7120 head volume?

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7120 head volume?

Postby ftpiercecracker1 » November 7th, 2012, 2:07 pm

I have read the FAQ question on cylinder heads, but it didnt contain the info i needed.

I did find this viewtopic.php?f=15&t=2773 after doing a google search, but i just wanted to start a fresh thread to make sure his figures were acurate.

What is the CC volume of a stock 7120 head? Stock valves, never been decked, no head work, period.
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Re: 7120 head volume?

Postby 604rail_king » November 7th, 2012, 4:59 pm

i never cc'd my untouched 7120 head prior to rebuilding as i did not have the tools/syringe to measure things, but im sure you've found that most stock 4.0 heads are typically 57-58cc (+- .5). i polished my combustion chambers but i did installed the magnum ss I/E valves, and with machining only a few thou, it yielded 61-62cc.

i believe it was mentioned the magnum valves will ADD 2-3 cc as they are undercut. polishing out the orange peel pours in the cc will also add 1-2cc.

from the FAQ's
For every .010 you shave, you lose 1.4cc's from the chambers.
Or for every .007 you shave off the head, you reduce the chamber volume by 1cc.


from all that info, it would for the most part confirm that my 7120 head started at 57-58cc roughly.


what are you trying to figure out above & beyond the info we already know about 4.0 heads ?
Last edited by 604rail_king on November 7th, 2012, 5:48 pm, edited 1 time in total.
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Re: 7120 head volume?

Postby ftpiercecracker1 » November 7th, 2012, 5:30 pm

My machinist just wants to know the volume of the head i will be using as he is not as familar with the 4.0 strokers as he is with everything else

calculating compression ratio in such, determining everything before the machine work
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Re: 7120 head volume?

Postby SilverXJ » November 7th, 2012, 5:55 pm

604rail_king wrote:installed the magnum ss I/E valves,
Which exhaust valve did you go with?
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Re: 7120 head volume?

Postby 604rail_king » November 7th, 2012, 6:40 pm

2.02/1.62 valves

head is fully assembled and just sitting on my work bench

http://www.ebay.com/itm/MOPAR-MAGNUM-2- ... 5aeb1c9767
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Re: 7120 head volume?

Postby Cheromaniac » November 7th, 2012, 11:52 pm

ftpiercecracker1 wrote:What is the CC volume of a stock 7120 head? Stock valves, never been decked, no head work, period.


Two 7120 heads that I've cc'd came out at 56.5cc and 57.0cc respectively.
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Re: 7120 head volume?

Postby racing89 » November 8th, 2012, 3:30 am

604rail_king wrote:i never cc'd my untouched 7120 head prior to rebuilding as i did not have the tools/syringe to measure things, but im sure you've found that most stock 4.0 heads are typically 57-58cc (+- .5). i polished my combustion chambers but i did installed the magnum ss I/E valves, and with machining only a few thou, it yielded 61-62cc.

i believe it was mentioned the magnum valves will ADD 2-3 cc as they are undercut. polishing out the orange peel pours in the cc will also add 1-2cc.
50ish cc on mine with the same mopar valves and .110 of the head ( because of the combustion chamber shape, the "standard "formula is only good to about .060 removal ?)
from the FAQ's
For every .010 you shave, you lose 1.4cc's from the chambers.
Or for every .007 you shave off the head, you reduce the chamber volume by 1cc.


from all that info, it would for the most part confirm that my 7120 head started at 57-58cc roughly.


what are you trying to figure out above & beyond the info we already know about 4.0 heads ?
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Re: 7120 head volume?

Postby ftpiercecracker1 » November 8th, 2012, 4:36 pm

Cheromaniac wrote:Two 7120 heads that I've cc'd came out at 56.5cc and 57.0cc respectively.




Thanks cheromaniac, thats what i needed. :cheers:
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Re: 7120 head volume?

Postby Muad'Dib » November 9th, 2012, 9:42 am

Our Stroker Calculator uses a default value of 58cc's.. which is consistent with what Cheromaniac stated.
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Re: 7120 head volume?

Postby Diesel_dog » November 12th, 2012, 6:27 pm

The stock cylinder head is cast iron and weighs 60lb. The valve head diameter is 1.91"
intake/1.50" exhaust. Casting numbers are as follows:
Year............Casting No
1987-90......2686
1991-95......7120
1996-99......0630
2000-01......0331
Cylinder head flow figures (cfm) at 28inH2O pressure drop are:
Non-HO head #2686 (Courtesy of Greg Friedman)
Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 122.0 168.0 186.0 189.0 192.0
Exhaust flow....88.0 114.0 130.0 134.0 138.0
Ported non-HO head #2686
Valve lift (in)..... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 124.0 183.0 197.0 207.0 216.0
Exhaust flow....87.0 113.0 138.0 153.0 159.0
HO head #7120 & #0630 (Courtesy of John Brown)
Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 66.0 128.0 179.0 206.0 209.0 209.0
Exhaust flow. 55.0 100.0 120.0 136.0 141.0 141.2
HO head #0331
Valve lift (in)..... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow..... 59.4 122.6 171.1 201.1 214.3 218.4
Exhaust flow...47.1 93.4 123.3 140.9 147.0 149.7
Ported big valve 2.02/1.60 HO head
Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5
Intake flow.... 73.9 142.4 197.8 229.8 247.0
Exhaust flow. 65.3 114.0 135.9 146.3 157.1
The early '87-'90 non-HO heads have low intake ports that flow rather poorly. The later HO


this is what i have found
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