I wanted to know if someone help me identify manufacturer of these rocker arms. They bolt to 351C A-3 heads. Photo attached
Thanks
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I know it's a chevy big block rocker arm.
Is the material stainless or aluminum?...Mark
Is the material stainless or aluminum?...Mark
quote:Originally posted by 1Rocketship:
I know it's a chevy big block rocker arm.
+1 but it is MADE for a Chevy BB. The good brands are proud of their products and put their name on them.
It really is next to impossible to identify it since there are so many manufacturers all over the globe. So many look exactly the same.
Looks a LOT like a Yella Terra rocker arm with the exception of an exposed roller...Mark
https://www.google.com/search?...ELYT5003%3B400%3B400
https://www.google.com/search?...ELYT5003%3B400%3B400
Thanks for the responses.
My rocker arm does appear to be a big block Chevrolet part and has been confirmed by others.
Regards
My rocker arm does appear to be a big block Chevrolet part and has been confirmed by others.
Regards
Interesting that Chevy parts are used in a Ford engine.
If the shoe fits,,,,use it.
If the shoe fits,,,,use it.
Some of the racers use various ratios on the arms to "fine tune" the hp and torque curves.
I've seen 1.65's on the exhausts and 1.8 on the intakes.
1.7's would be taking about 7 thousands off the normal lift (on a 605 lift cam)
I've seen 1.65's on the exhausts and 1.8 on the intakes.
1.7's would be taking about 7 thousands off the normal lift (on a 605 lift cam)
quote:Originally posted by PanteraDoug:
Some of the racers use various ratios on the arms to "fine tune" the hp and torque curves.
I've seen 1.65's on the exhausts and 1.8 on the intakes.
1.7's would be taking about 7 thousands off the normal lift (on a 605 lift cam)
On what would the 1.7's take .007" off the normal lift? Were the stock rockers higher than 1.7?
I thought 1.7 was kind of a high ratio, although I Have seen some rockers with numbers like 1.73. Is this what you're comparing against?
I'm not a Ford expert, but I thought stock rockers would be like 1.5 or something.
For the PO, would any 1.7 BB chevy rocker suffice then?
It was and it still is. 1.73:1.
You multiply the cam lobe lift by the rocker arm ratio.
1.5 is a Chevy small block ratio. 1.7 for a Chevy BB, 427.
Ford 289-302-351w is 1.6.
With a .605 valve lift, you would have a .3479" lobe lift with a 1.73:1 ratio.
With a 1.70:1 ratio, the valve lift would be .595".
With a 1.80:1, it would be .629".
The duration of the cam stays the same. Just the lift varies with the change in rocker arm ratios.
You multiply the cam lobe lift by the rocker arm ratio.
1.5 is a Chevy small block ratio. 1.7 for a Chevy BB, 427.
Ford 289-302-351w is 1.6.
With a .605 valve lift, you would have a .3479" lobe lift with a 1.73:1 ratio.
With a 1.70:1 ratio, the valve lift would be .595".
With a 1.80:1, it would be .629".
The duration of the cam stays the same. Just the lift varies with the change in rocker arm ratios.
The stock Cleveland ratio is 1.73 : 1
A rocker such as the one pictured, stamped with 1.7, indicates to me a BBC rocker arm, or it could be a high ratio 302/351W rocker arm. True, in a few instances people have used the BBC rocker arm as a substitute for Cleveland rocker arms, but the BBC rocker arms are not dimensionally identical to Cleveland rocker arms, the substitution is not ideal, it is not something I would do myself.
Yes stock 351C ratio is theoretically 1.73:1, as was the rocker ratio of hydraulic cammed FE engines and 385 series engines.
Yes stock 351C ratio is theoretically 1.73:1, as was the rocker ratio of hydraulic cammed FE engines and 385 series engines.
At one time there were differences in the forgings and you couldn't use a Chevy on a Ford.
MOST are now the same and clearanced to take the largest od spring retainers offered. As such the differences are where the push rod cup is located is the difference. That's where the ratios are changed.
Also you have a choice with many as to the size of the stud you want to use, 3/8 or 7/16.
If that rocker, for instance, has a 3/8 stud then you could use it on a SB Chevy or a SB Ford which uses a 3/8 stud BUT some racers change the studs over to 7/16".
Confused enough yet? I can do better?
MOST are now the same and clearanced to take the largest od spring retainers offered. As such the differences are where the push rod cup is located is the difference. That's where the ratios are changed.
Also you have a choice with many as to the size of the stud you want to use, 3/8 or 7/16.
If that rocker, for instance, has a 3/8 stud then you could use it on a SB Chevy or a SB Ford which uses a 3/8 stud BUT some racers change the studs over to 7/16".
Confused enough yet? I can do better?
The cup position on a BBC rocker is typically in a different position than a 351c due to the difference in deck height and pedestal/stud position between the two engines. The optimal pushrod geometry can differ accordingly. The change in the effective rocker arm ratio is probably subtle through most of the travel but at high lifts can become more of a factor. If you have low clearance, it can contribute to guide plate bind or interference between the pushrod and rocker body or possibly clearance between the pushrod and the head. Biggest issue is probably whether or not the pushrod end points significantly off center in the Rocker cup. If so, at extremes it becomes easier to spit a pushrod.
Best,
K
Best,
K
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K
Excellent illustrative comparison. Thank you for taking the time. I've always wondered about the comparability.
Excellent illustrative comparison. Thank you for taking the time. I've always wondered about the comparability.
quote:Excellent illustrative comparison
Ditto
Don't you just love it when someone puts science behind it!
Thanks Kelly!
Thanks Kelly!
quote:Excellent illustrative comparison. Thank you for taking the time. I've always wondered about the comparability.
AGREED! Thanks for that!
Thanks for the posts. Interesting topic for the OP. I can’t take credit for the picture. I think it may have actually been posted by Blizz on the old 335 series forum back in 2008. I snagged it because these two happened to be from the same manufacture for the two applications of 351c & BBC. It did show the two varied by more than just a small amount in ratio. I added the blue lines and shared what I had seen/measured and it was part of a pretty good discussion on the subject of BBC vs 351c rockers.
Before I posted that picture here I went back and tried to search the thread at the new forum but couldn’t find it. -Maybe someone handier than I can find it.
At the time I had bought a set of Comp Magnum steel rockers from Comp that were advertised 1.73 351c/460 but were marked 1.7 351c/460 when they arrived. The cup position did not appear different on them. When I called Comp they said they were all the same rocker which prompted some discussion but no satisfactory explanation. I did end up using them without issue. It was a hydro-roller stroker sbf. At the time, there seemed to be a rash of complaints of pushrod interference on rocker bodies, heads, and having to split guide plates which can happen due to a variety of contributing factors with about any rocker. At the time I was thinking the difference shown in the picture could have been a contributor. -I never had any problem with them though.
Best,
K
Before I posted that picture here I went back and tried to search the thread at the new forum but couldn’t find it. -Maybe someone handier than I can find it.
At the time I had bought a set of Comp Magnum steel rockers from Comp that were advertised 1.73 351c/460 but were marked 1.7 351c/460 when they arrived. The cup position did not appear different on them. When I called Comp they said they were all the same rocker which prompted some discussion but no satisfactory explanation. I did end up using them without issue. It was a hydro-roller stroker sbf. At the time, there seemed to be a rash of complaints of pushrod interference on rocker bodies, heads, and having to split guide plates which can happen due to a variety of contributing factors with about any rocker. At the time I was thinking the difference shown in the picture could have been a contributor. -I never had any problem with them though.
Best,
K
quote:Originally posted by Panterror:
Thanks for the posts. Interesting topic for the OP. I can’t take credit for the picture. I think it may have actually been posted by Blizz on the old 335 series forum back in 2008. I snagged it because these two happened to be from the same manufacture for the two applications of 351c & BBC. It did show the two varied by more than just a small amount in ratio. I added the blue lines and shared what I had seen/measured and it was part of a pretty good discussion on the subject of BBC vs 351c rockers.
Before I posted that picture here I went back and tried to search the thread at the new forum but couldn’t find it. -Maybe someone handier than I can find it.
At the time I had bought a set of Comp Magnum steel rockers from Comp that were advertised 1.73 351c/460 but were marked 1.7 351c/460 when they arrived. The cup position did not appear different on them. When I called Comp they said they were all the same rocker which prompted some discussion but no satisfactory explanation. I did end up using them without issue. It was a hydro-roller stroker sbf. At the time, there seemed to be a rash of complaints of pushrod interference on rocker bodies, heads, and having to split guide plates which can happen due to a variety of contributing factors with about any rocker. At the time I was thinking the difference shown in the picture could have been a contributor. -I never had any problem with them though.
Best,
K
Your experience was exactly mine and our thinking is similar.
I don't often get to line one up versus another so that picture helps.
What I am thinking though is that there are so many brands now that to one manufacturer there is no difference and yet to another even the forgings are not the same?
I didn't feel competent to disagree with Comp Cams on the subject.
I do know that some are using the BBC rockers on the Cleveland and there were no comments about unusual failures.
In glancing at specs recently I did notice that the cut to clear the valve spring retainers seems to have been standardized on the large side.
I also noticed that valves are now more commonly being listed as +.050, +.100, and even +.200 (wow!) on the valve stem lengths.
Careful planing on selecting valves and valve stem length could solve the problem of standardizing the location of the rocker arm roller itself to either shroud it or unshroud it with clearance to the spring retainer at full lift being the consideration?