|
|
#12---Big Mouth Heads: HP & TQ Comparisons | 10/29/2016 |
Small Block - Big Mouth Ports (Tested June 2012) (updated Jan 2014)
In this series of tests we are showcasing our CNC ported Edelbrock RPM LA heads (#60779-S3) with the large port volume intakes and the intake pushrods moved over .200”. With this modification the pushrod pinch is removed and now the narrow spot is the gasket opening. Moving the pushrod over increases the port volume 11cc to a total of 206cc. The cross section is 2.574 square inches, a Largemouth to be sure. We didn’t test the heads on the same short block but we will show the differences in two engines to give you an idea of what the Largemouth port volume does for horsepower.
----------------------Comparitive Dyno Tests--------------------
|
Big Engine / Standard Ports
|
|
Small Engine / Largemouth Ports
|
|
4.080”
|
Bore
|
4.030”
|
|
4.00”
|
Stroke
|
4.00”
|
|
418 cubic inches
|
Final Displacement
|
408 cubic inches
|
|
14.4:1
|
Compression Ratio
|
11.5:1
|
|
Standard195cc intake port volume with standard pushrod location
Our standard Stage 3 CNC port
|
Edelbrock RPM LA Fully CNC ported
2.08” intake & 1.60” exhaust valves
|
“Big Mouth” 206cc intake port volume with pushrod moved over .200” *
|
|
HTL6872AS-6 *
|
“real” Chrysler flat tappet cams
|
HTL6468AS-6
|
|
1.6: ratio standard offset
|
“real” Chrysler rocker arms
|
1.6:1 with intakes offset .200”
*
|
|
Edelbrock Super Victor w/ competition porting work
|
Intake Manifolds
|
See Below
|
|
AED 1000 (Custom built)
|
Carburetor
|
850 Holley (stock)
|
|
114 octane race gas
|
Fuel
|
92 Octane pump gas
|
|
602 HP
|
Average maximum horsepower after 3 runs
|
631 HP w/ Victor manifold
583 HP w/ RPM manifold
|
|
566 lb/ft
|
Average maximum torques after 3 runs
|
561 lb/ft w/ Victor manifold
567 lb/ft w/ RPM manifold
|
|
RPM
|
418 Engine with Stage 3 CNC Edelbrock Heads
195cc port
|
|
340 Victor manifold with
Competition porting
|
|
Performer RPM manifold with
Competition porting
|
| |
Torque |
HP |
|
Torque |
HP |
|
Torque |
HP |
|
3000
|
|
|
|
442.3
|
252.7
|
|
459.0
|
262.2
|
|
3100
|
|
|
|
441.0
|
260.3
|
|
464.5
|
274.1
|
|
3200
|
403.8
|
246.0
|
|
446.4
|
272.0
|
|
469.8
|
286.3
|
|
3300
|
401.9
|
252.5
|
|
446.5
|
280.6
|
|
477.3
|
299.9
|
|
3400
|
401.8
|
260.1
|
|
441.4
|
285.7
|
|
474.8
|
307.4
|
|
3500
|
398.9
|
265.8
|
|
436.8
|
291.1
|
|
471.8
|
314.4
|
|
3600
|
401.3
|
275.1
|
|
436.4
|
299.1
|
|
475.0
|
325.6
|
|
3700
|
405.7
|
285.8
|
|
440.5
|
310.1
|
|
482.5
|
339.9
|
|
3800
|
421.7
|
305.1
|
|
442.5
|
320.5
|
|
494.2
|
357.5
|
|
3900
|
423.2
|
314.2
|
|
449.4
|
333.7
|
|
514.7
|
382.2
|
|
4000
|
434.4
|
330.8
|
|
453.1
|
345.1
|
|
534.7
|
407.3
|
|
4100
|
456.8
|
356.6
|
|
468.5
|
365.7
|
|
546.9
|
426.9
|
|
4200
|
470.0
|
375.8
|
|
494.3
|
395.3
|
|
554.9
|
443.8
|
|
4300
|
534.3
|
437.5
|
|
525.4
|
430.1
|
|
557.6
|
456.5
|
|
4400
|
532.8
|
446.4
|
|
536.0
|
49.1
|
|
563.5
|
472.1
|
|
4500
|
547.0
|
468.7
|
|
546.7
|
468.4
|
|
560.9
|
480.6
|
|
4600
|
547.0
|
479.1
|
|
547.4
|
479.4
|
|
567.4
|
497.0
|
|
4700
|
547.5
|
489.9
|
|
551.1
|
493.2
|
|
561.2
|
502.2
|
|
4800
|
559.7
|
511.5
|
|
561.2
|
512.9
|
|
558.2
|
510.2
|
|
4900
|
566.7
|
528.7
|
|
555.0
|
517.8
|
|
551.6
|
514.6
|
|
5000
|
564.7
|
537.6
|
|
557.7
|
531.0
|
|
550.1
|
523.7
|
|
5100
|
565.6
|
549.2
|
|
547.7
|
545.4
|
|
553.3
|
537.3
|
|
5200
|
563.9
|
558.3
|
|
545.2
|
551.5
|
|
551.4
|
545.9
|
|
5300
|
555.8
|
560.9
|
|
541.2
|
552.7
|
|
541.0
|
546.0
|
|
5400
|
552.9
|
568.5
|
|
538.3
|
560.6
|
|
536.0
|
551.1
|
|
5500
|
539.9
|
565.4
|
|
536.9
|
566.8
|
|
533.6
|
558.8
|
|
5600
|
526.7
|
561.6
|
|
530.3
|
574.0
|
|
523.2
|
557.9
|
|
5700
|
525.8
|
570.7
|
|
516.9
|
582.7
|
|
516.1
|
560.2
|
|
5800
|
523.3
|
577.9
|
|
522.3
|
585.7
|
|
518.9
|
573.0
|
|
5900
|
513.3
|
576.6
|
|
517.8
|
580.6
|
|
509.6
|
572.5
|
|
6000
|
509.4
|
582.0
|
|
516.5
|
596.7
|
|
510.3
|
583.0
|
|
6100
|
504.0
|
585.4
|
|
520.4
|
601.4
|
|
495.9
|
576.0
|
|
6200
|
498.6
|
588.6
|
|
512.2
|
609.7
|
|
486.2
|
573.9
|
|
6300
|
498.6
|
598.1
|
|
506.8
|
624.2
|
|
|
|
|
6400
|
494.2
|
602.2
|
|
494.9
|
624.2
|
|
|
|
|
6500
|
481.3
|
595.7
|
|
488.3
|
627.2
|
|
|
|
|
6600
|
|
|
|
487.5
|
621.9
|
|
|
|
|
6700
|
|
|
|
479.4
|
623.0
|
|
|
|
|
6800
|
|
|
|
442.3
|
631.2
|
|
|
|
|
6900
|
|
|
|
441.0
|
629.8
|
|
|
|
As you can see, the big engine with the standard 195cc ports had all the advantages except for port volume:
- 418-vs-408 cubic inches
- 14.4:1-vs-11.5:1 compression (Race gas-vs-pump gas)
- Larger cam (* During testing 2 larger cams were tried on the big engine with no power improvement)
- Super Victor competition ported intake-vs-340 Victor competition ported intake
- 1000cfm custom carb-vs-box stock 850 Holley carb
But, it still had less power than the smaller 408 cubic inch engine with the Largemouth Edelbrock heads and much milder parts….29HP less! If we had installed these Largemouth heads on the bigger engine it should have made well over 675hp. Later on we installed the INDY 360-1 heads that we had fully CNC ported with large port volume on the engine and Shazam!!!!! 701HP....99HP more!.
Special Test:
We tried a competition ported Edelbrock RPM dual plane intake with the same 850cfm carb. Obviously it cannot flow the air of either of the single planes, but it represented itself very well with 583hp and 576 lb/ft of torque. But look at the lower RPM torque versus the single plane intakes. The small engine made more torque with the RPM intake rthan the big emngine. Especially at the low end, 67 lb.ft more.
Chart shows torque increase with RPM Dual Plane Intake Over a SIngle Plane Intake
|
RPM
|
Big Engine
|
Small Engine
|
|
3300
|
+76 lb/ft
|
+31 lb/ft
|
|
4000
|
+100 lb/ft
|
+81 lb/ft
|
|
4400
|
+31 lb/ft
|
+37 lb/ft
|
To view the flow chart for this head click the button below.
 What these test show is the need for more port volume on these larger cubic inch engines enabling them to make maximum power. What we did was plug the original pushrod holes and move the pushrod over .200” and then use .200” offset rocker arms. The port opening was CNC’d to the Largemouth configuration. This operation can be performed on any existing small block Edelbrock RPM cylinder head. But now we move the pushrod over .350" for a "BIG MOUTH" port with more port volume and ari flow. To complete the conversion you will need is our 4 LH and 4 RH intake rocker arms and slightly longer 3/8" pushrods. Give us a call!
Jan 2013 update: We are nowmoving the pushrods over .350" on LA heads and .420" on the Magnum heads. We have 1.6 ratio rockers for both applications and the big port heads are both called "Big Mouth". And, we can retro-fit yourexisting heads to Big Mouth. Check out our listings in the appropriate sections of our website.
* The "Big Mouth" ports both LA & magnum are now 225cc.
Offset Rocker
 
Standard Ports BigMouth Ports
|
|
| | Home | Phone: 309-745-9558 | Email: information@hughesengines.com |
