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?