Reply to "A 351C Fuel Injection Manifold is Finally Available"

> I personally do not like single plane intake manifolds for street engines.
> In general single plane & dual plane intake manifolds make about the same
> horsepower at about 5000 rpm. Below that engine speed the dual plane manifold
> will make better power, above that engine speed the single plane manifold
> will make better power, and extend the motor's powerband too.

Its not so simple. The port and plenum sizes, along with the cubic inches
and compression play into which intake will be better. In practice, the
variation within either group (single or dual plane) is very large.

> I have always thought of 2V heads as strictly street heads; 4V heads,
> 3V heads, SVO heads etc all have ports that are higher than the ports of
> the 2V heads. The high ports will flow better at higher valve lifts and
> are more appropriate for racing.

In my flow bench work, 3V, 4V and high port heads outflow 2V heads at all
lifts, not just high lift.

> So for me, if a person is going to use 2V heads on a street performance
> motor there is really only one smart choice for a carburetor intake
> manifold, that's the Edelbrock Air Gap manifold, because its a dual
> plane intake manifold.

I've not published the results yet but we built and tested a 393C with ported
Aussie 2V heads. The Holley Street Dominator, Parker Funnelweb and Weiand
Xcelerator single plane intakes all bested the Edelbrock Performer RPM Air Gap
dual plane manifold which had done so well during 351C-4V and 408-4V testing.
Even at 2500 RPM (the lowest RPM we tested), the single plane Funnelweb made
more power. Across most of the pull, the difference was 20 HP or more, not
just at the peak. At 5000 RPM, the difference was 36 HP. I thought the
Funnelweb would do well but the Street Dominator and Xcelerator single planes
surprised me but not my dyno guy. He's seen the same results on big block Fords
as well. Due to the cross-sectional area of the intake ports and the cubic
inches, the velocity in the ports is high enough that the dual plane plenum
effect is not needed and only serves to act as a flow restriction.

> BUT ... the new Trick Flow 225 CNC ported head may possibly bridge the gap
> between 2V heads and race heads. Trick Flow says it flows 330 cfm, but they're
> not saying at what valve lift ... yet.

I've not had a chance to independently test either of the new TFS 351C-2V heads
but one of the 335 Series forum members posted the results of his bench test.
The 190's flowed 271 CFM intake and 199 CFM exhaust at 0.600" lift versus an
advertised 299 CFM intake and 232 CFM exhaust. Not as good as advertised but
still better than the Edelbrock 351C-2V heads.

> However ... 330 CFM at 0.600" valve lift would be high port head territory.

Based upon the independent test of the 190's, I expect the 225 CNC 2V's will
still be short of the high ports but should still be pretty decent. Also,
you really need the flow over the entire lift curve (and the areas) to assess
the heads. Recently, we've tested some heads with very strong exhaust ports
but only fair intake ports. With the right cam timing, these heads made
surprisingly good power. The Aussie 2V's only flowed 220 CFM on the intake
but 200 CFM on the exhaust. On the dyno 393C, they weren't that far off the
408C with 4V heads that flowed 322 CFM on the intake side.

Arno, I got your email. After installing the floor pans, I had to go to China
Lake for some flight testing. I'm back now and have a few things to catch up
on. Remind me early next week and I'll see what I can do.

Dan Jones