#3---DYNO TEST 684HP 500CID 6-PACK & 4BBL (J CROSS) 01/2007

12/27/2014
DAVE HUGHES


  

DYNO TEST

684 HP 500 CID 6-pack & 4Bbl

(John Cross)

This is a 500 engine that we built and dynod in January 2007. We like to do these big-inch 6-pack engines because they always produce more power that they should. Yeah, I know they have 1350CFM carburetion, but look at that intake manifold, 55 years old, dual plane design. However, as the English say, we have breathed on it and it flows a lot better than stock.

This started out as a crank kit that was sent to us by a customer who wanted a dynoed 500 6-pack engine. He wanted a high quench motor that would be at home on the street running a blend of ¾ pump gas and ¼ race gas and a hydraulic camshaft. We had to re-balance the crankshaft and chamfer the bearings (what else is new?). The engine was 4.350 bore and 4.150 stroke with 7.100 rods. It has over 12.8:1 CR with flat-top pistons and Stage 2 ported Indy EZ heads. The block got our standard race-prepped kit block work (p/n KITBLOCKBB), main bearing stud girdle (p/n 7380K) and INDY EZ cylinder heads with 75cc closed chambers and our Stage 2 kit (p/n 4950K-S2). We knew that the customer needed to get real on his camshaft with one of our HER4652BL hydraulic roller cams. He wanted to know how the old-school mechanical secondary Holley's would stack up to a 4Bbl carb and intake, so we tested it with a fully ported 440 Victor intake manifold and with both a 950CFM Holley and a 1050 Dominator.

 

TEST #1

 
RPM
TORQUE
HP
3100
593.0
350.0
3200
579.0
352.7
3300
567.1
356.3
3400
564.5
365.5
3500
564.2
376.0
3600
574.9
394.1
3700
588.8
414.8
3800
608.4
440.2
3900
633.2
470.2
4000
648.2
493.6
4100
659.8
515.1
4200
678.4
542.5
4300
681.3
557.8
4400
678.2
568.2
4500
682.1
584.5
4600
677.5
593.4
4700
678.7
607.3
4800
671.9
614.0
4900
675.7
630.4
5000
676.9
644.4
5100
671.8
652.4
5200
664.7
658.1
5300
661.2
667.2
5400
652.5
670.9
5500
641.8
672.1
5600
633.6
675.6
5700
616.5
669.1
5800
585.8
646.9
5900
569.8
640.1
6000
554.8
633.9

Avg    4550            631.1                    548.6
Min    3100            554.8                    350.0
Max   6000            682.1                    675.6 
 
 
This is the best that we got out of it with the Holley 950 carb.

 

TEST #2

 
RPM
TORQUE
HP
3100
606.4
357.9
3200
586.5
357.4
3300
579.8
364.3
3400
576.9
373.4
3500
580.2
386.6
3600
585.6
401.4
3700
602.1
424.2
3800
611.2
442.2
3900
637.8
473.6
4000
654.8
498.7
4100
664.6
518.8
4200
679.1
543.0
4300
688.7
563.9
4400
687.8
576.2
4500
690.0
591.2
4600
693.4
607.3
4700
686.1
614.0
4800
686.3
627.2
4900
680.2
634.6
5000
681.3
648.6
5100
678.9
659.3
5200
672.4
665.7
5300
667.9
674.0
5400
658.1
676.6
5500
647.2
677.8
5600
629.0
670.6
5700
609.8
661.8
5800
585.2
646.2
5900
569.2
639.4

6000

551.6

630.2


Avg    4550                637.6                    553.6
Min    3100                551.6                    357.4
Max    6000               693.4                    677.8       
 

We changed to a 1050 Dominator carb and a funnel adapter. Notice how the power and torque were up everywhere, but not significantly---its the combination, stupid. The power is about the max for a 500 CID engine and with only a 242 @ .050 duration cam. It idles easily at 950RPM with 5.5 of vacuum.

 

TEST #3

 
RPM
TORQUE
Hp
3100
545.2
321.8
3200
532.9
324.7
3300
518.0
325.5
3400
515.5
333.7
3500
517.2
344.6
3600
512.1
351.0
3700
507.5
357.5
3800
507.0
366.9
3900
514.3
381.9
4000
561.9
427.9
4100
574.3
448.3
4200
604.3
483.2
4300
608.0
497.8
4400
611.3
512.1
4500
607.7
520.6
4600
616.5
540.0
4700
611.0
546.7
4800
608.9
556.5
4900
605.9
565.3
5000
609.1
579.8
5100
601.4
584.0
5200
600.4
594.5
5300
599.4
604.9
5400
586.1
602.6
5500
571.8
598.8
5600
564.0
601.4
5700
530.6
575.9
5800
514.2
567.8
5900
485.3
545.2
6000
474.1
541.6

Avg    4550                560.5                    486.8
Min    3100                474.1                    321.8
Max   6000                616.5                    604.9 
 
This was the first test with a 6-pack as our intake manifold. Talk about taking the wind out of your sails! OUCH! The BSFC told the tale that the carb setting was way off. With the practice we got, we were able to change carb jets in half the time that we did the first time around.

 

TEST #4

 
RPM
TORQUE
HP
3100
613.0
361.8
3200
602.0
366.8
3300
599.6
376.8
3400
597.0
386.5
3500
600.4
400.1
3600
621.8
426.2
3700
635.7
447.8
3800
638.4
461.9
3900
650.3
482.9
4000
658.0
501.1
4100
664.4
518.7
4200
675.8
540.4
4300
676.1
553.6
4400
677.9
567.9
4500
684.9
586.8
4600
684.5
599.6
4700
684.2
612.3
4800
682.8
624.1
4900
680.8
635.2
5000
675.7
643.3
5100
680.9
661.1
5200
669.8
663.2
5300
666.4
672.4
5400
660.2
678.8
5500
650.4
681.1
5600
636.9
679.1
5700
609.6
661.6
5800
589.2
650.7
5900
565.7
635.5
6000
550.7
629.2

Avg    4550                642.8                        556.9
Min    3100                550.7                        361.8
Max   6000                684.9                        681.1 

 
Finally, with the proper carb jetting and timing, we were rewarded with this pull. To start with, notice how the 3x2 carb setup had much more torque up to 4100RPM. (36 ft lb more torque at 3700 RPM, to be exact, over the single 4 Bbl Dominator). This 55-year-old manifold could do some damage on the street. It was up to 616 @ 3100 RPM, our best 6-pack yet. From 4100 RPM up to about 4800 RPM, the single Dominator was stronger, but from there it was back-and-forth. The HP curve was similar to the torque curve. The 6-pack being stronger everywhere except from 4100-4900 RPM where the single 4Bbl was better, (a best of 10HP at 4300RPM). Above the HP peak at 5500RPM, they were back-and-forth.

 

SUMMARY

The fact that the torque and horsepower were very close on the peak numbers tells us that the carburetion with any type of these 3 set-ups was no the controlling factor in the power output. It was the camshafts relatively small size. However, the horsepower and torque numbers are very similar, which makes a good street combination. Any more cam would trade off some torque on the low end and add it to the top at a higher RPM (same with the horsepower). Torque is what makes it fun to drive on the street. This basic combination could probably produce over 700 HP and still use pump gas.

 

 

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