “well-that-goes-without-saying” instances pop up, regardless.

I have the R&A book open as I am typing this. Step # 2, pg 25 says “Intake and exhaust valves on cylinders 1 and 6 are now closed and can be checked and adjusted at this point.” (When the flywheel shows PM 1/6) Oops. What they MEANT to say is “Cylinders 1 and 6 are now at TDC. The valves on one cylinder will be ready to adjust and on the other cylinder, both valves will be part way open and can be adjusted after the engine has been rotated another 360 degrees.”

Your second question concerns which way the lobes point. Assuming your engine was running before (as opposed to being assembled from a stack of parts) on the 1-6 bank, the lobes will be pointing towards each other when the valves are ready to adjust, but on the 7-12 bank the lobes will be pointing AWAY from each other when they are ready to adjust. In either case, the lobe will be “away” from the rocker (the valve has clearance) as opposed to holding the rocker down (the valve is open) when the valves are ready to be adjusted.

I just read your response to Tom’s post. The reason for the apparent discrepancy as to which way the lobes point is the fact that all the cams are rotating clockwise, but on the 1/6 bank, the exhaust is on the left and the intake is on the right, while on the 7/12 bank they are reversed—i.e., the exhaust is on the right and the intake is on the left. In all cases, the exhaust will finish closing as the intake is starting to open. It makes sense when you think about it. (Note “right” and “left” now assume you’re standing in front of the car, facing the engine. See first paragraph!)

It’s all pretty simple when you see the overall picture. Ferraris are just like every other 4-cycle engine. Just a few more cylinders than most. When adjusting valves, I like to start and stay with the right bank, the 1 to 6 bank, ignoring 7-12. Less running back and forth. Turn the engine 120 degrees between cylinders, and adjust in the 6-cylinder firing order 1-5-3-6-2-4. Then, go to the 7-12 bank and adjust them, 7-11-9-12-8-10. Which, you may note, is 1-5-3-6-2-4 if you imagine the left bank as a 6-cylinder engine, starting from the rear.

As for the cam timing index marks, these really have nothing to do with adjusting the valve clearance. They also may have nothing to do with adjusting the cam timing! My engine had the marks for both cams lined up perfectly at PM 1/6—just like all the books said they should be. But, the left bank (7-12) cam was mistimed. It turned out to be 27 degrees advanced! How did the cam get marked in the wrong position? I don’t know. I thought it ran pretty well before I retimed the cams; after all, it was a 12 cylinder Ferrari! (My first Ferrari, of course.) But after the cam timing was corrected, wow, what a difference! It suddenly ran like the proverbial sexually assaulted ape. I posted my cam timing method a couple of years ago. I guess what I’m saying is, don’t take the cam index marks cams as gospel…

I hope this helps. And if I got anything wrong, well, we’ll blame it on a typo; or I’ll say, “well, that goes without saying!”

Michael McClure
67 330 GTC
63 250 GTE

John Vardanian · Post by **John Vardanian** » Fri Sep 22, 2006 11:35 pm

Pardon my ignorance, but why does valve adjustment have to be so complicated. Just do it one cylinder at a time, from 1 to 12. That way you won't skip any. There is a point where the I and E lobes of each bore point to 4 o'clock and 8 o'clock.

I turn the engine around by rotating one rear wheel so as not to tax the starter. Does anyone else do this? You need to remove the plugs, put the car in top gear and lift one rear wheel off the ground.

Maybe I am oversimplifying. Am I? Thanks.

john

TOMKIZER · Post by **TOMKIZER** » Fri Sep 22, 2006 11:41 pm

Andrew, Michael's explanation of why the lobes point in different places on different banks of the engine is absolutely correct. I didn't even think of that when I wrote my note. By the way, I always talk about left/right and clockwise/counterclockwise as if I were sitting in the driver's seat. That's the auto industry norm also. If it's a transverse engine, pretend you are sitting on the engine looking at the end opposite the flywheel.
You don't have to be too precise about the crank angle when adjusting the valves. It's really only necessary to ensure that the rollers are on the cam base circles, which are each more than one engine revolution long. The need to get both valves on one cylinder closed at the same time is simply a convenience. In reality, if you wanted, you could adjust any valve that you "KNOW" is closed, regardless of what the crank angle is. It's just more difficult to keep track of what has been done and what has not yet been done. I always keep a note pad handy for taking notes and checking things of a list.
Tom Kizer

TOMKIZER · Post by **TOMKIZER** » Fri Sep 22, 2006 11:50 pm

No John, you are not oversimplifying, if you can see the lobes. It's pretty tight in there. And I also use the rear wheel to turn the engine. And I use the "Tighten the lash screw til I can feel the clearance go away and then back it off "X" degrees of the screw method", to get the lash correct. I don't even need feeler gauges.
Tom Kizer

andrew · Post by **andrew** » Sat Sep 23, 2006 12:22 am

Ok, maybe I can put this to rest -- the confusion for me boils down to this I think: there are 2 times when the lobes point to 5 and 7 o'clock (or 4 and 8 o'clock as John says). The way I described it was when the cam lobes are pointing away from their respective arm(s) and when the cam lobes are tucked under their respective arms. In each case, however, they are at 5/7 o'clock...

So, when Michael says "on the 1-6 bank, the lobes will be pointing towards each other when the valves are ready to adjust, but on the 7-12 bank the lobes will be pointing AWAY from each other when they are ready to adjust," do you (Michael; or anyone else) mean that the lobes will be pointing away from their respective arm(s) on 1-6 when ready to adjust (and therefore tucked under their respective arms for 7-12 when ready to adjust), or the reverse? Technically, the cam lobes are fixed, and therefore always in the same position in relation to one another (i.e., they don't point away or toward each other any more or less depending on cam rotation).

Thanks, everyone, for playing along and for your considerable help.

John Vardanian · Post by **John Vardanian** » Sat Sep 23, 2006 2:08 am

Thanks Tom.

Once both valves are closed, it’s a good idea to remove the rocker arm blocks to inspect the ends of the adjustment screws and the valve tips, and also measure the lateral (side to side) play of the rocker arms.

john

TOMKIZER · Post by **TOMKIZER** » Sat Sep 23, 2006 3:55 pm

A question for all: Speaking of inspecting the adjustment screws, who has tried the "Lash adjuster kit with the smaller roller and the fatter screw tip"? Does it work to REDUCE noise? Wear? Adjustment frequency? Wallet thickness? I forget who makes it and sells it and even what it's called. That's what happens when you get old.
Tom Kizer

Sleeper · Post by **Sleeper** » Sat Sep 23, 2006 8:57 pm

As long as we are on this subject, a very well known Ferrari mechanic told me that you only have to tighten the nut on the adjustment screw finger tight, and it will not loosen over time. Anybody have comments?

Stephanm · Post by **Stephanm** » Sun Sep 24, 2006 8:14 pm

The easiest way to set valve lash is to remove the distributor cap and note where the brass contacts are on the inside of it. You will see that there is a brass contact w/screw every 30 degrees. Visually recognize where the points would line up on the distributor body and use a sharpie marker to locate these points. Once the sharpie marks closely match the distributor cap contacts, you turn the motor over until the rotor points to one of those sharpie marks. It the rotor is pointing to the mark representing the distributor contact that attaches spark plug wire going to cyl # 4, adjust the lash on both the intake and exhaust valve on cyl #4.
If you need this described better buy a VW bug repair manual, it is much more clear than my wording.