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It is an extensive list of data though he doesn't mension that on street or street and strip cars the 4V heads runners are too large to to be of use to the rodder. Nascar engines used the 2V heads because the flow characteristics were better suited to their needs (8-9000 RPM) than the 4V heads. The smaller heads actually increased the volumetric efficiency of the 351C unless you were going to run the RPM past 10000.
Paul
 

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On 2006-10-23 02:10, PaulS1950 wrote:
It is an extensive list of data though he doesn't mension that on street or street and strip cars the 4V heads runners are too large to to be of use to the rodder. Nascar engines used the 2V heads because the flow characteristics were better suited to their needs (8-9000 RPM) than the 4V heads. The smaller heads actually increased the volumetric efficiency of the 351C unless you were going to run the RPM past 10000.
Paul
That is the same BS crap the magazines have been saying for years and thousands of unknowing people have repeated on the internet. It just shows a total lack of understanding of a great engine.
 

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On 2006-10-23 02:10, PaulS1950 wrote:
It is an extensive list of data though he doesn't mension that on street or street and strip cars the 4V heads runners are too large to to be of use to the rodder. Nascar engines used the 2V heads because the flow characteristics were better suited to their needs (8-9000 RPM) than the 4V heads. The smaller heads actually increased the volumetric efficiency of the 351C unless you were going to run the RPM past 10000.
Paul
Just - wrong.
 

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Some technical errors on the 1970 vs 1971 351 "M" code (4bbl) engine....1970 was higher compression. 1971 had lower HP rating...
 

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Discussion Starter · #6 ·
On 2006-10-23 07:36, allenman85 wrote:
Some technical errors on the 1970 vs 1971 351 "M" code (4bbl) engine....1970 was higher compression. 1971 had lower HP rating...
I believe 1972 was the year compression ratios dropped and the lower 'net' horsepower ratings were adopted.
 

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Some bad info on the later 4v Valve sizing to !!
 

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Not really. A lot of, but not all, '73 4v heads had the smaller 2v valves in them.

And this...
" It is an extensive list of data though he doesn't mension that on street or street and strip cars the 4V heads runners are too large to to be of use to the rodder. Nascar engines used the 2V heads because the flow characteristics were better suited to their needs (8-9000 RPM) than the 4V heads. The smaller heads actually increased the volumetric efficiency of the 351C unless you were going to run the RPM past 10000. "

...is entirely wrong.
 

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On 2006-10-23 14:33, kid vishus wrote:
Not really. A lot of, but not all, '73 4v heads had the smaller 2v valves in them.

And this...
" It is an extensive list of data though he doesn't mension that on street or street and strip cars the 4V heads runners are too large to to be of use to the rodder. Nascar engines used the 2V heads because the flow characteristics were better suited to their needs (8-9000 RPM) than the 4V heads. The smaller heads actually increased the volumetric efficiency of the 351C unless you were going to run the RPM past 10000. "

...is entirely wrong.
I've owned at least a dozen sets and have never run across small valves in the 4v heads.
 

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Same here. I have 5 sets in the shed right now, and have never owned a pair with the smaller valves. The only place I ever run across them was at swap meets, but I have seen them with my own eyes.

<font size=-1>[ This Message was edited by: kid vishus on 10/24/06 6:01am ]</font>
 

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I have a single D3xxx open chamber 4V head that has the 2V sized valves. They exist.
I sometimes hear them called the CJ head.
A head porter told me that they have way more meat (due to the smaller diameter) in the valve throat and you can massage them to a more favorable short turn radius.....
 

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On 2006-10-23 02:10, PaulS1950 wrote:
on street or street and strip cars the 4V heads runners are too large to to be of use to the rodder.
I can't tell.
 

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On 2006-10-23 15:53, n2omike wrote:
It's excellent info. A worthwhile read for any Ford, especially 351C fan.
It definatly is Mike, I enjoyed it.

I knew alot, If not most of it, But I kept on reading.


Thanks

Wildo
 

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I have a set of these D3xxx heads, they are 4V castings with 2V valves in them, we call them CJ heads, I have heard them called dog heads. I took them off and put aussie 2V cc heads on.
 

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They who? It depends who you talk to.

There were several versions cast but the only ones known to be beefier are the Nascar Blocks and they have some bad core shift issues. These blocks carried the casting number XE192540
http://www.aus-ford-uk.co.uk/html/engines.html
 
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