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old engine, need rebuild??

Discussion in 'The Garage' started by XHitman396, Apr 13, 2003.

  1. XHitman396

    XHitman396 1/2 ton status

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    i gotta 87 k5 with the original 350/700 setup, 146,000 miles, bone stock, all the way around. it runs fairly good i guess, but i got like zero power, unless its in 4L, but anyway, i was thinkin a rebuild would do very good before i put the cam/headers/intake/exhaust/lift/35's on, but i wanna know for sure it will help and is necessary. i was told a compression check would tell me whether i need one or not, and are rebuilds hard to do, about how many hours approx. with all the right tools, and 2 semi-engine smart 16 year olds, and one 40 year old mechanic? what EXACTLY is a compression check, and what EXACTLY is involved in an engine rebuild (whats replaced/upgraded generally?). and one more question, i checked to see if it was smokin, cuz its burnin about 1 quart of oil every 3500 miles, and there is no smoke whatsoever at lower rpms (revving in the driveway) but when i hammer it in park, some white smoke blows out, then stops when the rpms go back down, wuz goin on? thanks for all your help...
     
  2. bryguy00b

    bryguy00b 3/4 ton status

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    have you ever rebiult a small engine befor? thats a good thing to learn off of...thats what i started with..and im 16 to.
     
  3. mplogic

    mplogic 1/2 ton status

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    I'm no mechanic, so someone else check my info. Basically on the "learn as you go" program as well. /forums/images/graemlins/smile.gif

    A compression test is putting compressed air into a cylinder at top dead center (closed valves) and seeing how much leaks out. Or is that just a leak down test? Anyway, it's usually a good indicator of how much wear you've got. Some say anything over 20% leakage is rebuild time. Usually you'll find a couple cylinders that are much worse than the others.

    The most basic rebuild is valve job, rings, and bottom end bearings, but it can quickly turn into a bigger project once you open it up and actually find out what you have. With 140K you might get away with just honing the cylinders and a ring job, but if you're burning that much oil there will most likely be wear in the cylinders. A ring job will get you closer but you will probably still burn oil and lost compression is lost power.

    If the cylinder walls are tapered (worn) then they will need to be bored out by a machinist and you'll need new pistons. 350 pistons are about the cheapest of any engine, but there are lots of different ways you can go there. At that point, also have your crank and rods checked out. Sometimes you can get away with just a polish on the crank and sometimes it will need to be cut to make it all round again (just more machinist $$). A machinist will also check the block and see if it needs a line bore and replace the cam bearings.

    Heads are also something to have checked to see if they are warped or cracked. Every rebuild I've done so far I've had some warpage and had to have the heads shaved (maybe it's just the desert heat?). The machinist will tell you if you need new springs or if the old ones are passable. If you are putting a non-stock cam in it, then you'll probably want new springs anyway. A valve job on cast iron sbc heads is usually pretty cheap… now the 4.6L OHC in my grandma's Lincoln is another story, like $1000 on machine work on heads alone. /forums/images/graemlins/eek.gif

    After all the machine work is done and the extra parts are gathered (bearings, gaskets, seals, oil pump, timing chain, etc.) the put together is pretty straightforward and usually only takes a day or so. You will need a ring compresser and some other basic tools. Get a couple good books and they will basically walk you through it.

    So basically expect to pay anywhere from $500 to $1000 in machinist work, another $300-800 or so on parts (sky’s the limit if you want to get crazy). A day (or three) on tear down, a week (or three) at the machinist, and another few days to put it back together, paint it, and send it home. If you like working on your truck and have the patience to take your time with it, then I'd say go for it. It’s a great learning experience and a 350 is an affordable and fairly simple engine to work on. If you get frustrated easily and resort to violence or have the tendency to start banging on stuff with a sledgehammer, then you might want to just pay a good machinist/rebuilder to do it for you. /forums/images/graemlins/smile.gif
     
  4. Bruiser

    Bruiser 1/2 ton status

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    If your a learn as you go type, then got stop by Barnes and Noble and get you a book on rebuilding small block chevys. This will help you with some of the terms involved and most are quite informative on what is needed.

    A compresion test is using a guage pluged into where the spark plug hole and then you turn the engine over to see how much compression you have. You can do it once then spray some oil in and if it raises your compression this says your rings are worn.

    A leak down test is more accurate way to see how worn your rings are (since compression test can be affected by valves) since you put your piston you wish to test at TDC then fill the cylinder with compressed air and measure how long it takes to leak past the rings.

    If you use your K5 for daily duty than you may want to PU up a block at a wrecking yard and rebuilt it. Then swaping in the new engine can be done in a weekend (I pulled a V6 out of a monte carlo and dropped in a 350 out of a 69 byscanne in 18 hrs but i digress since they told me there was no way I would do it since was only 19 at the time)

    Basically do some research. Get you a good book or research online. /forums/images/graemlins/tongue.gif
     
  5. chevyracing

    chevyracing 1/2 ton status

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    Are you sure it is not a 305?

    John
     
  6. XHitman396

    XHitman396 1/2 ton status

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    nope, 350, and WOW, $1000 for a rebuild, geeze, but i gotta connection who is a machinist, so that'll help, and if i bore it out to a 383, how much worse will the gas mileage get, and is it a huge difference in power? and i was lookin at the rebuild kits, and they are fairly cheap, but i need to know the cc on my heads, stock tbi, and how expensive/hard to find in salvage are these vortecs ive been hearin so much about? and y is the kit with 9.73:1 compression 80 bucks more than the 9.35:1 ones? thanks for bearing with me while i learn, other info is welcomed, as well, thanks again...
     

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