73 Mustang 351C Rebuild – Tear Down’s Final Conclusion

Thanks for continuing to follow #ProjectSportsRoof.   The 351 Cleveland has been torn down and you’ve seen the major components and their deplorable condition and it is time now to get it to the machine shop.

It’s not easy finding a good shop.  While I was hunting around for a machinist I asked a few car guys I know for suggestions and found the two that were recommended were out of business.  That is not uncommon.  It is often times more expedient to just drop in a crate  or re-manufactured engine (long or short block) and that’s tough to compete against.  I was concerned that I’d have to transport the 351C block 100 miles away to check get the work done.

While I was searching for a shop, I was simultaneously search for a re-man’ed long or short block.  Of course I was specifically looking for a closely date code 351C and I was told that those blocks are not plentiful.   I took my local search to the hot rod shops (by hot rod shops I mean, shops that sell hot rod parts) in town and the shop I chose was recommended by several.  I double checked the review that were available and these guys have a very good rep.  I’m going to withhold the name until I get the block back.



 Luckily I had the block still bolted to the engine stand.  That and my cat-like reflexes (HA) kept a disaster from occurring.


Hoisted!!!                                                                                                                                                                    ^^^ lots of Mustang parts

Not withstanding my attempts to bounce the block off the garage floor it is finally suspended and ready to get loaded.

Tied Down

Tied Down – This is the fastest this engine has done in months!!!


Upon arrival at the machine shop two guys unloaded the block and I asked them to measure the current bore and the size of the crank.

The results were as follows:

The stock bore is 4″ and the measurements of the current bore is .030  under making the bore 4.030.   You’ve seen the condition of the cylinders and the shop recommended to take another .010 off making the proposed bore 4.040″.

Now the crank was measured as well and it was .010 machined from stock thickness.  Purposed is to take it down another .010 to .020 under.

The shop recommended to replace the cam, so that will happen.

This ended the speculation about the originality of the engine.  Clearly this was rebuilt at least once.

Now decisions need to be made.  But first let’s take stock of where we are and then play a little “What If”, shall we?

Using this standard formula for determining displacement:  Bore2 X Stroke X 0.7854 X Cylinders  (laid out below from a spreadsheet)

Bore X Bore  X Stroke X 0.7854 X Cylinders = Displacement
Stock 4 4 3.5 0.7854 8 351.8592
Current 4.03 4.03 3.5 0.7854 8 357.1568801
Proposed 4.04 4.04 3.5 0.7854 8 358.9315699

Just cleaning up the cylinders will move  the displacement  from 351 (stock) to 358 as proposed.  That is currently where we are.

Now let’s play What If!!!  What if I increased the bore a bit more?  Here is what that look like in displacement terms.

Taking up the bore one more .010 to 4.05″  looks like this.

Bore X Bore  X Stroke X 0.7854 X Cylinders = Displacement
Option 4.05 4.05 3.5 0.7854 8 360.710658

4.05 is the furthest  I want to do with the bore – if it’s possible.  I know one Mustang owner that has his bore 4.06″, however, I’m not comfortable with that. So we’ve increased the displacement 360.

Now let’s work on the stroke.  The machining of the crank will net little to no change in the displacement. To increase that I’d have to go with a different crank.  So what do those number look like?  Leaving the bore at 4.04 and increase the stroke yields the following increases:

Bore             x                  Bore                      x             Stroke                    x                   0.7854                    x        #Cylinders                                            Displacement

Option 4.04 4.04 3.75 0.7854 8 384.5695392
Option 4.04 4.04 4 0.7854 8 410.2075085 Basically the 400

Let’s go a bit further with the increase in bore:

Bore             x                  Bore                      x             Stroke                    x                   0.7854                    x        #Cylinders                                            Displacement

Option 4.05 4.05 3.75 0.7854 8 386.475705
Option 4.05 4.05 4 0.7854 8 412.240752
Option 4.05 4.05 3.85 0.7854 8 396.7817238 Off the shelf long stroke cranks
Option 4.04 4.04 3.85 0.7854 8 394.8247269 Off the shelf long stroke cranks

Care to share your thoughts on the build?   Drop me a note!!!

Thanks for reading.





73 Mustang 351 Cleveland Tear Down Video 7 – Mains and Pistons …

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Thanks checking back in with the 1973 Mustang (#ProjectSportsRoof). I’m moving right along with getting the progress on the 351C tear down posted up.
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3 Responses to 73 Mustang 351C Rebuild – Tear Down’s Final Conclusion

  1. Tim Sweet says:

    Pistons are available for 4.050. https://www.summitracing.com/search/part-type/pistons/make/ford/engine-size/6-4l-390/bore-in/4-050-in

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    • Tim Sweet says:

      [–]thatguywillt88GT 1 point 3 hours ago

      That’s surprising as hell. But that’s also good news. That means theoretically, you’ve got 2 more motor builds after .040″.

  2. Tim Sweet says:

    From Reddit 73 Mustang 351C Rebuild – Tear Down’s Final Conclusion

    from thatguywillt via /r/Mustang sent 22 minutes ago

    I wouldn’t hone the block any further than it needs to go. If it’ll clean at 4.040″, then leave it there and play with the stroke. You want to have some rebuildability left after this is done. I’d be shocked if 4.050″ was an available size, but I’m sure 4.060″ is pretty common, presuming the the cylinder walls are thick enough to support it.

Let me hear from you!!! Drop a note!!