decking the head and 181 cam

K

Kiff

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Sep 7, 2009
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Had to deck the head 0.015". I am installing a Hamilton 181 cam and large bowl pistons, I'm wondering if I have to worry about the valves hitting the pistons? How much clearance do these motor have? Do I need a thicker HG?
 
Or check the clearance with a stock thickness gasket so you don't have to lower the compression anymore than the pistons are going to. And actually if the head is done right it shouldn't matter, the valves typically are supposed to be recessed back into the head after it is decked.
 
I am worried about the exhaust stroke. I don't want to put a .020" gasket in "just for the hell of it", trying to keep compression up. I will slowly roll the motor over to check and see how it is, but was hoping someone might have some insight on the issue
 
I had originally pulled the motor out to deal with a blown headgasket, but the motor had 60# valve springs in it when I bought it, so the only thing I can guess is that whoever did those didn't strip the head down in the proper order and thus the tweaked head.
 
pm me the valve depths and I will let you know if you are good to go or what. Don't burn a gasket for nothing!

Zach
 
yes you can do it without a headgasket just take into consideration the COMPRESSED tickness of the head gasket with your mesurment.... just make sure when you rotate the motor if there is any resistance to stop IMEDIATLY just in case it's valve to piston contact. hope this helps.
 
Kiff said:
I had originally pulled the motor out to deal with a blown headgasket, but the motor had 60# valve springs in it when I bought it, so the only thing I can guess is that whoever did those didn't strip the head down in the proper order and thus the tweaked head.
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Nothing to do with it, if you had said that the head was .009 off from end to end I'd say that is the top but .014 is the worse, no worries just trying to learn more, last one I ever heard going that far was a bad fire ring job.....botw, I have a block that had to go .012 so it's not new.

Jim
 
DLV8 said:
yes you can do it without a headgasket just take into consideration the COMPRESSED tickness of the head gasket with your mesurment.... just make sure when you rotate the motor if there is any resistance to stop IMEDIATLY just in case it's valve to piston contact. hope this helps.
Click to expand...

You have to have a gasket installed to do the check, as the pistons protrude out of the block at TDC.
 
Just use your old gasket and put a little "disc" of plumbers putty between two pieces of wax paper on top on a piston. I put two separate pieces like that on mine towards the edge of each valve. Also fwiw I checked it with tight valve lash, I think I did .005" intake and .010" exhaust just incase.
 
Why can't you just reset the valves depth in the head to stock specs and be good? Is that too far to cut the seats or something? Wouldn't doing that solve your problem?
 
If you cut the head, you sink the valve in the cylinder...... a good thing. If you go ahead and sink them in back in the head, you are giving up hp. If you want it to be easy, sink them back in the head and don't check the piston to valve clearance. Now if you want hp, that is totally diferent. Do the work, check the clearance. Keep your compression as high as possible on your street rig an get that head flowing as well as possible.


If your piston prorusion is good to go, you valve depth is .030" or greater, there is a good chance you can roll without backing up the cam or thicker head gasket. Worst case scenario, you can run the stock gasket and back the cam up 2 degrees.

Take the high road, put in the work, choose HP!

Zach
 
I just got a call today about this from the shop building mine. Told me they'd need a second head gasket. One to use for checking clearances and a second one for when they put it together.
 
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