Rocker Arms

[blykins]

Can't go wrong with the T&D's....

3.70-4.10 would probably help out mucho better, but I think you're leaving power on the table with that particular grind.  It's kind of a wonky cam....not enough split, not optimal on valve lift, etc.  If you don't have it yet, I'd look elsewhere.  If you do already have it, jab it in there and see what happens.

[scott foxwell]

The factory rockers work exceptionally well for mild cams.

Thanks for your answer but the problem is I don't have a mild cam. What about the com rockers or do recommend something else? Btw, this thread got out of hand on this geometry business which really didn't address my question?

Bad geometry can ruin the best rockers and a good set of heads. Getting the geometry right will go a LONG way to making valve train happy. Most people don't even know what "rocker geometry" is, or how to check it. It's not the same between stock (shoe type) rockers and roller tips. It amazes me that people will assemble tens of thousands of dollars worth of engine parts and poo poo rocker geometry, or not even give a darn. To each their own.

[blykins]

It's because they don't know to check it.  Obviously there's no excuse for an engine builder to do it, but the average home builder just doesn't know how/when/why to check it. 

[Tobbemek]

Google MID LIFT teori and you get the right answer to what proper rocker arm geometry is. sometimes engine builders has to compensate for rocker arm push rod clarence given the parts being used. One should always try to get the rocker geometry as perfect as possible with all means, and some rockers is just not proper build t, and should been change to right ones. The rocker arm and stands should bee in relation of the cyl head layout used.   

[scott foxwell]

It's because they don't know to check it.  Obviously there's no excuse for an engine builder to do it, but the average home builder just doesn't know how/when/why to check it.

I think it's time we change that. We sell pushrods to our customers but we don't order or ship them until the customer tells us what length they need. They get educated on rocker geometry. I did a video for our customers (and anyone who wants to watch) on how to set proper rocker geometry for stud mount roller tip rockers. The principles apply to ALL rockers. The method for setting or correcting the geometry is different and some of the checking parameters are different between OEM (shoe) type rockers and roller tip rockers but the fundamental goal is the same.
I'm going to be setting up the geometry on my FE motor before long. I think it's time I did a little tutorial. 

[scott foxwell]

Google MID LIFT teori and you get the right answer to what proper rocker arm geometry is. sometimes engine builders has to compensate for rocker arm push rod clarence given the parts being used. One should always try to get the rocker geometry as perfect as possible with all means, and some rockers is just not proper build t, and should been change to right ones. The rocker arm and stands should bee in relation of the cyl head layout used.   

Yep!

[blykins]

Same here.  I sell pushrods as part of my cam/lifter packages, but I don't ship unless I get a confirmed pushrod length with some tutorial on how to optimize it and check it. 

There's more than one way to skin a cat, but I have never really been a mid-lift theory guy.  To me, I'm looking for as narrow of a pattern as I can get, which is backed up by the least amount of valve lift loss that I can get.  As long as it's generally near the center of the valve stem, I'm good.  The old wives' tale, "It has to be dead centered on the valve tip" doesn't float here. 

I do agree that even a rocker arm swap will totally jack things up for you though.  I was building a 460 inch Clevor and spent an hour getting the geometry right with a Comp Cams Ultra Gold 1.73 ratio rocker.   Those rockers are pretty large and beefy and I soon realized that after I had spent time squaring up the top end that I was going to have pushrod contact.  I switched to a 1.73 RR Comp XD rocker which allowed a lot more room for the pushrod, but I never could get the same pattern that I got with the first set of rockers, even after spending another hour on it. 

I also use a lot of "new" factory non-adjustable rockers and it seems like I always have to shim up the stands with the valves that I use in my heads.

[scott foxwell]

Same here.  I sell pushrods as part of my cam/lifter packages, but I don't ship unless I get a confirmed pushrod length with some tutorial on how to optimize it and check it. 

There's more than one way to skin a cat, but I have never really been a mid-lift theory guy.  To me, I'm looking for as narrow of a pattern as I can get, which is backed up by the least amount of valve lift loss that I can get.  As long as it's generally near the center of the valve stem, I'm good.  The old wives' tale, "It has to be dead centered on the valve tip" doesn't float here. 

I do agree that even a rocker arm swap will totally jack things up for you though.  I was building a 460 inch Clevor and spent an hour getting the geometry right with a Comp Cams Ultra Gold 1.73 ratio rocker.   Those rockers are pretty large and beefy and I soon realized that after I had spent time squaring up the top end that I was going to have pushrod contact.  I switched to a 1.73 RR Comp XD rocker which allowed a lot more room for the pushrod, but I never could get the same pattern that I got with the first set of rockers, even after spending another hour on it. 

I also use a lot of "new" factory non-adjustable rockers and it seems like I always have to shim up the stands with the valves that I use in my heads.

You're on the right track. Centered is secondary to proper geometry, I agree. What you're trying to accomplish with minimum sweep IS mid lift geometry. Get the mid lift geometry right and you will have minimum sweep...get minimum sweep and you will have mid lift geometry. They are one and the same. The only way to change geometry with a shaft rocker system is to raise or lower the shaft.
Here's a link to my video just for reference. It's for stud mount roller tip rockers, but the principles apply to all.

https://www.youtube.com/watch?v=o5is9BsH5OU&feature=youtu.be

[blykins]

Well thanks for validating the way I've been doing it for the past couple decades....

What I meant by saying that I wasn't a "mid-lift" theory guy, was that I don't just find that mid-lift point and call it quits, as Paul Kane would suggest.   You can use that point to get a good starting point, but you can always "tweak" from there.

[scott foxwell]

Well thanks for validating the way I've been doing it for the past couple decades....

What I meant by saying that I wasn't a "mid-lift" theory guy, was that I don't just find that mid-lift point and call it quits, as Paul Kane would suggest.   You can use that point to get a good starting point, but you can always "tweak" from there.

Well, sorry. You just lost me at "Paul Kane".
Mid lift is perfect geometry on the valve side. We can only change one side of the rocker...either the pushrod side or the valve side. I focus on the valve side since that involves things like springs, valve tips and guides. I worked with Sharp a year ago to "perfect" a stud mount rocker for the AFR BB Chevy head. At .700" lift, it has perfect 90* geometry on both valve and pushrod side. That took some time. If the pushrod side of the rocker is WAY off, then sometimes a compromise might be necessary, or you get a different rocker.

[blykins]

Haha, anytime someone references the "mid-lift" theory, that's automatically who I think of.    There's a lot more to it than just finding the mid lift point and calling it quits.