Shim Under or Shim Over?

Great pic. Thanks for the help. I was just unsure of where exactly the interference was.

We have a milling machine at the shop where I work - it will make itself useful - hardly anybody even uses it anymore. I'll practice on my junk head (I have 8 tries to get it right and lookin' pretty)

-Dave

I clearanced mine with a drill and was so easy even a caveman could have done it.

beefsquasher wrote:

The head is already ported and I have new valves. guides. springs,etc... so it should be able to take the big cams. If I don't like how the cams perform, i'll just take them out and put my andrews 2x cams back in.

<RANT>it seems like every time I ask a question about building up my head, I am told to just have Larry Cavanaugh do it, "I'm going to screw it up", "don't bother, its a PITA", and so on. It's not that I don't have enough money to send my stuff out to get done, but simply that I want to learn and to do it myself. I have already ruined a junk head I got on eBay by experimenting. I'm bidding on another right now. I got some EXCELLENT, and very specific advice from Larry on how to port these things, and it is coming along nicely. I love screwing around with motorcycles - it's about the journey, not the destination. If my bike was perfect and never broke and was as fast as a Hayabusa, then what fun would it be? I wouldn't get to take it apart and put it back together again a million times.
</RANT>

But.. back to our regularly scheduled program:

I can't find any info about how you clearance the head for the cams - on Larry's site or anywhere else. Any ideas?

-Dave

Just place the cam into the channel and rotate it. If it hits than remove metal until it no longer touches. Using a die grinder is SOP for even the better shops. Unless you write a subroutine for a CNC machine or you have a horizontal mill with a cutter that that is .850" over the base circle you choose, that you can mount on a cutting shaft 24' long, (not the standard vertical mill) It will take you 20x longer to do than if you just do it with a die grinder. It need not look pretty, you will not see it anyway, This not meaning that you cant be neat and careful. I attempted to do it on a standard "Bridgeport" mill and it took me two hours to do one pocket with all the setups. It took me less than that to do the other seven with the die grinder. On a "J" or GPz head the grinding would not be bad but on a KZ head the grinding will be substantial for a cam larger than .380

Excellent advice. Thanks guys.

-Dave

beefsquasher wrote:

<RANT> ... It's not that I don't have enough money to send my stuff out to get done, but simply that I want to learn and to do it myself... I love screwing around with motorcycles - it's about the journey, not the destination... If my bike was perfect and never broke and was as fast... what fun would it be? I wouldn't get to take it apart and put it back together again a million times.
</RANT>

What an attitude! You gotta love this guy. :kiss: :blush: :laugh: :laugh: :laugh:

Wrench-on
Bill

Our 410 is the largest we recommend with sot. There are two reasons shims spit out, high lift pushes the edge of the shim into the relief groove around the edge of the bucket which allows the other side of the shim to raise up out of the bucket.

Second is valve float. During a float situation, the bucket and shim can separate and the lobe comes around went knocks it out of the park. This can happen with stock cams., 365s, etc.

We clearance the heads in a Bridgeport.

Jay

die grinder and a 1" flapper wheel that is what i use for most of my clearancing.

Old Man Rock wrote:

Just out of curiosity and for upgrading my brain here....

Under bucket shim configuration/conversions...
How the hell are the shims replaced?

Meaning you have to remove the camshafts (lift up) to change the shims for clearance specs.... :ohmy:

That seems like a total PITA... I can also see where due to constant removals, striping a top idler bolt/thread or cam cap bolt/thread would be come highly possible...

No thanks, .365 cams with over bucket shims is good enough for me.... I have enough issues to deal with... :blush: :laugh:

yep it is a PIA, the 650s are under bucket. the first time is not fun since you have to tear everything down to see what shim is in, if you dont have shims, you have to order the sizes and wait. put everything back to and recheck.

"the first time is not fun since you have to tear everything down to see what shim is in, if you dont have shims, you have to order the sizes and wait. put everything back to and recheck. "...

Well that sucks, especially if you check/change shims every 3K-5K miles. Or in a new build, this is sooner... :S Maybe I'm just too anal about verifying my clearances... :blush:

Other than for drag racing where the increased cam lobe durations & power, I can understand the need to go under bucket shims but for a street ride/street mod.... :S

Screw that, for just a little added umphka just doesn't seem worth it... Again, 29mm carbies, .365 cams, ported head & Kerker w/1.5" comp baffle... good enough for that desired added zip... No need to convert nor grind away at the valve cover...

OMR

It's not fun even if you DO have the shims. I don't race any more so i will stick with the SOT setup. As I said before .420 lift and 10k RPM and had no problems on a GPz1100 head. But you have to make sure that you have after market springs to prevent valve float.

What about brazing up the relief groove for the shim in the bucket and machining it back to flat - is this a good way to counter any shim-spitting? Does it compromise oiling of the shim for rotation or anything like that?

-Dave

beefsquasher wrote:

What about brazing up the relief groove for the shim in the bucket and machining it back to flat - is this a good way to counter any shim-spitting? Does it compromise oiling of the shim for rotation or anything like that?

-Dave

We used to do that. Silver soldered them.