talking to a machine shop and was told to hone it with a torque plate and get it round it will end up being taken 20 or 30 over so that the bore is actually round especially since the motor has about 75,000 on it, he then went on about needing new pistons and what not and that they sold them, of course using the stock pistons would result in a noisy motor as it would have to much clearance. Can you really not hone with a torque plate and get it round while keeping it at a 350 displacement? It sounds a bit off compared to what I've heard but kinda makes sense as well


he then said if I wasn't going to do that I might as well just take a brush to it to clean it up.

 

Why do you want to rehone you cylinders? Are you getting lots of leakdown or was it bad on a compression check? If yes, then it may need rings. Just reringing and deglazing the cylinders with a flexhone or "bottle brush" probably isn't good economy if you plan to drive it a while and especially if you want more oomph.

At 75000 you probably have more bore wear than out of round. Unless you are putting in new pistons there's no real way honing will help you. It probably won't take .020 to "clean up", but that's probably the first economically obtainable oversize stock-replacement piston. Honing more than a couple thou (.001s) or so may fix the bores, but it will screw up the piston to wall clearance which yo don't want to do.

The labor to replace the rings, including pulling the engine and tearing it down, etc. is almost as much as putting oversize pistons in. After 75000 the ring grooves in the stock pistons may be a little sloppy also.

Consider going .020 or .030 over with either stock replacement pistons of exactly the same weight (no rebalance required), or aftermarket hypereutectic pistons. If it were my LT1, which has 93K on it, and it wasn't smoking or losing lots of compression, I'd leave it alone until I decided to stroke it with a Scat 9000.

My $.02

 

I got a used shortblock from a 97, the oil pan was just sitting on it and I don't feel comfortable putting it in the car without a quick rebuild, the other motor had some spun bearings.

I need to get a motor together that I can drive around for a year while I finish up the build on yet another block I have laying around and I'm not rushing that one it's getting finished up right(yes that's 3 blocks).

so this shortblock is here, I was going to clean up the bores put in some rings and new bearings and drive it around for a bit until the other motor is finished. Never done or planned a cheap rebuild, but I need to have somehting to drive and figured I could make this work for a bit.

not looking to make something to get max power, just something that will run and not knock and smoke/burn oil etc until I finish up my other motor

 

If you only plan to drive it for a year or so before replacing it, why go to the bother/expense of changing things if they are OK. Look at the cylinders, do they have a significant ridge or damage to the bores? If not, leave the pistons and rings alone. Same thing for the bearings. Pull the caps and if they look OK and plastiguage OK put new gasket/seals in it and run it. From what I read, lots of guys get 150,000+ miles without shortblock problems.

 

can you pull it apart and retorque it without negative consequences?

there's twice now I have had an LT1 with about 75-80 000 miles spin a bearing within the first 10,000 miles, basically I'm wanting to avoid this as I haven't gotten a year out of a salvaged bottom end for the last two years and it really makes things "difficult" and slows down the building of the other motor

how would I go about plastigauging this? wanna give me a quick rundown?

 

You definately SHOULD be able to disassemble and reassemble without causing any damage if the shortblock is in good condition to start with. Many racers do teardowns to check parts and if no problems are found put it back together. If it ain't broke, don't "fix" it would seem to apply.

As far as using plastigauge goes, it is fairly easy to use. It is not as accurate as measuring all of the parts but millions of motors have been checked using it. Plastigauge is some type of special "plastic like" materials that comes in strips with a precise diameter (several diameters available, for measuring different clearance ranges). When the strip is squeezed by the 2 surfaces pressing against it, it flattens out. The tighter the clearance the more it will flatten out. The plastigauge will have a chart on it. You put the chart beside the flattened out plastigauge and it will tell you the clearance. When using the plastiguage you should wipe all of the oil of the crank journal and bearing (plastigauge is oil soluible) and you must make sure not to rotate the engine with it in place.(also make sure to relube before final reassembly or turning crank) Place the appropriate plastiguage strip on the oilfree journal, put the oilfree cap on and torque it to proper spec, then disassemble and check the clearance using the plastigauge chart. If it is within tolerance and the surfaces look OK, put it together and run it.

 

So I remove the bearing, put in the plasti gauge and then torque it down to find the clearance. Then if things are kosher I put the old bearing back in?

This seriously is an acceptable means to take care of this situation? I really don't want to have to pull this damn thing after a week or two goes by.


Is there any way anyone knows of that I can clean this bottom end out? It's been exposed during a 2 hour trip up to me, one of the big reasons I'm so nervous about just using it.

 

The plastigauge is used WITH THE BEARING IN PLACE. It checks the clearance between the journal and bearing.

If you have gotten debris in the motor then you probably will need to take it apart to get it cleaned out properly. This is not dificult to do. If there is not a significant ridge on the cylinders (should bore and install new pistons/rings if there is) (if it catches your fingernail it should be considered significant) you simply take the rod caps off and using a piece of wood (wood hammer handle works well) tap on the big end of the rod until the piston and rod come out of the top of the cylinder. Use caution to prevent the rods or rod bolts from damaging the crank journals. Before you take the caps off you should mark the rods and caps. You MUST keep the caps, rods and bearings together. If you don't have #/letter stamps you can use a punch to mark the rods and caps. Start at the front and put one punch mark on the rod and one on the cap. Second rod/cap 2 punch marks and so on. Don't hit the punch too hard or it could deform the rod/cap/bearking. Just a light tap is all it will take to leave a punch mark. Once the rods are out you remove the main caps and lift the crank out.

If you don't have an engine stand I would highly recommend that you buy one. Makes the whole process go much easier. Once you have the piston/rods/crank out you can use a pressure washer (or car wash) to thoroughly clean the block. You MUST dry it immediately or it will start to rust within just a few minutes. The best was to dry is with compressed air but you can use rags/paper towels. As soon as you have it fairly dry spray it down with WD-40 and put it in a large garbage bag. Parts cleaner would work well for the crank and piston/rods but you can to do it with just HOT soapy (lots of dishwashing liquid, Ivory works well) water and a scrub brush. A garbage can works well as a wash tub. Once again you need to dry immediately and spray with WD-40. Before you reinstall the pistons I would suggest putting engine oil in the pin bores of the pistons and try to make sure sure there is oil between the pins and piston when you reinstall. Us assembly lube, oil or STP engine treatment on journals/bearings when you put them back together.

 

so take it apart scrub it down and reassemble like it was? I can reuse the rod bolts and the main bolts....they don't need replaced like the head bolts?

the motor doesn't have any visible debris, just I'm a nervous bastard, and no ridge on the cylinder walls so I suppose I'm good there as well.

 

If there is no visible debris, you may not need to do anything except check the clearances with platigauge and bolt it back together. Where you really need to avoid dirt is in on the crank/bearing surfaces. If there is some dirt inside the block it will get washed into the pan by oil returning from the heads/cam etc. It would not be good for the oil pump but probably would not hurt is significantly and should then get caught in the oil filter.

I am not a EXPERT on LT-1 motors but as far as I know the rod and main bolts can be reused. I was not aware that the head bolts could not be. Why do you think they can't be? . .

 

well the service manual doesn't actually state that you need to replace the head bolts, I've have just heard repeatedly that the head bolts are torque to yeild and they need replaced, the packet that you get with the bolts state the same thing, that you need to replace the head bolts, I didn't find this info in the GM service manual I have though, it's just a common practice I have fllowed in the past when redoing top ends on these motors.......in all fairness it has been mentioned by some very reputable members on the board that the torque to yeild warning may be nothing more than a way to further revenue, but it's cheap insurance really at $40

The rod and main bolts/studs it doesn't mention replacing them, it sounds like you can use them repeatedly and they aren't torqued that terribly tight so I wouldn't imagine it would be an issue, the service manual gives the same run down that youve given me though, there is no visible debris in the engine anywhere, it all looks fine, I'm going to go ahead and follow your reccomendations and the ones that are listed in the service manual and hope this holds together for the next 9 months to a year so I can finish up my other build and get it right and not have to worry about the motor for awhile as the car has a few other areas that need attended to and this replacing an LT1 every 9 months or so is definitly making it difficult to finish things up as it is my daily driver...............I know, probably not the wisest decision in teh world LOL!

Wednesday I'm going to pick up a high volume oil pump for some added assurance form spinning a bearing and the rest of the gaskets and button her back up and stick her in the car. I'll spend the money I save on the other motor and hopefully have it done by mid summer.

I REALLY REALLY REALLY apreciate your help on this and if you have any other reccomendations I'm all ears as I've never messed with a bottom end before this