All 4 of my valve springs are hitting the inside of the bottom rocker box.

What causes this?
Can I just grind down my rocker boxes to fix this?

 

Do not alter the rocker boxes. Something else is wrong/broken. Check your service manual to see how everything is supposed to go together.

 

This is very common with aftermarket cams, I routinely grind out the rocker boxes when fitting certain cams.

 

I've cut out the rocker box for larger Valve and Cams or Cam installed.

 

I know this ain't your problem but aftermarket rocker boxes need relieving sometimes.
A buddy of mine bought some Xzotic knucklehead rocker boxes for his Evo and they needed quite a bit of metal removal for the valve spring retainers to clear and I'm not surprised that some HD boxes may need a bit of relieving with changes made in an engine.
Just getting a valve job could move the spring retainers closer to the rocker box.

 

In the next few days I'm gonna take the heads and jugs to the machine shop.
should I take the bottom rocker box as well to make sure I get the right clearance?

 

The cam selection has nothing to do with the interference BUT the valve spring top retainer and keeper location does -- as well as the total valve length if its been alterted

the normal installed height in a harley is 1.850 and the travel ( key to any cam change ) < distance between the bottom of the top retainer and the top of the valve guide seal - determins the total size of the cam you can use // with out machining the valve guide top down to allow more travel for the bigger cam, and or replacing the valve spring package with a performance one ( what does that do - it moves the top retainer up -- reason for your problem ) - that allows more travel and it has stronger springs with more IH distance IH = < installed height / and ends up with more pressure via better springs -- stock is around 120 lbs @ 1.850 - IH pressure and an after market spring set USUALLY has 160 Lbs IH -- for a moderate performance unit -- its the open pressures that is increased that the use of better lifters are needed, as stock open valve spring presures its around 225 Lbs open pressure < when the valve is open to the max - and a performance set its increased it to 325 lbs so you see lots of info that only a real machine shop can, with special tooling determin what is going on, and what may be needed to correct this issue - and yes removing some from the box might be needed in a normal package MAYBE, But if it were high ended with a big cam, you might have to grind the rocker arm stem top as it hits the top cover as the hydrolic lifter pumps out at high RPMs -- this is about 5 percent i could write on the subject but you get the idea --

hope i dident confuse the issue -- jz

 

In other words, clearance the boxes and call it good.

 

we stopped using flat springs years ago so i do not know what they are selling today and what might be his reason, BUT i have in the past when we used flat springs put 600 lift cams in stock evo heads and did not have this issue, but we had our own cam grinds - BUT ///

Now stock harley springs do slinky at high revs / you can see this in the retainer / keeper attach site ( rubbing each other )

hight is hight its a given so something else is going on -- i am not going to speculate

i hope it works out in his favor -- jz

 

Would you recommend I go with some of those new beehive springs?