Author Topic: HEAD MILLING  (Read 1671 times)

Offline 170cuda

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HEAD MILLING
« on: November 25, 2006 - 04:46:23 PM »
How much would I have to cut off my 516 heads to go from 78cc to 70cc? Whats the formula for this? Thanks




Offline Chryco Psycho

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Re: HEAD MILLING
« Reply #1 on: November 25, 2006 - 06:15:29 PM »
I wouild need to do some math to figure it out But I would guess around .060 , you have to remove a lot less on a open chamber head as the area is much larger , Why do you want to go so small 

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Offline Oldschool

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Re: HEAD MILLING
« Reply #2 on: November 25, 2006 - 06:19:32 PM »
I wouild need to do some math to figure it out But I would guess around .060 , you have to remove a lot less on a open chamber head as the area is much larger , Why do you want to go so small 

 :iagree:   Be careful milling the heads.  It brings with it several new challenges for you.  Rocker arm geometry and intake alignment are only a couple........     :ylsuper:   :cooldancing: 
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Offline 170cuda

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Re: HEAD MILLING
« Reply #3 on: November 25, 2006 - 07:29:20 PM »
I did a compression check and have 120 psi of cylinder pressure. Would like to go higher without going to different pistons.

Offline oldkimmer

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Re: HEAD MILLING
« Reply #4 on: November 25, 2006 - 07:37:13 PM »
well then just offset grind the crank.060.........youll gain 1 comp point.........kim
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Offline 170cuda

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Re: HEAD MILLING
« Reply #5 on: November 25, 2006 - 07:58:18 PM »
Offset grind the crank?? I don't get it?

Offline Chryco Psycho

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Re: HEAD MILLING
« Reply #6 on: November 26, 2006 - 01:52:15 AM »
how far down the hole are the pistons now ?
 I really do not recommend miling the heads , it causes a Bunch of other issues to fix , intake fit , pushrod length pistons could be chaeper
 offset grinding the crank adds stroke but is also costly to alter everything needed

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Offline oldkimmer

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Re: HEAD MILLING
« Reply #7 on: November 26, 2006 - 08:34:04 AM »
If u offset gring the crank .060 u will gain usually .050-.055 depending if the crank was turned before or how much wear was on it to start with.they will also index all the throws to make the stroke the same for all cylinders (never assume it is). u will need .060 bearings.  one trick= more cubic inch+1point in compression.I have this done with every low comp engine. What this does is slow down the bearing speed ,which makes for less stress on the crank.I have done this trick with both forged+cast cranks and have never had a problem, even with brand x stuff. It moves the centerline out so it is recomended to rebalance the crank.U have to remember the stroke increase is x2 because it pulls the piston down+ also pushes it up that much farther.It costs usually twice there labor rate to offset grind because the is alot more involved in the setup time.............Contrary to what other people think balancing is the only other added expence , which should be done at any engine rebuild, whether it is for your daily driver or your racer..............older+wiserkimmer......................................Any questions?.....feel free to ask.........I dont claim to know everything, but I do know something.......Ofcourse, like anyone else my age I may have forgot something.........
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Offline bb71challenger

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Re: HEAD MILLING
« Reply #8 on: November 26, 2006 - 09:43:45 AM »
:iagree:   Be careful milling the heads.  It brings with it several new challenges for you.  Rocker arm geometry and intake alignment are only a couple........     :ylsuper:   :cooldancing: 

yup true there. I had my heads machined .050 and had to have the intake rails machined .062 to have the intake align properly. I guess you could shim the rocker arms but I just bought some aftermarket 1.6 ratio rockers.
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Offline 170cuda

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Re: HEAD MILLING
« Reply #9 on: November 26, 2006 - 04:35:34 PM »
Pistons are .022 in the hole and I use a mopar steel shim head gasket to get .042 quench. Rotating assembly is balanced and assembled. I use adjustable rockers so pushrods should'nt be a problem. If I get the heads milled they can do the intake side also. To me it makes sense to get the most out of this combination without changing the entire combo. If I deck the block I would have to go with a thicker head gasket so that makes no sense. I thought people do this all the time to get the most out of a performance engine am I wrong?

Offline Chryco Psycho

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Re: HEAD MILLING
« Reply #10 on: November 26, 2006 - 08:10:03 PM »
it can be done , I have just seen problem in the past , make sure your machinist is good
 I had a situation with a engine that costantly leaked water into the oil turned out the intake was not milled at the correct angle leaving a gap at the bottom of the coolant passages 

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