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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