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I recently purchased a 72 Pantera that came with an all aluminum block and heads. Said to be 373 cubic inches (SVO). I am curious if this engine could be rebuild to the larger displacment of the 427 or "Hammer" engine. I would like to try to reach the 550 HP+ level and possibly set it up to run a 175 to 250 Nitrous shot.

Also, what are the limits of the compression ratio that I could still run pump gas (93 octane)?

Are these reallistic goals for the aluminum block?

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You mentioned you have an aluminum block, your block is most likely a Fontana block or possibly a Ford SVO block. The blocks can vary in deck heights (9.2" or 9.5") and the cylinder liners will allow a certain amount of over-boring, which I don't have the particulars for. Without knowing the particulars for your block, we can't determine the maximum displacement you can achieve.

Over simplifying the subject, the deck height will limit the maximum allowable stroke & the cylinder wall (liner) thickness will limit the maximum allowable bore.

The standard 351C has a 9.2" deck height and thin cast cylinder walls, prudent overbores on the 351C are usualy limited to 0.030". With the cylinders at 0.030" over bore, the displacement for a 351C will be as follows for commonly available stoker cranks:

3.5" (stock) = 357 cubic inches
3.7" (off set ground stock crank) = 377 cubic inches
3.75" = 382 cubic inches
3.85" = 392 cubic inches
4.00" = 408 cubic inches

With a 4.00" stroke & a 6.00" center to center connecting rod, the piston in the 351C is pulled quite a distance out of the bore, and the wrist pin intersects the oil ring groove, which will cause the engine to burn oil.

The 351W has a 9.5" deck height, which allows a bit more stroke, which in turn is how a 427 cubic inch motor is achievable with that block. A 9.5" deck Fontana block can definitly be bored & stroked to 427 cubic inches.

The maximum allowable compression will be determined by the camshaft you are running. Your cam grinder will determine what compression ratio your motor should be set at.

Last edited by George P

Which is the better block, SVO or Fontanna?

Also, I had been told that the aluminum engine is not very deirable as they tend to blow head gaskets easily do to the engine expanding and contracting often.

Any thoughts on this?

Would I be better off to start with any entirely different engin/heads?

I was thinking the aluminum was the better deal when I bought the car as it was lighter. It doesn't sound like there is any configuration that adds up to 373 cubic inches. It is possible the previous owner was not accurate.

I have never owned any Ford products before this, and have very little experience.

Thanks for the info. Hoping to do this engine thing right the first time!


373 cubic inches is a 3.7" stroke crankshaft with a 0.010" overbore. This odd combination makes me wonder if the aluminum block you're running isn't perhaps an old Ford experimental block from the '70s (an XE block). If so, its still a great block, a cut above an everyday cast iron production block. Desireable because it is rare and made of aluminum, but not as desireable as a Ford Racing parts, Dart or Fontana block.

If it is not an XE block, then most likely this engine was built by a professional engine builder, you should contact the previous owner & get the name of the builder, he will be able to tell you exactly what you have.

Your non-XE aluminum block, whether its a Ford Racing Parts, Dart or Fontana block, is a GREAT engine block, the Ford & Dart blocks are in the $4K price range, and the Fontana block is even more (the Ford block is a dry sump only block, you most likely have either a Fontana or Dart block). Same with your aluminum cylinder heads, they are either Ford Motorsport A3, B351, C302, Yates, Brodix, Blue Thunder, CHI or AFD. They are all racing parts capable of supporting huge amounts of horsepower. If you need more, you should only have to bore, stroke & re-cam the engine.

You have no need to fear aluminum parts being prone to blowing head gaskets. Properly assembled, they are reliable.

My suggestion is 2 fold, contact the engine builder if possible; then take your car to a chassis dyno and see "what she can do". 400 bhp on a chassis dyno equates to 500 bhp at the crank.

Hey George & Steve.
Forgive me for jumping in here guys, but ur coment re. the 351C not being too comfortable with the 4.00" stroker crank with a .30 bore caught my attention. Can I then asume a 3.85" (393cu in.) crank would work fine?
My mix is 62.4 cc, close-chambered 4V 'squench' hds. Flat tops, Hyd.roller-rockers, SIG ERSON, ( short duration / hi- lift ) 228 @ .50 / 5.45" lift cam, fed by 4x 48 IDA's on a Hall IR - inlet, & Hall's 180 degree exh.system with very low restriction end-cans / mufflers.
To achieve 'good' cooling across the chamber, of the advancing flame-front,- for good burning & toleration of more compresion, - ( BTW, much more efficent than the 'Other' cyl. hyds. IMHO.)what should be milled of the blk? George, would u say,-how much should we take off the block ? More than a chip?.......
What do u estimate the comp-ratio would be then ?: + - 11.00 ? with this set up.

Yes indeed Steve, whatever ur blk. is, its sounds like a gem. Nurture it. Let us no what it all weights, when u get around to it. Thats one spl. motor.
Good luck. Cheers.

In order to reap benefits from your closed chamber cylinder heads, the clearance between your piston domes & the flat surface of the cylinder head, at top dead center, MUST be no greater than 0.040". The head gasket is about that thick (0.038"). Therefore the piston dome, at top dead center, should be level with the block, or perhaps even protude a very small amount. It requires machining about 0.025" - 0.030" off the block. This process is referred to as "zero decking" the block. Not only does this process bring the pistons even with the block at TDC, it also "levels" the cylinder head mating surface (AKA the deck), because most often, from the factory, the deck is not parallel to the cranshaft, resulting in variations in compression between the cylinders front to back.

Now here's the big news. A zero decked Cleveland, with a 0.038" head gasket, flat top pistons, 4V closed chamber heads, standard stroke crankshaft, has a compression ratio of about 10.0 to 1. Although advertised as 10.7 to 1, as it came from the factory the Cleveland was actually about 9.5 to 1.

As far as the compression ratio of your motor, you didn't mention if you have a standard stroke crank, or if your block has been zero decked. If so, then you are in the ball park of 10.0 to 1.

When computing compression ratio, all the small volumes in the combustion area must be added into the calculation, not only the volume of the combustion chamber in the head, but also the volume of the hole in the head gasket, the volume of the valve reliefs notched into the pistons, the volume of the area between the cylinder wall & piston above the top ring, plus the volume above the piston at top dead center if the block has not been zero decked.

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