Welcome to
GT Ford Performance
595 Keilor Rd Niddrie 3042
Phone ( 03 ) 9351 0351
GTHO PHASE III
What's The Diff ?
This Page Will Explain The Difference Between a Standard XY GT Falcon and What You Got When
You Ordered It With The GTHO Option.
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EXTERIOR
There are only 2 external differences between the XYGT and
the XY GTHO.
1) Rear Spoiler and 2) Front Spoiler and that’s it. Front spoiler was made of
plastic and not aluminium and the rear spoiler was from the 1971 Mustang which
was a fibreglass composite type spoiler with die cast hollow aluminium legs
with the Ford logo and part numbers cast inside. The greatest falsehood of all
is that most people think that the rear spoiler was aluminium because they
bought one from Ford. Well there was a rear spoiler available from Ford but it
was an accessory Motorcraft type spoiler which was
probably a third of the price of the original Ford one at the time.
INTERIOR
There are only 2 interior differences between the XYGT and
the XY GTHO.
1) Choke in dashboard where V8 badge goes in the GT. opposite cigarette
lighter.
2) GT-HO. Decal on glove box lid instead of GT badges.
Apart from the fact that the GTHO was only available in 4 speed manual.
SUSPENSION
Rear
springs are the same as the 4 speed manual GT. Six leaf - 4 under main spring
and one upside down on top of main spring.
Front springs longer than the GT to suit the later model type XA stub axle and
upper control arm.
Upper control arm was XA type with 3 stud ball joint not 4 as in XR - XY and
shorter length for better handling.
Front sway bar that was 1 inch and a rear sway bar that was 3/4 inch thick.
Shock
Absorbers were the same as GT
BRAKES
Front
discs were the same as the GT but most were fitted with PBR type floating head callipers,
instead of the Kelsey Hayes type . Front splash plates were removed
Rear drums were finned and shoes were 2.5 inches wide . Rear wheel cylinders
were increased in size to .9375 inches to further assist brake balance and to
accommodate the larger lining area.
A proportioning valve was fitted to the drivers side shocker tower beneath the
master cylinder . This works only on the rear brakes. It reduces pressure to
the rear since the same amount of hydraulic pressure would cause more braking
by the self energising effect of the rear shoes compared to the non energising
front discs.
A vacuum reservoir was fitted opposite the battery on the inner skirt panel and
was a modified vacuum tank that was fitted to the later model LTD with the pop
up headlight covers. An extra one way valve outlet was fitted underneath the
standard one on the brake booster and a special ‘T’ outlet was on the rear of
the intake manifold to accommodate two hoses.
DIFFERENTIAL
The diff
housing was the same width as a normal XY type 9 inch housing but there was two
differences with it. There were no wedges welded to the bottom of the plates
that mount to the rear springs as in the XW - XY - ZC - ZD 9 inch and there
were two small mounting plates welded to the housing for the rear sway bar
rubbers to mount on.
Axles were 28 spline as well as 31 spline . Most 28
spline axle fitted cars had 3.25 : 1 ratio centres. All other ratios were
available but most cars were fitted with 3.25 :1 - 3.50
:1 and 3.91:1
There were no spacers on the axles behind the bearing or on the end of the axle
tube as in the other 9 inch applications. The diff centre was of a high nodular
iron content and there were more casting ribs . Also there was an ‘N’ cast in
the centre of the housing as well as the bearing caps to denote high nodular
iron content.
Diff centre was available in either Daytona type ( Normal LSD ) or Dapco No Spin - (
TAILSHAFT
Long and
thin gets right in but short and thick does the trick. Big 1330 uni’s front and rear with a 3.5 inch diameter shaft necked
down to take the yokes. Shorter in length to accommodate the extra length of
the gearbox. Pink and light green stripe code on shaft.
GEARBOX
Yes of course it’s a Toploader. Long extension housing 31
spline output shaft in a choice of two ratio’s.
Standard ratio = First gear and reverse - 2.78:1
Second - 1.93:1
Third - 1.36:1
Fourth - 1:1
Close ratio = First gear and reverse - 2.32:1
Second - 1.69:1
Third - 1.29:1
Fourth - 1:1
CLUTCH
A
modified version of the twin plate clutch was used on the Phase 3. Cylindrical
steel adaptor plate drive lugs were used in place of the cast iron lugs. The
adaptor plate has been reduced in thickness by 10 thou . The pressure plate is
now positively located in relation to the pressure plate cover and diaphragm
spring by 3 dowel pins which are riveted to the pressure plate cover.
ENGINE
Well
where do we start. Lets go from the top down. The engine was basically a pulled
down and reworked 351 4V out of the crate .
Shaker was the same as the GT but with 2 mods. The hot air intake snorkel was
removed and blanked off and the cold air intake shut off flap was removed so
that there was cold air intake all the time.
Carby was a 780 Vac Secondary Holley specially made
for Ford. Part number on carby horn DOZF 9510 Z. A bakelite spacer was used underneath for the PCV valve
connection as there was none on the carb.
Intake manifold was standard cast iron dual plane 4V type with 2 modifications.
The two front venturi’s were opened out slightly and the exhaust gas heat
exchanger holes were blocked off with grub screws.
Distributor was a modified Autolite dual diaphragm,
dual advance unit as fitted to the GT and converted to a dual point mechanical
advance type
Heads were machined to take screw in studs and 5/16 inch pushrod guide plates.
Single groove valves and locks were used in place of the triple grooved ones.
Different spring and damper combination was fitted all ready to take the solid
stick.
Water pump had a .750 inch diameter dual ball bearing race assembly fitted to
improve load carrying ability and it is less sensitive to bearing bore
machining variations.
Block had 2 bolt crank caps and not 4 bolt as a lot of people seem to think, as
it was just a pulled down 4V remember.
Bottom end was balanced along with the new Boss 351 harmonic balancer . One
thou undersized special compound bearings were fitted. Standard capacity sump
had one mod . It had a crank scraper type windage
tray spot welded at the rear .
EXHAUST
Head Mod
( HM) headers were used and these were a specially designed interference type through
a 2.25 inch exhaust to a special sports muffler at the rear then 2 inch
tailpipes as in the GT. However they were subject to a recall and fitted with
extra front resonators in the early stages. Must have sounded pretty loud
without them.
RADIATOR
A 14 fin
per inch 2 core ( Not 3 core ) radiator was used as fitted to any 351 optioned
car with factory air conditioning.
WHEELS
Wheels
were 14" x 6" five slot JJ safety steel rims. 14" x 6"
ELECTRICAL
The
famous Rev Limiter as used on the Boss Mustangs, some Torino’s and Cougars with
429 SCJ engines in the
EXTRAS
The only
thing that was standard on the GTHO that was optional on the GT was the 36
gallon fuel tank. You had to pay extra for the left hand mirror. You had to pay
extra for the radio. You had to pay extra for the bumper bar overriders and you
had to pay extra for the privilege of owning the greatest race car ever
produced by Ford
So that's
what you got for your money. Do you think it was worth the extra bucks?
GT and GTHO Parts ?
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Back to the Garage
GTHO, gtho, phase 3,phase iii, xygtyho, phase 111,
GTHO, gtho, phase 3,phase iii, xygtyho, phase 111,
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