I never rebuilt an engine in all my years as a tech.My question is when rebuilding my Lt-1(in future),how do I know what crank & rod bearings I need?Example-I get a Scat or aftermarket crank & some higher performance rods.Do they come with bearings for the Lt-1?If they don't,do I install my old bearings using plastigauge then determine the bearings I need?Do put the plastigauge on twice on a bearing to check each part of the bearing(at 12 & at 6 postion on the crank/rods) or only need to put it in one place?When doing research,one person said to install the plastigauge on a completely dry surface while another says to put a dab of vasoline on crank so plastigauge stays in place.Which is the correct way?Would having vasoline cause an inaccurate reading on the plastigauge because its a liquid & cannot compress?How do I determine which size thrust bearing thats needed?Would a smaller(thinner plastigauge reading)be best for the bearings as it would allow the engine to last longer as long as its in spec?Example-if the spec is .0003 to .0006,would you recommend getting the clearance down to the low end(.0003)?Any Lt-1 specific books that can help with the rebuild & torque specs?
Sorry for all the questions guys but I am very through

 

Checking running engine clearances on the crankshaft main and connecting rod bearing journal diameters are best checked with a calibrated micrometer and dial bore gauges that will read down to ten thousands of an inch (.0001").

Subtract and You have your running oil clearances.

Plastic-gage will work ok if used correctly. The crankshaft journels must be clean and dry to use it correctly.

You can use a dab of 10w30 motor oil if you want to hold the plastic guage in place, but presonaly I dont.

A factory GM service manaual for LT-1 Corvette will show you step by step how to rebuild your small block V-8 engine.

Or a Good Chiltons or Motor manual will show you how to rebuild the engine also.

Lots little tricks of the trade assembling and blueprinting an engine.

Have to start somewhere.

I rebuilt my 1st engine over 35 years ago.

Allways a Fun and Rewarding Experience.

BR

 

All I can add to this advice is for you to get a friend who has done it (successfully) before and have him watch & advise you as you do the work. Once you have gotten a mentor, be sure you keep the building area super clean and bag the engine every time you stop working on it. Don't try to get someone to help over the 'net or here even though there are lots of good builders here. You need your advisor right there with visual contact. There is a ton of little things that need special attention during a build.

 

I have never gotten the plastic strip indicators to work correctly, probably user error, but it has a lot to do with exact (i.e. very good torque wrench) and bolt stretch.

 

Crankshaft end play can be checked with a dial indicator on either end of the crank. Lever the crank in one direction between a counter weight & the block. Zero the indicator then lever the crank in the other direction & take a reading. Dress the thrust bearing to acheive the desired clearance. A feeler gauge can also be used between the thrust bearing & crank.

Check the con rod side clearance with a feeler gauge. This is the clearance between the con rod big ends when they are mounted on the crank.

Before removing the main caps insure that they are numbered as to position in the block.

Good luck.

 

Thanks guysSo the new crank or rods do not come with the bearings?What I learned here is to use bore gauge to find out what bearings I need,use a dial indicator to check crankshaft endplay to determine thrust bearing size.But how do I come up with the number/bearing size for the bearings?What math formula do you use?Does using a oil to hold the plastigauge in place cause a incorrect reading as liquid doesn't compress?

 

If you get an aftermarket crank, basically the bearings will either come with it (depending) or there will be a referral for the correct bearing.

Do NOT assume the bearings you get are the bearings you need.

First determine if your crank journals are standard or undersized and then look at the bearing (not the box); on the back side of the bearing shell should be "std" (standard), .001 (.001 thicker to compensate for normal wear on an otherwise good used crank or on a new crank machined at the lower end of its tolerance range), .010 (.010 inch thicker to compensate for a crank turned .010 under; i.e ten thousandths under); etc.

Factory bearings may or may not have numeric stampings; they may be stamped with a letter code instead, in which case you're kinda on your own.

If you reuse your crank, at the very least, have it measured with a micrometer; besides showing the size of the journal, it will show whether or not the journal has become "egg" shaped through use.

Yes, definitely plastigage your bearings. HOWEVER there is a much misunderstanding about how to go about this correctly.

In essence, you want the crank journal to be (gently but firmly) against the opposite side of the bearing from that where you are placing the plastigage.

The simplest example is measuring main journal bearing clearances. If the engine is out of the car, on an engine stand, and upside down, there is no problem, since gravity is pulling the crank down against the side opposite from where the plastigage is being placed.

If the engine is still in the car, a jack has to be placed under the crank and the crank gently forced upward.

The same rationale applies to the rod bearings.

In either case, the plastigage is meant to measure the entire bearing clearance at the point where the plastigage is inserted. Failure to do this will give erroenous readings indicating bearing clearance that is typically LESS than the actual clearance.

Done correctly, plastigage is reasonably accurate. And good insurance. If you have the time and access to inside and outside micrometers, micrometers can tell the ENTIRE story because micrometer measurements are taken at several different points around the inner circumference of the bearing and outer circumference of the crankshaft journal.

There is at least one very good book about rebuilding LT engines, entitled "REBUILDING LT1/4 ENGINES" (or something very similiar). Most any aftermarket source stocks this book. It is way better than any Chilton or Haynes and much easier to follow than the (expensive)Factory Service Manual (although I highly recommend the FSM highly since it covers everything on the car).

Good luck, go slow, be patient and don't be afraid to ask lots and lots of questions.

 

nobody answered your original question.no---you do not use your old bearings to check for the new.and no ,you do not need an id mike or bore gage. the new crank should have a data sheet for bearing sizes.then you can use plastigage with the new bearings to verify proper clearances. if you have a magnetic base dial indicator available,it's my prefered way to check the thrust bearing clearance.if it's a standard transmission car,don't forget the pilot bearing.

 

Please allow me to sing my song again:

Before you do anything buy a book or two on rebuilding a SBC, May want to buy the rebuild DVD also. These will explain the process step by step. After you have a full understanding of the process you can begin to as questions to clear up points that are not fully understood.

 

I've never heard of jacking the crank before. Probably torquing down the caps works better. I agree with the last post. Gotta get a book and read up on motor assembly before taking a plunge. Asking step by step instructions on the forum will take forever and can get you in trouble quick.

 

Thanks guysThis has taught me alot & may help others as well.