Since dyno time is expensive, I have not compared the Weiand single plane vs. the OEM dual plane on the same engine;
something I plan to do in the future - but I have built & dyno’d several engines with similar internals and here is some data to
consider bearing in mind these Dyno sheets reflect break-in numbers only and no real tuning:
402” Poly Stroker (4.0” bore x 4.0”Stroke)
10 to 1
Ported heads with 211cfm intake/150 cfm exhaust @.500” lift
290/.492”adv. 234@.050” 110LC Hyd. Cam
2.02/1.60” valves
Weiand single four – single plain manifold
Tri-Y style headers 1 3/4” tubes into dual collectors - 2.5” & 3.5”
405HP@5600rpm/442ft.lbs@4400rpm
vs.
390” Poly Stroker (3.94”bore x 4.0” Stroke)
9.5 to 1
Ported heads – same flow as 402 heads
Same cam profile
1.94/1.60" valves
1957 Cast Iron Dual Quad w/500cfm Edelbrocks – single plane manifold
Same headers
412HP@5500rpm/438ft.lbs@3700rpm
NOTE: Averaged 428ft.lbs. Torque from 3400-5400 RPM and Averaged 375HP from 3700-5700RPM, better than most
engine’s peak numbers with alum. heads, modern Air Gap intakes and such!
vs.
396” Poly Mild Street Stroker (3.97”bore x 4.0”Stroke)
10 to 1
Ported heads – same flow as 402” heads
284/.480” adv. 224@.050” 110LC Hyd. Poly Cam
2.02/1.60” valves
Cast Iron OEM single four intake - dual plane w/750Holley dbl. pmpr. or 500cfm Edelbrock – same power
Same Headers
361HP@5000rpm/441ft.lbs.@3500rpm
vs.
392” Poly Stroker (3.948”x 4.0”Stroke)
9.8 to 1
Ported heads
284/.435” adv. 224@.050” Hyd. Poly Cam
2.02/1.60” valves
Edelbrock P600 Three Deuce Intake – dual plane
Headers
390HP@5500RPM/435ft.lbs.@4000rpm
The dual plane cast iron four barrel OEM Poly intake performs well up to 5000rpm and then only slightly drops in HP according
to your cam profile...it outperforms all single plane manifolds, both the single four barrel Weiand and Cast Iron dual quad
intake, up to 3600RPM on both HP and Torque and it does it with ten degrees less at .050” (224@.050”) Cam vs. the 234@.050”
Cam.
The dual plane cast iron four barrel OEM Poly intake compares nicely with the dual plane Edelbrock P600 Three Deuce intake.
The OEM four barrel surpasses the P600 in both HP & Torque up to 3800RPM and makes more peak torque than the P600.
Additionally, the 396”Poly Stroker with 224@.050” Hyd. Cam and cast iron four barrel OEM intake outperformed a 383 Brodix
headed/Roller Cammed Chevy Stroker motor on both HP & Torque up to 3500RPM!
The Stroker Poly’s performance against a 360LA engine is impressive as well. The small cammed (224@.050”Hyd.) 396 Poly
Stroker with cast iron four barrel OEM intake surpassed the Edelbrock RPM Airgap equipped LA360 to the tune of 58ft.lbs.
more peak Torque. It also made more HP and Torque up to 3700RPM than the RPM Air Gap and exceeded the LA360 on torque
alone up to 5000RPM; see the LA360 specs below the Chevy data.
vs.
383” Chevy Stroker (4.03”bore x 3.75”Stroke)
10 to 1
Brodix Aluminum Heads
not ported
218/228@.050” 108LC Comp Cams Hyd. Roller Cam
2.02/1.60” valves
Edelbrock RPM manifold – 600cfm Edelbrock carb
4 into 1 Headers 1 5/8”
414HP@5600RPM/461ft.lbs.@4300RPM
vs.
383” Chevy Stroker (M. Veraldi) (4.03”bore x 3.75”Stroke)
10 to 1
Edelbrock Aluminum Heads
Lightly ported
218/224 @.050” 110LSA 106 In. LC
Edelbrock RPM Air Gap manifold – 650 AVS Edelbrock carb
4 into 1 Headers 1 5/8”
407HP@4900/5000RPM/468ft.lbs.@3900RPM
vs.
360LA Mopar (4.0”bore x 3.58”Stroke)
10 to 1
Edelbrock Aluminum Heads
not ported
308/318 adv. .510”lift 234/244@.050” 112LC Hyd. Edelbrock Cam
2.02/1.60” valves
Edelbrock RPM Air Gap manifold – Holley (unknown CFM)
TTI Headers 4 into 1 1 5/8”
400HP@6100RPM/383ft.lbs.@4100RPM
A “ported” cast iron Poly four barrel intake (dual plane) promises to equal or surpass the RPM Air Gap and the single plane
Weiand in both HP & Torque all the way to 6500RPM. I have a ported and highly modified OEM Poly four barrel that has yet to
be tested...but will be proven on the next dyno session.
Also take note that the larger cammed 234@.050” Poly 390-402” Poly Stroker motors outperformed the LA360 at all levels and
came within 3HP and 19ft.lbs. of the “Peak” numbers of one 383 Chevy Hyd. Roller Cammed motor with all its “modern”
equipment and bested the second 383 Chevy Stroker by 5HP.
Bottom line; the cast iron four barrel Poly intake is the best performing intake for a stock or mildly cammed Poly engine with a
stock stroke and is more responsive under 3500RPM than a single plane manifold. It will perform well up to 5000rpm for street
duty in both stock stroke and long-stroke (street-stroker) applications. The Weiand single plane and the dual quad single plane
design is the best performing manifold with larger cammed engines or for Stroker Poly applications and performs best at
3500RPM and above.
The aforementioned copious data substantiates why I say “if 425HP and 450Torque or less will satisfy/meet your needs, then
build a Poly motor if that is what your Mopar came with.”
Have a Blessed Christmas!
Gary Pavlovich