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Thread: How far will a 6.2L bore?

  1. #1
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    Default How far will a 6.2L bore?

    How far can a 6.2 block be safely bored? Can I bore it to stock 6.5L specs? Got an old 6.2 sit'n around that needs rebuilt and I just as well make it a 6.5 if I can. Everything I have has the bigger engine in it anyway.

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    Depends on which 6.2 block it is.

    If it's a block which has a casting number ending in '599, then yes, it will bore to 6.5.

    If not, the only really safe (for all blocks) will be a .040" overbore.

  3. #3
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    Arrow

    My own personal opinion is that ALL 6.2L blocks can be bored to 6.5L specs. My reasons:

    (1) The 6.5L is the same engine as the 6.2L, with just a bigger BORE.

    (2) The 6.5L develops cracks more often than the 6.2L....is this because of thinner cylinder walls? Hmmmm....

    (3) The 599 block was just a TRANSITION block....the 6.2L was being phased out, and the 6.5L was being phased in. I have seen no concrete evidence that the 599 block has thicker cylinder walls than earlier 6.2L blocks.

    (4) The Diesel Depot has an early non-599 6.2L block that they've bored out and installed stock 6.5L pistons. They've put a lot of miles on it with no problems.

    I used to believe that the 6.2L couldn't be bored out to a 6.5L, but now I'm a firm believer that the 6.2L can be safely bored to 6.5L and larger bores.

    I wish someone would cut out 6.2L and 6.5L cylinder walls and measure them so that we could put this question to rest once and for all!

    Casey
    1995 K1500 Tahoe 2 door, 6.5LTD, 4L80E, NP241, 3.42's, 285/75R16 BFG K02's; 1997 506 block; Kennedy OPS harness, gauges, Quick Heat plugs, and TD-Max chip; Dtech FSD on FSD Cooler; vacuum pump deleted, HX35 turbo, Turbo Master, 3.5" Kennedy exhaust, F code intake; dual t/stats, HO water pump, Champion radiator; Racor fuel filter

  4. #4
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    This has been hashed out before, but no solution yet..

    Check this thread out, especially what More Power had to say about an engine builder boring 6.2's to 6.5 and having cylinder bores crack.

    Another Myth...

    I think I was supposed to cut a piece out of a block. Well the shop finally has some room to get to that block, so it's coming apart this weekend, and being cut by plasma torch at work the following week...

  5. #5
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    I think I was supposed to cut up my 6.5 block too... I guess I'd better get with it now that I broke it loose and took it apart.
    white '93 K2500 started it all..
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  6. #6
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    As per the linked thread I posted above, the feeler gauges were used in between the "jugs".

    I'm wondering where I should take my sample.

    Here is my block:

    (7) (5) (3) (1)

    (8) (6) (4) (2)

    Should I take the chunk out here:

    (6)<- (4) --- the side of the bore left or right (in the middle of the bore)

    Or take it out of the topside of the bore (middle probably) or bottom side (middle as well)?

    Where ya taking your sample Justin?

  7. #7
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    I don't know where to take a sample at??? I'll give ya a ring so we both can do this the same for the sake of research.
    white '93 K2500 started it all..
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    black '93 K3500 daily driver
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    I ended up going for the #1 cyl first. Eventually I might do all but #4 since it's been sleeved, but only time will tell. I used an oxy/acetelene torch to make the cuts. As a result they are not the nicest, but it gets the job done. If only I had a band saw... I made the cut in the middle of the cylinder starting at the bottom. I took out a 1"x2" chunk first. I then cut from there up both sides cutting out chunks that were a little more than 1/4 the size of the cylinder. I then cut out the top piece. (not pictured)

    With out adding the .040" that this block was bored out back to the number I came up with the cylinder wall is an average of .25" thick. I noted a high of .27" and a low of .23". This was all done with a digital caliper though. I'll either have to go to the machine shop or send them to John to be miced.

    Here's a couple of pics of what I did.









    If anyone has an old cracked 6.2 or 6.5 block laying around I'd ask that you do something similar so we can get an idea of what blocks have the good thick walls and which don't. Maybe anyone interested could contact myself or John through the private messaging here if we really want to continue looking into this.

    On a side note, I was looking into the water jackets through the new hole I made in the block to see if I could tell where the bolts go from a set of splayed main caps. I noticed that it doesn't seem like there is much material where the bolts go at first glance. I need to further examine things after I get more iron cut out, but I'm curious how these diesel castings compare to a gas block in how much iron is down there.
    Last edited by dieseldummy; 03-18-2006 at 18:55.
    white '93 K2500 started it all..
    red '94 K3500 old faithful
    black '93 K3500 daily driver
    '83 G20 conversion van
    '74 C65 truck diesel conversion...

  9. #9
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    Lightbulb

    Here's what I know about the boring (TIC) question....

    1- GM's recommended maximum overbore is .030".
    2- I've heard from an individual in South Africa and one in Australia (those guys don't have nearly the access we do to engine parts) who reported longitudinal splits in cyl walls after boring a 6.2 to std 6.5 (and I assume some number of miles thereafter).

    Based on the above, I can't suggest boring a 6.2 to 6.5 specs, except in the case of the 599 blocks (which were bored either 6.2 or 6.5 in the 1992-1993 model years by GM). But, experimentation is fine with me.... Let us know how they do after having been on the road for a while.

    Jim

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    I guess I should have mentioned that the block I cut up is a '93 vintage '599. It was a 6.5 then it was bored .040" over. I agree with GM on only going .030" for many reasons.
    white '93 K2500 started it all..
    red '94 K3500 old faithful
    black '93 K3500 daily driver
    '83 G20 conversion van
    '74 C65 truck diesel conversion...

  11. #11
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    Did some cutting...

    First off, I did a rough mic of the cylinder bores by transferring the diameter from a telescoping gauge then to the micrometer. So it's not near as accurate (and falls victim to technique) as a dial gauge set up for bores, but we're gonna try...

    I decided to do the center cylinders in the block, cylinders:

    #4 = 4.0069
    #6 = 4.0074
    #3 = 4.0083
    #5 = 4.0082

    The block was bored out .030 as stamped on the block and the pistons were 75mm (.030).

    Just a refresh on bore size here..

    The Stock bore size for a 6.2 is 3.9774" (101.026 MM)

    So, for my bored block, 3.9774" + .030" = 4.0074"

    My measurments were close, and I'm sure that the engine had at least worn .001" during it's use, although it didn't have much of a detectable ridge ring, anyways...

    So, I did some cutting at work finally!

    #4 = .2799 .2798 (measurements are at opposite ends)
    #6 = .2319 .2515 .2382 (took some of the side, verses bottom on this cut)

    #3 = .2621 .2418
    #5 = .2509 .2660

    Hmm, the smallest I measured was .2319, so thats what I feel confortable numbers wise with..

    The proof (images)!









    I'm going to make a speculation, but I don't feel that the 6.5 is a bored out 6.2L... Lets do some more testing, I'm gonna need Justin's measurements and we'll see.
    Last edited by john8662; 04-07-2006 at 23:28.

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    Thumbs up

    Then,we'll wonder what a 6.5 block would look like?
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  13. #13
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    I'm jealus John, your cuts are much nicer than mine...
    white '93 K2500 started it all..
    red '94 K3500 old faithful
    black '93 K3500 daily driver
    '83 G20 conversion van
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  14. #14
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    UPDATE!!!

    Going to make some kind of inconclusive conclusion to "how far will a 6.2 bore?"



    I received a box with some block cuttings from a 6.5 from Justin, so I got to do some measuring and thinking. Basically we want to see if we can squash the little rumor of whether you can bore a 660 cast 6.2 to 6.5 dimensions.

    Here's another pic of Justin's 6.5 cuttings:




    Ok, here are the measurements:

    Large Piece

    .2399" (bottom)
    .2436" (bottom)
    .2490" (side)
    .2000" (side)

    Small Piece

    .1984" (bottom)
    .1989" (bottom)
    .2179" (side)
    .2314" (side)

    Looking at the above measurements it's easy to see that the smallest recording is .1984" thickness.

    OK, just like we did above, let's review 6.5 bore dimensions.

    Stock 6.5 bore dimensions are technically 4.0544" (102.981MM)

    Note: we don't have any mic'ed dimensions prior to cutting for this block, so we're gonna wing it, I'd say that our error should be around ~.005"

    Block was overbored .040"

    So... 4.0544 + .040 = 4.0944"

    Our 6.5L in question should have a 4.0944 bore with no wear and with the .004" piston to bore clearance.

    Now for the fun...

    Let's compare the cylinder bore casing outside diameter between the two engines so far.

    '82 6.2L .030" '660

    We'll take our calculated measurement for the bore inside diameter (4.0074") and add the thickness of the thinnest measurement recorded (.2319") doubled (casting on two sides right?).

    4.0074" + (.2319" x 2) = 4.4712"

    Estimated 4.4712" Total Diameter of the outside of the bore casting (what you normally can't see, besides viewing through a freeze plug hole).

    '93 6.5L .040" '599

    We'll take our calculated measurement for the bore inside diameter (4.0944") and add the thickness of the thinnest measurement recorded (.1984") doubled (casting on two sides right?).

    4.0944" + (.1984" x 2) = 4.4912"

    Estimated 4.4912" Total Diameter of the outside of the bore casting.

    So...

    6.2L IS ~4.4712"
    6.5L IS ~4.4912"

    What's the difference?

    -------> .02" <--------

    OR! .020" ironically..

    According to these numbers, there IS a difference in cylinder thickness between a 6.2L (pre 599) and a 6.5L (at least a 599, others may be different).

    But, if this difference THAT significant?

    Check my math and logic here guys!

    Couple more observations...

    The measurements did make a range, depending on the position of the cast, whether it was on the opper part of the bore, the lower part of the bore, or next to another cylinder part of the bore (you know what I mean). I took the thinnest measurements mainly because I'm looking for the safety margin. The bores do seem to be thinner at the tops, which I really didn't get from my 6.2L cuttings... Hmm...

    J
    Last edited by john8662; 06-15-2006 at 14:46.
    1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
    1982 C10 SCSWB 6.2NA, 2.73 700
    1986 C10 SCLWB 6.2TD 3.73 700
    1989 V20 SUB 6.2NA, 3.73 400
    1994 G20 VAN 6.5NA, 3.42 60E
    1994 K20LD ECSWB 6.5TD, 3.42 80E
    1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
    1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
    1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
    1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
    1995 C20LD ECSWB 6.5TD 3.73 80E
    1995 K20LD SCLWB 6.5TD 3.73 80E
    1996 K30 DRW 6.5TD 4.10 80E
    1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway

  15. #15
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    One thing that I should ad is that the cyl to piston clearence on this block was more along the lines of .007". That will make some difference in the calculations I suppose. I'll let you take care of the math, makes my head hurt
    white '93 K2500 started it all..
    red '94 K3500 old faithful
    black '93 K3500 daily driver
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  16. #16
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    Quote Originally Posted by dieseldummy
    One thing that I should ad is that the cyl to piston clearence on this block was more along the lines of .007". That will make some difference in the calculations I suppose. I'll let you take care of the math, makes my head hurt
    Head hurt? I was thinking along those same lines!

    So, basically we can say that the 6.5L block is (fudging a bit) nearly .030 thicker if you say that the bore clearance was .007, then factor in wear from HD use...

    I'd be interested in cutting a STD bore 6.2 with cracked main webs or other abnormality, as well as a 6.5. I think I've got another cracked 6.2 to cut thats STD bore, but don't (hopefully) have a cracked 6.5 to cut (yet)...

  17. #17
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    Quote Originally Posted by dieseldummy
    I ended up going for the #1 cyl first. Eventually I might do all but #4 since it's been sleeved, but only time will tell. I used an oxy/acetelene torch to make the cuts. As a result they are not the nicest, but it gets the job done. If only I had a band saw... I made the cut in the middle of the cylinder starting at the bottom. I took out a 1"x2" chunk first. I then cut from there up both sides cutting out chunks that were a little more than 1/4 the size of the cylinder. I then cut out the top piece. (not pictured)

    With out adding the .040" that this block was bored out back to the number I came up with the cylinder wall is an average of .25" thick. I noted a high of .27" and a low of .23". This was all done with a digital caliper though. I'll either have to go to the machine shop or send them to John to be miced.

    Here's a couple of pics of what I did.









    If anyone has an old cracked 6.2 or 6.5 block laying around I'd ask that you do something similar so we can get an idea of what blocks have the good thick walls and which don't. Maybe anyone interested could contact myself or John through the private messaging here if we really want to continue looking into this.

    On a side note, I was looking into the water jackets through the new hole I made in the block to see if I could tell where the bolts go from a set of splayed main caps. I noticed that it doesn't seem like there is much material where the bolts go at first glance. I need to further examine things after I get more iron cut out, but I'm curious how these diesel castings compare to a gas block in how much iron is down there.
    Going back in time here, but did anyone had a chance to cut a block trough the pan rail to see where the best place is for splayed main bolts?

    I felt trough a freeze plug hole , and did not think there was that much meat up at the panrail area. Kinda hard to figger out how deep to drill without going trough in the water jacket.
    I would have cut a block apart myself if i could have found one in my area.

    Thanks Simon
    98 GMC sierra 2500 ext cab 4x4 auto tr 6.5 td 252000 km. needs new engine, next project
    95 GMC sierra LE 2500 ext cab sh box 4x4 auto tr 6.5 td 328.000 km. my wife's truck .remote pmd on cooler
    89 GMC sierra SLE 1500 ext cab 4x4 auto tr 6.2 720000 km engine swap at 665000 km because of broken oil cooler line. 6 bolt wheels.
    Waldon wheelloader repowered with a 6.2 na

  18. #18
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    Got a good idea of how to section the block?

    I don't think a cutting torch is a good choice here...

    I've got three cracked blocks sitting around that I'd like do some experimenting with, if I had a way to cut it, then i'd go for it.

    But you're right, there really isn't that much meat there for the splayed bolts, and you'll certainly run the risk of hitting the water jacket.

    My splayed 6.5 fell victim to hitting the water jacket on a couple of holes.

    J
    1982 C10 SCSWB 6.5TD, mods too extensive to list. (13.69 1/4 mile @94.6 MPH) RACE TRUCK
    1982 C10 SCSWB 6.2NA, 2.73 700
    1986 C10 SCLWB 6.2TD 3.73 700
    1989 V20 SUB 6.2NA, 3.73 400
    1994 G20 VAN 6.5NA, 3.42 60E
    1994 K20LD ECSWB 6.5TD, 3.42 80E
    1995 K20 SUB 6.5TD, Wrecked, ran into by stupid teen.
    1995 C3500HD DRW 6.5TD, 12' Flatbed 5.13 80E
    1995 C3500HD DRW 6.5TD, 18' Rollback Wrecker 4.63 80E
    1994 C20HD ECLWB 6.5TD 3.73 80E Wifes Truck.
    1995 C20LD ECSWB 6.5TD 3.73 80E
    1995 K20LD SCLWB 6.5TD 3.73 80E
    1996 K30 DRW 6.5TD 4.10 80E
    1997 C10 Tahoe 2Door 2WD 5.7L to 6.5 Conversion Underway

  19. #19
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    Quote Originally Posted by john8662
    Got a good idea of how to section the block?

    I don't think a cutting torch is a good choice here...

    I've got three cracked blocks sitting around that I'd like do some experimenting with, if I had a way to cut it, then i'd go for it.

    But you're right, there really isn't that much meat there for the splayed bolts, and you'll certainly run the risk of hitting the water jacket.

    My splayed 6.5 fell victim to hitting the water jacket on a couple of holes.

    J
    I think if you take a 7" angle grinder with a 1/8" cutoff blade and start 3" from 1 side of a mainweb and cut a groove under a angle towards the head, and then cut straight down right beside the web till the cuts meet .
    you should be able to get a nice wedge out of there me think
    you just need a real steady hand, and brace yourself good. it wil cut like butter. Maybe leave the last 1/4 inch sit , take the piece out with the hammer, prevents the piece from jamming the grinder if it breaks loose. is safer that way me thinks
    98 GMC sierra 2500 ext cab 4x4 auto tr 6.5 td 252000 km. needs new engine, next project
    95 GMC sierra LE 2500 ext cab sh box 4x4 auto tr 6.5 td 328.000 km. my wife's truck .remote pmd on cooler
    89 GMC sierra SLE 1500 ext cab 4x4 auto tr 6.2 720000 km engine swap at 665000 km because of broken oil cooler line. 6 bolt wheels.
    Waldon wheelloader repowered with a 6.2 na

  20. #20
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    Cutting with an angle grinder kindof sounds like a suicide mission... A much better choice would be a band saw. If I had access to one I would have taken a cross-section of the block. There isn't much meat in the pan rail area for splayed mains. I guess there doesn't need to be since the idea behind splayed mains is just to spread the load out over the block more evenly. I'm still not certain it is worth it though...
    white '93 K2500 started it all..
    red '94 K3500 old faithful
    black '93 K3500 daily driver
    '83 G20 conversion van
    '74 C65 truck diesel conversion...

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