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Richard · Joined: 28 Nov 2005 Posts: 178

A '98 Chevy pickup 3/4 ton, 4wd. Its knocking, no change in fuel mileage, doesn't use oil, still has power. I am considering replacement of rod bearings through the pan. Can this be done without lots of trouble ?
150 k miles, would changing only the worn bearings make any sense, doing it myself ?

Matt Porter · Joined: 27 Feb 2007 Posts: 19

Richard,

My 2 cents: In for a penny, in for a pound. Take it all the way down and do it all, unless the truck is not worth that much to you and is starting to nickel and dime you to death. Chevys are the cheapest vehicle to buy parts for and the time it takes to do it all won't be that much more.

Matt Porter

minniemobuddha · Joined: 08 Jun 2007 Posts: 70 Location: oelwein,ia

let me take that one step farther....the rest of the engine is probably as worn,so i would just go with a reman motor from a reputable dealer.with vehicle prices as stupid high as they are now,it would make a lot of sense,and would still have a warranty.

Matt Porter · Joined: 27 Feb 2007 Posts: 19

Even better, a small block chevy from GM is under the price of most rebuilds. Factory and new. I personally won't buy SBC's remanned from auto parts stores, they don't seem to hold up. You can rebuild yourself fairly cheap or buy new and you will know what you have. Find a reputable machine shop to do your block, crank and heads, find a good cam that meets your requirements and put it together with new oil pump. If you just rebuild the bottom end it is usually a crap shoot as to what will fail next.

Matt Porter

Kelvin · Joined: 28 Nov 2005 Posts: 275 Location: Richfield, NC

Since we are all putting in out 2c. I would check the oil pressure with a known-to-be good guage-not the idiot thing in the cab. There is a small chance the oil pump relief spring is broken. Old chevys used to do that pretty often.

Especially if know the truck has had regular service in the past. I pulled my 84 GMC with 305 down Spring a year ago and all the bearing clearances were still within specs. The crank was only worn .001 or so. So those engines can go at least 150,000 before they need work.

If the oil pump is putting out the oil at pressure and you decide to fix it yourself, you definately need to mike the rod journals on the crank. Clean it up good if there is a lot of goop in there, just doing a halfway job could bring about more trouble when some of that goop plugs a lifter or pushrod.

Another thought is that at 150K, its time for new rings even if it hasn't started using oil yet.

Matt Porter · Joined: 27 Feb 2007 Posts: 19

Exactly right Kelvin, in for a penny, in for a pound. A new oil pump is a must, even if it is the only thing you do. A standard rule that I have always lived by: if you do the bottom end, you should do the top. New heads/valves raise the compression ratio enough to cause the rings to show their age and vise-versa, which also puts more strain on the crank, which can lead to bearing failure, etc. SBC's are too cheap to fix not to go all the way. If it were me, I'd have the crank turned, just to be sure. Have the heads rebuilt, new cam/lifters, water pump, oil pump, soft plugs, steam cleaning. When it came out of the garage it would not cost me any more money for a long time.

Spending a little more now will save you a lot in the long run. If the truck isn't worth the money, try a new oil pump. If that doesn't quiet it enough to get the last few miles out of it, it's time to move on. My .02.

Matt Porter