Re: Holroyd BBC Rocker Arms
 

Mike I dont know about that, I was breaking rockers on my 427 vette in 1976. The motor in question was built by Ralph Truppi, ran like a raped ape but always broke a rocker when you least wanted it. 427-400 tri power, glide, long slot rockers, stock springs.

Re: Holroyd BBC Rocker Arms
 

There is no going back, might as well stop fantasizing about it. The options are ammend the rules to either allow non-OEM in appearance such as shown here or allow an aftermarket replacement; which is entirely what these Holroyd rockers are anyway.
If NHRA wants to inhibit RPM and performance by keeping a stock OEM rocker then thats fine, enforce the rules. If NHRA wants to allow racers a better rocker that doesn't break (yes, always at the wrong time!), then allow Holrod are Crane, it really doesn't matter since neither look or perform as intended from the OEM.
And I believe shaft rockers should be where shaft rockers were placed by the OEM & stud rockers where placed by the OEM.

Re: Holroyd BBC Rocker Arms
 

Jeff, They are GM rockers, the only BB rocker you can buy first and second Clark had the mod approved by nhra. What more dose one need to do, he went thru the channels, is that west coast ? I dont think so, everybody on the east coast has them too. I could care less, I poked my nose in because I told Clark and a few others where to find the marine take-off rockers. I wish I had them in 76.

Re: Holroyd BBC Rocker Arms
 

Bob, I don't see anything incorrect here.

Re: Holroyd BBC Rocker Arms
 

Bill,
What other engines are they approved for? Do you have a picture? Approx cost?

Thanks

Re: Holroyd BBC Rocker Arms
 

Mark, it dont effect me I dont use them. Weather or not legal or not it was nhra that gave the go ahead. Besides the mod the rocker is the same as before, it is bigger in the pocket for the 9/16 ball that helps spread the pressure better. When used with Alum heads I have seen them pull the stud out so there is still a problem waiting to happen, ask Kevin Helms.

Re: Holroyd BBC Rocker Arms
 

Mark,
I have direct knowledge that they are approved for Pontiac and Olds engines. If you like I can take a picture but it looks exactly the same as the BBC modification. Clark only has the one insert to my knowledge. The first time I talked to Clark he said to send him a set of the rockers I wanted modified and he would let me know if he could fit his insert in. They fit, he welded them in and I have not broken a rocker since. I couldn’t go 12 passes without breaking one. And for Mike; that’s in a motor with only 364 lift at the valve and 150# seat pressure.
And for those who are not using them and would like to but don’t know if they are approved I would suggest you do exactly what I did; I asked my division Tech Director if I was allowed to modify my rocker arms like the ones approved for BBC’s . Dave wrote back to me saying he was unsure and asked me not to run them until he consulted Glendora. Few days later he wrote back saying Bruce said they are approved.
Cost was around $250 to have Clark do rockers I supplied.

Re: Holroyd BBC Rocker Arms
 

with weaker springs most time breakage comes from valve float or bounce which beats valvetrain to death most of the time when you have float the keeper grooves will be burred
and have to dress them down to get valve through guide and valve seat will be wider where valve has hammered it.
I believe alot of rocker breakage with higher spring pressure is from flex,they get wiggled to death. Which I say Clark's rocker reduces.
You break studs or pull threads out of head most likely there is valve float.
You may agree or disagree but stocker valve train have been push to edge and over whether in spring pressure/duration,overlap checked rules or current rules,and no matter what the rules are they will still be on the edge,because most everyone is going for all they can get.
Mike Taylor 3601

Re: Holroyd BBC Rocker Arms
 

Here are some close ups of Clarks work.

Re: Holroyd BBC Rocker Arms
 

Thanks...how about a bottom view on the pushrod cup?