Originally Posted by Panther (Post 4405581)

After doing a lot of research I think I'm leaning away from the EQ heads for this build and I'll state the reasons why.

First, it has nothing to do with the quality of the head. From what I'm reading and hearing they're a good head.

However, I don't think the head is going to meet the needs of my build primarily because the intake runner is too large (320 cc). I'm building a 509" MPI engine and there is a lot of restriction in the throttle body and more importantly the intake manifold. With a 320 CC intake running, it's probably going to have most of it's power gains above 5000 rpms and this engine is going to be a 5200+/- engine.

EQ also makes a replacement GM head but looking at the spec sheet, there's no real advantage (in my opinion) of going with that head because it doesn't have a rolled valve angle, raised exhaust port, upgraded valve seats or bronze guides for example. So even though it's cheaper, it doesn't meet my needs.

I feel that I need to put a head on this package which has a smaller intake runner such as the Edlebrock Performer RPM, Victor Jr, AFR 290 or largest port being the Dart Iron Eagle 308 CNC.

Originally Posted by Panther (Post 4405595)

Thanks for the info! I'm expecting this build to be around 500/525hp.

Originally Posted by phragle (Post 4405599)

Arcticfriends has a thread going with a lot of dyno time wth the mpi intake and different throttle bodies

Originally Posted by MILD THUNDER (Post 4405598)

Just my opinion, but i wouldnt write a head off simply on port volume. If the part is designed properly, it will have better airspeed and flow. The stock merc head has similar volume, however, the overall flow and port speed is lacking. Hence why if you were to swap that merc head, out for even a 335cnc afr head, you will still likely see more torque and power across the board from better cylinder filling.

Big ports dont necessarily mean poor airspeed, and small ports dont necessarily mean better airspeed.

I know of a builder who recently did a pair of 525 merc upgrades. 525 has edelbrock rectangles, which arent big flowing heads, and have a 315cc port, made 650 plus ft lbs of torque, and around 590ish hp at 5300.

Id be hard pressed to believe, that the EQ head, with its good airflow, good wet flow characteristics, would perform any less than those edelbrock stock exhaust port location heads .

The afr 290 is a sweet head, but whats the price difference ?

Originally Posted by Panther (Post 4405603)

I've been watching it, it's a great thread. Very informative.

The intake runner/plenum is going to be modified but not the TB on this build unless the owner wants to invest in it.

Originally Posted by Panther (Post 4405595)

Thanks for the info! I'm expecting this build to be around 500/525hp.

Originally Posted by SB (Post 4405622)

BTW#2 Panther: I would strive for a little better transition into the top of those MPI runners than what is shown in the pic. At the min, round over that center divider. Remeember, air has mass, and when it goes into those runners as in the pic, air will try to flow towards the center of the runner (again, at the runner) and effectively make that section of the runner act if it was narrower.