O/T= Chevy 350 in Frm truck

Hope you guys can help me. I was given a brand new chevy crate 350 with 2-3 hours on it. Problem is, it has one bent connecting rod. It had a problem with the head and something got into the one cylinder. The crank and all other cylinders look brand new. The cylinder in quetion has scored cylinder walls, but not that bad. If I hone it smooth and find that it"s too big, would it be possible to bore just one cylinder and install a new piston and rod? I sure hate to replace 7 perfectly good pistons if I do have to get it bored. Thanks for any help.

Can you feel the "score" with you fingernail?

If not, I'd put 'er together and run 'er fer about 50K miles. :>)

Allan

If you want to do this on the cheap, (and it sounds like you do), hone the cylinder and just replace the broken parts. If it has just 2-3 hours, it will not have a cylinder ridge. Individual rods and pistons should be available from your local parts store. If it uses a little oil, just run it on a diet of the cheapest stuff available.
I'm assuming this is on a grain truck like a C-50 or similar and not a pickup?

The engine will be going in a pickup. It's a 2 bolt crate engine. The grooves can be felt with a fingernail, but they are not that bad. Thanks for the help.

You could have a machine shop install a sleeve in the bad cylinder. This is not usually thought of but I have done this a few times and it works well. There are dry sleeves made for the small automotive engines. I personally would not bore one cylinder as a fix. There may be enough weight difference in that one piston to create a severely out of balance engine that would eventually self destruct.

I've got a V-8 that dropped a valve and cratered one cylinder. Replaced the piston and had a machine shop sleeve the one bad cylinder with a dry sleeve. I 've put another 100,000 hard miles on that truck and it's still holding together.

Worked for me, too. I once had a 350 that had one cylinder worn to where boring to .060 wouldn't clean it up. I had the machine shop install a sleeve in that one cyliner and bore the sleeve to .060 to match the rest. Worked fine.

I get nervous at the thought of one cylinder being a different size than the rest.

if you overbore one cylinder, it will be out of balance and will have a vibration to it. like the other guys said, sleeve it or just hone it if possible and run a new piston.

I dont necessarily recommend it but we did use a .030 overore in 1 hole in a race motor once. Put the piston and rod on a postal scale and matched the weight exactly to the other rods. Had no vibe and ran all season with no problems or signs of unusual wear. Now that is no indication of what the long term effect may be , but it has been done before. Your choice to gamble or not.

I wouldn't be too worried about one piston being .030 over sized on a V8 engine. How many times has an engine that seems to be running OK but a little low on power been found to only have good compression on six or seven cylinders? Now if this were the case on an engine that had a "complete overhaul" with some serious money invested in it I'd ***** like **** over a half right job.

While not ideal its nowhere near a deal breaker.


What would concern me more is what exactly was the problem with the head on their "rebuilt" engine to cause this problem in the first place?

Replace bent rod and probably piston, hone cylinderenough to get scratch close to even while not going over .010,.015 over, use a set of service rings and put back together after making sure no nuts or loose valve seat, no faulty keepers on valves. Run it 100,000 miles. One or 2 cylinders different oversize not that uncommon on mid price or low buck rebuilds. Chicago area years back when working auto parts counter and Jeep dealer the quick commercial engines for cabs and delivery vehicles often got that kind of service/rebuild- unground slightly worn cranks got thicker bearings, ridge ream and lap with the oversize service rings on standard pistons, mix and match rods and pistons for balance, grind and lap valves and grind a bit of valve stem. Ford has crank bearing that are +002, through .005 thicker for crankbearing wear- couple of the local salvage tow trucks do the in chassis bearing replacements when oil pressure low and slight knock. Knurling pistons still done for slight piston slap when using service rings and stock piston to take up extra clearance on side. Won"t get more than 90 day warantee but but $300.00 to $600.0 is better than $1200.00 to $1800.00 crate rebuild and close to the $200.00 to $500.00 salvage engine cost. 2bolt with 8.2 to 1 compression dished pistons should last awhile if it doesn't have a Camaro cam in it. 225 degree or so was a mild stock cam used in some years- met EPA and had good torque at low end, was in some pickups and vans. RN

I suspect if you weigh the pistons there MAY be more variation within a set of OEM pistons than there might be between an oversize piston and the rest of the original set. Easy enough to weight the old one and the new OS one and find out!

That being said, a have done the oversize piston thing in one or two cylinders of several 350's with NO unusual vibration or other ill effects.

OBVIOUSLY not the thing to do with a "blueprinted" high RPM racing engine, but likely a VERY workable fix for a simple run-of the-mill farm truck engine.