I figured it out 1966 block everything else a 71.. question

[mauve66]

I'M sure all the factory, Mass production 383's got "Blueprint Quality" machine work with zero deck blocks. I'm all but positive every single 383 came out the factory making exactly the same 335 HP.

i agree, didn't they have ISO 6625-6626 specs back then
my car was made 2 days before xmas, i bet it didn't make the published HP rating either

[brigond]

Here is thOur final mod, not surprisingly, was a good old-fashioned cam swap. There was, however, nothing old-fashioned about the grind. Competition Cams has recently introduced a line of Mopar-specific grinds which take advantage of the Mopar engine's .904-inch tappet diameter. Mopars have a tappet diameter of .904 inches, while Fords measure .875 inches, and Chevys .842 inches. Why is this significant? The larger tappet raises the limit on the possible cam velocity in a flat tappet cam. This allows the cam designer to develop more aggressive profiles, giving a faster rate of lift. More lift means more open area at the valve, and typically more power than a lower lift cam of the same duration. Most cam profiles are simply designed to be compatible with .842-inch tappets, since it is the lowest common denominator, and will work with that tappet size or larger.


With the new cam, the engine...
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We were eager to try one of the new Comp grinds, and ordered up an XE285HL-10. This is a fairly serious hydraulic profile, rated at 285/297 degrees gross duration and spec'ing out at 241/247 degrees duration at .050 inches, with .545/.545-inch lift on a 110-degree lobe separation. The cam was degree'd in at four degrees advance and topped with a set of matching Comp lifters. We were still budget-conscious with this engine and elected to retain the stock 383's valvetrain. Unlike some competitive brands of engines, the big-block Mopar hydraulic shaft-mount system is rugged. We upped the valvesprings at the same time to Comp's PN 924 dual-spring assemblies since the high lift cam requires more spring than the stock 383 cam. We used an on-the-head spring compressor from Powerhouse to make quick work of the job.

Back up and running, with the big stick, the 383 had a weightier thump. With the stock heads, the cam would likely not realize its full potential with our present combo, but we still expected a gain and expected to pull higher rpm. With that in mind, the dyno controls were reset to 6,200 rpm, and we opened up the 383 once again. It pulled cleanly through the revs and we now had a 455 hp 383. Peak power was actually 454.9 hp at 6,000 rpm, and 456.6 lb-ft of torque at 4,800 rpm. With the big cam we lost 5-10 hp at the bottom of our test range, but from the mid-range up the big stick just pulled away like a freight train for a gain of nearly 50 hp. The useable rpm range of the engine was extended by better than 500 rpm in the bargain.

We were impressed with the 383. Stock with the exception of the headers, cam, intake, and carb, we were solidly over 450 hp. That's dollar value per horsepower.

Is that the end for this 383? We'll likely revisit it a few issues down the line, looking to increase the head flow capacity and compression ratio. We can handle that in one swap. Maybe a solid lifter cam to up the rpm range, and who knows how far the under appreciated 383 can go.

Dyno Results
Tested at Westech Performance Group on a Superflow 901 Dyno

Torque
RPM   STK   HDRS   CARB   INTKE   CAM
3000   382.7   406.3   427.1   405.5   394.2
3200   388.1   406.6   422.6   410.9   400.0
3400   388.3   412.6   431.9   421.2   414.7
3600   394.6   411.2   433.7   426.1   431.5
3800   392.4   408.3   430.8   430.0   435.5
4000   387.2   401.3   424.6   433.0   446.5
4200   377.8   396.2   416.4   430.1   451.5
4400   371.4   390.2   409.7   430.1   451.8
4600   367.8   384.6   402.0   427.8   454.2
4800   361.6   379.5   398.5   424.3   456.6
5000   355.1   373.4   385.6   421.3   450.3
5200   337.2   357.8   368.1   407.7   449.1
5400   322.8   348.5   351.4   395.1   435.8
5600       417.0
5800   407.6
6000   398.2
Horsepower
RPM   STK   HDRS   CARB   INTKE   CAM
3000   218.6   232.1   244.0   231.6   225.2
3200   236.5   247.7   257.5   250.3   243.7
3400   251.4   267.1   279.6   272.7   268.5
3600   270.5   281.9   297.3   292.1   295.8
3800   283.9   295.4   311.7   311.1   315.1
4000   294.9   305.6   323.4   329.8   340.0
4200   302.1   316.8   333.0   343.9   361.1
4400   311.1   326.9   343.2   360.4   378.5
4600   322.2   336.8   352.1   374.7   397.8
4800   330.5   346.8   364.2   387.8   417.3
5000   338.0   355.5   367.1   401.1   428.7
5200   333.9   354.2   364.5   403.7   444.6
5400   331.9   358.3   361.3   406.3   448.1
5600       444.6
5800   450.1
6000   454.9


Read more: http://www.moparmusclemagazine.com/techarticles/engine/mopp_0209_upgrading_the_383_magnum_avs_carb/viewall.html#ixzz2KR0B324Se rest of the article...