Setting Valve timing

So now I can get the shims out.

#1 exhaust - Shim is a 3.75, clearance is .305mm, so the shim for .500 clearance is 3.555. I inserted a 3.55 shim and double checked the clearance with a feeler gauge. Dial indicator on and I first detect movement at 53* BBDC, keep turning and movement stops at 21*ATDC. Well, the duration matches the manual, but that's 17* advaced from my manual. That seems like a lot. Am I off a tooth on the belt? Maybe I missed when swapping belts? Maybe I got it exactly like the pervious belts and they were off a tooth? Maybe the whole cam is just off? And add this to the mysterey - there are two sets of marks on the cam cap. One is factory and one I asume is from a mechanic at some later date. Neither lines up with TDC right now.
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Before knowing if I'm off a tooth on the exhaust cam I might as well see how that intake cam is. I have an issue here where I have mismatched cams. The intake cams are from a later car - these appear to be 1979 cams (exhaust cams are 1975 series 1, apparently). They have different lift and duration from early carb cars. This and a typo in the WSM was giving me fits. So #1, intake cam - Shim is 3.45, clearance is .229. For .500mm clearance I need a 3.179 shim, the closest would be a 3.20 shim. The Volvo shop doesn't have a 3.20, their thinnest is a 3.30, even the Ferrari manual says that the smallest shim is a 3.25, but even that is one size too big and I already rounded up a little. Rifledriver says that we can go zero clearance + and measure .500 valve lift, so that's my only option here. 3.45 shim + .229 clearance is 3.679, round up to next shim size for a 3.70. Slide it in, hook up the indicator. Turn the engine until I have .500 lift and I'm at 14* BTDC. Keep turning and .500 lift is at 40* ABDC. OK ,the 14* is 20* off, close to the 17* off of the last cam. Hmmm. But the closing spec is very close to being right - should be 46* and I'm at 40*. That's close. Not right on, but way closer than the opening event. I think I should time this to whatever 1979 cars are spec'd to, but no one has come forward with that info yet. I'll have to start a new thread and see if I can get smeone to check their manual. With the much decreased duration I'll have to see what Ferrrai said to do with this cam.

Next cam is the front bank intake. I can't crank on the crank and see the dial indicator at the same time. Perfusion came over this afternoon and cranked the motor over while I crouched on the intake and tried to figure out WTF. First we needed to move the degree wheel to line up with 5-8 TDC. We could do the correction on the degree wheel, but I was already pushed to my mental limit. I made up a piston stop earlier in the day and we used this to find TDC. This picture is mostly for Perfusion who actally used this tool today, but never got to see it!
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We did the #8 intake lobe and came up with opening at 10*BTDC, closes at 44* ABDC. Just for giggles we also did the #5 intake lobe just to see if it would be the same and it was. Wow, repeatablility, who whould have guessed?

OK, so the two intake cams have the same duration (whew! It's about time something went well) and they are timed very close to the same, just 4* different from each other. I'll guess that whomever timed these cams at least did it this way on purpose since they are both skewed the same way. I don't know if it is right, but the car did run ok at the very least.

On to the front exhaust cam and I can't get the dial indicator in there. The firewall is just too close. I'll need either a different indicator or a contraption. More to come on that. So it looks so far like the 1-4 exhaust cam is out 17*. I hope that I didn't botch the belt replacement, not because I don't like to screw up (well, I don't, but I'm used to it), but perhaps it was like this before and I'll get a few more HP with a well timed cam. That is why I'm going to the trouble, after all!

 

OK, I got the specs for the intake cam. Goood news is that the intake cam is very close to spec. Should be 16 and 48, and I have 14 and 40. So the duration is right, and the cam is timed in the right neighborhood, which is comforting.

I just need to measure the 5-8 exhaust cam now without cutting a hole in the firewall. Then the fun begins of putting this all right!

 

It doesn't have to be .020" or .5mm or any specific number, but it needs to be up the ramp a way to make sure you are past the very beginning of the ramp. It doesn't matter what the number really is, but you don't get to pick the number if you are using the factory specs! Whoever made the cam gets to pick the number and then you have to use it for timing the beginning or end events. If you time by center of the lobe you will probably be close enough, but to make it factory perfect the exhaust opening and intake closing times are very important for getting the most from scavenging effects. I've been looking at cam theory stuff for the past few days and these two events are paramount. Moving these events around changes not only where the power is delivered in the RPM band, but also the efficiency of the engine overall.

I'm not planning on playing with these from factory - yet.

 

Re-read what you quoted from me. You don't get to pick the number if you are using factory specs. I have not seen any mention in any factory manuals for where the center of the duration is supposed to be. They give open and close. Those are the factory specs. If you want to use the factory timing specs you have to use their lift spec. If you calculate your own specs, then you can use your own measurements.

I think that if everything is as it is supposed to be that using the center of duration will work. If the cam is worn or something is not as it should be this could be disasterous for performance. I know my car is the exception with mis-matched cams, but if I had just gone with center of duration and my workshop manual I'd be in big trouble. That said, I think that center of duration would be fine for most cars. But since you have to put an indicator on the valve anyway, why not just do it Ferrari's way?

 

Craftsman feeler guages in .001" increments with a metric equivalent marked on them. They really offer the ultimate experience when it comes to illusion of accuracy, so I use them. It helps to continue using the thousandths of a mm decimal place even though the feelers make jumps by a few tenths of a mm at a time.

You're just checking to see how much of this I actually believe, right? I don't think I'm under any illusions of how important it is to keep everything accurate to .000001mm. But if it is worth doing, it is worth doing right.

Or at least .0001mm close to right.

 

Progress has been slow here with rebuilding the water pump and getting a dial indicator that will fit into the confined space of the 5-8 exhaust cam, but I finally got everything set up and Perfusion came over and turned the engine over while I perched on the intake again. It took close to three hours to get the cam timing where it will be. Initially the cam was more than 15* off. Perfusion put the engine at the correct place and I moved the cam. That's not easy as my cams have no flats and I'm working against a lobe trying to open a valve. Next time I have the cams out I'm going to grind at least a small flat to get some traction. Of course the holes didn't line up anywhere close, so I had loosen the belt, pull the cog, advance a tooth, put it all back together and try again. Are holes so expensive that we couldn't have a few more to choose from? I believe it was my Alfa that had a continuous ring of holes to choose from.

We also spent probably 20 minutes trying to find the pin once when it popped out, bounced off of something in the engine compartment and vanished. Aaron finally found it hiding on a frame gusset by digging around with a magnet.

So after about 2.5 hours the front exhaust bank opens at 35* BBDC, one degree off of factory specs. We didn't measure the closing of the valve, and we should have, but I did previously measure duration and it was correct, so the other side should be correct. In hindsight we should have done everything with the exhaust closing, not opening, but as I said duration was correct so it will also be 1* off. And I'm going to call 1* close enough. It is about a 15* change, so I'm hoping for a dramatic performance improvement.

So that should have been the hardest cam to do, and it is done. I hope the remaining three go more easily and quicker! So has anyone else done this on a GT4 with the engine in? What a job! It might actually be easier to pull the engine.