Head and valve measurments 16v - Alfa Romeo Forum
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(Post Link) post #1 of 7 Old 03-11-09 Thread Starter
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Head and valve measurments 16v

Mitch the plan was to confirm the tolerance for timing belt mistiming i.e how many teath does it take to bend a valve and which ones strike first?

Its only theoretical becuase when the engine is hot the measurement will be different but as a rough idea, i think that one tooth is very very close to valve damage...

With the adjustment in the inlet pulley making it more likely that the inlet could be more or less than the exhaust...

Does this sound crap...

Oh and my plans for the head is routine maintenance nothing special, maybe smooth some of the roughness out of the ports...
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I can tell you on the ts its not as close as you'd think. The inlet yes as it has the variable valve timing. The exhaust I can tell you from experience will go quite far. I'll explain how I found this out. Take one head rebuild (again) take one injector light on (= cam timing) I know the sensor is fine as had the same problem when i put new cams in it last time. It was set up using the timing blocks. Mine seem to set it up out by a couple of teeth on the exhaust every time?? When I moved the exhaust cam two tooth the light went out. Car actually ran a couple of teeth either way on the exhaust cam. Very rough though. Again I stress please don't copy me as the engine I did it on wasn't that important and it was just to see if the sensor was the culprit. ALWAYS USE THE TIMING BLOCKS!

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(Post Link) post #3 of 7 Old 03-11-09 Thread Starter
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Quote:
Originally Posted by Joss View Post
ALWAYS USE THE TIMING BLOCKS!
Cheers joss, unlike yourself the engine i'm rebuilding is my everyday car and cant affor to naff it up but i do have cam blocks for all the later petol engines (1.6, 1.8, 2.0ts and 2.0jts) and it is important to use them i know the belt tension can upset things also... like i mentioned its a just theory i want to find out just so this wuestion might have a slightly more definate answer...
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The belt tension can make it slip or jump off but as with the way the engine turns the tensioner is on the back side of the rotation if you get my meaning so yes it upsets the motion but not the timing as such. A thicker head gasket, decking the block or skimming the head would change this slightly though
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My GTV was 2 teeth out and every valve was bent.

The red marks show position at TDC and then how far I had to move it to get the cam locks to fit.

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depends in which direction you are out.... you only have a couple of degrees in one direction but a LOT in the other. in theory the intake valves open around TDC, and close at BDC... if the valves open sooner, you get contact almost immediately, if they open later you have about 90 play
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(Post Link) post #7 of 7 Old 05-11-09 Thread Starter
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Thats a good point i'll kep that in mind when i to me measurements... next week i hope cams and valves are out of the head at the moment.
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