1974 Chev truck, 350 engine, rod knock

Discussion in 'Shop Talk' started by fud2468, Oct 30, 2006.

  1. fud2468

    fud2468 Active Member

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    I'm inspired to ask this here--haven't had much luck on the Chev truck sites.
    This pickup was given to me "as is" to pay a debt of $350. It's in good shape otherwise but has one or more bad rod bearings. The engine has good compression and I want to know if the bearing or bearings can be changed without pulling the engine. It has duals, so at least there's no crossover pipe to deal with.
    Looking at it from underneath, it looks like there's enough clearance to be able to drop the pan. However there's a deep crossmember under nearly the whole front of the pan that looks like it would then prevent me from easily getting at the front rod bearings (if that's where the knocking is).
    So would I have to raise the front of the engine to get better access?
    Or if I had to do that, would I be better advised to pull the engine and get it upside down on a bench to work on it?
    Probably a rebuilt short block would be ideal, but the top end is in such good shape I hate to tear it down more than necessary.
    Thanks,
    Ray Mac.
     
  2. skruzich

    skruzich Well-Known Member

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    Personally, I would pull the motor. IF you have a bad rod bearing, and it has been knocking against the crank, your never going to get a new set of bearings to last in that rod.
    The best thing you can do at this point is pull the crank, mic it and order one from the parts store and replace the crank, get a set of oversized bearings, Pull the pistons out and check the rings and feel up inside the cylendars and see how much of a groove you have in the walls. IF its negligible, just put the pistons back in, replace crank, with oversized bearings and put back together.

    Actually what i would do is rebuild the motor. It only costs around 186.00 for a rebuild kit, and 75 bucks for a crank 100 bucks to vat and bore the block.
    Total cost with new water pump, new valves, and other misc parts shouldn't run more than 500 bucks.

    AND a 350 is worth rebuilding. Their hard to find. Before you spend a dime though, check where the starter bolts on, and make sure that the block is not cracked where the starter bolts go into the block. IF they are, get that welded before it breaks. IF it breaks, its trashed.
     

  3. fud2468

    fud2468 Active Member

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    Thanks, skruzich, you make good sense. Good chance the crank is out of round, etc. I appreciate your detailed reply.
    Actually I may have another way to go: I had a '72 wagon that I junked, but I kept the 400 small block that was in it.
    I saved that because they're scarcer than 350's and supposedly valuable for their cranks, but I might just rebuild that instead. I hope it's basically a drop-in, though the deck height would be greater. Exhaust manifold outlet location is something else I need to check on too. Come to think of it, the deck height would probably affect alignment with the exhaust pipes.
    Maybe I'll do the 350 after all, just thinking out loud here.
    Ray Mac
     
  4. skruzich

    skruzich Well-Known Member

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    Personally i wouldn't waste my time with a 400. Their notorious for overheating because of the siamese cylendars. That is the two middle cylendars do not have a water jacket in between them so they overheat. BUT
    I would take the crank and rods out of that sucker, and take that 350 and bore it 60 over and build a stroker 383 out of it using the 400 crank and rods!!!
    It will cost you a bit more because the boring will be more and you will have to put bigger pistons in, and you will also have to do some grinding on the block to get the clearance for the crank to turn without hitting the block but you would have a 383. :D
     
  5. dagwood

    dagwood Well-Known Member

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    Re-build the 350 and sell the 400. The 350 will go the long haul for you and that 400 won't even come close.
     
  6. mightybooboo

    mightybooboo Well-Known Member

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    And dont forget the crate 350 from your chevy dealer.BIL put one in his suburban and to say he is pleased is an understatement.But do shop around the dealers for the best price,can vary up to 700 dollars,big savings just by shopping around.Get em for 1300 dollars,thats huge bang for the buck for a new engine.

    BooBoo
     
  7. farminghandyman

    farminghandyman Well-Known Member Supporter

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    also if your one who drive with there foot to the floor, the 400 will blow way before the 350, the rods cant take that much stroke at high rpm,

    also you may need to replace the rods on the cylinders that are lose as they may have stretched, the bearing caps, and if the bearing has spun more problems, new crank or regrind depending on the situation,

    but I would pull the motor, and use a engine stand, I may be wrong but I don't think you can pull the piston out from the bottom of the motor, you will have to go through the top, remove the head, and if your that far in to it I get the valves ground and go through it with new seals, and bearings and possibly re-bore it pistons and ring it, if you can do the assembly your self parts are not bad, and machining is some but you will save,

    IF the 400 is in runnable condition It should bolt into place, may have to change the exhaust manifolds,

    a lot has to do what your wanting to do with the pickup, and how your going to use it, if if just to take the trash out once or twice a year or are you wanting to use it ever day as a work truck,

    if your just going to use it minimally or sell it, I just drop the 400 into it and use it, (how many miles are you wanting out of it), and how many does it have on the machine now?

    if you need serious work truck then rebuild the 350 right and go for it,
     
  8. fud2468

    fud2468 Active Member

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    I would only use the truck occasionally and probably total 2 to 3 thousand miles a year at most. Main use would be light local hauling on level terrain and to haul firewood from my flatland property up to my daughter's place 130 miles from me, where all she has to burn is manzanita. That requires going up to about 2000' elevation a couple of times a year, but I would keep my foot out of it and would not strain it.
    IIRC, putting the 400 crank in a 350 also requires offset grinding crank journals undersize for clearance purposes. A lot of work, and I don't need that much power anyway. I failed to say the truck is a 3/4 ton with automatic and a 3.42 rear.
    Until now I wondered why guys didn't just mod a 400 rather than build up a 350 to 383, but I guess the 400 overheating issue must be part of the reason.
    Looks like I will stay with a 350.
    Thanks again,
    Ray Mac.
     
  9. skruzich

    skruzich Well-Known Member

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    Yeah 400's were basically a piece of crap as they did a poor design on the middle cylendars.
    Ehhh yeah you have to do some grinding work on the journals for a 383, but then you have a 383 :D I built two already and put one in my camaro, now I am taking it out and dropping a l2 corvette motor with 700r4 into my 1980 camaro.
     
  10. MELOC

    MELOC Master Of My Domain

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    are you racing this truck or what? i see no need to bore out a 350 to a 383. 350's S & G plenty good, lol. the 350 stock motor is awesome and reliable.
     
  11. skruzich

    skruzich Well-Known Member

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    LOL yeah i know what your saying! And with a 3/4 ton with a 343 rear end it would be a waste!
    I did however build a 383 out of a 350 4 bolt main and drop it into my little red pickup 76 scottsdale, with a 700r4 an 273 rear end. That sucker would S&G as well as idle down the road at 80mph

    I pulled it and dropped it into my camaro, and have three more 350 4 bolt main engines in the workshop. One i am building to a 383 to drop in my little red s-10 out back, and I am going to take another one that has a busted ear where the starter bolts up and I am going to attach a 350 transmission to it to drive a generator, build a special carb for it to attach to a wood gassifer.

    The other one i have i have no idea what to do with it, its fully built ready to drop into a vehicle. Just sitting there.
     
  12. MELOC

    MELOC Master Of My Domain

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    i just trashed two of the dual bolt pattern turbo 350 auto trannies. they were taking too much space and i needed the scrap money... $10 each. i have had many GM products in my day. i kept alot of parts for many years. those universal tranny cases were an example. i shipped out 2 1972 olds cutlass', and a 1973 buick century this summer. also i junked a 1970 ford fairlane with a 302. last year it was a 1969 catalina with a 400 big block.

    i had a small block 350 in a 1976 monte carlo. it was my first car and my favorite. the other GM stuff, the cutlass', the 1973 century and a 1972 skylark had 350 big blocks...i think. i really enjoyed that GM stuff, but i never had the money to restore any of them.

    i have a 1964 Rambler i would like to fix up, but i think i will never be able to afford to work on it. it will probably be scrapped as well.
     
  13. skruzich

    skruzich Well-Known Member

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    Wow the rambler would be well worth keeping.
     
  14. ericjeeper

    ericjeeper Well-Known Member

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    have a set of hardened valve seats put in the heads. No lead in the gasoline nowdays. to cushion the seats.
    valves will end up beating up into the heads.
     
  15. fud2468

    fud2468 Active Member

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    After fixing the engine I was thinking of a 700R4, as I'm all for economy, it would give me about a 2.4 final drive ratio.
    However I would think a 2.73 rear would be too tall if it was in a truck with 700R4 and would lug the engine too much, final drive would be about 1.9, right?
    Ray Mac
     
  16. skruzich

    skruzich Well-Known Member

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    hmm should be close. I think 4th is 1.63 at the yoke. too early to do math :p

    You shouldn't lug the motor in it. 350 should be able to handle that ratio.
     
  17. Beeman

    Beeman Well-Known Member

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    Please throw that junk 400 in MY garbage pile and I'll make sure to dispose of it for you.
    As for fixing your motor the crank is only a part of the problem. to fix properly rods would need to be resized as they are most likely damaged from knocking bearings.
     
  18. HermitJohn

    HermitJohn Well-Known Member

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    Yep they are cheap to rebuild, but I absolutely hated the early 70s Chev 350 and in a real working Chev pickup of that era the 292 straight six with a 4 spd was way to go. That was a good lugging engine (not a "fast" engine), not the longevity of a Ford 300 six, but still decent engine. Or the Olds 350 and 403 would last forever if treated decent or even abused a little. Those were probably absolute best engines GM ever made. Early Buick 350s would get great gas mileage (long stroke engine) but tended to throw rods up close to 100k. But when I replaced the Chev 350 in old 1973 3/4ton when it seized up, I threw in an early Buick 350 I got cheap. Mileage went from 7mpg to 16mpg. Not bad in a 3/4ton especially with non-overdrive automatic and as heavy as that rust bucket was. And I had a big old '71 Buick LaSabre with 350 that got 22mpg. By '79, simular car with Buick 350 had been pollutioned down so only get like 13mpg but they solved the problem with longevity by that time. Think the longevity issue had to do with oil pump/gallery as Buicks had funky design oil pump. The late 70s ones would go 150k to 200k miles. The Chev 350 was only GM made 350 left in 80s and beyond and they greatly improved its longevity from what I hear, but I had soured on Chev 350s by that time and wouldnt personally own one no matter what.
    Oh big block Chevy was great. No pickup came with 366, they only used them in medium duty trucks, but big block 366 was good engine. It was designed for commercial market where longevity was demanded. I'd much rather have one of them than a small block Chevy of any kind. Really only nice thing I can say about small block Chevy was they were compact, cheap to rebuild, and cheap/easy to soup up since hot rod crowd adopted them because of compact size.
     
  19. farminghandyman

    farminghandyman Well-Known Member Supporter

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    You have a $350 pickup, and If I under stand right you have a Ok running 400 chevy small block, (no it may not be the greatest engine, but did you have problems in the other car?)
    and can do some of the work your self, both are automatics transmissions, if I am reading right,
    why spend money a engine that is shot if you have a running unit to drop into it, by your own statement your going to use it little,

    yes if both engines need to be rebuilt then rebuild the 350 over the 400, even if you want the 350, drop the 400 in it and take your time to rebuild the 350 the way you want it, and then install it,

    If you have an engine hoist it is probably only about a days job to swap engines in that unit,with a little help, (my son was down to about 3 hrs on his truck), and had put 350's in it and a 400 small block, and then another350, and then a 4xx one of chevys big block's, then I that is when he rolled the truck.

    that way you have a running truck for next to nothing. and then you can check out the rest of the truck with out much investment,

    that is my opinion,
     
  20. swamp man

    swamp man Well-Known Member

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    For a work vehicle,I'd go with a plain-jane 350.If you wanna' stomp down on the gas and grin from ear to ear,a 383 is pretty tough to beat.I have a 383 in my '81 GMC,and she's a fire breathing beast that runs fine at low idle,and is very streetable.A little over 100,000 miles on the last rebuild,and still fit as a fiddle.With just a mild performance cam,low-rise aluminum manifold,and a wee little 625 CFM(I think)carb,she runs like a scalded dawg,and hasn't left me stranded yet.In all my days of hot-roddin' everything from chainsaws to big blocks,I've had the most fun with this 383.The old TH375 tranny is gettin' tired(and yes,there is too such a thing),and she'll be twice the truck when I upgrade to a 700r.
    Just for work and hauling,another great GM engine is the 305 V-6.I had one in a '62 GMC,and it would pull about anything.