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max mill on a slant six head.
https://mail.slantsix.org/forum/viewtopic.php?t=52153		 Page 1 of 3
Author:  USAJon [ Wed May 22, 2013 8:38 am ]
Post subject:  max mill on a slant six head.
wondering what the max amount u call mill a 1987 truck slant six head.

can it be saftley mill'd more then .125?

I do not want to diseebley the block and hve the deck mill'd if I can just do the head...

a project...high comp project. :wink:
Author:  Reed [ Wed May 22, 2013 8:41 am ]
Post subject: 
You can mill just the head, but there is sufficient variation in the stock castings to make it impossible to have a generic maximum amount that can be removed. You will have to remove the head and measure the combustion chambers before you can determine how much can safely be removed from the head.
Author:  sandy in BC [ Wed May 22, 2013 10:02 am ]
Post subject: 
If you are not going to disassemble the block it wont have much potential to be a sucessful high compression project.

Do you know how to CC the head before you start?

Are you installing larger valves?

Will they clear the deck after this big mill? Will they be shrouded? Can you notch the bore with the pistons still installed?


There are good reasons to mill the deck when increasing the CR a large amount.
Author:  USAJon [ Wed May 22, 2013 10:08 am ]
Post subject: 
yes OK

been here b4 with other then slant six heads

OK
wondering how much has anyone ever milled a head, period.
Author:  Reed [ Wed May 22, 2013 10:22 am ]
Post subject: 
I milled an early 70s head a full .11 inches. Ran fine but pinged like crazy on premium. I know the cam regrind shop didn't give me the cam profile I wanted, so I know my dynamic compression ratio calculations were off on the motor I put this head on. This head is currently in my garage awaiting use on another project once I get to the point of calculating the dynamic compression ratio in said project.
Author:  USAJon [ Wed May 22, 2013 10:28 am ]
Post subject: 
Quote:
I milled an early 70s head a full .11 inches. Ran fine but pinged like crazy on premium. I know the cam regrind shop didn't give me the cam profile I wanted, so I know my dynamic compression ratio calculations were off on the motor I put this head on. This head is currently in my garage awaiting use on another project once I get to the point of calculating the dynamic compression ratio in said project.
was this a stock motor pistons ..
what was the real comp on this motor removing .11
Author:  Reed [ Wed May 22, 2013 2:43 pm ]
Post subject: 
The motor had been overbored .060, but the pistons were otherwise stock flat top pistons. I cannot say what the true static or dynamic compression ratio was since the cam was not ground to the specs I gave the cam grinder. I was shooting for mid to high 8:1 compression so the motor could still run pump gas, but I cannot say what the compression ended up being due to the unknown cam profile.

I have since swapped heads and cams on this motor, so I can't give you any more info. Sorry.
Author:  DusterIdiot [ Wed May 22, 2013 3:29 pm ]
Post subject:  About..
On late heads I wouldn't pass the .125 mark since they don't have as much variation as the drool tube heads, they vary at most between 52-54 CC...my last head went .125 and we started into widening the coolant passages as we cut that much off, also the cut started into the shelf of the chamber and there was no longer the round bore, so the .0066=1cc no longer applied and the volume went down pretty quick.

I know that THOR had milled an early head for .180, and got the community college teacher a little upset since it took so long and left a large mess on the floor...but I don't think it amounted to much being an early head maybe 40cc chambers.

Sandy is correct if you are going larger valves, you'd have to unshroud them and stock bore is not going to work well for breathing...also if the block has stock rings in it and some miles you'll run the risk of losing them quickly past 9:1....you will also need to mock up your valves and cam if you decide to go with bigger than stock as the valve heads may collide with the piston at higher lifts... I also know that due to the piston design, typical deck height, valve insertion into the bore at a .52 lift, you get limited by the geometry and the need for custom pistons is necessary if intending to get into the upper 12's-low 13's compression wise...the old timers running that high used to use Jahns domed pistons to make it happen.


-D.Idiot
Author:  USAJon [ Wed May 22, 2013 4:58 pm ]
Post subject: 
have a local speed/machine shop quoted $150 to mill .125 stripped head.

said same price to deck block.
Author:  Rick Covalt [ Thu May 23, 2013 2:00 pm ]
Post subject: 
My engine guy just did mine for $80 in February.

Rick
Author:  NCDemon1971 [ Thu May 23, 2013 3:43 pm ]
Post subject: 
Quote:
My engine guy just did mine for $80 in February.

Rick
How much cut was that ???
Author:  Rick Covalt [ Thu May 23, 2013 5:54 pm ]
Post subject: 
Had one cut .080 and another .025. Both the same price
Author:  slantzilla [ Thu May 23, 2013 7:33 pm ]
Post subject: 
I paid $100 to have mine cut .066". It was a complete assembled head.
Author:  USAJon [ Fri May 24, 2013 8:01 am ]
Post subject: 
Burtonsville machine is theshop that quoted me $150
there 17 miles from me.
I would rather travel to a rural area even if the price is the same. Mary and I like to country side....may see an old slant six or two for sale...
Author:  slantzilla [ Fri May 24, 2013 8:45 am ]
Post subject: 
Honestly, $150 isn't too bad for a .125" mill. That's a lot of passes with the cutter. :D
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