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SBC Engine Rebuild guidance

Discussion in 'The Garage' started by 73k5blazer, Jul 10, 2005.

  1. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    I'm just looking for some expertise in what to do here. This engine is my daily driver, it was starting to miss and burn fuel in the exhaust, had 150k on it, leakdown test showed no. 3 was losing 40%, all others were holding tight at 15% loss, wet vs. dry compression on all cylinders was about 15% increase on wet.
    Upon teardown there was massive buildup of crud (oil sludge) in the lifter valley, and I think I found the problem with the no. 3, the intake lifter there was sticky, hence the intermittenance of my missing problem. It tooke a vice to compress the plunger and when I did, it didn't come back up. Cam had massive varnish on it. One cam bearing looked a little scored, one main bearing looked a little score, nothing terrible though more or little burn than a score. Cylinder walls look excellent, pistons only needed slight tap to come out, no ridge reamer nessesary. Vavle stems had alot of oil on them (it was starting to burn oil too)
    So what I'm thinking is to hone it, buy stock main bearings, stock rings, new cam/timing set. What about the heads? They look fine, I'm thinking new seals? (guides are part of the head right, can't replace those?).
    Not looking for any radical performer here, just a good dependable Daily driver.
    I know I could buy a crate motor for arond $1500, but I kinda of want to do it my self, just for the learning experience. Never done a complete whole engine before. How much does machine work cost? (I'm thinking hot tanked and honed)
    What would you all do?
     
  2. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    It is possible to turn the crank, resize the rods, hone the cylinders, new bearings and rings for under $1000. depending on where you go.
    If you need headwork done with all new valve seats, guides, and a valve job that will run you close to $500..
    so all said and done you could be in it around $1500.
     
  3. mudslinger99

    mudslinger99 1/2 ton status

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    You can get a complete rebuild kit for about $300 bucks..
     
  4. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Is it nessesary to turn the crank? It looks fine. I mic'd all the journals, they are all well within stock spec. I was thinking I didn't even have to do that, but like I said, never done a whole engine before, so I don't know what "should" be done.
     
  5. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    I don't know. i needed to have my crank turned when the machinst measured it and told me it was out of round. :crazy:
     
  6. K5Chris

    K5Chris 1/2 ton status

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    labor: boil block & heads, bore .030" over, hone, linebore mains, install cam bearings, install freeze plugs
    grind & polish crank
    resize rods, computer spin balance on rotating assembly
    3 angle valve job, install new seals, guides & springs

    new parts: cam & lifters, double roller timing chain, oil pump, all gaskets & seals, new hyperutectic pistons, rings, all new bearings, freeze plugs, valve springs, guides & seals.

    parts cost bout 300, and labor was bout 600. did the dissassembly and reassembly myself. out the door price after tax and enviromental, was right at $1000
     
  7. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Line bore. Hmmmm.. Is that a nessesary service?
    I'm not trying to cheap out, but am I'm trying to not spend more than is really nessesary. The body on my DD will probably fall off in another 100,000. Plus, once the price starts approaching the $1500 range, it's kinda of stupid to not get the GM motor, with warrenty, assembled and all the machine work done for you.
    I think kinda from what I'm hearing here, i need to just take the parts to a machine shop and have them reccomend what the thing really needs.
     
  8. LongIslander26

    LongIslander26 1/2 ton status

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    Well....

    Since this is a job you don't want to have to do again any time soon, and you admittedly have limtied wrenching skills in this area, I would spend the money to have a machine shop check things out and recommend services you need. (A line bore probably isn't one of them), but they can at least measure everything to make sure it's good to go back together. (After you double check their work, of course) You can save yourself some $$ by cleaning the block as best you can before and after machining. There's always SOME grunt work requiring some elbow grease that the machine shop will do, for a fee, or you can do it yourself, just ask them what and how. There's no problem wanting to screw it back together yourself, you just want to be sure it's going to work real good and last a long time when it's all said and done.
     
  9. dirtwarrior17

    dirtwarrior17 Banned

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    Make sure you get the block and heads magnufluxed if you do rebuild it yourself. no point in stuffing good parts in a bad block. The heads usually crack right between the exhaust and intake valves especially if the motor has gotten good and hot more than a few times.
     
  10. K5Chris

    K5Chris 1/2 ton status

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    i did about all there is to do, and only spent $1000, and mine is a 87+ tbi engine, which parts cost more on. definately take the parts to a good machine shop and see what they reccomend. do your homework though, check the bbb on them first.
     
  11. diesel4me

    diesel4me 1 ton status Premium Member

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    at least have the crank checked...

    I've had a few "backyard rebuilds" go south because I just assumed since the crank "looked" fine and had no visible wear,I could get away with putting standard size or .001 or .002 under bearings in with no problem..WRONG!...a few thousand miles later,the bearings were rapping,one motor spun one,and ruined the crank and block...I forgot about "taper"..the fact bearings dont always make full contact across the entire surface,but often rub mostly on one side more than the other..this leads to rapid wear,and early failure!..I'd have the crank miked by a pro,and polished or ground undesize if needed to ensure the bearings make full contact...I learned the hard way just because it "looks" good,or even mikes out OK,it might still need to be turned... :doah: :(


    For the record,you can buy a crate motor from GM brand new for less than 1500 bucks,WITH a warranty!...sometimes thats the best route--then its ALL new,no "rebuilt" and "bored out" and "turned down" parts that already have 100,000 miles on them... not to mention the time and labor saved..:crazy:
     
  12. Mad-Dog

    Mad-Dog 1/2 ton status

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  13. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Yep, I know that, (I think I mentioned that in my first post). That aws my first thought. But then I was like, $1200, plus misc crap is probably going to be more like $1400 when it's all said and done, do I really want to put $1400 into my rusted out Daily driver?

    I took the parts to the machine shop this morning, he said he's going to mic the crank to check, but looking at it and the bearings he said he thinks it probably just needs polished. Cylinders do need bored/honed. Calculating all the parts I need and his machine work and misc crap, I can get out the door doing it myself for about $750, and thats with a new edelbrock intake which I'll have to put on a GM engine anyway (the 1200 engine doesn't come with intake).
    I know about the warrenty, but like I said in my orig. post, I kinda of want to do it my self just so I can say I built an engine. That's almost half the cost too, and I can pick my parts (cam, valvetrain, pistons, etc...). If it craps out, well then I guess I'm out $700, but like we say on the trail, getting stuck is half the fun right?
     
  14. diesel4me

    diesel4me 1 ton status Premium Member

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    Its your time,money,and truck!

    Its your call which way you want to go...I'd personally go for a new engine,but I've rebuilt a lot of them,and am getting tired of all that work,only to have something screw up in the end sometimes...its a toss up as far as the cost,its about the same for a quality rebuild VS a new crate motor.

    .I can see your desire to build it yourself--it IS satisfying to say "I Built This Motor"--but only if it all pans out and it lasts..sometimes using old parts,it does not always turn out that way..working in an auto parts store with a machine shop,I saw my share of horror stories,like when an old block is bored and honed,and it cracks the first day back in the vehicle,or a valve that was re-used after being ground dropped its head into the combustion chamber...

    One motor we completely rebuilt to the tune of 1500 bucks had the starter bolt portion of the block snap off when the owner put the starter back on!--we never saw the crack there,we were too busy looking INSIDE the cylinders and main bearing web areas to notice!... :doah:

    As for "dumping" 1200 bucks into a rusty truck--I would not worry,you can always yank the motor out and use it in another truck,or sell it to recoup your losses... :crazy:
     
  15. Z3PR

    Z3PR Banned

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    That $1,500.00 for the crate motor looks better and better when you consitter the warrenty. Then you can build a monster motor as funds permit (No hurry) with the motor you'll be pulling out. :thinking:
     
  16. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Well I totally know what your saying, and it is a little worrying (especially after some of the stories here). But I'm think I'm going to do it, if for nothing else than to say I did it at least once.
    I already dropped the parts off at a shop this afternoon. But he won't get to it for another week or so, so I could back out if I really wanted.

    I have a couple of questions, now that I've been doing more research.

    1) Since the eninge does need bored, should I get oversize rings, or oversize pistons? The guy at the shop just said to use oversize pistons and stock rings, what's the diff?

    2) If you do use new pistons, isn't a complete balancing job required then because you've screwed with some main components? Or does balancing just refer to the crankshaft itself and nothing else.

    3) From what I see, most master kits, or rebuild kits don't include rocker arms. It is unwise to re-use those? Should I buy new ones?

    Thanks for all the input so far!
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    "Stock rings" I assume he meant moly. Your rings match the bore diameter just like the piston does. For instance, .030" over stock bore, 4". Pistons have this stamped on the top.

    IMO you want hypereutectic pistons and moly rings.

    I wouldn't assemble another motor without balancing it. Changing pistons alone affects balance to a large extent, so it's insurance towards longevity. You hear of people building motors and them coming apart, another opinion is that shortcuts cost you money in the long run, not balancing being a shortcut. Around here a full balance is just over $100, not too much once its all added up.

    I wouldn't re-use rocker arms, stock are very cheap to replace. Nothing like sending a pushrod through a rocker arm tip. :) Besides, aftermarkets are generally considered to be more accurate/consistent than stock.

    Heads are one place to really look at for cost. For "not much more" (just like everything else lol) than the cost to completely rebuild a set of junk old heads, you can get some heads that are MUCH better, brand new. Depends on applciation, etc., but for even a stock rebuild, I think heads are the largest expense in building a motor where you can take some pretty different paths, and the cost is still worth the gains.
     
  18. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Ok, so let me ask this, do you need new pistons, and if you don't, do you need balancing? Again, not trying to cheap out, but more curious than anything.
    The pistons are fine, I think? What goes bad with them, the ring grooves?

    BTW, and I hope nobody gets mad, this is a 4.3l V6 Chevy engine. Very similiar to V8 SBC, middle two cylinders cut out, many parts are interchangable (pistons, timing chain, etc...etc..). Nobody makes aftermarket heads anymore, there is no choice but to rebuild them.
     
  19. Mad-Dog

    Mad-Dog 1/2 ton status

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    If ya bore the block then ya need oversize pistons bro....and rings to go with em
    The piston skirt will get scuffed from sliding up n down n the bore but u can take a some emory cloth and clean it right up

    If the bore is still concentric or perfectly round (which i doubt) after 150,000 miles then ya can slap standard size rings on the pistons, hone a little cross-hatch into the cylinders to help seat the rings and slide the slugs back in the holes.

    If you don't replace the pistons then balancing is not required for your particular application.

    If any of the main or rod bearings had babbit showing then ya gotta turn the crank .010" under and replace the bearing shells.

    We were thinking this was a SBC this whole time.....why didya wait so long to drop the bombshell............ :dunno:
     
  20. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Essentially it is a SBC, but missing a couple cylinders. :blush: I know, sorry about that.
    I appreciate all the help though!
     

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