Edelbrock 351C Head Flow Numbers

Rodger, here is the Aussie cast iron 2V head data you're looking for

..............Aussie 2V..Aussie 2V
valve lift...as cast.....ported & 4V valves

0.100"......59/44.......79/75
0.200"......112/79.....154/109
0.300"......156/109....206/156
0.400"......178/130....231/180
0.500"......187/153....244/200
0.550"......188/164....250/207

AND, here is the data for the 2V alloy heads from Edelbrock's Australian competitors, AFD & CHI

valve lift...AFD 2V.....CHI 2V

0.100"......64/55.......77/64
0.200"......122/108....147/114
0.300"......186/151....207/153
0.400"......239/185....255/185
0.500"......272/205....286/200
0.550"......286/211....296/208
0.600"......290/216....300/214
0.650"......297/218......N/A


CHI also manufactures 2 versions of the 3V cylinder head, and a 4V cylinder head. The intake port of the 3V head is a 2V size port raised about 3/8". The 2 versions of the 3V head differ in the cross sectional area of their intake ports, and therefore in the volume of the intake ports; the smaller port being 185cc in volume, the larger port being 218cc in volume. CHI's 4V head has 3V size intake ports that are flared open to mate with standard 4V intake manifolds. One last mention is that AFD also manufactures a "stuffed" intake port 4V head, stuffed referring to the fact that the floor of the intake port is raised in relation to a standard 4V port.

air flow data does not indicate 100% which head would make the most power for your application, I realize there is little else to base a purchasing decision on, but the air flow data does not tell the whole story. Recommendations from a trusted engine builder experienced with these heads would be the best help in making a buying decision. In general, Edelbrock has a reputation for producing heads that are NOT great performers out of the box, but normally their heads can be made competitive with porting. I have not yet read any feedback on how well the Edelbrock 351C 2V heads perform after a good porting job. Since the Australian heads are competitively priced with Edelbrock, either of them would represent a better value for the money, as they are better performers out of the box.

Your friend on the DTBB, George

Not sure if the forum software will preserve my formatting but here's some additional head flow data on the Ford high port head family:

Valve C302 C302 C302B C302B C302B A3 A3
Lift Intake Exhaust Intake Exhaust Exhaust Intake Exhaust
(inch) 2.15" 1.65" 2.19" 1.65" 1.65" 2.19" 1.71"
Tulip Std (from
C302)
0.025 --- --- --- --- --- 33 33
0.050 063 047 051 --- 047 48 45
0.100 096 073 081 --- 073 84 67
0.150 125 102 120 --- 111 119 86
0.200 160 123 157 131 124 154 108
0.250 --- --- --- --- --- 187 128
0.300 218 155 223 180 156 211 142
0.400 274 191 266 210 188 257 169
0.500 313 220 306 223 206 299 191
0.600 318 234 331 228 215 327 214
0.650 --- 241 --- 230 220 --- ---
0.700 --- 242 --- --- 222 309 226
0.800 --- --- --- --- --- --- 234

The flow is in CFM and was tested at 28" pressure drop on a SuperFlow 600
flow bench at Stiegemeyer Racing Heads in St. Charles, Missouri. A 4.155"
diameter tube was used to simulate the bore and the intake was flowed without
a manifold, using a piece of clay around the intake port. No pipe was used
on the exhaust. When Dave Williams had a pair of iron 4V Cleveland heads
tested on Jim Kuntz's bench, the operator mentioned that naked intake ports
usually flow 20-30 CFM less than a port with manifold. I'm also told an
exhaust port with pipe picks up a similar amount.

Both sets of cylinder C302 heads have had some work done to them. The bowls
were blended and the ports smoothed but the ports were not hogged out and
remain fairly small. The C302B's have intake port volumes of 217 cc's and
exhaust port volumes of 112 cc's, roughly similar to the CHI 3V heads. The
C302B's were also fitted with titanium tulip exhaust valves. We swapped a
standard exhaust valve from the C302 head to see how it compared to the tulip
valve in the C302B. Note that the valve was simply dropped in the port and
flowed, no valve job was done. Stiegemeyer says the tulip shape works even
better on heads with large seat areas but makes the valve heavier. That's
not a problem with titanium but I plan on swapping to stainless steel instead
since my engine is a street stroker and won't be turning extreme RPM.
The A3 heads were not ported but were given a quick clean up with a sanding
roll.

Stiegemeyer likes high flowing, moderate cross-sectional area, cylinder
heads mated to high flowing single plane race intake manifolds (Roush/Ford
Motorsport, Edelbrock Victor and the like). More than just the raw CFM of
the heads, he was quite impressed with the velocity of the C302 and C302B
heads and thought either pair would make for a killer street engine.
Actually, the heads flowed a bit better than the numbers suggest as the
lifts were actually lower than the reading due to the angle required by
the test fixture (the lift gauge was at an angle to the valve). Stiegemeyer
has since ported a friend's set of C302 heads which flowed over 350 CFM on
the intake side.

Dan Jones

How much did it cost to port the C302 heads to get them to flow these numbers? What was the final intake volume/exhaust volume of the ports?
Race teams liked the C302 heads better then anyone else.
They didn't mind spending $5000 of their own time to beat the competition.
I think the A3 head is the best value out of the box accross the board, but that's just my opinion.
At half the price it's twice the head.

> How much did it cost to port the C302 heads to get them to flow these numbers?

I don't know. I bought the heads in ported form. Seller claimed 358 CFM peak
but that was on a different bench and flow over 0.600" lift didn't matter to
me as I'm using the heads on the street with a cam of 0.620 maximum lift.
The guy who ported my last set of (aluminum Buick V8) heads gets $700 for a
full port job including valve job.

> What was the final intake volume/exhaust volume of the ports?

Intake port volumes are 217 cc's and exhaust port volumes are 112 cc's.
Plenty of material left if you wanted to go larger but these flow well
enough for my use. I've seen numbers as high as 364 CFM from C302B's
and a local porter gets over 350 CFM from his standard port job on them.
At the manifold face, the intake ports measure 2 1/4" tall by 1 3/8" wide
and the exhausts measure 1 5/8" by 1 1/2" (D port flat bottom with circular
roof). Valves are 2.19" diameter intake and 1.65" diameter exhaust.
Relative to the valve diameter, the heads have a small minimum throat area
with tulip valves on the exhaust side.

> Race teams liked the C302 heads better then anyone else.

The C302 heads were designed to be ported. The trend continues with the
latest Ford race heads. They are delivered with ports your thumb would
get stuck in. They are just holes to locate the CNC machine. The smaller
the port, the more room the porter has to work with.

> I think the A3 head is the best value out of the box accross the board,
> but that's just my opinion. At half the price it's twice the head.

Yup, they are good bang for the buck. They flow enough to support 750 HP
with little work. The port volumes work better on larger displacement engines
but they still work fine on standard 351C's, assuming the rest of the motor
is built correctly.

Dan Jones

Dan, those volume numbers are very close to the out of the box B351 head.
I know you mentioned it but you didn't state it this way: more flow doesn't NECESSARILY MAKE MORE HORSEPOWER.
I learned that one the hard way.
Thanks for being frank and sharing information. I thought that I was dillussional. I hear voices in my head you know. The problem is I don't know what they are saying. They are in a foreign language. (And you thought you were crazy huh?)

> I know you mentioned it but you didn't state it this way: more flow doesn't
> NECESSARILY MAKE MORE HORSEPOWER.

When I was putting my engine specs together, I had head flow numbers and
cross-sectional areas from several sets of heads I had personally put on
a flow bench, as well as independent flow numbers from other people's heads
and CHI's claimed (also from another source) numbers. When I ran them
through Dynomation (a high end simulation package), using actual dimensions
for everything, my C302B's made the best power (peak and average) in the RPM
range I'm interested in, followed closely by my A3's and spare C302's and
then by the Brodix BF300's and CHI 3V's. Stock 4V's were way behind and the
Edelbrock Performer 2V's were even worse. If I had bowl ported the A3's,
I'd bet they would have made more than the C302B's. Understand this isn't
an apples-to-apples comparison given the different levels of porting and
the results would likely be different on a different engine. There are also
limitations to simulation program. It can not predict the effect of the
chamber shape on swirl and tumble, for instance. That said, the important
things (to the program at least) are the flow average within the lift range
of the cam chosen (some heads like the Blue Thunder flowed better at higher
lifts but made less power due to the cam chosen, with a bigger lift solid
roller and more compression those results would likely change), the ratio
of intake-to-exhaust flow (Smokey Yunick's porting experiment holds here),
intake tract speed (there's a flow speed that's best and larger port volumes
can sometimes make better power than a head with smaller port volumes and
the same flow numbers), as well as how well the rest of the engine parameters
(bore, stroke, compression ratio, intake and exhaust dimensions, cam timing,
etc.) suit the heads.

> I hear voices in my head you know. The problem is I don't know what they are
> saying. They are in a foreign language. (And you thought you were crazy huh?)

It's not I who am crazy, it's I who am mad!

Dan Jones

Dan - Would you be willing to run the Dynomation simulation software using the specs from my engine? As I recall that software is about $400 to $500 and I can"t justify spending the money for the little that I would run the simulation. I would be willing to pay you for the simulation run.

> Dan - Would you be willing to run the Dynomation simulation software using
> the specs from my engine? As I recall that software is about $400 to $500
> and I can't justify spending the money for the little that I would run the
> simulation. I would be willing to pay you for the simulation run.

I'd be willing to run the program for you. Are you looking to optimize a
combination or get a prediction of what your current engine produces (or
should produce)? Good simulation programs are best for assessing the effect
of a particular change or series of changes. They may not be so good at
predicting the actual power output since there are things the program isn't
aware of. For instance, David Vizard did a series of tests on reducing
crankshaft drag. He started with a stroker crank in a stock oil pan.
Then in, successive steps, he aero profiled the crank, Teflon coated it,
and installed a race pan with wingage tray and scrapers. The HP difference
from start to finish was very large (40+ HP). A simulation program won't be
able to predict that. However, Vizard said the program is very accurate in
predicting the effect of incremental changes. He said whenever the program
said a 3" increase in collector length would be worth 10 ft-lbs, they found
10 ft-lbs on the dyno.

To do this properly, we will need accurate inputs:

bore
stroke
rod length
compression ratio
carb or injection information
cylinder head flow
intake tract length and cross-sectional area
air to fuel ratio
header dimensions
cam type and timing (in SAE specs or Cam Doctor type lift vs. duration curve)
rocker ratio
wrist pin offset
boost & compressor map (for foced induction)
nitrous info (if so equipped)

The old computer programmers GIGO credo applies here: garbage in = garbage out.
The program needs accurate data. Actual measurements from your particular
engine, particularly head flow and intake/exhaust dimensions are best but I've
spent a fair bit of time measuring intakes and heads and can likely come up
with reasonable estimates if you can't come up with the required data.

Dan Jones

Dan - Can you give me your email address so that we can take this discussion off the board? Mine is b_deeny@comcast.net. I have made a chassis dyno run with my car so that I know what it is putting out now. I would like to know what improvements would be made if I went to the CHI 3V heads.

> Dan - Can you give me your email address so that we can take this discussion
> off the board? Mine is b_deeny@comcast.net. I have made a chassis dyno run
> with my car so that I know what it is putting out now. I would like to know
> what improvements would be made if I went to the CHI 3V heads.

daniel.c.jones2@gmail.com

To start, I'll need a baseline on your current engine. Need all the specs
mentioned in the post.

Dan