Rebuilt head but now the cam timing is advanced

[HizAndHerz]

I recently had a machine shop check an N42 head that came off a a rebuilt engine I recently acquired. They ended up milling the head "slightly" to remove surface imperfections. The head was installed with a new timing set on a low milage F54 block. After I got the front cover and damper on, I noticed that the damper mark was 1/2" to the right of 0-degrees with the cam marks lined up. I figured I jumped the chain one notch so I moved the chain.

 

Now, with the crank at TDC, the sprocket notch is not directly under the center of the groove on the thrust plate, but the notch is to the right (cam timing is advanced). The notch is still under the groove, but it looks like this:

 

___

--V

 

instead of this:

 

___

-V-

 

I am assuming all of these issues are from the head being milled too much. I asked the shop what the minimum head height should be, and they just said "it'll be fine", they didn't have any Z-engine specs.

 

This engine is for a daily driver and has flat-top pistons (0.20 over) and a Felpro head gasket. With the cam timing advanced this much, what performance ramifications are there? Should I pull the head and check the valve to piston clearance?

 

TIA!

[Mr.INSANE]

Call me crazy but those marks look the same

[Flexicoker]

If I remember correctly (it was only 3 days ago) the little line is supposed to be to the right side of the V, ie. the leftmost end of the line lines up with the right most side of the V.

[HizAndHerz]

Yeah, the leading spaces got removed from the post so I just changed the spaces to dashes.

[HizAndHerz]

If I remember correctly (it was only 3 days ago) the little line is supposed to be to the right side of the V, ie. the leftmost end of the line lines up with the right most side of the V.

Hmm. In Tom Monroe's "How To Rebuild..." book, he says the marks should line up:

Check the cam sprocket-to-thrust-plate timing marks. If they align, cam timing is OK. However, if the sprocket mark trails - is to the left of the thust-plate mark, the cam must be advanced to the next dowel hole... you must retard the cam if [the sprocket mark] is to the right of the thrust-plate mark.

There's also a picture on page 131 that shows the V being slightly to the left of the groove before adjusting the sprocket (cam is retarded), and a picture that shows the V directly under the groove after adjusting the timing by moving to the next dowel hole.

 

The 1978 FSM says the marks should line up as well.

 

Hmmm.

[Flexicoker]

It makes perfect sense that they should line right up, thats what I did when I put mine togethor the first time, but the second time I consulted my '73 FSM and it said the slot should be to the right of the V.

 

...weird

[HizAndHerz]

It makes perfect sense that they should line right up, thats what I did when I put mine togethor the first time, but the second time I consulted my '73 FSM and it said the slot should be to the right of the V. ...weird

My 1978 FSM states:

Set timing chain by aligning its mating marks with those of the crank shaft sprocket and camshaft sprocket at the right hand side.

Confusing statement, but I'm pretty sure that they're only talking about matching up the timing chain marks, not the sprocket marks.

[Flexicoker]

I can get you a picture from my book on Friday if you'd like... it has a diagram of the V and the _

[HizAndHerz]

To follow up, I checked 3 factory manuals from different years and 5 aftermarket manuals. 6 of the 8 manuals show that when properly adjusted, the mark of the sprocket should be to the right of the oblong groove on the thrust plate. Just like everyone on the forums says it should be. Like this:

 

___

---V

 

With the milled head and new chain, I ended putting the sprocket on position #2. The only thing to worry about is valve to piston clearance.

 

I've been messing with these engines for some time and thought I knew what I was doing, but that "How to Rebuild..." book by Monroe really confused me with its incorrect picture. Especially when the caption says "Courtesy of Nissan Motor Co".