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Discussion Starter #1
Hello,

I used the method described on the DIY porting website, including the same syringe and the graduation sheet provided on the site, to measure the chambers on a rebuilt GT-40p head. The head has been milled an unknown amount, but only enough to assure a true surface according to the shop I got them from.

I'm getting 56-57 cc per chamber. Factory specs indicate a 59 cc chamber (I've also heard 60-61 cc as well). Given the milling and variation in the factory casting, does this sound reasonable. Or is my measuring method suspect. Anybody else use the tools described on the DIY Porting website?

Thanks a bunch.
 

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I use a 250CC graduated cylinder with valve. This way I only have to subtract the last reading from the first reading to get my measurement. Filling and refilling a syringe opens you up for more errors in the process. Having 2-3 CCs under the factory number with a milled head sounds about right. If you are consistant in your process then you should get the same measurement on the same chamber if you do it several times. Doing that will give you an indication of your accuracy.
How close are you trying to get the chambers?
 

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Discussion Starter #3
Thanks for the response PaulS1950. I did re-check 3 of the 4 chambers on the one head I've had time to measure thus far, and the measurements were pretty consistent. I was just a little surprised that the chambers were running 2-3 ccs under the factory spec since I assumed the amount of milling would have been minimal.

You're right about the method having some error potential, I think I may get a graduated cylinder and use this as an additional measure. I know an actual buret cc kit would be better, but its out of my current budget.

I'm just trying to nail down the compression pretty close to guide my decision making on any additional milling (thinking no at this point) or a thinner head gasket. Goal compression is around 9:3:1.
 

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Generally a truing cut is .005" which is around 1-2 cc's per chamber, so your measurements sound accurate to me.
 

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Generally a truing cut is .005" which is around 1-2 cc's per chamber, so your measurements sound accurate to me.
I have a set of GT40 heads from a '94 Lightning with the 64cc chambers. I had them milled .030, so does that mean the chambers are now 58cc or less?

That just seems like a lot. Does anyone know what the final CCs would be from taking .030 off a 64cc GT40 head?

Thanks
 

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I have a set of GT40 heads from a '94 Lightning with the 64cc chambers. I had them milled .030, so does that mean the chambers are now 58cc or less?

That just seems like a lot. Does anyone know what the final CCs would be from taking .030 off a 64cc GT40 head?

Thanks
How do you know your heads actually had 64 cc chambers?
 

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I have a set of GT40 heads from a '94 Lightning with the 64cc chambers. I had them milled .030, so does that mean the chambers are now 58cc or less?

That just seems like a lot. Does anyone know what the final CCs would be from taking .030 off a 64cc GT40 head?

Thanks
Generally speaking for ford small block heads, you can use .005 to .006 per cc or in your case about 5 ccs were removed
 
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