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Discussion Starter #1
ive been goin threw some of the old tech and i dont get why you would have to retard your timing back by 1 degree if your mill off .020 off of the head. if you mill its not changing anything with the timing. the timing marks are still lining up. everything about performace motors ive learned from my dad, he was another smokey yunick around here with small block chervrolets.
 

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you are reducing the amount of distance between the 2 pullies, effectively turning the cam gear when the timing teeth grab it. i know there is a diagram in the archive with a more in depth description
 

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you bring them clother but the timingbelt still has the same length, so you must correct timing
 

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your bringing them closer but it still isnt changing the time, tune wise why would you retard the cam?
yes you are. the teeth on the timing belt are spaced a specific destance apart. when the distance between pullies is changed, the cam gear has to turn one way or another to acommodate for that change
 

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The tensioner takes up the new slack, and it's only on one side... If the slack was taken up equally on both sides then it wouldn't matter, but that's not possible.
 

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Discussion Starter #7
im hearin that you want to retard it is for safe tuning. making the combustion chambers smaller will cause more heat towards the valves guides and melt them down. that what i was figuren it was but why not run a smaller belt, retarding cam timing would be losing power wouldnt it
 

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Brokedick Millionaire
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distance between crank centerline and cam centerline is lessen, therefore making the cam "late" as it is drawn counterclockwise by the timing belt.

1mm = .039" = 1 degree cam timing change

After being corrected about misinfo I was given from Larry @ ENDYN, don't worry about cam timing after milling a SOHC.

Mill .078" (2mm) which would be a HUGE jump in compression, 2 degrees cam retard would be a plus when trying to crank the motor over.

Static compression vs. Dynamic compression
 

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I understand your misunderstanding this

I also have come from a strong V8 background and have had several 11 second big block FE fords. The difference here is that on a V8 head milling doesn't matter in cam timing because the cam is not in the head, but push rod length does. It would be like modifying a small block chevy so the that the camshaft is located .040" lower in the block (which isn't really possible). The timing chain would be too long then, thats why you have to modify cam timing. Its not losing power, but by ritarding it 1 degree you bring the cam and crankshaft timing back to normal. Now if you left it alone and did not ritard the cam timing then you would probably be losing power. Hope that helps to clear it up for you.
 

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Is it the same for an dohc zc? 1mm mill = 1 degree cam timimg?
 

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same size as b16 cam gears, I found 1 degree for every 0,012" mill.


SO we must retard 6 degrees, the head is 2mm milled
 

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Brokedick Millionaire
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very likely, WRONG.

How many teeth on your cam gear.

Pics of the register on the head to show you milled it .075-.080" please.
 

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the head is milled 1,3mm and the cometic gasket is 0,7mm thinner than stock

 

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I dont...



measured both gaskets, the cometic is 0,7mm thinner
 

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I hate to break it here, but the real answer is to degree in your cam.

Only way to be sure the valve events are happening at the right time.
 

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Kinda interesting. After reading this thread I understand why we had issues with my friend's Lotus 7 replica. We put an 01 Focus ZX3 engine in it. Shaved .060 off the head and were 3 degrees off on the cam timing. This gives a nice explanation as to why were off if it is the same for Ford engines.

--Doug
 
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