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.
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 – 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.
Tim
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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[–]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″.
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.