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Thread: 6.2L vs 6.5L--what say you?

  1. #1
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    Default 6.2L vs 6.5L--what say you?

    I'm sure that this has been hashed out before, but I tried searching and didn't find anything. If you have a link to a valid thread, please post it. Otherwise, I'm here to ask what you guys think about the 6.2 vs 6.5. Let me give you a little background into why I'm asking. I need to pull the engine in my '99 CCLB to investigate the sudden low oil pressure (and metal in the oil). It's not the original engine in the truck so it might be a newer Navistar cast, oil cooled 506 or an older block rebuilt by some less-than-respectable company. I'm hoping for the 'good' squiter, but my luck says not. If it proves to be something less desirable I will probably start over from scratch on the build. I have been looking for a 2001+ block, but have had trouble finding a used one. I was reading about Heath's LSR truck and noticed that he used a 6.2 as the foundation because he likes some of the design features better. Should I go the same route? If so, what are the better casting numbers to look for? What ones should I avoid? Never owned any 6.2's so I don't really know where to begin. Also, if I go with a 6.2, how do you guys feel about having my machinist put the piston oil cooling holes in the block? I want POC, but I realize that lots of people get by just fine without it, and just as many hate it all together. Last question. Is there any credence to the idea that the 6.2 might get slightly better fuel economy? I'm trying to tell myself that it might, just as a way to justify using a 6.2. OK, let's hear it.
    1999 GMC K3500 CCLB-Light Pewter SRW 4X4 6.5L 4L80E 304K original WP!(6900# Best 17.24s@79.4)
    DE exhaust & Fluidampr from Burning Oil Battery/GP harness & HX40 adaptor from Racedaymechanic Tune, GPs, & turbo controller from Heath Diesel Gauges from eguages.com/PML trans pan/EnergySuspension mounts/Dmax fan/ARP studs/Snow stage 3/Heath HO injectors/ATT(still to come)
    1997 GMC-K1500 ECSB-White Z71 249K(Coming Soon-334 stroker, 0411 ECM, Magnaflow SS)
    1993 GMC Typhoon #1440-White/Argent Not stock, HANG ON!! 113K

  2. #2
    Hope and Change 3500GMC's Avatar
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    6.2's are awesome. Been around for a long time. Will be around for a long time to come.

    It's my opinion that a 6.2 block is stronger (GM for GM, stock for stock) than a 6.5. The difference is in the bore, and in that, the block isn't 'hogged out' as much around the main web areas. More meat in between the cylinders too.

    Heads are slightly different, be can be used with all 6.5 peripherals no problem. 6.2 heads have bigger valves and have the potential of flowing lots of air with some work. Pre cups will interchange.

    I wouldn't get too excited about the squirters, not a 'priority'..

    6.2's came in GM trucks at a time where the wheezer gassers were barely in the teens on MPG. The 6.2 is a MISER in stock form- effectively doubling the MPG of a gasser. As with anything, you start hotrodding it (boost&fuel) and leaning on it, the fuel mileage suffers.

    I am doing an '81 6.2 long block swap into the '93 6.5 one ton right now, as a matter fact.
    '93 GMC Sierra SLE K3500 RCLB 4L80E 4.10 axles, lockers, JB8 13x3.5 brakes, 4X4 SRW 1TON, 6.5TD now a fully ported big valve '82 6.2 turbocharged, mandrel straight pipe w/ warpspeed x-over, Fluidampr, tweeked DB2-2831-4911 IP, Battery relocation, H/O W/P, CDR elim custom vent, PYO wheels w/285-75 Dick Cepek FC-II's - Quasar Blue and Argent Silver two tone.

    ...and other various GM cars and trucks


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    Registered User buddy's Avatar
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    You dont want the oil squirters, just one more way to make the block weaker. The 599 casting of the 6.2 should be desirable. The difference is small, like 1/16" inch more metal could be left between cylinders compared to a 6.5. If using turbo youd want to use the 6.5 heads as they are designed to run with boost, whereas 6.2 was not.
    94 6.5TD C1500 ECLB w/ 50 gallon aux tank/box; 235/75R17 tires on Alloy wheels; 3.42 gears; A-Team Turbo; 4" Aero Turbine 4040 muffler to 5" Aero Turbine 5050XL muffler to 6" tip before rear axle; FSD heatsink, marine injectors; "F" intake; SynBlend 10W-30 oil; Walbro FRB-5 w/ 12 micron prefilter; Feed The Beast; WMI and Propane fumigation; OPS extension & relay; 110K original miles; Engh GMTDScanTech
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    I would use the 6.2 the same way I'm planning to build my 6.5. That being with thicker head gaskets to lower the compression a little(19.5:1), gear drive, girdle, Heath ECM(GLE), HX35, 4" exhaust, ATA charge air cooler, and maybe a few other goodies as I can afford them. What I want is to make 280-300hp at the crank and do so reliably. That's what I think a '99 diesel should have been, and deserves to be. I've got quite a collection of 6.5 stuff from my previous years of loving these things so heads, manifolds, injectors, etc. isn't a problem.(plus all the parts on the truck now) I just wonder if I should skip building one of the blocks I have and go find a good 6.2, if I can't locate a good navistar cast 6.5L.(this is assuming that the block in the truck isn't one) I want a girdle like the one that Inlinesix has been talking about, but I don't know if he'll have any avaliable when I get to that point so I'm going to see what my machinist thinks he can do to come up with something like that. LB7 power and mileage in my GMT400 with 5.7 vortec relaibility. That's the goal.
    1999 GMC K3500 CCLB-Light Pewter SRW 4X4 6.5L 4L80E 304K original WP!(6900# Best 17.24s@79.4)
    DE exhaust & Fluidampr from Burning Oil Battery/GP harness & HX40 adaptor from Racedaymechanic Tune, GPs, & turbo controller from Heath Diesel Gauges from eguages.com/PML trans pan/EnergySuspension mounts/Dmax fan/ARP studs/Snow stage 3/Heath HO injectors/ATT(still to come)
    1997 GMC-K1500 ECSB-White Z71 249K(Coming Soon-334 stroker, 0411 ECM, Magnaflow SS)
    1993 GMC Typhoon #1440-White/Argent Not stock, HANG ON!! 113K

  5. #5
    6.5 nut job/addict
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    Good used 6.5 blocks are extreamly rare and very expensive.6.2s are cheap and plentiful.There has been a few military take outs on the gov. liquidation auction in kansas. They go for a minimum of $150 http://www.govliquidation.com/list/c7601/lna/1.html
    Barry



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    Walking J Designs Veg_Out's Avatar
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    I'm building a 6.2 to 6.5 hybrid now. I'll let you know.

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    Does anyone have experience buying stuff on govliquidation? I've looked at stuff on there before, but never bought on any of it. I just wonder what the process is like. If the goverment is involved I'm sure there's more hoops than a dog show!
    1999 GMC K3500 CCLB-Light Pewter SRW 4X4 6.5L 4L80E 304K original WP!(6900# Best 17.24s@79.4)
    DE exhaust & Fluidampr from Burning Oil Battery/GP harness & HX40 adaptor from Racedaymechanic Tune, GPs, & turbo controller from Heath Diesel Gauges from eguages.com/PML trans pan/EnergySuspension mounts/Dmax fan/ARP studs/Snow stage 3/Heath HO injectors/ATT(still to come)
    1997 GMC-K1500 ECSB-White Z71 249K(Coming Soon-334 stroker, 0411 ECM, Magnaflow SS)
    1993 GMC Typhoon #1440-White/Argent Not stock, HANG ON!! 113K

  8. #8

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    Quote Originally Posted by buddy View Post
    The 599 casting of the 6.2 should be desirable. The difference is small, like 1/16" inch more metal could be left between cylinders compared to a 6.5. If using turbo youd want to use the 6.5 heads as they are designed to run with boost, whereas 6.2 was not.
    The 599 is desireable but hard to find. Most are 660 2 piece RMS blocks. The difference in bore on the 6.2 is 2mm less than the 6.5 (101mm vs 103mm respectively). If the 6.2 heads are within warpage limits (.003" laterally, .006" longitudinally), I would just swap the precups with some diamond cups from a 6.5 and keep the larger valves of the 6.2 as the precups and valves are the only real difference. Pocket porting for a performance build couldn't hurt anything either.
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  9. #9

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    Steel Soldiers has a whole sticky on buying from GL.
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  10. #10
    Hope and Change 3500GMC's Avatar
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    Quote Originally Posted by randomid25 View Post
    ...keep the larger valves of the 6.2 as the precups and valves are the only real difference.....
    Watch the injector angle on the early 6.2 heads with the long coarse threaded body injectors as there are no short injectors to be had to thread right in these heads. As we know, the 4&6 injectors are wedged behind the manifold on a 6.5 turbo. Makes things interesting for retro 6.2 N/A swaps. Been there, done that.
    '93 GMC Sierra SLE K3500 RCLB 4L80E 4.10 axles, lockers, JB8 13x3.5 brakes, 4X4 SRW 1TON, 6.5TD now a fully ported big valve '82 6.2 turbocharged, mandrel straight pipe w/ warpspeed x-over, Fluidampr, tweeked DB2-2831-4911 IP, Battery relocation, H/O W/P, CDR elim custom vent, PYO wheels w/285-75 Dick Cepek FC-II's - Quasar Blue and Argent Silver two tone.

    ...and other various GM cars and trucks


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    Quote Originally Posted by Acesneights1 View Post
    Steel Soldiers has a whole sticky on buying from GL.
    Ah-Ha! Thanks for that. I'll check it out.

    I'll probably use all 6.5L stuff from my truck except for the short block. I understand that the big valve heads are more prone to cracking between the valves and I don't know that they are as big of an advantage in a boosted application.

    Is the 599 the only 6.2 with a one piece rear main seal? I've grown quite attached to that design and it's oil control abilities.(in the gassers anyway)
    1999 GMC K3500 CCLB-Light Pewter SRW 4X4 6.5L 4L80E 304K original WP!(6900# Best 17.24s@79.4)
    DE exhaust & Fluidampr from Burning Oil Battery/GP harness & HX40 adaptor from Racedaymechanic Tune, GPs, & turbo controller from Heath Diesel Gauges from eguages.com/PML trans pan/EnergySuspension mounts/Dmax fan/ARP studs/Snow stage 3/Heath HO injectors/ATT(still to come)
    1997 GMC-K1500 ECSB-White Z71 249K(Coming Soon-334 stroker, 0411 ECM, Magnaflow SS)
    1993 GMC Typhoon #1440-White/Argent Not stock, HANG ON!! 113K

  12. #12

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    Quote Originally Posted by restoguy View Post
    Is the 599 the only 6.2 with a one piece rear main seal? I've grown quite attached to that design and it's oil control abilities.(in the gassers anyway)
    Yep, its the only 1 piece RMS 6.2l.
    1983 Suburban 6.2/700r4 4x4
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    (Don't tell my dodge, but the burb is funner to drive)

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  13. #13
    Well it hits on 7 of 8... WarWagon's Avatar
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    A 6.5 is no more than a bored out 6.2. To keep the rotating mass the same GM thinned out the 6.5 pistons vs. the smaller bore 6.2 pistons. Thinner pistons at the top mean they are easier to melt when you turn up the pump and abuse it. You did get a 3500 for abuse right?

    Save some cash and go with a 6.2. Buy new heads as your 6.5 heads likely have cracks. Or do military surplus 6.2 and specify they check the injector length. $950 plus shipping from Boyce with a 30 day warranty. You will not get a 6.5 from a junkyard for that.

    Replace head gaskets and use 6.5 injectors. Precups are a good idea.

    A re-built 6.2 from Heath diesel with ceramic coated pistons and balancing is cheaper than a 6.5 with the same treatment.

    Precups, a bad pre turbo exhaust leak, made my 6.2 repower smoke a lot. Make sure you replace exhaust manifolds, $100.00 each on ebay, when you pull the engine.

    But for $1200 shipped Boyce surplus 6.2, new heads gaskets, new starter I was back on the road in 3 weeks and total cash outlay ~$2000.00 recovering from a from a blown 6.5.
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  14. #14
    6.5 nut job/addict
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    14 more 6.2s added on gov liq. auction in fort riley this week. From what I'm told,it takes 4-6 weeks to get approved the first time. Much faster after that. Many times the container can be sold for what was paid for the engine and container. It's a $150 minimum bid for any item on the auction.
    Barry



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  15. #15
    Hope and Change 3500GMC's Avatar
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    Quote Originally Posted by WarWagon View Post
    ....You will not get a 6.5 from a junkyard for that.....
    I doubt you could GIVE me a used 6.5 from a junkyard... The 6.2 repower isn't really a slam dunk either. Just ask me. ):h
    '93 GMC Sierra SLE K3500 RCLB 4L80E 4.10 axles, lockers, JB8 13x3.5 brakes, 4X4 SRW 1TON, 6.5TD now a fully ported big valve '82 6.2 turbocharged, mandrel straight pipe w/ warpspeed x-over, Fluidampr, tweeked DB2-2831-4911 IP, Battery relocation, H/O W/P, CDR elim custom vent, PYO wheels w/285-75 Dick Cepek FC-II's - Quasar Blue and Argent Silver two tone.

    ...and other various GM cars and trucks


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