Whoa, Pard ...Put the wrenches down for a moment...


We're not ripping the victim open just yet.  If you've ever watched a procedural cop show on TV, you know that a critical 1st step is identifying the victim.  So let's make sure the victim in front of us is what we think it is.


The next of kin (previous owner) ID'd the vic, right?  We all know of previous owners who swore the engine was one thing when it turned out it was something different all along and that they were mistaken.

Step 1

Let's start at the top.  And lookie here, a nice little plaque on the valve cover confirms it as a 261 -- Case closed, right?


Wrong.  Although a pretty good clue, it only confirms the valve cover itself came from a 261.  There is no way to confirm it is original to the engine.  And even if it is a 261, is it an early 261 or a late 261?

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No problem.  We just check the serial number stamped in the boss behind the distributor ...  Oops ... There isn't one.  It's blank.  That means we have a replacement engine (crate motor) and we still don't know what it is for sure.


Oh wait, 261's all have those "captain's bars" cast into the block behind the starter ...  Those aren't there, either.  Hmmm, But not all 261's have Captain's bars -- the 1st year castings (1954) did not have them.   AND ... this block has the high-mounted water pump (a feature shared by the early 261's and all previous sixes.  So, it's either a 1954 261 or it's a 235...


Let's move on to ...  The casting numbers!

Like finger prints and dental records, the casting numbers will reveal the victim's identity.


The first one, in front of the distributor boss, reads "3733950."


Checking our casting number guide, we discover that this block is, indeed, out of the 1954 mold.  But ...


Cross checking with the casting date code (behind the distributor boss), though, tells us this block was cast in February of 1959.


Why is this important?


Knowing that this is a replacement engine for a '54-'55 1st Series application, they used the older mold to cast it (to get the proper water pump placement, among other things).  This is important to us because it will help us understand some things we will discover as we get into this particular engine.


It will also ensure we get the right part$ ... ;)

Step 2
rocker arm assembly

With the engine on a stand and all the ancillary systems removed (water pump, thermostat housing, generator, starter, intake/exhaust manifold, valve cover, push rod cover), It's time to start disassembly!


  • Remove the rocker arm assembly (it separates in the middle) and carefully disassemble it, keeping all the parts in order.


  • Check the rockers and tubes for scoring or other damage and replace if necessary.  A little scoring is to be expected, but it will still contribute to oil pressure losses.


  • Clean everything and reassemble it.  Set it aside.
Head removal



  • With the rocker arm assembly out of the way, remove the push rods.  Keep them in order so they can go back in the same place if you end up keeping your lifters
  • Remove the head bolts in the reverse sequence of the head bolt tightening procedure.  The head may stick to the block so be gentle and try not to destroy the head gasget if you can --  you may need it for a template if you are planning to use an 848 head (see below).
  • Once the head is off and on the bench, check for obvious issues -- visible damage, etc
Step 3

Now would be a good time to send the head off to the machine shop for several procedures:


  • Magnaflux the head for cracks, other issues.  If good,  proceed
  • You may need to deck the head slightly to ensure it's flat on the mating surface -- the machinist will tell you
  • Get new valves, valve seats and valve guides installed.  Ensure the exhaust valves won't strike the piston (if the head was decked, this could be an issue.  If so, the exhaust valves will need to be recessed more into the head.  This will affect the rocker arm geometry, as well)
  • If using an 848 head, ask the machine shop to drill the 4 steam holes to mate to 261 block.  If intact, you can use your old head gasket as a template.  See the picture at right.
next steps
Head details
Step 4

Now that you've successfully decapitated your engine and gotten the head safely into the hands of the machinist (who will have it for awhile ...), let's flip the patient upside down and start on ... the block!

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