Its actually a 330 cc iron eagle in the cnc version.

runners are too big... and the chamber size is too large also.

Pretty sure its basically a ported 308. When you port a chamber, it gets larger. Same goes for ports. Hence the 330cc and chsmber grows from 121 to 126.

Id personally take the benefits of valve unshrouding, and low lift airflow gains, with a ported chamber , over 5cc worth of volume

Compression ratio would be too low so the gains could be lost. Would have needed to build the engine around the head in my opinion. And again, not really looking to test the theory on someone else's stuff.

I'm not sure if you've worked with the MPI's before but the intake runners are very long and restrictive. The throttle body is also very restrictive. Because of that it's a restricted engine and need to have a good amount of port velocity and make power in the mid-range up to about 5200-5400 rpm. I'd rather put a smaller port head on it that's going to maximize flow within the operating range and in general that's going to be something with a 280-290 port size.

I'm sure it would work, just not certain it would be the best choice. Also, taking compression away can also be a negative affect.

Too many generalizations and assumptions regarding port volume and head performance. Head performance comes form flow and velocity. They have to work together. The velocity factor comes form the minimum cross sectional area of the port and on a conventional BB Chevy head this area is usually just past the push rod "pinch". Mean flow numbers are what they are, and the smaller the cross section, the more velocity the port will have. Old school BB Chev heads like the OEM rectangle ports and older Brodix and Canfield heads that were designed after that have a lot of volume in the front of the port with large minimum cross sections ( big rectangle port) but have relatively small bowls. Then you can look at something like a Dart or AFR and you see the port is a lot smaller in the front with smaller minimum cross section and more of the volume is in the bowl, after the short turn. You can have three different 320cc cylinder heads and have three completely different velocity profiles and three completely different power potentials. I just finished a set of AFR 315's and did a 2.300 intake valve upgrade with a lot of bowl and short turn work. I didn't change the minimum cross section at all because it's already a little on the big side for what i want but the work increased the airflow significantly, so now the velocity will be closer to where I want it through the minimum. These heads are probably in the 325cc range now, bit with the small cross section of the 315 and they will out flow the 335 cnc. My guess is (without measuring them) the EQ heads are probably relatively small in the front and will work fine on a 500+ci engine with the right cam. They're not ideal, but for the price could be made to work real well. I wouldn't lose a minute's sleep over using them.

Here's the 315's I'm doing. I'm leaving the burr finish.




My office...


For those interested in numbers:
Flow: (4.50 bore, 2.125" pipe on ex)
right / left / ex

.2 165.5 / 164.2 / 120.8
.3 249.2 / 245.6 / 204.4
.4 306.9 / 300.5 / 249.7
.5 351.7 / 344.7 / 277.3
.6 382.9 / 364.2 / 290.2
.7 398.1 / 382.9 / 302.7
.8 404.2 / 394.6 / 313.4
.9 411.0 / 401.9 / 318.2
1.0 412.1 / 405.6 / 321.7

Right port on 4.60 bore (just for reference to AFR's numbers)

.2 166.0
.3 250.7
.4 312.4
.5 357.0
.6 389.3
.7 403.0
.8 406.2
.9 412.8
1.0 415.4

Great explanation scott.

I see way too many people generalizing over a port volume, rather than talking about the port itself, and how its designed. Pretty much everything you said, is what my cylinder guy has told me in coversation.

I think generalizing that a 320cc head wont work, but a 308cc will, without any further discussion of the port, is incorrect way to put a combo together. I also disagree that a static compression number, is a make or break of an engine combo, within reason. Ive seen 9:1 engines smoke 11:1 engines.

Sometimes the final performance numbers tell us something. I am changing some things on my engines this winter. I will be redynoing the engines, on the same dyno as i used previously, and am looking forward to whether they gain, or lose, based on my choices made, and ultimately how the boat runs when its together.

A set of cnc heads would have been nice, but the budget only goes so far.

I have said a few times now that I'm not looking to use something that I haven't seen results I can go to the bank with. I also said a few times they might be a good choice but I don't feel they're ideal for me for a few reasons. We can speculate all day about port design, flow characteristics, cross sections etc but until I see that it works for what I'm doing I am not going to recommend spending someone's money and rolling the dice. I don't mind innovation but I don't use my friends money for R&D. It's really that simple...

Having said that, I still appreciate all the input.

I've got an odd question. I don't believe I've ever seen it asked so here it goes.

Why haven't I ever seen a flow bench done with an intake manifold bolted up?

Like in my case, you have a very small and long intake runner that could be potentially matched up to a large intake runner.

When porting and flowing, would it be beneficisl to have the intake bolted up so it's a part of that equation?

I'm not a head guy so I'm just curious?.