History
The following history was
found online, but unfortunately I have lost the source reference. If anyone
knows the original source, please let me know so I can link to it and give
proper credit.
For use at Indy in 1963, Ford prepared a
special version of the recently introduced 260 CID engine (small block
Windsor V8). In stock form this engine produced 157 BHP. After an extensive
series of modifications, the final engine displaced 255 CI and produced 376
BHP with good durability. Many parts were replaced with aluminum or
magnesium to trim the weight down to 350 lbs. While impressive for a
hotrodded 260, successful competition at Indy in 1964 was simply going to
require more horsepower. And to do this, the breathing of the engine had to
be improved.
For 1964 a dual overhead cam version of the engine was produced. The block
was cast of aluminum alloy, using patterns modified from the production 289.
Cast iron cylinder sleeves were a shrink fit in the block, and were sealed
at the heads with copper laminated steel O-rings. In order to clear the two
banks of camshafts in the heads, the 10 attaching studs were moved in closer
to the cylinder centerline. An additional 8 studs protuding from the heads
maintained the clamping force needed to seal the combustion chambers. The
space occupied by the camshaft in the normal production engine was replaced
with an oil tube. This acted as a gutter and collected oil as it drained
from above to keep it off the reciprocating assembly.
The bottom end was beefed up considerably. The special forged steel
crankshaft was held by 4-bolt bearing caps on numbers 1 through 4. Main and
rod bearing journals are the same size as the 289, as is the engine's stroke
- 2.87". The rod journals are crossdrilled for better oiling at high engine
speeds. The rods are from the 289 HiPo, having been modified for floating
pistons pins. The pins are 289 HiPo pieces. The oil pan is cast magnesium
and is a structural part of the engine as is common in Indy and Formula car
design. Ears cast integrally with the pan provide the engine mounting points
in the chassis.
The cam-ground forged aluminum pistons have a pent-roof dome to closely fit
the combustion chambers. Compression is 12.5:1. The cylinder heads used 4
valves per cylinder with a central spark plug location. The plugs are canted
toward the 1.64" diameter intake valves. Exhaust valves are 1.36" diameter.
The camshafts run in bearing bores in the cylinder heads, directly over
their valve banks. Valve clearance is adjusted by the selective fitting of
the followers. Intake ports are between the cams, with exhaust out the top
of the heads between the vee. This was done to do away with the nightmare of
exhaust tubing normally required. Hilborn injection is used having been
selected for its light weight and simple low-pressure design.
The complete 255 CID engine weighed 406 lbs. and produced in excess of 425
BHP at 8000 RPM while giving a fuel economy of 7 to 8 MPG. Maximum speed is
9000 RPM while the minimum useful speed on the racetrack is around 6000 RPM.
1964 Ford twin-cam 255 Indy engine. Note that
exhaust exits at the top where the intake normally resides.
Image source
unknown.
This was taken at a Carlisle Ford meet in
Spring of 2007. A fellow had this "NOS" DOHC Indy motor for sale along with
a bunch Gurney Eagle stuff. He said he had 9 more of them too. Image
credit:
Virgil Hilts
Twin-cam 255 Indy engine installed in a GT-40
(Image source unknown). This is a Ford GT40 MK I P103 owned by Larry
Miller.
More pictures of this car can be found here.
Image source unknown.
Image source unknown.
Not necessarily a quad-cam like above, but
appears to be a Gurney Eagle reconfiguration of a production block for
racing with carbs mounted where the exhaust ports typically would be and
exhaust exiting where the intake usually resides.
Image source unknown.
1966
Gurney Eagle Indy Car for sale with Ford twin-cam 255 engine
Images below courtesy of Live
Auction.
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