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Installing head - Need some help with timing!


turbogrill
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Hi,

 

This should be basic stuff but I want to make sure I get it correct and don't messup my new rebuild. First time I am assembling an engine.

 

According to the manual two things need to be done bore installing the head:

 

- Camshaft on the head should be aligned to a mark, this is easy. (I guess the mark is 0 degress TDC)

- #1 cylinder needs to be TDC, this is where I am a bit confused.

 

When finding TDC without the head there is no concept of compression stroke vs exhaust? I just need to make sure the #1 piston is at it's topmost position? I don't have to worry about if it's 0 or 360 degrees in the 720 4 stroke cycle. This only matters once the camshaft is installed, correct?

 

Is finding TDC visually good enough or do I need a dial indicator? (maybe this depends on the engine..)

 

Thanks

 

 

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 You can verify your timing marks by setting a nickle on top of the #1 or (or 6)  pistons.  Place a straight edge over said 5 and roll the crank back and forth . Now mark the crank pulley at the point where the straight edge lifts clear at both ends of the crank  pulley travel.  Bisect the marks and you should be looking at your TDC mark. The longer the distance between  rotation marks, the higher degree of the accuracy of the TDC mark.  If the 5 cent is not over 4-5 in of travel use a thicker item ,like a nut etc.

For really high tech , check # 6 after you get done with #1. Old forged cranks often get a twist over time.

 

 For setting the head, TDC the crank and then roll it back about 1 in downthe hole. Set the head on, zero the cam , roll the crank up to TDC. Set the chain. 

 

 Roll the engine around a few times, check the crank marks  to cam marks. . If you cut the head or block, the cam will be llate a few.   010 is usually about 3degrees.   Over 3 degrees you may find a loss of power or the toque band moved up a few hundred RPM. 

 

 Edit. For all of my race engines that require a stock throttle body the best dyno results have been with the cam at zero or ahead 3.

 

   

Edited by flyinglizard
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1 hour ago, zack_280 said:

The #1 cylinder should be at the top of it's stroke (obviously and as you already mentioned).  Top is top.  The cam:crank revolution ratio doesn't change the bottom end TDC.  

 

^^ This. And I expect that any OE crank pulley will have a notch and a corresponding mark on the block to indicate TDC of #1. Even without the pulley on my old I-6 Toyota engine the pulley keyway in the crank lines up with the mark on the block. 

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