Low compression in #4 after rebuild

[V12StealthHunter]

[djape1977]

lobes on cams on n1 cyl should be facing eachother when timing is correct, or on n4, i don't remember. i'll see if i can find an angine at my workshop to take pics

[V12StealthHunter]

I checked all my valve clearances and they were all completely out of spec. I think I understand how this has happened now. When the valve seats were ground its changed the geometry of the valves in the head. Effectively pushing all the valves slightly higher into the head. Which in turn has affected valve clearances.

You live and you learn!

[V12StealthHunter]

Did the valve adjustment and now I have compression! Didn't start with the previous timing so I timed it back to 5deg BTDC and it started! Running smooth now. So my cam timing was fine to begin with it. I had (negative) 0.007" clearance on #4 that was causing all the issues.

[laverdaas1]

regarding the discussion about cyl #4 to be at TDC compression for setting timing marks on pulleys. From FIAT user manual (can be retrieved in italian here http://www.fiat124spider.it/file/Libret ... _serie.zip)

for 124AS 1438cc engine, it clearly states that all timing marks should be set with cyl #1 at TDC compression. Also it says that ignition advance is 10Deg. I'm puzzled can anyone could shed a light here?

[131]

regarding the discussion about cyl #4 to be at TDC compression for setting timing marks on pulleys. From FIAT user manual (can be retrieved in italian here http://www.fiat124spider.it/file/Libret ... _serie.zip)

for 124AS 1438cc engine, it clearly states that all timing marks should be set with cyl #1 at TDC compression. Also it says that ignition advance is 10Deg. I'm puzzled can anyone could shed a light here?

1 & 4 are at TDC at the same time, when you line up the cam pulleys, number 4 is at the top of the compression stroke. I've always set ignition at 10 degrees, the yanks do it differently, their weazy low compression smogged lumps are different to what the rest of the world got.

[bobplyler]

it clearly states that all timing marks should be set with cyl #1 at TDC compression. Also it says that ignition advance is 10Deg. I'm puzzled can anyone could shed a light here?

Don't mix up cam timing with ignition timing. The cam timing needs to be done with 1st cylinder at TDC. The ignition timing can be done on either cyl 1 or cyl 4.

[131]

The cam timing needs to be done with 1st cylinder at TDC.

Or 4th cylinder at TDC, considering they're both there at the same time.