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Rocker arms
#1
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.
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#2
Use the 1.73 on a 351C, you still need to check pushrod length if your block has been decked.
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#3
just curious, what are you putting that cam in and what is the part number for it? 312 is a lot of duration.
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#4
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.
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#5
(11-30-2018, 11:46 AM)barnett468 Wrote: 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.

Gas is for cleaning parts, alcohol is for drinkin, nitro is for racin
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#6
(11-30-2018, 11:46 AM)barnett468 Wrote: 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
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#7
(11-30-2018, 01:34 PM)RCH71 Wrote:
(11-30-2018, 11:46 AM)barnett468 Wrote: 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.
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#8
(11-30-2018, 08:43 PM)barnett468 Wrote:
(11-30-2018, 01:34 PM)RCH71 Wrote:
(11-30-2018, 11:46 AM)barnett468 Wrote: 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?
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#9
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.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#10
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
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