390, what do I have exactly?
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Cross-Country
Joined: Apr 2011
Posts: 93
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From: Chandler, AZ
390, what do I have exactly?
Don't have details from previous owner other than the following:
It is a 1973 F100....came from the factory with a 2 barrel carburetor.
It currently has a Holley/Motorcraft 4160 4 barrel which I think is 600 cfm and headers into big single exhaust.
The engine was rebuilt at .20 over, and the head's aren't stock. They are 1960 era C4AE-9060G's.
The heads were re-done with Manley oversized valves, bronze guides and Stellite hard seats.
Has a Cloyes double roller chain
Since the truck engines of the early 70's were lower on compression, etc, what 'ballpark' compression ration and HP do you think this thing has instead since it has the above changes?
It is a 1973 F100....came from the factory with a 2 barrel carburetor.
It currently has a Holley/Motorcraft 4160 4 barrel which I think is 600 cfm and headers into big single exhaust.
The engine was rebuilt at .20 over, and the head's aren't stock. They are 1960 era C4AE-9060G's.
The heads were re-done with Manley oversized valves, bronze guides and Stellite hard seats.
Has a Cloyes double roller chain
Since the truck engines of the early 70's were lower on compression, etc, what 'ballpark' compression ration and HP do you think this thing has instead since it has the above changes?
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Joined: Apr 2004
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x2. They are or can be identical on the outside.
As for stock '70s PU truck compression, figure about 8.2 for the 390 or 360.
Those heads, if they have the smaller combustion chambers, might have been an effort to raise compression on the stock short block.
Or not.
Check the stroke. Put a wire or thin dowel down a plug hole at BDC and TDC. 3.5" = 360 or 352. 3.78" = 390.
As for stock '70s PU truck compression, figure about 8.2 for the 390 or 360.
Those heads, if they have the smaller combustion chambers, might have been an effort to raise compression on the stock short block.
Or not.
Check the stroke. Put a wire or thin dowel down a plug hole at BDC and TDC. 3.5" = 360 or 352. 3.78" = 390.
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Joined: Jul 2002
Posts: 42,561
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From: Long Island USA
There's no way of telling. If the bores were punched out, who knows what replacement pistons were put in.
Without taking it apart, or knowing exactly what pistons were used, it's a crap-shoot.
If it was a STOCK type piston that was put back in, same as original, it's probably low-to-mid 8's.
Without taking it apart, or knowing exactly what pistons were used, it's a crap-shoot.
If it was a STOCK type piston that was put back in, same as original, it's probably low-to-mid 8's.
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Cross-Country
Joined: Apr 2011
Posts: 93
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From: Chandler, AZ
Maybe I should have specified. I created the subject line with 390 in it. What I'm saying is that I know it is a 390. What I'm asking is what horsepower/torque and compression ratio ballparks would those heads with oversized valves, headers, and a 600 cfm 4 barrel be compared to factory/stock ones?
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IF those heads are 64cc combustion chambers, and
IF they were put on an 8.2 CR sunken piston 390 with a stock bore,
THEN the change in CR from a 72cc head to a 64cc head changes from
8.21 to 8.77 with the numbers I used for the motor.
(.040 gasket, 6cc piston head volume, both of which are probably not the case with your motor)
IF they were put on an 8.2 CR sunken piston 390 with a stock bore,
THEN the change in CR from a 72cc head to a 64cc head changes from
8.21 to 8.77 with the numbers I used for the motor.
(.040 gasket, 6cc piston head volume, both of which are probably not the case with your motor)
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