920 vs. 302 Heads

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Confusedcuda

Confusedcuda

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Does anybody know what the flow numbers are on the 67 920 heads and the 302 heads. Runner difference, Combustion Chamber volume etc. Thanks
 
I don't think I have ever seen them flowed. The chambers are all similar as advertised and the ports are as well. I have read that the 302's flow slightly better than the 920's but I haven't seen any flow numbers. The 302's do have hardened valve seats which is a plus. There's also emission ports that have to be plugged.
 
Splittin hairs. Pick one and go. I'd go with the 302 since it is a much more modern head.
 
copied from shadydells website...302 flow numbers!
LIFT-------AS CAST------PORTED

.100”-----51.8/N/A--------71.8/N/A
.200”-----92.5/70.7--------148.4/86.3
.300”-----130.1/104.3-----212.2/113.9
.400”-----163.9/113.2-----241.5/131.1
.450”-----169.1/115.2-----244.6/137.7
.500”-----170.4/117.3-----246.7/139.7
.550”-----172.2/119.0-----242.6/144.9
.600”-----172.5/120.4-----240.8/144.9

All #’s at 28” of water
No flow tube on exhaust
As cast #’s are 1.78”/1.50” valves, Ported is with 2.02”/1.60” Ferrea 5000 Series, No Back Cut.
Ported Intake Runner Volume is 151 CC’s
 
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302's gotta better combustion chamber design. set up right with right pistons can make lil better power and do it with less timing! high velocity ports will breath more efficiently aswell! thay respond well to porting, to an extent!
 
dirty white boy said:
copied from shadydells website...
LIFT-------AS CAST------PORTED

.100”-----51.8/N/A--------71.8/N/A
.200”-----92.5/70.7--------148.4/86.3
.300”-----130.1/104.3-----212.2/113.9
.400”-----163.9/113.2-----241.5/131.1
.450”-----169.1/115.2-----244.6/137.7
.500”-----170.4/117.3-----246.7/139.7
.550”-----172.2/119.0-----242.6/144.9
.600”-----172.5/120.4-----240.8/144.9

All #’s at 28” of water
No flow tube on exhaust
As cast #’s are 1.78”/1.50” valves, Ported is with 2.02”/1.60” Ferrea 5000 Series, No Back Cut.
Ported Intake Runner Volume is 151 CC’s
Click to expand...

But which casting is that? I assume the 302?
 
There ya go. Thanks DWB. I was hoping someone would pop in with some numbers. Now if we can dig up some 920 numbers. It would be interesting to find out how different (or not) the 2 are.
 
in the small block book larry says the 302s the best factory head for a 318 all way around! no sense wasting time or money on 920s if you got 302s!
 
Here's a comparison between the #675's and the #920's from 69 cuda 440

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.
 
dirty white boy said:
copied from shadydells website...302 flow numbers!
LIFT-------AS CAST------PORTED

.100”-----51.8/N/A--------71.8/N/A
.200”-----92.5/70.7--------148.4/86.3
.300”-----130.1/104.3-----212.2/113.9
.400”-----163.9/113.2-----241.5/131.1
.450”-----169.1/115.2-----244.6/137.7
.500”-----170.4/117.3-----246.7/139.7
.550”-----172.2/119.0-----242.6/144.9
.600”-----172.5/120.4-----240.8/144.9

All #’s at 28” of water
No flow tube on exhaust
As cast #’s are 1.78”/1.50” valves, Ported is with 2.02”/1.60” Ferrea 5000 Series, No Back Cut.
Ported Intake Runner Volume is 151 CC’s
Click to expand...
And factory 2.02 360 had is 155 cc.. while factory 1.88 is 160cc. Yes, the factory 2.02 tulip valve eats that much bowl volume...

The flow is better with a 675 open chamber fwiw.
Of the 2. I like the 920, it's a heavier casting than the 302. I have the 302 on the shelf and the chamber of early is the swirly.lol
I get 215 cfm with a 1.78 in a 675, I did a set of 920 with 1.88 and had them at 228cfm by .500 with a mild approach.
Really the difference between the 2 is marginal
 
MOPAROFFICIAL said:
Really the difference between the 2 is marginal
Click to expand...
BAMM BABY!

That’s really it right there. If your racing for the money.... do what needs to be done.

If your in the street, you’ll never see, feel or know the difference. Actually, you would be really hard pressed to see it at the track.

On Ryan J’s numbers, those work very well for a 318. There about equal (wiggle room fellas!) to a fresh bowl ported 360 head that has less velocity. This making the 318 head better for performance useage.

This can be seen from the publications from MoPar.
They had in there old catalog a loaded ported 318 where they claimed a 55hp advantage over a 360 head.

They sold them like hot cakes.
 
Good info guys. Please help me with those flow numbers tho! What do those numbers mean or represent? Obviously lift is the amount the valve is opened but what is the 2 sets of numbers intake/exhaust? And what does the number represent? How much water will flow thru in a given amount of time? Thanks sorry for stupid questions I'm still learning the performance side of things
 
Do a search on 920 heads. A "class" racer posted flow numbers and stock 920's flow better all around than stock 302's. Both are closed chambers. Remember, the chamber volumes you are quoting require milling the head approximately .040. After porting, all bets are off.
 
dartfreak75 said:
Good info guys. Please help me with those flow numbers tho! What do those numbers mean or represent? Obviously lift is the amount the valve is opened but what is the 2 sets of numbers intake/exhaust? And what does the number represent? How much water will flow thru in a given amount of time? Thanks sorry for stupid questions I'm still learning the performance side of things
Click to expand...

Sit back, this is a long winded AJ type of answer.....

It is pretty self explanatory.


Lift is the valve rise and should be measured at the valve tip.
Next is as cast. That is the head as it is made and delivered to you.
Ported is after the ports are reshaped for the search of more power.
The first number on the left the amount of air that flows down the port, past the valve in cubic feet per minute. AKA - cfm on the intake valve. The second column is the exhaust valve.

The ported side shows how the air flow has (hopefully) improved after the porting work was done.

Now, how does this help?
It helps show you how the port was improved by way of the increased amount of cfm. Increasing the cfm allows the engine to breath deeper at the same valve lifts prior to porting.

How can this be useful?

Basically, at a layman’s level of interpreting, one can use a simple math equation of cfm X 2 = potential HP. The equation is over simplified but accurate enough for beginners to grasp and get a reasonable estimate of the possible power out come. Of course, this power potential is if you only try to reach it with a worthy build. You can exceed the power level with more extreme builds parts.

The list also can show the balance in percentage of intake to exhaust flow. Professional porters and racers look for a percentage between the intake and exhaust flow. The wider the percentage the more the builder looks to a split duration camshaft to help the exhaust to get out of the engine for a better intake air and fuel charge.

If the percentage is closer to each other, a single pattern cam might be chosen.
If there very close, sometimes a split pattern cam is chosen with the intake haveing more duration than the exhaust.

Also note below, the ported heads intake flow slightly dips. This can be seen or it is known as the port is stalling. The air finds resistance in the higher lift range. The flow chart below shows a very minor amount. Other heads outright crash. If the cfm flow crashes, lifting the valve to that point becomes pointless. On the head flow chart below, it is not pointless because the flow rate is still very good. Lifting the valve that much would still produce more power. Also remember the valve see max lift one but all other lifts twice.


What doesn’t it show?

Important information is missing. Racers and head porters can make anywhere from a pretty accurate guess to out right knowing “How many cc’s the ports are” and also, “The amount of velocity the air is moving at” which is important.

A smaller port vs a larger port with the same cfm rating will have two different velocity’s down the port past the valve. The experienced & knowledgeable will also point out that the air flow can turn turbulent. No longer smooth flowing but still flowing. Some seem not to care where others take exception.

I hope this helps.

I’ll post my W5 heads ported numbers later.

LIFT-------AS CAST------PORTED

.100”-----51.8/N/A--------71.8/N/A
.200”-----92.5/70.7--------148.4/86.3
.300”-----130.1/104.3-----212.2/113.9
.400”-----163.9/113.2-----241.5/131.1
.450”-----169.1/115.2-----244.6/137.7
.500”-----170.4/117.3-----246.7/139.7
.550”-----172.2/119.0-----242.6/144.9
.600”-----172.5/120.4-----240.8/144.9
 
Another word or two on this head flow.
Below are my ported W5’s. They were bare heads and they were not assembled & tested with there as cast ports.

Now I had the head porter flow them and then my machinist flow them. You’ll see two different set of numbers.

...... Head Porters #’s ....... My Machinists #’s .....

Lift ... intake/exhaust..... intake/exhaust

.100 .... not recorded ...... 60/53
.200 ......121/110 ............. 115.5/100.4
.300.......180/151...............172.6/141.8
.400.......228/184...............220/176.9
.500.......278/206...............275.7/198.1
.600.......308/218...............294/212
.650.......312/NR..........................
.700.......NR/235................288.6/222

Why the different flow rates?

Both tests were conducted @ 28”
Different pressures will deliver different results.
But here the bore sizes are different.
The head porter tested on a 4.125 test bore plate.
My machinist test plate was 4.03, what I told him it would sit on.
A larger cylinder bore allows for better air flow. Less obstruction. (Cylinder wall) And that’s one of the reasons why the 340 performs so well.

Swirl. Or how smooth the air is flowing. I didn’t list this above, but my machinist looked at this as well.

.100....110
.200....550
.300....240
.400....280
.500....640
.600....2100
.700....2917

What he said about the numbers. IF, IF, IIRC .... LOL

The lower the number the smoother the flow. He said the 2100 @ .600 is fine but the .700 was going turbulent. I asked about lifting the valve that high.
He said your racing with this head? Then don’t worry about it. Flow goes down a little bit. 6 cfm is nothing though. He then asked if I wanted to retest at higher lifts. I declined.

I was a little disappointed that they couldn’t be ported further. I’ll try my other set later one day.
 
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Ahhhhhh that makes alot of since I get it! I never really thought of the bore affected the flow I guess I always figured by the time it got there it was going the other way lol
 
Well, it gets pretty dynamic in there and everything has an effect on everything. Sometimes more, sometimes less. Just when you find a benefit in one spot it can become a hindrance elsewhere. Sometimes it can help in huge ways.

Almost needless to say, if I could get these heads on a 4.125 or better cylinder bore, I would be very happy.
 
My Dart running in D/S back in 1966 ran a best of 12.92 and 105 mph. This was with stock 920 heads, 7" wide slicks and rosin. The car was launched and shifter at from 6700 to 6900 rpm's. So the stock 920 heads are pretty good. I believe the car was only run competitively in 1966.
 
ddartdude said:
My Dart running in D/S back in 1966 ran a best of 12.92 and 105 mph. This was with stock 920 heads, 7" wide slicks and rosin. The car was launched and shifter at from 6700 to 6900 rpm's. So the stock 920 heads are pretty good. I believe the car was only run competitively in 1966.
Click to expand...
Were the 920's a CAP head? Why did the DDarts use them.
 
I believe the 920's were used on all of the 66 273 engines - both 2 and 4 barrel. The w/CAP engines had a different intake PN and distributor. The D/Dart had the w/CAP intake, Holley, adapter, manual choke, cam, headers, mechanical advance distributor, and unique unsilenced air cleaner. The fuel line was rerouted up and over the passenger side inner fender.
 
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