Milling the heads on SBC 30k - Team Camaro Tech
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post #1 of 9 (permalink) Old Jun 16th, 14, 09:30 AM Thread Starter
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Milling the heads on SBC 30k

I am just curious, but I have heard from a motor builder that by milling heads on a SBC by 30k, does that increase the compression? If so, by how much on a stock motor?
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post #2 of 9 (permalink) Old Jun 16th, 14, 09:37 AM
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Re: Milling the heads on SBC 30k

Don't know how much but if you take off too much then your intake will not line up and then it'll need to be milled. You need to cc the chamber and calculate what head gasket is needed to arrive at the compression you want. Then mill the amount of head surface. But as I said you could run into an intake matching problem.

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post #3 of 9 (permalink) Old Jun 16th, 14, 10:22 AM
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Re: Milling the heads on SBC 30k

Yes it will raise compression but:

In addition to mucking up how the intake mounts, milling the heads that much may put the valves too close to the piston and might require changes to the valve train, i.e., you might need a shorter push rod...

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post #4 of 9 (permalink) Old Jun 16th, 14, 11:27 AM
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Re: Milling the heads on SBC 30k

It's easier to buy new pistons than milling and screwing up the alignment with the intake, that's what I did.
Or you can use the thinest head gasket if your not already there.

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post #5 of 9 (permalink) Old Jun 16th, 14, 12:28 PM
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Re: Milling the heads on SBC 30k

Well Ty here's the deal.030 is the absolute max that you can remove without having a bolt up problem per say because sometimes you do at .030. I believe the formula is every.00 6 thousands you remove 1 cc of combustion chamber . You can angle mill and do more but there is also a lot more to it and is more expensive. the thing is what are you trying to achieve? Sometimes your better off buying a new set of heads . The Summit heads #152123 are in reality Dart s/s heads with their name on them . They are a real nice well made H/D fuely replacement head . They flow better than any G/M factory head except for the vortecs and are a great head for a street motor up to 406 cubes and work well clear to 55/5800 rpm. they make good torque and give excellent throttle response with the right cam for the engine being built. Alex
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post #6 of 9 (permalink) Old Jun 16th, 14, 03:23 PM
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Re: Milling the heads on SBC 30k

Like the guys above... once u get over around 20 thou u start running into trouble aligning heads / valley covers, stress and oil seepage leaks.
Generally one skims heads (and decks) a couple thou, just enough to get matched surfaces.

So best to get the chamber sized head that will give u the compression , dynamic compression ration for the rpm range u are looking at to work in and the octane of the fuel u intend to use.

And keep in mind, when u bore that also increases the compression ratio....

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post #7 of 9 (permalink) Old Jun 16th, 14, 05:28 PM
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Re: Milling the heads on SBC 30k

if it was back in the day, I would say go for it as I did, but not today with all the parts that are available
in the early 70s I took a 327 and added 12:5:1 pistons cut the heads .040 AND HAD THE INTAKE CUT TO MATCH.
started that rascal up and it ran great for about 5 minutes. it developed a mis. pulled the wires found the mis. the plug was not gapped. started it again, another 5 minutes or so the same thing.
we finally used a .010 index washer to solve the problem
there was no problem with the push rods, rockers or any valve geometry
we ran that engine on the dirt track for 2 years with out a problem
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post #8 of 9 (permalink) Old Jun 17th, 14, 12:05 PM
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Re: Milling the heads on SBC 30k

If you're going to mill the heads a bunch, you also need to mill the sides and front and rear of the intake manifold in order to maintain bolt and hole alignment; see chart below.

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post #9 of 9 (permalink) Old Jun 17th, 14, 01:08 PM
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Re: Milling the heads on SBC 30k

I milled my heads .010 on my 350. And i ran a.thin head gasket just to.raise the cr a bit more. From what I remember a .010 cut will raise your cr about a 1/4 point. No manifold.alignment issues.
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