Which GM cam to perfect the L31?

Discussion in '96+ Vortec Performance + Computer Swaps' started by sharpe.trey, Jun 29, 2018.

  1. slowburb

    slowburb all motor

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    Cool. Good for you. You're so ten years ago man.
     
  2. Biggershaft96

    Biggershaft96 Cant Getrite

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    I missed something good i think lol
     
  3. 89GMCJOHN

    89GMCJOHN I'm Awesome

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    The difference in those two cams per GM is 6 hp and 4 ft lbs with about a 500 rpm peak spread ..... but every few hp tq counts I guess . See post 35 graphic

    For penny pinchers the 151 SPO cam is $315.54 at Summit ...the 395 marine cam is $194.36 at Summit ...so is 6 hp and 4 ft lbs and 500 more rpm worth $121 :)

    I assume this video is your Express with the SPO cam in it ?


     
    Last edited: Jul 11, 2018
  4. L31MaxExpress

    L31MaxExpress I'm Awesome

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    Not quite that simple. The Ramjet comes with 1.6:1 full roller rockers. Those were worth 20 hp on the HT383 that Hotrod tested hears ago. The Ramjet also has EFI and a better flowing intake with roughly 4" long runners that further boosts power. If you were to dyno both in a Ramjet crate engine with the same equipment the 151' cam would make 30-40 hp more than the 395'. A Ramjet 350 with a LT4 Hotcam, spring upgrade and matching ECM reflash is right at 425 HP.

    If that 357 HP 350 SPO was dyno'd the same was as the GM 350 HO 330 HP crate engine in Car Crafts Humble Pie series it would be in the 390-400 hp range. The 330 hp rated engine made 377 hp with no internal engine modifications.

    There was also a budget build done a few years ago that was a freshened up 350 vortec. They installed a takeout marine cam from a machine shop. Tested with a dual plane intake and carb it made 320 hp.
     
    Last edited: Jul 11, 2018
  5. L31MaxExpress

    L31MaxExpress I'm Awesome

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    I think I know why I really do not like you. If there is a differing opinon that anyone makes that does not coincide to your experience of one cam in your suburban you have to act narcassistic about it.

    Over the past 10 years I have had 5 different cams, 4 different sets of heads and two different intake manifold setups in the same 350 in the same van with both the stock ignition and PCM and the 24x setup with an 0411 PCM. I had more than enough seat time with each setup to understand how it ran. Just have to add it has never run better than it runs now ANYWHERE in the powerband, part throttle or WOT.
     
  6. L31MaxExpress

    L31MaxExpress I'm Awesome

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  7. slowburb

    slowburb all motor

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    K thanks for sharing. I'm so glad that's what you think and that you got an opportunity to express yourself.


    Careful with those dyno charts. There can't be too many more message boards left that you haven't been outed on, bruh.
     
  8. L31MaxExpress

    L31MaxExpress I'm Awesome

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    So one thing still puzzles me.

    I still do not understand your comment with my comment being wrong with the LSA so please express yourself or is LSA a concept you have a poor grasp of?

    Yes tighter LSA builds more cylinder pressure and brings the RPM for peak torque down. However it also increases overlap. On any vehicle with an actual exhaust system that is not designed like a race car exhaust the added overlap will dilute the intake charge at lower rpm like off-idle and part-throttle which will hurt low end torque despite the increased cylinder pressure.

    I also had 2 different cam grinds in my 2006 Hemi Ram when I owned it. With the stock torque converter, 4.56 gears, 32" tall P305/50R20s, BBK shorty headers, stock cats, magnaflow Y and a magnaflow muffler at the time I ran back to back testing in very similar weather conditions. First cam was a dual pattern grind. 214/222 @ 0.50 on a 112 LSA and 3° advanced. The second cam was a 214/214 @ .050 single pattern cam on a wider 114 LSA with 4° advance and it had a 60' time that was nearly 0.2 of a second quicker. It ended up being a full 1/2 second quicker in the 1/8 mile. The 1st cam was a modern Crower grind. 2nd cam was a Comp with XFi lobes. 1st cam had a bit of idle lope. 2nd cam had a very stock like idle and nearly 3 in/hg more vacuum. The single pattern cam also got as much as 4 mpg highway better when it was in MDS (4cylinder)mode. 1st cam ran a 9.3 @ 76 on a dead hook 2.2x 60'. 2nd cam ran an 8.8 @ 77 on a 1.98s 60'.
     
    Last edited: Jul 11, 2018
  9. 89GMCJOHN

    89GMCJOHN I'm Awesome

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    89GMCJOHN writes : According to Chevrolet.com they use 1.5 NOT 1.6's in the ramjet .....

    Ram Jet 350 Tech Specs
    • Part Number: 19355815
    • Engine Type: Chevy Small-Block V-8
    • Displacement (cu. in.): 350
    • Bore x Stroke (in.) : 4.000 x 3.480
    • Block: Cast-iron with two-bolt main caps
    • Crankshaft (P/N 10243068): Cast-iron
    • Connecting Rods (P/N 10108688): Powdered-metal steel
    • Pistons (P/N12571703): Hypereutectic aluminum
    • Camshaft Type (P/N 14097395): Hydraulic roller
    • Camshaft Lift (in.): .431 intake / .451 exhaust
    • Camshaft Duration (@.050 in.): 196° intake / 206° exhaust
    • Cylinder Heads (P/N 12528913): Vortec iron; 64-cc chambers
    • Valve Size (in.): 1.940 intake / 1.500 exhaust
    • Compression Ratio: 9.0:1 nominal
    • Rocker Arms (P/N 12367346): Aluminum roller style
    • Rocker Arm Ratio: 1.5
    • Recommended Fuel: Premium Pump
    • Ignition Timing: 34° Total @ 4,000
    • Maximum Recommended rpm: 5200
    • Balanced: External
    L31 writes "Here is the Ramjet cammed carbureted 350 dyno test I mentioned before. Looks like GMs rating is actually about 37 hp higher than the engine tested here.

    https://www.hotrod.com/articles/how-to-build-a-cheap-small-block-chevy/"

    No it actually dynoed with its 98 scrapyard shortblock , used cam, shimmed used valve springs ,used rockers and used pushrods and cheap summit non airgap intake 321 hp 4600 399 ft lb 3600 .. so 29 hp and 1 ft lb short which is probably due also partly to the out of the box carb and dist settings they used in this test vs the Chevrolet factory ram injected setup. With carb tuning, a better intake and dist tuning I bet they could have narrowed the gap even more but never equaled the fuel injection. Again basically its a carb setup vs injection .
    .
    HOT ROD ran the RAMJET crate engine and it scored better than advertised at Ramjet 413 lb-ft at 4,100 rpm and 364 hp at 5,000.

    https://www.hotrod.com/articles/gm-performance-parts-ramjet-350-crate-engine/

    My point here is the little 246 duration Ramjet cam does a great job for what it is in the end - a street torque cam with high vacuum and shouldnt be discounted - again 399 ft lbs and 321 hp at around 9:1 WITH A CARB for a cruiser that does occasional towing imo isnt a slouch compared to the factory L31 ratings at 250HP @ 4600RPM 330FT/LBS @ 2800 RPM which is the starting point and what this thread is about .
    ...As far as the larger cammed SPO 357 putting out 390-400 hp as you say I think GM marketing would have called it the SPO 360,370,380,390,400 instead if they could get away with it and it was consistently capable of putting down those numbers . 246 256 431 451 109 vs 265 273 473 473 ... Cams arent really in the same class on paper (19 and 17 degree difference) but surprisingly close in performance IMO PEACE .

    RPM HP LB-FT
    3,000 220 385
    3,200 241 395
    3,400 258 399
    3,600 273 399
    3,800 285 394
    4,000 300 394
    4,200 311 389
    4,400 319 381
    4,600 321 366
    4,800 320 350
    5,000 318 334
     
    Last edited: Jul 12, 2018
  10. L31MaxExpress

    L31MaxExpress I'm Awesome

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    I have had a stock Ramjet apart. It came with the same 1.6 self align designed rockers that came in the 1996 LT4 Vette and the LT4 Hotcam package came with that was goin into it.

    Net rating and engine dyno are also two different things. A STOCK 255 hp rated L31 makes over 300 hp with a dual plane intake, 650 cfm carb and headers on an engine dyno. Stock LT1 makes over 350 hp tested with the GMPP dual plane. The LT4 was offered as a crate engine and GMs rating was 375 hp. With the Hotcam package the LT4 was a 425 hp crate engine if you want to compare apples to apples. The marine L31 is marine net rated a 292 hp with the marine intake, freer flowing marine exhaust, and the 395' cam.

    Also FWIW when you look at the timing curve in the Ramjet ECU it is exactly the same as the timing curve in the GMPP HEI used in the HO350 and the ZZ4 engine.
     
    Last edited: Jul 12, 2018

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