01-02-2014, 06:09 PM | #1 |
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mill head
I have a stock Model B head, not a A head with a B on it.I would like to mill it to raise the compression on it. The stock B head is about 4.4 to 1.
Has anyone had there B head milled? If you have done this how much did you take off and do you know how much it raised the compression. Thanks, Gary |
01-02-2014, 07:36 PM | #2 |
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Re: mill head
I always thought a B head had a higher compression than an A head. Shaving a head does not raise it that much-unfortunately.
Mike
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01-02-2014, 08:47 PM | #3 |
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Re: mill head
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01-02-2014, 09:09 PM | #4 |
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Re: mill head
The model B head with the letter C is claimed to be only 4.6 compression ratio.It has the improved heart shaped combustion chamber.Check out the Piranio's dyno sheets.
htt://modelaparts.net/dynosheets.htm/dyr The dyno sheet shows that the C head on the stock model A engine gives 6.77 horsepower increase or 46.77 horsepower at 2200 rpm. The C head is thin and I would be cautious about shaving off very much. IF you had an F3 head that also uses the 3 bolt water pump you could shave more because it is a heavier casting but uses the same improved heart shaped combustion chamber. The C and F3 heads are the poor mans high compression head. I have run them in the past and can feel the improvement. The model B had 50 horsepower. The head gave 6.77 of the increase. The B grind cam,B carb , manifold and improved ports gave 3.3 horsepower increase for a 10 horsepower increase over the model A engine |
01-02-2014, 09:56 PM | #5 |
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Re: mill head
My personal experience with C heads and B cams agrees with the Piranios dyno tests. I have used NOS and good used B cams. I feel that the B cam is highly over rated. Without the use of a higher compression head, no increase can be felt with the B cam alone. If a B cam is used in conjunction with a higher comression head, such as the 4.6 C head and B carb and manifold, you will gain a few hundred RPM and a little top speed but it won't be felt in the seat of the pants. The increased compression and improved combustion chamber gives the power that a person can feel. This isn't theory or hear say but hands on experience over a lifetime. Everybody is intitled to their own opinion. This is my personal experience.
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01-03-2014, 02:32 PM | #6 |
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Re: mill head
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01-03-2014, 04:50 PM | #7 | |
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Re: mill head
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01-03-2014, 04:54 PM | #8 |
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Re: mill head
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01-03-2014, 08:14 PM | #9 | |
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Re: mill head
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01-04-2014, 01:01 PM | #10 |
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Re: mill head
I wanted to raise it to 5.5 to6.1. But from what every one is saying I am not able to mill any off. I will just have it decked and leave it at that. Gary
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01-04-2014, 01:56 PM | #11 |
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Re: mill head
The C head is said to be 4.6 and the A head is 4.22. the C head is almost a half compression point over the A head. The shape of the chamber has as much or more effect as the .4 increase in compression. The C head can be milled some but is a very thin casting and will be weakened. If you look at the valve side of the combustion chamber you will notice the area is dished way more than the stock A head. This was Fords attempt to reduce shrouding of the valves. If very much is shaved you will lose clamping area on the head gasket on the valve side and part of the gasket will be exposed to fire in the combustion area, not a good thing!!! Milling away the counter bore may raise the compression ratio to around five to one (just a guess) but would probably cause more problems . I have had C heads milled slightly but would leave a depth of at least .030 in the counterbore. The C head was the poor mans high compression head, it will give a slight increase in hill climbing and driveability power but not as much as a Snyder 5.5. I'm quite sure that there are others on this forum that have used the C head and noticed the boost and used it for that reason. People that have never run a C head on an A engine will give opinion. Opinion without actual experience isn't worth much.
Last edited by Purdy Swoft; 01-04-2014 at 07:12 PM. Reason: added inforeworded a sentence |
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