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Chasing dreams with a ball bat
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Discussion Starter #1
Guys,

I have 230cc Pro 1 alum. heads on my SBC. Currently have 64 cc chambers. How far could these be milled to raise compression? I don't know much about milling heads at all.

What else would be required to make it all work? Mill the intake? Shorter pushrods? Etc.?

If I could get to 60cc or under, that would make it worth it to me. Couple that with (maybe) a thinner head gasket, and I could have my compression without changing pistons.
 

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A .025 cut would get you at 60cc. These heads are alright with that amount. You will have to cut the intake. Sides and ends.

Why so much compression?
 

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Chasing dreams with a ball bat
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Discussion Starter #5 (Edited)
johnsongrass1 said:
230cc is a lot. What do you have now and what are you wantin?
When i built the motor (406 in a 68 camaro), I did not know about such calcs as DCR. So I got the pistons (reverse dome) that put me at 9.9:1 SCR.

With the cam I have (306/314 hyd. roller, 240/248 @ .050), more compression would make it run a good bit better.
 

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Chasing dreams with a ball bat
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545 Posts
Discussion Starter #6
71C10 said:
Here is a PDF with specs on the Dart 215 Pro 1:

http://www.dartheads.com/manager/uploads/Tech - 215 PRO1 SBC.pdf

The link to the 230 Pro 1 is not working at the moment.

I see they list .060" as the limit, which gets me to 58 cc.

I ran this through Engine Analyzer and it said only an increase of about 10HP to go from 9.9 to 10.5 :1

Does that sound about right? I thought it would be more than that. The overall averages were up by about 6 HP and 4 lb-ft or something - nothing earth shattering.
 

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Race it, Don't rice it!
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Calulators blow chunks becasue they assume everything in a perfect world. Since you are way down on compression anyway, eve a little would be substanial improvment.

Now for your real improvement, 230 cc heads with low compression and that long cam is bound to make a slug. Even with short gears.

I would change heads to 200cc for street use or 215 for race use and get the compression to min 12:1 with angle milling or use the 49cc head. If your street running, ditch the cam and keep the heads for now. You'll need less cam than usual for the head port size.
 

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The increase in compression will help the average power through out the power curve, enough for you to feel it was a good move. You can flat mill the heads until you run into the intake valve seat. Angle mill will allow much more.

Low port velocity should be the primary concern with the large intake port volume; the combination will run best above 4500 RPM.
 

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Chasing dreams with a ball bat
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545 Posts
Discussion Starter #9
johnsongrass1 said:
I would change heads to 200cc for street use or 215 for race use and get the compression to min 12:1 with angle milling or use the 49cc head. If your street running, ditch the cam and keep the heads for now. You'll need less cam than usual for the head port size.
Got too much in the heads to change them out. Just a street car. Crane recommends 10.5 - 12.0 SCR with the cam. If I put flat tops in it, I could get to 11.5, but would that be too much for pump gas?

Guess I could try Singh's grooves then and see what they would do. . . .
 
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