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Wanted:
Specs for the 1960 283/290 HP Cam
Thanks,
Steve
Specs for the 1960 283/290 HP Cam
Thanks,
Steve
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Re: C-1 Specs Wanted for 1960 283 / 290 HP Cam
DUNTOV CAMSHAFT
Part number, camshaft and indexing pin assembly, 3736097
Lift from Chevrolet drawing number 3736098 for finished camshaft
Tappet lift, inches, measured from point of maximum lift in cam degrees
OE indexing points of maximum lift: Inlet 108.5 deg. ATDC, exhaust 112.5 deg. BTDC (see notes)
................INLET LOBE............................................. EXHAUST LOBE
........Opening (shown) and closing.................... Opening and closing (shown)
Angle, Lift, Velocity, Acc. x 10, Jerk x 100........ Lift, Velocity, Acc. x 10, Jerk x 100
0 0.26250 0.000000 -0.001600 0.000000 0.26650 0.000000 -0.001600 0.000000
1 0.26242 0.000160 -0.001600 0.000000 0.26642 -0.000160 -0.001600 0.000000
2 0.26218 0.000320 -0.001600 0.000000 0.26618 -0.000320 -0.001600 0.000000
3 0.26178 0.000480 -0.001600 0.000000 0.26578 -0.000480 -0.001600 0.000000
4 0.26122 0.000640 -0.001600 0.000000 0.26522 -0.000640 -0.001600 0.000000
5 0.26050 0.000800 -0.001600 -0.000125 0.26450 -0.000800 -0.001600 0.000125
6 0.25962 0.000960 -0.001575 -0.000375 0.26362 -0.000960 -0.001575 0.000375
7 0.25858 0.001115 -0.001525 -0.000375 0.26258 -0.001115 -0.001525 0.000375
8 0.25739 0.001265 -0.001500 -0.000125 0.26139 -0.001265 -0.001500 0.000125
9 0.25605 0.001415 -0.001500 0.000000 0.26005 -0.001415 -0.001500 0.000000
10 0.25456 0.001565 -0.001500 0.000000 0.25856 -0.001565 -0.001500 0.000000
11 0.25292 0.001715 -0.001500 0.000000 0.25692 -0.001715 -0.001500 0.000000
12 0.25113 0.001865 -0.001500 0.000000 0.25513 -0.001865 -0.001500 0.000000
13 0.24919 0.002015 -0.001500 -0.000125 0.25319 -0.002015 -0.001500 0.000125
14 0.24710 0.002165 -0.001475 -0.000375 0.25110 -0.002165 -0.001475 0.000375
15 0.24486 0.002310 -0.001425 -0.000375 0.24886 -0.002310 -0.001425 0.000375
16 0.24248 0.002450 -0.001400 -0.000125 0.24648 -0.002450 -0.001400 0.000125
17 0.23996 0.002590 -0.001400 0.000000 0.24396 -0.002590 -0.001400 0.000000
18 0.23730 0.002730 -0.001400 0.000000 0.24130 -0.002730 -0.001400 0.000000
19 0.23450 0.002870 -0.001400 0.000000 0.23850 -0.002870 -0.001400 0.000000
20 0.23156 0.003010 -0.001400 0.000000 0.23556 -0.003010 -0.001400 0.000000
21 0.22848 0.003150 -0.001400 0.000000 0.23248 -0.003150 -0.001400 0.000000
22 0.22526 0.003290 -0.001400 -0.000125 0.22926 -0.003290 -0.001400 0.000125
23 0.22190 0.003430 -0.001375 -0.000375 0.22590 -0.003430 -0.001375 0.000375
24 0.21840 0.003565 -0.001325 -0.000375 0.22240 -0.003565 -0.001325 0.000375
25 0.21477 0.003695 -0.001300 -0.000125 0.21877 -0.003695 -0.001300 0.000125
26 0.21101 0.003825 -0.001300 0.000000 0.21501 -0.003825 -0.001300 0.000000
27 0.20712 0.003955 -0.001300 0.000000 0.21112 -0.003955 -0.001300 0.000000
28 0.20310 0.004085 -0.001300 -0.000125 0.20710 -0.004085 -0.001300 0.000125
29 0.19895 0.004215 -0.001275 -0.000375 0.20295 -0.004215 -0.001275 0.000375
30 0.19467 0.004340 -0.001225 -0.000375 0.19867 -0.004340 -0.001225 0.000375
31 0.19027 0.004460 -0.001200 -0.000125 0.19427 -0.004460 -0.001200 0.000125
32 0.18575 0.004580 -0.001200 -0.000125 0.18975 -0.004580 -0.001200 0.000125
33 0.18111 0.004700 -0.001175 -0.000375 0.18511 -0.004700 -0.001175 0.000375
34 0.17635 0.004815 -0.001125 -0.000375 0.18035 -0.004815 -0.001125 0.000375
35 0.17148 0.004925 -0.001100 -0.000250 0.17548 -0.004925 -0.001100 0.000250
36 0.16650 0.005035 -0.001075 -0.000375 0.17050 -0.005035 -0.001075 0.000375
37 0.16141 0.005140 -0.001025 -0.000375 0.16541 -0.005140 -0.001025 0.000375
38 0.15622 0.005240 -0.001000 -0.000250 0.16022 -0.005240 -0.001000 0.000250
39 0.15093 0.005340 -0.000975 -0.000375 0.15493 -0.005340 -0.000975 0.000375
40 0.14554 0.005435 -0.000925 -0.000375 0.14954 -0.005435 -0.000925 0.000375
41 0.14006 0.005525 -0.000900 -0.000250 0.14406 -0.005525 -0.000900 0.000250
Angle Lift Velocity Acc. x 10 Jerk x 100 Lift Velocity Acc. x 10 Jerk x 100
42 0.13449 0.005615 -0.000875 -0.000375 0.13849 -0.005615 -0.000875 0.000375
43 0.12883 0.005700 -0.000825 -0.000500 0.13283 -0.005700 -0.000825 0.000500
44 0.12309 0.005780 -0.000775 -0.000500 0.12709 -0.005780 -0.000775 0.000500
45 0.11727 0.005855 -0.000725 -0.000500 0.12127 -0.005855 -0.000725 0.000500
46 0.11138 0.005925 -0.000675 -0.000750 0.11538 -0.005925 -0.000675 0.000750
47 0.10542 0.005990 -0.000575 -0.001375 0.10942 -0.005990 -0.000575 0.001375
48 0.09940 0.006040 -0.000400 -0.001875 0.10340 -0.006040 -0.000400 0.001875
49 0.09334 0.006070 -0.000200 -0.002375 0.09734 -0.006070 -0.000200 0.002375
50 0.08726 0.006080 0.000075 -0.003500 0.09126 -0.006080 0.000075 0.003500
51 0.08118 0.006055 0.000500 -0.004625 0.08518 -0.006055 0.000500 0.004625
52 0.07515 0.005980 0.001000 -0.005000 0.07915 -0.005980 0.001000 0.005000
53 0.06922 0.005855 0.001500 -0.005000 0.07322 -0.005855 0.001500 0.005000
54 0.06344 0.005680 0.002000 -0.005000 0.06744 -0.005680 0.002000 0.005000
55 0.05786 0.005455 0.002500 -0.004625 0.06186 -0.005455 0.002500 0.004625
56 0.05253 0.005180 0.002925 -0.003250 0.05653 -0.005180 0.002925 0.003250
57 0.04750 0.004870 0.003150 -0.001375 0.05150 -0.004870 0.003150 0.001375
58 0.04279 0.004550 0.003200 -0.000250 0.04679 -0.004550 0.003200 0.000250
59 0.03840 0.004230 0.003200 0.000000 0.04240 -0.004230 0.003200 0.000000
60 0.03433 0.003910 0.003200 0.000000 0.03833 -0.003910 0.003200 0.000000
61 0.03058 0.003590 0.003200 0.000000 0.03458 -0.003590 0.003200 0.000000
62 0.02715 0.003270 0.003200 0.000000 0.03115 -0.003270 0.003200 0.000000
63 0.02404 0.002950 0.003200 0.000000 0.02804 -0.002950 0.003200 0.000000
64 0.02125 0.002630 0.003200 0.000250 0.02525 -0.002630 0.003200 -0.000125
65 0.01878 0.002310 0.003150 0.000875 0.02278 -0.002310 0.003175 -0.000625
66 0.01663 0.002000 0.003025 0.001375 0.02063 -0.001995 0.003075 -0.001375
67 0.01478 0.001705 0.002875 0.001750 0.01879 -0.001695 0.002900 -0.002000
68 0.01322 0.001425 0.002675 0.002500 0.01724 -0.001415 0.002675 -0.002625
69 0.01193 0.001170 0.002375 0.003375 0.01596 -0.001160 0.002375 -0.003375
70 0.01088 0.000950 0.002000 0.003875 0.01492 -0.000940 0.002000 -0.003875
71 0.01003 0.000770 0.001600 0.004000 0.01408 -0.000760 0.001600 -0.004000
72 0.00934 0.000630 0.001200 0.004000 0.01340 -0.000620 0.001200 -0.004000
73 0.00877 0.000530 0.000800 0.004000 0.01284 -0.000520 0.000800 -0.004000
74 0.00828 0.000470 0.000400 0.003500 0.01236 -0.000460 0.000400 -0.003500
75 0.00783 0.000450 0.000100 0.001875 0.01192 -0.000440 0.000100 -0.001875
76 0.00738 0.000450 0.000025 0.000250 0.01148 -0.000440 0.000025 -0.000250
77 0.00693 0.000445 0.000050 0.000000 0.01104 -0.000435 0.000050 0.000000
78 0.00649 0.000440 0.000025 0.000250 0.01061 -0.000430 0.000025 -0.000250
79 0.00605 0.000440 0.000000 0.000125 0.01018 -0.000430 0.000000 -0.000125
80 0.00561 0.000440 0.000000 0.000000 0.00975 -0.000430 0.000000 0.000000
81 0.00517 0.000440 0.000000 0.000000 0.00932 -0.000430 0.000000 0.000000
82 0.00473 0.000440 0.000000 0.000000 0.00889 -0.000430 0.000000 0.000000
83 0.00429 0.000440 0.000000 0.000000 0.00846 -0.000430 0.000000 0.000000
84 0.00385 0.000440 0.000000 -0.000125 0.00803 -0.000430 0.000000 0.000125
85 0.00341 0.000440 0.000025 -0.000250 0.00760 -0.000430 0.000025 0.000250
86 0.00297 0.000435 0.000050 0.000000 0.00717 -0.000425 0.000050 0.000000
87 0.00254 0.000430 0.000025 0.000250 0.00675 -0.000420 0.000025 -0.000250
88 0.00211 0.000430 0.000000 0.000125 0.00633 -0.000420 0.000000 -0.000125
89 0.00168 0.000430 0.000000 -0.001000 0.00591 -0.000420 0.000000 0.000000
90 0.00125 0.000430 0.000200 -0.003125 0.00549 -0.000420 0.000000 0.000000
91 0.00082 0.000390 0.000625 -0.003500 0.00507 -0.000420 0.000000 0.000000
92 0.00047 0.000305 0.000900 -0.002500 0.00465 -0.000420 0.000000 0.000000
93 0.00021 0.000210 0.001125 -0.000125 0.00423 -0.000420 0.000000 0.000000
Angle Lift Velocity Acc. x 10 Jerk x 100 Lift Velocity Acc. x 10 Jerk x 100
94 0.00005 0.000080 0.000925 0.003625 0.00381 -0.000420 0.000000 0.000000
95 0.00000 0.000025 0.000400 0.004000 0.00339 -0.000420 0.000000 0.000000
96 0.00000 0.000000 0.000125 0.002000 0.00297 -0.000420 0.000000 0.000000
97 0.00000 0.000000 0.000000 0.000625 0.00255 -0.000420 0.000000 0.000000
98 0.00000 0.000000 0.000000 0.000000 0.00213 -0.000420 0.000000 0.000000
99 0.00171 -0.000420 0.000000 0.000625
100 0.00129 -0.000420 0.000125 0.002500
101 0.00087 -0.000395 0.000500 0.003875
102 0.00050 -0.000320 0.000900 0.002625
103 0.00023 -0.000215 0.001025 0.000000
104 0.00007 -0.000115 0.000900 -0.002250
105 0.00000 -0.000035 0.000575 -0.003625
106 0.00000 0.000000 0.000175 -0.002875
107 0.00000 0.000000 0.000000 -0.000875
108 0.00000 0.000000 0.000000 0.000000
BASE CIRCLE RADIUS: Inlet .65165/.65365"; Exhaust .64765/.64965"
NOTES:
1. Both inlet and exhaust lobes are symmetrical including flanks and clearance ramps.
2. Inlet and exhaust lobe difference is clearance ramp height. -
Re: C-1 Specs Wanted for 1960 283 / 290 HP Cam
Here are the "simple" #'s for 3736097:
Lift: Intake .381
Exhaust .380
Duration at .050 lift: Intake 222 Degrees
Exhaust 221 DegreesComment
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Re: C-1 Specs Wanted for 1960 283 / 290 HP Cam
Thank you very much for the long and the short of it!
Regards,
SteveComment
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Re: C-1 Specs Wanted for 1960 283 / 290 HP Cam
valve timing,intake 35/72,exh 76/31 seat to seat. this is at valve lash of .012/.018 i think.Comment
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Re: C-1 Specs Wanted for 1960 283 / 290 HP Cam
The actual duration at .050" lifter rise is 228/231 in most published sources, but it will vary a degree or so depending on the source. Duration at .050" lifter rise above the tops of the clearance ramps on both sides is 220 degrees, and this is the number you should use to compare to the .050" duration of hydraulic lifter cams. You can verify these conclusions from the data.
The lobe separation angle is the arithmetic average of the POMLs, which is 110.5 degrees - fairly narrow for a the duration, so this cam has high effective overlap for the duration - more than is optimal for a street engine with manifolds and a typical OE exhaust system, but it was designed to win races, so the overlap is suitable for the cam's intended purpose.
Actual lift at the valve based on the typical 1.44:1 rocker ratio achieved by SB rockers at peak lift is:
(.2625-.008)1.44 = .366" inlet
(.2665=.012)1.44 = .366" exhaust
The tops of the clearance ramps can be determined by looking at the velocity and acceleration. Velocity is constant and acceleration is near zero until about .008/.012". The only difference between the lobes is the height of the clearance ramps. Note that from the POMLs to near the tops of the clearance ramps the difference in lobe lift at each angle is exactly .004".
Based on my measured rocker ratio at low lifts of about 1.37:1 the maximum running clearance (rounded down) should be:
.008(1.37) = .010"
.012(1.37) = .016"
The lobe is symmetrical - the only symmetrical lobe cam dating to that era. Even the base engine hydraulic cam from '57-'66 is asymmetrical - with milder dynamics at the closing end than the opening end.
Although the overall dynamics of this lobe are mild, peak jerk occurs just a thou or two above the tops of the clearance ramps, so it is not wise to run "loose" clearance on this cam.
Flow achieves maximum range when lift achieves about 1/4 of valve diameter, which is .430/.375" for the 1/72/1.5" valve set, so inlet lift is a little short, and it's even worse on 327s with 461X heads/1.94" valves.
Effective duration is very similar to the L-79 cam (222@.050"), but overlap is greater. The Duntov cam is a very good "3/4 race cam" for a 283, but is not well optimized to a 327 with the larger valves, which is why it's not the best design for a high output 327. However, despite the Duntov lobe's dynamic deficiencies, I'm using the exhaust lobe on the exhaust side of my new design "Special Mechanical Lifter" camshaft for 327s with the 30-30 lobe on the inlet side.
Yes, I'm using lobes from the two cam everyone thinks "I love to hate most"!
The Duntov cam will work better on a 283 if the lobe separation is spread to 114 with the inlet POML indexed at 110.5 ATDC. This would make it essentially a mechanical lifter version of the L-79 cam, albeit with less lift.
DukeComment
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PS
If anyone is rebuilding a Duntov-cammed 283 and is interested in trying my "Modified Duntov" cam, let me know. An off-the-shelf Duntov cam costs about $60-125, depending on the manufacturing source and retailer.
Modifying the POMLs makes it a custom grind, and the current price from Crane for a custom grind is $250.
Though not listed in their catalog that I could find, Jerry Clay at Crane confirmed to me that they do have the Duntov lobe masters and can grind a Duntov cam or use the lobe masters for any other design.
Their part number for the Duntov cam is 11-3736097, Grind Number 3736097.
The wider LSA will smooth out the idle somewhat to something a similar to the L-79 cam, but I think it can pass a PV by leaning out the idle mixture a little to roughen the idle a bit. Depending on the tradeoff one wants to make between low end torque and top end power the inlet POML can be placed somewhere between 108 and 114 degrees, but the reduced overlap should yield greater low end torque and better low speed driving characteristics, even if the inlet lobe is indexed at 114.
With massaged OE 283 heads with 1.84" inlet valves, it should make useable power to 7200, but you will need better than OE connecting rods to rev this high without risk of busting a rod.
DukeComment
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