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    Another OBS Suburban - new L31 or go LS

    Well, the old 98 K1500 burb may get a temporary stable mate while I size up the needs of the new one. I am probably picking up a 99 K1500 burb over the weekend.

    The 98 has 205k on the 350 while the new one has 258k on the truck. They are basically the same truck: 350-4l60e-np246-3.73 while mine has an 0411, 4l80e conversion and was converted to 3.73. I have spent quite a bit of time and money on mine but the 99 is a good deal and the body is almost perfect. My body needs some love.

    Anyway, the new truck supposedly needs a motor due to a dead cylinder. This may be true but I plan on going through compression test etc anyway. It may just be a broken valve spring or something minor. Either way, it has a lot of miles.

    Once I get a feel for what I am dealing with, I plan on swapping everything to the new truck that makes sense and then selling the old one.

    Swapping: 0411, 4l80e and tcase, shocks, wheels and tires, MPFI??

    I won't be swapping the motor between trucks so if the 99 truly is dead, should I go for another L31 crate motor or get a 5.3 or 6.0? What are the costs of going to the LS? What headaches are there and what are the advantages in economy or power?


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    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    Registered User 96ImpSS's Avatar
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    Re: Another OBS Suburban - new L31 or go LS

    Since you'll have a spare vehicle on your hands, have you just considered rebuilding one of the L31's?
    If not, I'd go with a crate L31 over a 5.3 for sure. I have both, and unless that 99 'burb has 4.10 gearing or more, I think you'll be disappointed in the 5.3 in a heavy vehicle. My L31 pickup with 3.73 gearing walks all over my 5.3 Suburban with 4.10 gearing when towing 5000 lbs.
    And a 5.3 or 6.0, no matter how cheap you find one, will nickel and dime you to death by the time you get it in and running.
    And there's the unknown history/service life of a used one versus a slam dunk 200k+ miles you'll get out of a new crate motor.
    '98 XCSB, ZZ4 cam, Tri-Y's, Yank SS3600 TC
    PCMFORLESS.COM 87 octane tune
    14.30 @ 92.2 on motor
    13.47 @ 99.2 w/ a 50 dry shot

    '96 ImpalaSS
    10.98 @ 122 NA, 10.35 @ 128 on a 100 shot
    stock bottom LT1

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    Another OBS Suburban - new L31 or go LS

    I'm sure there will be differing opinions but I'm sure my wife will appreciate your response.



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    Last edited by azfansinnc; 02-25-2014 at 08:27 AM.
    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    Large Marge sent me SUBURBIAN's Avatar
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    Re: Another OBS Suburban - new L31 or go LS

    There's something to be appreciated about a drop in/bolt in direct replacement. Of course there's a time and a place for an LS swap, but per your original post, I just don't think this is it. If you said you had an unlimited budget, all the time in the world, a plan to change gears and transmission anyways, it would be s different story, but you didn't.
    '96 K1500 SUBURBAN

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    Another OBS Suburban - new L31 or go LS

    You guys both make good points. I would have to sell off the 98 to finance the 99 motor. I have my daughters wedding to finance so I need to be as close to net zero as possible.

    The 0411 and 4l80e are likely keepers and would move over so I would need to rewire both trucks. This also gives me some future tuneability. Probably a different topic but if I was to build an L31 are there any areas I should focus on assuming the stock injection?

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    Last edited by azfansinnc; 02-25-2014 at 08:29 AM.
    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    Re: Another OBS Suburban - new L31 or go LS

    Quote Originally Posted by azfansinnc View Post
    You guys both make good points. I would have to sell off the 98 to finance the 99 motor. I have my daughters wedding to finance so I need to be as close to net zero as possible.

    The 0411 and 4l80e are likely keepers and would move over so I would need to rewire both trucks. This also gives me some future tuneability. Probably a different topic but if I was to build an L31 are there any areas I should focus on assuming the stock injection?

    Sent from a can on the end of a string
    I would spend some time cleaning up and porting the stock lower intake manifold. The factory casting leaves alot to be desired as far as casting flash, the entry radius to the ports, and port flow. I spent about 3-4 hours with a some carbides and sanding rolls and cleaned mine up nicely when I was still running it.

    If you plan to go 4L80E and towing, I would seriously consider a 383 with a very mild cam upgrade if you rebuild the 350. Definately more torque in the RPM range that you will be running in 95% of the time than a 5.3/6.0 swap.
    1997 G1500, 5.7, 906s 2.02/1.60, GM 395' marine cam, 1.7 RR's, Marine Intake, BBK TB, 85mm MAF, 6.5 aircleaner, Thorley Tri-Ys, Thunderbolt 2.5 cats, Dynomax 22865 muffler, 4L80E, 0411, Hydroboost, 9.5" 14-bolt 3.73s, 8800 GVW front calipers, March 4490 pulleys, AD244 alt, D-Max fan

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    Well, I just converted the 98 to the 4l80e so I would probably move it forward and stick the 99 ECM in the 98 to follow the 4l60e. I see that GM offered the ht383 as a direct drop in but they are pricey. Could probably build one with similar specs for less but how much of an economy hit would I take?

    I did lose 1-2 mpg around town with the hd trans and didn't gain anything on the highway.

    I plan on using the 98 to drag the other one home. It's about 100 miles.


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    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    I vote stroking a 350 to a 383 (cheaper than a crate) with an upgradable intake (HSR, etc.) and drop a cam in it. My 383 in a '92 rcsb probably gets 20+ highway, driving it like a normal everyday driver.

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    '92 Sierra (TBI 383/Vortecs/Comp 08-412-8/EBL/4L60/3.08s), '78 Malibu (Vortec'd 350/4-speed/2.29s), '87 Pontiac Fiero GT (2.8 v6/5-speed)


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    A 383 would be nice but I would need to figure a way to do it cheaper than a crate. Vortec 383 would need to sit under the stock spider injection with MPFI. The GM HT383E would be nice. I checked into Blueprint engines and the reviews are all over the map. If I could rebuild mine for under $3k as a 383 it might be doable.


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    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    Re: Another OBS Suburban - new L31 or go LS

    The only major difference is the rotating assembly, you can use the rest of the engine just fine. You will likely pay under $2k for a short block (supplying your block and having them do the clearancing needed), and you reinstall your heads, water pump, new timing set, etc. etc. etc.

    '92 Sierra (TBI 383/Vortecs/Comp 08-412-8/EBL/4L60/3.08s), '78 Malibu (Vortec'd 350/4-speed/2.29s), '87 Pontiac Fiero GT (2.8 v6/5-speed)


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    Still need to cost it out with the local machinist etc. Of course, I need to see what the current 350 has to offer first.


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    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    The 383 will make tons more torque down low. With a small 212/218 cam in mine with Vortecs, it pulls hard from a stop all the way to 5000, and that's with a 3.08 gear.

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    '92 Sierra (TBI 383/Vortecs/Comp 08-412-8/EBL/4L60/3.08s), '78 Malibu (Vortec'd 350/4-speed/2.29s), '87 Pontiac Fiero GT (2.8 v6/5-speed)


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    5TOCK silverado_lover's Avatar
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    Re: Another OBS Suburban - new L31 or go LS

    Many know I'm a strong supporter of LS swaps...I wouldn't run a 4L80e with a LS engine unless you plan on boost and at least a 2800 stall. 4L80e torque converters aren't cheap nor is boost.
    '95 C1500, LT's, 3200 stall, and some PCM tweaking


    Quote Originally Posted by Chevy4life11 View Post
    ive got 8 inches and i still wish i had 6 more

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    Re: Another OBS Suburban - new L31 or go LS

    Quote Originally Posted by silverado_lover View Post
    Many know I'm a strong supporter of LS swaps...I wouldn't run a 4L80e with a LS engine unless you plan on boost and at least a 2800 stall. 4L80e torque converters aren't cheap nor is boost.
    Everyone knows I cannot stand the 700r4/4L60E and would not, not have a 4L80E or 4L85E in a truck.
    1997 G1500, 5.7, 906s 2.02/1.60, GM 395' marine cam, 1.7 RR's, Marine Intake, BBK TB, 85mm MAF, 6.5 aircleaner, Thorley Tri-Ys, Thunderbolt 2.5 cats, Dynomax 22865 muffler, 4L80E, 0411, Hydroboost, 9.5" 14-bolt 3.73s, 8800 GVW front calipers, March 4490 pulleys, AD244 alt, D-Max fan

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    5TOCK silverado_lover's Avatar
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    Re: Another OBS Suburban - new L31 or go LS

    Everyone knows you're also
    '95 C1500, LT's, 3200 stall, and some PCM tweaking


    Quote Originally Posted by Chevy4life11 View Post
    ive got 8 inches and i still wish i had 6 more

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    Re: Another OBS Suburban - new L31 or go LS

    Quote Originally Posted by silverado_lover View Post
    Everyone knows you're also
    NOPE, just broken enough of the gay 700r4 based transmissions to know there is something stronger and better out there that suits my driving style and torque output.
    1997 G1500, 5.7, 906s 2.02/1.60, GM 395' marine cam, 1.7 RR's, Marine Intake, BBK TB, 85mm MAF, 6.5 aircleaner, Thorley Tri-Ys, Thunderbolt 2.5 cats, Dynomax 22865 muffler, 4L80E, 0411, Hydroboost, 9.5" 14-bolt 3.73s, 8800 GVW front calipers, March 4490 pulleys, AD244 alt, D-Max fan

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    Quote Originally Posted by Fast305 View Post
    Everyone knows I cannot stand the 700r4/4L60E and would not, not have a 4L80E or 4L85E in a truck.
    So, what trans would you run? I think you are out of options unless you go 6l80e or manual. Don't you have an 80e in your Express?

    Personally, I like the solid feel of my 80e but even the 3.73 gears are not really enough to get the pig moving with a 200k L31 350...and that's the current truck. The new truck will come with a 60e that will prob get swapped with the 80e. I guess I would rather have the solidness of the 80 vs the accel of the 60, all else being equal.

    I am fairly certain the 383 is out of reach. What bolt ons will help a crate 350 wake up but not hurt the warranty? 1.6 rockers and cam is where I am looking. I plan on going this on the stand, prior to install.


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    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    Another OBS Suburban - new L31 or go LS

    Here is the next project soon after purchase. New dual exhaust. Bad cyl 4 misfire. Good body with a few dings. Needs some love but should be a good driver when complete.

    4l60e has a 150k on it but seems to shift fine. Gotta get under it and do a full eval.



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    Last edited by azfansinnc; 03-01-2014 at 06:18 PM.
    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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    Re: Another OBS Suburban - new L31 or go LS

    I see Fast305 has been hanging around here alot lately since he was banned on the titan forum. LOL I have ran a 4l80e and loved it, also ran plenty of 4l60es as well, never had a problem. The 4l60e transbuilderguy built me was a beast, I plan on him building the trans in my current truck as well.

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    Another OBS Suburban - new L31 or go LS

    Well, the L31 in the 99 is toast. It runs but immediately codes with a p0304 with good reason. I checked the compression on #4 and it has 65psi dry and 180 with oil. At minimum, rings are bad.

    Decision time. I either need to mix and match and remotor one or just sell off the 99.


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    Last edited by azfansinnc; 03-10-2014 at 08:49 AM.
    The Black Sheep - 1998 GMC K1500 Suburban SLT - 5.7L Vortec, NP246, 265/70/18 Bridgestone Dueller Revo 2. - Hecho en Mexico, baby!
    Mods: 4L80E, 3.73's. 0411 PCM by Lextech

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