Just about was,what I expected.
#920 vs. #675 Heads "Compression vs. Cylinder Flow"
- Thread starter 69 Cuda 440
- Start date
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Just about right 'A-Body-Man' with keeping it at 5000 RPM's between shifts.
We expected 15.80's.
Probably could have taken it up a notch to 5400 RPM's between shifts, but the
owner was reluctant to push it, especially with the 'Inland Shifter'.
64 SRT8 Dart
Well-Known Member
675 Heads Results??
lilredridinghoo
Well-Known Member
any news on this project...would really be interessted in the results (as i also do have to choose which one of the headcastings would be the better choice, got both laying in my garage - a pair of ported and polished #675 and a pair of untouched #920)
cudavert
DARTAHOLIC
That's really cool!!! So I guess it's safe to say, those earlier heads are worth a tenth in the quarter! I've always thought "compression is your friend" too. Thanks for that, 69cuda440!
Cudavert,
Thanks for the compliment.
Numbers
The #920 Cylinder Head gives you about .35 more compression than the #675 Cylinder Head,
when calculating 57.3 CC's - to - 60.6 CC's.
Probably about 5 more Horsepower. Track numbers result was -.09 Elapsed Time and +.63 MPH
better performance with the #920 Cylinder Heads.
Though, I agree that the #675 has a little better cylinder-flow which closes the gap difference a bit.
Since the 'stock' 273 Commando Camshaft {.425" Lift ~ 248* Duration ~ 26* Overlap} was used,
there is no real issue with valve-shrouding in the #920 small combustion chamber.
Thanks for the compliment.
Numbers
The #920 Cylinder Head gives you about .35 more compression than the #675 Cylinder Head,
when calculating 57.3 CC's - to - 60.6 CC's.
Probably about 5 more Horsepower. Track numbers result was -.09 Elapsed Time and +.63 MPH
better performance with the #920 Cylinder Heads.
Though, I agree that the #675 has a little better cylinder-flow which closes the gap difference a bit.
Since the 'stock' 273 Commando Camshaft {.425" Lift ~ 248* Duration ~ 26* Overlap} was used,
there is no real issue with valve-shrouding in the #920 small combustion chamber.
fishy68
Tyr Fryr's Inc.
Nice job 69Cuda440! Great to see someone take time to post the results of a test like this
X2 !.^^^
lilredridinghoo
Well-Known Member
thanks 69cuda440 ... so i guess i would go with my already done #675 instead of putting money in the #920
General Overview,
The #920 Cylinder Head gives you about 2% more Power {5 Horsepower} over the
#675 Cylinder Head.
When using the 'Stock Engine Components', and relative minimum Factory CC Specifications
for each Cylinder Head {#920 = 57.3 CC.s} and {#675 = 60.6 CC's}.
With the 'stock' Commando Camshaft {.425" Lift ~ 248* Duration ~ 26* Overlap},
shrouding of the Valves is not an issue in the #920 Head.
Compression defeats Flow
#920 Cylinder Head 'Compression'... {+ .35 Higher Compression} = 2% Power Gain = 5 Horsepower
#675 Cylinder Head 'Flow'...............{+ 4%}
----------------------------------------------------------------------------------------------
Next Test,
To take the #675 Cylinder Heads and mill them an additional .021" to bring the CC Level
down to 57.3 CC's {Equal to the #920 Heads}.
Then test the 273 with the #675 Heads, with an 'equal' Compression-Ratio to the #920 Heads.
The #920 Cylinder Head gives you about 2% more Power {5 Horsepower} over the
#675 Cylinder Head.
When using the 'Stock Engine Components', and relative minimum Factory CC Specifications
for each Cylinder Head {#920 = 57.3 CC.s} and {#675 = 60.6 CC's}.
With the 'stock' Commando Camshaft {.425" Lift ~ 248* Duration ~ 26* Overlap},
shrouding of the Valves is not an issue in the #920 Head.
Compression defeats Flow
#920 Cylinder Head 'Compression'... {+ .35 Higher Compression} = 2% Power Gain = 5 Horsepower
#675 Cylinder Head 'Flow'...............{+ 4%}
----------------------------------------------------------------------------------------------
Next Test,
To take the #675 Cylinder Heads and mill them an additional .021" to bring the CC Level
down to 57.3 CC's {Equal to the #920 Heads}.
Then test the 273 with the #675 Heads, with an 'equal' Compression-Ratio to the #920 Heads.
This is probably pretty much on par with the 318 302 vs standard open chambers no really performance difference for the time and money. I don't know how many people on this site been talked into a $500- $1000 swap with no real benefits. Or been discouraged into doing nothing.
yellow rose
Overnight Sensation
I'm a Clit Commando !!! 
MOPAROFFICIAL
Oogliboogli
FWIW every 675 head I have cc'd has been right at about 68 cc's. You had to mill the Piss out of them to get 60cc's. The last 920 heads I did cc'd 66.4.
Im somewhat of a clitsmith myself.I'm a Clit Commando !!!
yellow rose
Overnight Sensation
Evidently, most have missed the cut of the jib.
Be care though. Next thing you know, a month from now, you'll get hammered on and called a woman hater.
Be care though. Next thing you know, a month from now, you'll get hammered on and called a woman hater.
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