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| head milling ? https://www.slantsix.org/forum/viewtopic.php?t=39613 |
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| Author: | mp67dart [ Sun Mar 28, 2010 8:25 pm ] |
| Post subject: | head milling ? |
I have begun a super 6 swap on my 70 dart with a stock 198 with 46k original miles. The exhaust manifold had a broken off bolt in the back next to the fire wall.So instead of tring to drill it out I pulled a head off of a 225 I have and carried it to the machine shop to be cleaned and checked. Should I go ahead and get the head milled and if so how much. |
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| Author: | Reed [ Sun Mar 28, 2010 8:37 pm ] |
| Post subject: | |
Wow, you are really opening up a can of worms here.  Milling is a good idea, IF you take the time to do the right measurements and the math to calculate how much to remove. If you don't know how to calculate dynamic compression ratio, then I would suggest you have the machine shop take off just enough to clean up any warping of the head. Otherwise, leave it alone.
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| Author: | 66aCUDA [ Sun Mar 28, 2010 9:12 pm ] |
| Post subject: | |
I disagree with Reed. The stock head gasket WAS .020 the replacement Felpro is .042 so you need to mill.022 just to get back to stock. Then if you want to increase your ratio to a REAL 9 to 1 (which is still mild) then you need to mill off more. I do agree you need to know how far down the hole your pistons are and what cc your chambers are. So you still need to measure. JMHO, Frank |
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| Author: | mp67dart [ Sun Mar 28, 2010 9:23 pm ] |
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The motor has never been rebuilt.I have seen on here a lot of people milling there heads .090. Just didn't know if this would be to much for a stock motor. |
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| Author: | 66aCUDA [ Sun Mar 28, 2010 9:30 pm ] |
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The short answer is maybe ok, maybe not. You can get away with it on most engines and still use the factory push rods. Most of the tolerances were on the big side. I would be willing to take the gamble you could go .080 and use a NOS head gasket if you need less then go with the Felpro. Frank |
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| Author: | Reed [ Sun Mar 28, 2010 9:47 pm ] |
| Post subject: | |
True, I forgot about the gasket thickness. You would be safe milling at least .022 then. |
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| Author: | dakight [ Mon Mar 29, 2010 5:39 am ] |
| Post subject: | |
The truth of the matter is that if you don't do the measurments then you don't know what you'll end up with. I had my head milled .075 to get the combustion chambers to 49-50 CC. Then I took another . 100 off the block to get my calculated compression ratio to 10.3:1. Your best bet is to measure the deck relief, mine was .186, then get the head CCd and see where you are. Then you can use an engine calculator to determine how much to mill to get where you want to be. Can you safely mill .090? Probably, but when you're done you will have raised the compression but you'll have no idea by how much. |
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| Author: | mp67dart [ Mon Mar 29, 2010 5:57 am ] |
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Thanks, I don't know how to determane compression or any of the other stuff. I wanted to add sum pep will I was replacing cylinder head .I have only done minor motor repairs before. And have always payed sumone to build my motors. |
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| Author: | Charrlie_S [ Mon Mar 29, 2010 6:23 am ] |
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Quote: Thanks, I don't know how to determane compression or any of the other stuff.
It is not rocket science. I would suggest you do a little reading and learn how to do this. Quote: I wanted to add sum pep will I was replacing cylinder head .I have only done minor motor repairs before. And have always payed sumone to build my motors.
Your goal is a good one, but by doing this yourself, you will be able to save money.If you don't want to bother checking the measurements, you will not get the best results. In that case I would recommend milling about .060 off the head, and use a aftermarket head gasket. That will give you a little more compression, and still be safe (unless of course, the head was milled in a past life). |
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| Author: | mp67dart [ Sat Apr 03, 2010 4:36 pm ] |
| Post subject: | haed milling |
Well I went be the machine shop yesterday and spoke to the machinist and decided on milling the head .060 for now. The machinist said it appeared the head has never been milled and would need harden exhaust seats installed. Now all I can do is wait until there ready. |
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| Author: | Aggressive Ted [ Sat Apr 03, 2010 4:49 pm ] |
| Post subject: | Compression ratio the easy way |
Is he installing new valve guides? and cleaning up the valves by doing a valve grind? Have him pocket port under valves since he is putting in the seats. It will only take a few minutes and is well worth it since he will already have the the set up. Before you put the head back on have him cc a few of the chambers and save that number. When the piston is at TDC, measure how far the piston is down in the cylinder. Then you will have the info you need to get your compression ratio. It is easy once you get those two numbers and the brand head gasket. Give us the numbers and we can tell you the compression ratio. 
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| Author: | mp67dart [ Sat Apr 03, 2010 7:17 pm ] |
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Thanks for the info I will find out and be sure to have it done. And for sure have the heads cc. |
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