Comparing Street Dominator versus RPM - Opinions?

[My427stang]

I am freshening up my 390 in my F-100.  Actually more of a reseal and blueprint with a little head work.

I have a 1247 gasket matched Edelbrock RPM off the Mustang with some additional rubbing on the shelf, and an untouched Holley Street Dominator on the truck now. 

Jay's testing shows them pretty close to each other at WOT, and the truck runs great now, but wondering if anyone thinks I'd see a gain with the RPM, not just WOT, but in any situation.

Here's the specs on the motor

9:1 (estimated, will soon be seen, been 20 years since I had the heads off) 390 + .040
C8AE-H heads, currently unported, going to do a gasket match, bowl cleanup, and modern valves this time
Comp 280H hyd flat tappet
Duraspark
750 Holley vac sec
Headers and 3 inch mandrel bent duals to rear bumper

4100 lb 4x4 truck
4 speed, 3.50 gears and 32 inch tall tires

Not expected to tow much if ever, maybe the Mustang on an open trailer for a special treat 

I am leaning toward the RPM, but I have been pretty happy with the SD on this motor.  What's everyone think?

[rcodecj]

I lean towards the RPM.
3.50 gears, 32" tires, and heavy, I think you'd like it better way down low.

[My427stang]

Well, that's really the question, is the RPM any better in that RPM range?

The ports are much bigger in the RPM, but the are longer.  I would assume overall volume is greater in the RPM.  I am not certain it makes more torque down low.

[jayb]

If you are looking for sub-2500 RPM torque, I think I'd lean towards the RPM also.  Just a feeling on my part, no data to back it up...

[rcodecj]

Well, that's really the question, is the RPM any better in that RPM range?

The ports are much bigger in the RPM, but the are longer.  I would assume overall volume is greater in the RPM.  I am not certain it makes more torque down low.

In Jay's book the 428 thunderbird engine made 411.5 tq at 2500 with the RPM
The same engine makes 394.4 tq at 2500 with the Edelbrock Streetmaster.
No data but I would expect the Holley Street Dominator would be slightly less tq than the Streetmaster below 2500.
While I have not compared the RPM vs Dominator, in all cases on other engine combos, I have always lost tq by going to a single plane from a dual plane below 2500 rpm's.
Heck below 2500 rpms, I even lost tq by going from a small dual plane to a larger dual plane.
I'll still bet on the RPM for below 2500 rpm tq.

[My427stang]

I am certainly not saying your logic isn't correct, but in one of Jays tests the average torque of the SD was 428 ft lb and the port matched RPM was 421.

So in that case, average torque was slightly better with the single plane.  My guess is that in this specific case, the differences may be a wash anyway. Although the RPM shows better peaks on Jay's dyno testing, the averages are a wash or a nod to an unported SD for averages.

My 489 was a completely different animal, it was a pig at the upper RPM levels with a Streetmaster, but loved the RPM right up to 6500.  Which is really why I am putting a little thought into this, something that was happy feeding 489 inches seems to be pretty big for 399 cid.

I may have to just throw it on there to try it, I doubt it'll lose power anywhere with the RPM, I haven't seen that happen on anything, and it's a sweetheart with the SD right now, so really a win-win either way.

Ross