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Hemi head shaving?

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Champ2014

New member
I was asked this question and frankly I do not know the answer. Was hoping you all could help. On a hemi predator head. How much can u safely shave the head before u run into the threat of the piston hitting the valves? Thanks in advance.
 
well I took .080 off an with a stock head gasket they just kissed ,when I checked it , it looked like I had clearance but after I tore it down they had touched at some point during the season . during a refreshen I fly cut the piston now its good.
 
AML_RACING_DAD_98 said:
Depends on cam lift and deck height of piston.
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sometimes you can get away with a guess, but this advice is really good. I know it's a lot of work for someone not equipped to do it, thus kart shops, but you're really taking a chance if you don't check these things.

Engines have different piston deck heights, cams have different lifts, gaskets compress to different thicknesses, all come into play. One way to check is with modeling clay. Press a layer of clay on the top of the piston, reinstall the head, reset the valve lash and turn the engine through top dead center a couple of times. Pull the head and measure how thick the clay is where the valve hits it. Add a little for stretch, maybe .010", and you'll be safe.

If winning was easy, everyone would be winning.
 
If you are not running high lift cam (.300+), you can just leave the piston in the hole .030-.035 and cut however much you want off the head, but still need to check the clearance after your done to make sure you aren't going to have the piston smacking the head. Always run at least .025-.030" piston to head clearance with modified engines, especially high rpm engines. You have to account for rod stretch at high rpm when setting the clearance
 
I used a black mamba cam in a Hemi with .070" cut from the head and a thin .009" head gasket. Piston was about .004" in the hole, valves were a little too close. Mine would have given me about .030" piston to valve clearance if I only cut .040" from the head. Keep in mind I also removed the .039 thick stock hemi head gasket and replaced it with a .009" to get there. I'm sure every one is not exactly the same so I would recommend measuring it but that is where mine landed.
 
I have good clearance with .30 off the head and a 274 260 duration cam with the stock head gasket. piston is .003 in the hole. for compression I welded my head quite a bit
 
The big thing you have to look out for is some can get away with this but when you change rod and piston your numbers will change too.no one has said what rod and piston combo they are using.
 
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