Rocker arms

[RCH71]

Hi people! I need help with my new engine setup. Is anyone here using Edelbrock 61629 heads with the 7168 camshaft? I need to decide which rocker arm ratio to use and pushrod length.

According to the installation instructions the heads are designed to use Boss 302 7/16” stud mounted rocker arms, which to my knowledge uses 1.73 ratio rockers. But today I called tech support and they assure me that the Boss 302 with 7/16” studs uses 1.6 ratio rocker arms! And to add to my confusion, in the summit Racing Q/A section for the 61629 heads, Edelbrock states that 1.7 ratio rocker arms should be use and to stick with the stock specs of a 351C. mixed information.

Please your advice!

Cams specs:

Intake Duration at 050 inch Lift:234

Exhaust Duration at 050 inch Lift:244

Duration at 050 inch Lift:234 int./244 exh.

Advertised Intake Duration:312

Advertised Exhaust Duration:322

Advertised Duration:312 int./322 exh.

Intake Valve Lift with Factory Rocker Arm Ratio:0.562 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio:0.588 in.

Valve Lift with Factory Rocker Arm Ratio:0.562 int./0.588 exh.

Lobe Separation (degrees):112

 

Heads specs:

 

Exhaust Valve Diameter (in):1.600 in.

Valve Springs Included:Yes

Maximum Valve Lift (in):0.580 in.

Rocker Arm Nut Thread Size:7/16-20 in.

Guideplate Pushrod Size:5/16 in.

 

[Canted 393]

Use the 1.73 on a 351C, you still need to check pushrod length if your block has been decked.

 

[barnett468]

just curious, what are you putting that cam in and what is the part number for it? 312 is a lot of duration.

 

[Ed Raver]

Rest assured that the  69 and 70 Boss 302's use  a 1.73 ratio rocker arm. I own a 69B2.  DO check pushrod length for sure. It is cheap and easy to do and will head off a possible disaster.

 

[Studdley]

just curious, what are you putting that cam in and what is the part number for it? 312 is a lot of duration.

I was gonna say the same thing. Though he did put some heads on it.

 

[RCH71]

just curious, what are you putting that cam in and what is the part number for it? 312 is a lot of duration.

Went with the full Edelbrock performer RPM package.

Performer RPM heads part # 61629

Performer RPM air gap intake # 7564

performer RPM CAM and lift kit # 7168

 

[barnett468]

just curious, what are you putting that cam in and what is the part number for it? 312 is a lot of duration.

Went with the full Edelbrock performer RPM package.

Performer RPM heads part # 61629

Performer RPM air gap intake # 7564

performer RPM CAM and lift kit # 7168

ok, I hope you have a stall converter if you have an auto trans and at least 3.43 gears and at least 9.5 compression.

 

[RCH71]

just curious, what are you putting that cam in and what is the part number for it? 312 is a lot of duration.

Went with the full Edelbrock performer RPM package.

Performer RPM heads part # 61629

Performer RPM air gap intake # 7564

performer RPM CAM and lift kit # 7168

ok, I hope you have a stall converter if you have an auto trans and at least 3.43 gears and at least 9.5 compression.

Yes! did my homework. Got my converter according to my car setup by ACC torque converters. got a 3.25 in the rear but soon will be searching for a 3.50 posi.

right now I am stuck with the rocker arms dilema. Instructions states: heads are designed to use the preferred boss 302 7/16" stud mounted rockers. acording to my research and Ed Raver they shoul be 1.73....guess thats my answer!

whats the stock pushrod lenght?

 

[Don C]

Yes, 1.73:1 is correct.

For the pushrod length, Part No. D0AZ 6565-A for Cleveland engines is 8 7/16" (8.4375") long - available 0.062" shorter (-B) or longer (-C).

Different heads, head gaskets, camshaft, and rockers require checking/measuring for the correct length so the rocker tip is close to center on the valve stem through it's full stroke. It should move from one side of center to the other side as it pushes the valve down.

 

[c9zx]

You will need an adjustable checking pushrod, light checking springs, one solid lifter, Prussian blue, time and patience. You are looking for the narrowest contact pattern (less than .090). It will likely occur slightly inboard of the center of the valve stem tip. Once you find it, add the hydraulic lifter preload, usually about .030. The minimum wall thickness for the new pushrods should be .080, more is better. The lengths for intake and exhaust pushrods will likely be different. I've had good dealings with Smith Brothers pushrods. I consider getting this right a must do if you want optimal performance and valve train life. A good article on this is on the Trend Pushrods website. Chuck

 

[barnett468]

Went with the full Edelbrock performer RPM package.

Performer RPM heads part # 61629

Performer RPM air gap intake # 7564

performer RPM CAM and lift kit # 7168

ok, I hope you have a stall converter if you have an auto trans and at least 3.43 gears and at least 9.5 compression.

Yes! did my homework. Got my converter according to my car setup by ACC torque converters. got a 3.25 in the rear but soon will be searching for a 3.50 posi.

xlnt, it should run well!

.

 

[RCH71]

Tnks to you all! Took my time to check the whole valve train geometry. 1.73 was the right size for the rockers and 8.410 the lenght for the pushrods.

Enviado desde mi SM-G9600 mediante Tapatalk

 

[Don C]

Very good, sounds like you are getting close to the start up. Remember, oil type is critical for break-in and be sure to prime it.

 

[Spike Morelli]

Not mentioned here yet, but has been used successfully, is the use of big block Chevy rockers and pivot balls. They are available in "long slot" versions for bigger than stock lifts, and if memory serves, are super close to the Cleveland's ratio. Something like 1.73:1 for the Cleveland, and 1.71:1 for the big Chevy. Of course, you'd need to be using a 7/16 stud and guide plates, and probably valve covers with the oil dripper fingers underneath to keep the balls oiled. Specifically, I don't have any info as to any friction loss benefits to changing from Ford's sintered iron "sled" pivots, to Chevy's ball style. I can only summize that the Chevy rockers would be fairly cheap ( the reason lots of guys run Chevys ). Personally, I think I'd just go ahead and purchase proper aftermarket Ford rockers...….but I just thought I'd throw this nugget of information into the conversation 'cause some guys do it.

 

[RCH71]

Got the car to the 1/4 mile yesterday. New setup worked great!....now i have traction problems. Had to be gentle on the gas all the way trough 1st gear and then step hard on 2nd gear, otherwise it only spins the tires. It is only my second time at the track, so still a noob at this. Will change to better tires and try again.My best time was 14.8 secs.

What is a good 1/4 mile time for a 1971!?

Enviado desde mi SM-G9600 mediante Tapatalk

 

[c9zx]

Congrats on getting it to the track. What was the MPH in the quarter? Chuck

 

[RCH71]

Congrats on getting it to the track. What was the MPH in the quarter? Chuck

RT = 0.729

60 ft = 2.752

330 ft = 6.786

Mid speed = 79.34

660 ft = 9.951

1000 ft = 12.643

speed = 97.71

ET = 14.93 (correction con my time!..was not 14.8)

Also thinking about re jetting the carb next time on the track. The track is at sea level and I live at 6,900 ft over the sea level. it is a 48 mile drive.

 

[c9zx]

The MPH would support low 14s or high 13s with good traction and technique. If the carb is truly optimized for 6900 feet, increase about 3 jet sizes for 600 feet ASL. Keep at it and good luck. Chuck