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I'm having a 455 built, and I'm having a technical problem with my engine builder. He doesn't like the Comp Cam roller rockers that I have, and claims that the body on them is just too thick. He doesn't seem to think that he can get the geometry right on them. I believe at this point he has a 9.72 length pushrod. What is everybody running for pushrod length if you are running these Comp Cam rockers. These are the aluminum full rockers, the older style. I also ordered two rockers of the new style, and he doesn't like those either. Any advice or help is greatly appreciated.
I would have him explain and show you why he doesn't like them.
I'm a little confused. I don't build engines, that's why I took it to him, but what he said, was that the actual body of The Rocker was too big, and would not go down far enough for proper adjustment and geometry. If you look at the pictures, he actually milled down part of the rocker stud, in hopes of getting the rocker to go down further. Common Sense tells me that a longer push rod should be able to solve the issue, and he is using a 9.72 pushrod which is longer than stock, but I didn't know if there was a certain protocol as far as length or actual rocker placement, that is taboo, that is keeping him from going to a longer push rod. I'm not in the know of valve train, and this is a first for me, and I don't think that he is a huge old guy. But if these rockers were made for Oldsmobiles, then they should work, and the reason that I posted on this board was to see what some of the various pushrod length that other fellow Oldsmobile people were using, so that I could relay that information back to him, and show him that it's normal to use a longer pushrod in some instances.
I'm a little confused. I don't build engines, that's why I took it to him, but what he said, was that the actual body of The Rocker was too big, and would not go down far enough for proper adjustment and geometry. If you look at the pictures, he actually milled down part of the rocker stud, in hopes of getting the rocker to go down further.
I'm guessing stock iron heads? If so your machinist/engine builder should've milled the rocker stud pad, at least the same amount as the guide plate thickness. It's a simple step called "mock up". Get another builder as apparently he has tunnel vision.
Jmo.
Same mistake was made on my engine , the rocker stud "nut" will eat up the bottom of the rocker as happened to mine simply because the guy doing the head work did not machine a "pocket" for the valve guide plate. Your machinist is clueless re: Olds building, as was mine.
Someone posted this on another thread about pushrod length and it is absolutely the best way I have seen it explained on how to measure for the correct pushrod length.
if the pushrod length is wrong, you can really hurt your valvetrain with unnecessary harmonics and tip pushing movement that accelerates wear on the valve guide, seat, and valve stem and tip, as well as the stem seal.
make sure and note what thread size and pitch your rocker arm studs are before you do this procedure
Same mistake was made on my engine , the rocker stud "nut" will eat up the bottom of the rocker as happened to mine simply because the guy doing the head work did not machine a "pocket" for the valve guide plate. Your machinist is clueless re: Olds building, as was mine.
you can't use others measurements. You need to go by the witness marks left after trying it on your specific engine.
I understand that, just trying to see what some of the lengths are that people came up with. Trying to figure out what length people are using on they're own builds because my builder doesn't want to go to a longer pushrod. Can he use a pushrod longer than 9.72. Has anyone used a pushrod longer than 9.72. Why is he against using a longer pushrod?
Your “builder” goofed plain and simple. And now he’s trying to take the easy, but incorrect way out.
Tell him remove the heads and mill the rocker stud pads down the way he should’ve in the first place.
Oherwise take your stuff elsewhere. His longer pushrod idea is a bandaid at best.
I understand that, just trying to see what some of the lengths are that people came up with. Trying to figure out what length people are using on they're own builds because my builder doesn't want to go to a longer pushrod. Can he use a pushrod longer than 9.72. Has anyone used a pushrod longer than 9.72. Why is he against using a longer pushrod?
I can double check but believe mine were 9.80 ( stroked small block with al. heads)
The only real way to find out the answer is to mark the tip of the valve and play around with rocker arm position until you get the geometry correct. The geometry has NOTHING to do with whether he machined the head down at the rocker stand. The stand might very well need to be machined down to get the proper geometry but you have to figure out the rocker arm position first. Once you do that you can pick a pushrod length. It may very well end up that the rocker pad on the head will have to be milled down to get the geometry correct but it is not a given. Only way to know is to check it.
Here is a very detailed (and long) article that explains it all very well:
The only real way to find out the answer is to mark the tip of the valve and play around with rocker arm position until you get the geometry correct. The geometry has NOTHING to do with whether he machined the head. Only way to know is to check it.
Here is a very detailed (and long) article that explains it all very well:
Hmmm yes it does. Question, if your geometry is best with a lower rocker/shorter pushrod, but the rocker hits the stud, then how do you know?
His machinist/builder goofed, at the very least to allow himself to check it correctly. Secondly by machining the rocker stud the way pictured, he just weakened it significantly.
OP, do what you want but your guy doesn’t have a clue.
Hmmm yes it does. Question, if your geometry is best with a lower rocker/shorter pushrod, but the rocker hits the stud, then how do you know?
You are absolutely correct. My point though was that you have to check it first to find out what the problem really is. There is a very good chance that the rocker pads will have to be machined but there is no way to know other than to start checking. If you get to the point that the rocker needs to go down further then you know what has to be done. You could put them on without the guide plates and check them too.
I feel pretty confident that you are correct and the heads will have to be milled down. Cutting the studs down sure looks like it would weaken them a bunch to me too.
The only real way to find out the answer is to mark the tip of the valve and play around with rocker arm position until you get the geometry correct. The geometry has NOTHING to do with whether he machined the head down at the rocker stand. The stand might very well need to be machined down to get the proper geometry but you have to figure out the rocker arm position first. Once you do that you can pick a pushrod length. It may very well end up that the rocker pad on the head will have to be milled down to get the geometry correct but it is not a given. Only way to know is to check it.
Here is a very detailed (and long) article that explains it all very well:
February 5th, 2019, 10:42 PM
