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Putting new valves against old seats is poor practice. When an engine is down this far for a rebuild the head should be also be rebuilt.
WHAT? You are proposing replacement of the valve seats? Do you know anyone who can that job? It is common practice to replace vales and just re-cut or grind the seats.
 

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I don't think so. But it is common too REGRIND the existing seats, as well as the new valves. New valves and old seats don't commonly fit well. Common valve machines can make them exactly the same angles, and adjust the seat width to the desired spec.

In fact, RJ has developed a grind-angle spec that improves air flow at the valves. See his thread for details. Its a common machining procedure, so most any good engine shop can do this, as long as they have the right angles available in their tools. They should also measure the guide bore diameters to verify the valve fit - too loose will cause untold problems, which is why the bronze guides are often replaced. Also not too expensive, and cheaper that the old-school approach of knurling the guide bores and then reaming them to perfection. [new guides still need to be reamed to correct diameter].

After the seats and valve are reground, THEN you can lap them to perfection.

This MUST be done accurately. Any misfit of the valves and seats will sap the engine's performance, and possibly damage the engine.

It's also common practice to replace the springs - they are not expensive. A really good engine shop will measure the spring heights and tensions, and add or remove spring spacers (they go into the steel spring seats) to match the spring tension across all the valves. Seats live forever, as do spacers (as needed), and the spring retainers and the little valve keepers.



Robert
 

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WHAT? You are proposing replacement of the valve seats? Do you know anyone who can that job? It is common practice to replace vales and just re-cut or grind the seats.
Sorry I wasn't more clear. I meant, of course, regrinding the seats. A well done regrind doesn't need lapping, which can fling grinding paste about. A good shop will check the fit of the valve to the seat with vacuum or compressed air.
 

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Discussion Starter #266
Ok, I guess I'll just stick with the old valves.
 

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Shakey, you can stick with the old valves as long as that's what you want to do! New valves, lapped into old seats, are fine. Old valves, lapped into old seats are fine too. If you want to R/R the seats that's a bigger job. Personally, I would never regrind and replace without lapping the valves. Its therapeutic to lap the valves in. Need to make sure you get everything clean afterwards, use soap and water to remove all traces of grinding compound then use brake cleaner, etc.

With respect to guides, a quick n dirty is to see how much vacuum the stem can draw when you retract it in the guide, and how long the vacuum holds.
 

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71 Berlina 74 GTV 17 Giulia Q4
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If you want to do it right lightly cut the seats for a new surface and put in new valves. That would be the minimum. You could resurface the valve faces if you are on a tight budget but then you run the possibility of needing really thin shims. Even if it hurts you will be glad you got new valves down the road. New seats are not necessary for a good rebuild. I've replaced the seats in a couple of heads but my seats had been ground down and the shims were getting pretty thin but the main reason was to have the seat just proud of the edge of the combustion chamber. That aids flow in that the air doesn't have to turn down or up depending on how you look at it to enter and exit the chamber. When you've spent hours porting the head and installing new guides every last little bit helps plus it's kinda fun. On a standard rebuild not necessary for a well performing motor. It's a good, better, best kinda thing. the head doesn't have to be resurfaced everytime it comes off but if it's never been done it's not a bad idea at least have a shop check it for flatness. No matter what you do you will have to adjust the valves! Something that is easy to do is to check the seal of the valves. you can do it with compressed air and mineral spirits but another easy way is to put a strip of the waxed paper that in in a Hersey's Kiss between the seat and valve and points around the valve. let the valve drop down and there should be some resistance when you pull out the strip of waxed paper. If there is no resistance it's not sealing. Again clean everything with scotch brite and brake cleaner.
 

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If the old valves and seats are in good condition, it really is no problem using the old valves in their same position with lapping to assure a good seal.


If you re-assembled in the same order, most of the shims will be in the right range. If you just need a couple of different shims, I'm sure some here would trade you for the right thickness ones!

As you can see, many here are racers and like to go to extremes in preparation and modification.......
 

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You measure the cam clearance with a feeler gauge. But you will find that there is a lot of "feel" to the task. To check that last 'thousandth, rather than slip in the thinnest blade of the feelers, switch to a pair of larger ones. E.G. if you have 0.014 thou gap , measure the next thicker with a .007 and a .008 blade (total 0.015) rather than using a 0.14 and an 0.001. I've bent and crumpled a lot of 0.001 blades.....

Robert

BTW - like many here, I've been doing this for several decades, and have collected a bunch of spacers. To keep them in order I made a holder as pictured below - two or three spacers in each slot. Since I am pretty much OC, I've sorted them in half-step sizes so I can adjust the gaps to 0.0005! Note the wooden plugs where the spacers currently in the engine are. There are another 70 spaces on the other side of this block, where all the exhaust spacers ended up. At current prices, there's over $1000 in spacers. Most cost me under $0.50 four decades ago.
 

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I am going to show my ignorance here, but I love to learn new things, about anything. The Alfa manual shows a meter being used, which reminds me of my old vacuum meter that I used to set the air flows on SU carbs. Is the AFI meter a more accurate vacuum meter? Second, 1 1/2 percent of what, idle compared to max air flow? What is the stock factory percent?

Factotum
What your looking at is how to set the throttle valve to its correct setting. This is set at the factory and should never be messed with.

Attached are the pages for the factory shop manual on adjust the CO. The AFI meter takes the place of the old CO emissions testing machines we used to use. You will need to print a conversion chart off the internet converting the AFI number to the CO number.

Once you set the CO. I recommend around 1.5 percent. When you plug theO2 sensor back up the percentage should drop. If it doesn't the O2 sensor is not working.
 

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71 Berlina 74 GTV 17 Giulia Q4
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Always put a towel under the chain when taking the master link out. I realize you probably already know that but just in case:)
I use a small stub flat head screwdriver to take the masterlink apart. From the intake side of the car put your left hand under the chain and with the right hand put the flat head on the open end of the master link and pull it towards you. The open end always goes towards the exhaust side. The bolt on the front of the head that locks the tensioner in doesn't have to be gorilla tight, just tight. There are a lot of these little things that will help you enjoy the process and have a motor you can be proud of. :thumbup:
 

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Always put a towel under the chain when taking the master link out. I realize you probably already know that but just in case:)
I use a small stub flat head screwdriver to take the masterlink apart. From the intake side of the car put your left hand under the chain and with the right hand put the flat head on the open end of the master link and pull it towards you. The open end always goes towards the exhaust side. The bolt on the front of the head that locks the tensioner in doesn't have to be gorilla tight, just tight. There are a lot of these little things that will help you enjoy the process and have a motor you can be proud of. :thumbup:
Uhhh. The chain accelerates toward the exhaust side when the throttle is pushed. Therefore the open end of the link should go to the INTAKE side.

One of us is wrong. If it's me, it won't be the first mistake today, but I think I'm right. IF not, why?

Robert

BTW - I always put a wire thru each side of the chain before removing the link - it only took dropping the chain into the engine once to understand why. Towel - yes, me too. And I stick a big magnet on the chain too, so no loose part goes anywhere. I learned this according to Rule One.

[Rule One - we never learn from success!]
 

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Uhhh. The chain accelerates toward the exhaust side when the throttle is pushed. Therefore the open end of the link should go to the INTAKE side.
Agree.
I have always tied the ends of the chain in order to retrieve them but I helped Rob Mocas replace a head gasket on his race car at Watkins glen in September and he just let the ends drop. He retrieved them with a magnet and that is how I plan to do it next time.
 

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Discussion Starter #276
I initially tied a strand of parachute cord to each end of the chain for easy retrieval. Obviously, once I completely disassembled the engine, it was a moot point.
 

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71 Berlina 74 GTV 17 Giulia Q4
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:) yeah, I put safety wire on the ends but the magnet works ok too. Only thing about the chains being down is if for some reason the motor needs to be rotated which I will some times do to have all four pistons half way up, or down. The reason being is I can turn the cams to adjust the valves although I have to remember which way I turned it so I can come back to where I left. My thinking on the split link is that the motor rotates clockwise looking at the front so the open end is leading and the closed end will keep it on when I hit the gas. The first law. Now if the motor seized it could fling itself off (the third law). I figure if that happens I have bigger problems than the split link staying in motion.:)
 

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Most of my chain experience is with motorcycles and everyone I know or have known has fitted the clip with the closed end pointing in the direction of motion.
 
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The fish always swims upstream !
 
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