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VIP Periodic Award Fun Question for 5-21-2011
cobra3073

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#1
tunes  VIP Periodic Award Fun Question for 5-21-2011
Good Day Superstars:

This is the second VIP Periodic Fun Question (PFQ) for 2011.

For this particular exercise, the Site has donated a $50.00 store credit with one of our sponsors (Motorcity Mustangs). Since Motorcity does not have a store front store, he has consented to have his "turn in the barrel" to go to a store front store. So the award will be for Ohio Mustang Supply {OMS}).

We recognize there is sometimes conflicting information from different sources relative to our hobby but we are making every effort to ensure the questions are from industry accepted sources. With that in mind, we will only accept the pre-determined answer as being correct.

Remember, the exercise is PRIMARILY meant for FUN.

The "problem" this week pertains to a Member who has a 1972 Q coded Mustang. The Member has decided to convert his motor to the specifications of the 1972 351 R coded Mustangs.

Please explain the recommended procedure for modifying the cylinder heads to R Code specifications. This should include specific "numbers" or "dimensions" for any machine work.


The "winner" will be identified in a post to this thread at approximately 7:00 PM (CST) on Monday, May 23, 2011.

Good Luck!


BT
The 72 HO heads are essentially the same as the 72CJ/4V heads. The major difference is the fact that the HO heads are set up for adjustable rocker arms (and a mechanical camshaft). To convert the CJ/4V heads, one must have their pedestals machined for screw in rocker studs.

This entails milling the pedestals 0.0300" parallel to the original surface. This is done so that rocker studs 0.376" - 0.372" in diameter with a 0.88" depth can be used. Tap 7/16" 14UNC 2B THD 0,68" deep, champfer 0.469" DIA x 60°.
david020278

Do the RIGHT thing.
05-21-2011, 12:26 PM
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Comments
#2
combustion chamber volume should be 73.9-76.9
valve spring pressure should be 88-96@1.820 299-331@1.320
valve spring free length approx 2.03

My garage http://www.7173mustangs.com/forum-garage...rxt_uid=40

73 mach 1 351c 4v cc ported, torker2, 750 edelbrock,C6.
73 fastback 351c 2v,performer intake,600 edelbrock,fmx, 325 trac-lok.
  Reply
#3
The Q code and R code basically shared the same head design Open chamber 4v low compression with 74-77 CC's Int. valve dia. 2.19" Ex. valve dia. 1.71", Intake port dia. 2.50 x 1.75" Exhaust port dia. 2.00 x 1.74" would be the specs to to obtain. The main difference's would be the dome pistons with a compression ration of 11.1:1 (1971) verse's the flat piston's with a compression ratio at 8.8 ( 1972) But if you want to build to 1971 R code specs. you will need a set of closed chamber heads same specs on valves and ports.These heads also have machined valve spring seats for use with mulitple coil valve springs. The high performance heads utilize single groove valve stem locks.

[Image: 2zdx09d.png]
Yea,Tho i cruise through the valley of the shadow of rice,I will fear no Turbo,For Torque art with me.Thy rods and crankshaft,they comfort me. Big Grin Robert
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#4
1972 R-code (351 HO)

The R-code 351 Cleveland for 1972 was considerably different. It had reduced compression (8.8:1) with forged flat top pistons for emissions compliance and used open-chamber heads. It had a solid lifter camshaft (Ford's last); however a four-barrel carburetor was retained. It produced 275 hp (205 kW) using the new SAE net system. Cast cranks that had been tested for hardness were used in both the Boss and HO.
Q-code (Cobra-Jet)

The Q-code "351 Cobra Jet" version was produced from May 1971 through the 1974 model year. It was a low-compression design that included open-chamber "4V" heads, a special intake manifold, special hi-lift long duration hydraulic camshaft, special valve springs and dampers, a 750 CFM 4300-D Motorcraft Carburetor, dual-point distributor, and 4-bolt main bearing caps. It was rated at 266 hp (198 kW) (SAE net) for 1972 when installed in the Mustang and 248 hp in the Ford Torino and Mercury Montego. The horsepower rating dropped in 1973 to 246 hp for the 4-barrel for the intermediate Fords, and still retained the higher 266 hp rating in the Mustang. The 351 CJ (now referred to simply as the "351 4V") was rated at 255 hp in 1974 and was only installed in the Ford Torino, Mercury Montego and the Mercury Cougar.
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#5
The 71 Boss (closed chamber) and the 72 HO (open chamber)haeds have machined pedesals for screw in rocker studs and machined spring seats for multicoil valve springs.

Head modyfication for mechanical cam:

Machining the pedestal mounts by milling to accept adjustable rockers.
Mill 0.300" paralel to the pedestall , mesure from the top of the pedestall. Mill paralel to the original slott.

Drill the existing pedestal screw holes (in line to the old holes!) to accept the rocker studs to 0.376"-0372" DIA. x 0.88" deep , Tap 7/16" 14UNC 2B THD 0,68" deep, champfer 0.469" DIA x 60°

Machining the valve spring seats to accept the smaler inside and larger outside diameter Boss springs.
Machining inside diameter to 0.690"-0.700" and outside to 1.59"-1.61"

[Image: t5Banner.jpg]
  Reply
#6
The R code in '72 had open chamber heads with flat top pistons. So no change in chamber or valve size to convert Q to R-code specs. But will need to machine the '72 Q heads to accept adjustable rocker arms with pedestals to accept a Boss 302 type valve train and mechanical cam. The head is flat and the spring sits in stamped spring seat. The rocker arm is mounted on a slotted pedestal, moves on a “sled” fulcrum, and is retained by a bolt.


[Image: 386_07_10_13_5_58_42.jpeg]
My Mustangs:
71 M-code Mach 1, Medium Blue/White Sport, 4R70W, 3L50, Factory Ram Air.
72 Q-code Mach 1, Pewter/Black Sport, 4-spd, 3L25.
73 F-code Convertible, Planned: color TBD/Black top/White Int., 351C, 5-spd, 3L50.
65 Convertible, Britney Blue/White/White, more modified than original.
05 Convertible, Legend Lime/Tan/Tan, future classic??
  Reply
#7
SUPERSTARS!

We do have a winner - - david020278!

The 72 HO heads are essentially the same as the 72CJ/4V heads. The major difference is the fact that the HO heads are set up for adjustable rocker arms (and a mechanical camshaft). To convert the CJ/4V heads, one must have their pedestals machined for screw in rocker studs.

This entails milling the pedestals 0.0300" parallel to the original surface. This is done so that rocker studs 0.376" - 0.372" in diameter with a 0.88" depth can be used. Tap 7/16" 14UNC 2B THD 0,68" deep, champfer 0.469" DIA x 60°.

Again, we do have a winner. Please join me in congratulating David!!

BT

Do the RIGHT thing.
  Reply
#8
Good job David.Smile

My garage http://www.7173mustangs.com/forum-garage...rxt_uid=40

73 mach 1 351c 4v cc ported, torker2, 750 edelbrock,C6.
73 fastback 351c 2v,performer intake,600 edelbrock,fmx, 325 trac-lok.
  Reply
#9
Good job David.

Where was the detailed info for the machine shop found?

[Image: 386_07_10_13_5_58_42.jpeg]
My Mustangs:
71 M-code Mach 1, Medium Blue/White Sport, 4R70W, 3L50, Factory Ram Air.
72 Q-code Mach 1, Pewter/Black Sport, 4-spd, 3L25.
73 F-code Convertible, Planned: color TBD/Black top/White Int., 351C, 5-spd, 3L50.
65 Convertible, Britney Blue/White/White, more modified than original.
05 Convertible, Legend Lime/Tan/Tan, future classic??
  Reply
#10
Cool, thanks guys :-) . I found these Information in the book : "Ford Performance , includes all modern performance engines" , by Pat Ganahl , ISBN 0-931472-05-9

[Image: t5Banner.jpg]
  Reply



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