And the rest of the pertinent info from that thread follows:
BY ABOMINATION
Ray, have you or Benno ported a poly head before? Hell, has anyone ported a poly head before, or enough of them to have a "method" they follow, or a "rule of thumb"?
If so, feel free to color over the posted pics and show us what to watch for when porting, and where/how much to take off!
~Jason
BY RAY BELL
Ben hasn't started on them yet. At the moment he's doing another Holden engine for HQ racing, I think... and for the Dodge he's working on the panels while he awaits the right time to test all the blocks to see if there's one he can safely take out to 4" bores without offsetting them.
Believe me, when he gets serious there will be a lot of learning going on! His mate's flow bench will be working flat out for weeks, I suspect, only interrupted by the grinding of metal out of ports (and maybe the refilling of parts where they've been ground to see if the flow's better that way...).
BY ABOMINATION
Gary had to get the following info from somewhere. Maybe he's ported a few?
Here's a blatent copy/paste from the 318 Poly Yahoo group, from Gary Pavlovich:
"The baseflow of a Poly head @ 28" water
is as follows (all heads differ slightly in flow):
Lift Intake/Exh. Ported Poly flow Int./Exh.
.100" 50/45 69/48 +19/3
.200 116/83 145/88 +29/5
.300 149/106 188/113 +39/7
.400 171/126 202/134 +31/8
.500 183/159 211/150 +28/9
.600 n/a 218/164
Bone stock un-cut Poly heads really perform "as is," however, the added cfm gained from porting is significant.
I imagine that any good head porter can achieve these results (need a little more exhaust work here) but I have seen far less cfm gains from reputed "good" head porters as well as a little more flow; just depends.
Head porting prices range from $550-1200+ depending on the person doing the work.
Yes, a Poly motor is capable of 500+HP with the right parts/machine work, although a 400HP Poly will blow-away wedge engines with much more "advertised" HP.
I smoked a "built" 360 Mopar Wedge engine with larger mechanical cam, more compression, Edelbrock aluminum heads, and better headers that ran on the dyno before my motor; our Poly made more peak HP/Torque at lower rpm and more average HP/Torque than the 360 wedge motor.
The 402" stroker Poly made the following peak #'s:
405HP @ 5600rpm and
442Torque @ 4400rpm
(pay attention to the last sentence after all these HP/Torque numbers)
and averaged over
400ft. lbs. torque to 5200rpm and still pulled
397HP @ 6000rpm;
From 3700rpm-4600rpm the average torque is 436ft.lbs.;
from 4400rpm-6000rpm the average HP is 391;
and these numbers were all made WITHOUT TUNING, extremely lean 17 A/F ratio (air fuel ratio on the dyno), no cool air ducted into the motor or dyno room, and a severe exhaust restriction with #1 & #2 cylinder tubes feeding into one common collector that was collapsed in half; this is "the rest of the story" that I did not add to the Mopar Muscle articles I wrote in 2001.
A conservative estimate of HP/Torque for this single four barrel package w/the above problems corrected would yeild 435HP/450Torque in my opinion.
Poly 402 specs:
Head flow as listed above,
290/.492" Hyd. cam (234@.050)
10.1 to 1 true compression ratio w/74cc chambers
and JE pistons w/.927pin,
4" Mopar Performance crank
Weiand #7503 single four intake (really crummy intake isn't it...?) and 650dbl. pumper Holley/850 TQ used,
Ferrea 2.02/1.60" valves...
Gary Pavlovich"
There's even a poly head conversion for B/RB/Hemi motors:
www.nrcperformance.com/ (Those guys also have a sweet offset distributor).
No wonder folks want the poly head on their big blocks.
"A well-ported Poly head will increase approx. 30cfm on the intake
side at .500" lift over a stock unported Poly head; worth the effort
to port & polish these heads.
Gary Pavlovich"
~Jason