I asked the question and got an answer. The answer was incorrect and I presume was based on poor understanding of how much torque (how little, actually) would be applied to the crank by pushing the car in 4th, versus to putting a breaker bar on the damper bolt.

The radius of a wheel and tire is roughly equal to the length of a typical breaker bar. Pushing a car applies torque to the axles via the wheel, and the amount is roughly similar to amount of torque applied by yanking on a breaker bar.

Difference is that the torque is reduced via the differential at a ratio equivalent to the gearing- ie a 3:36 diff will reduce the torque to the crank to 1/3 of it's original value.

Putting the transmission in a lower gear (as suggested by others) will reduce the torque again by the ratio of output vs input.

So, please tell me again why it's a bad idea?

 

PB Blaster and some time. Small wiggles and it will come free. After it comes loose change oil and crank motor without plugs until oil pressure is up and steady. Then I would do a compression test while the plugs are out but regardless of the test I would still fire it up!!!! You will probably get lucky with alot of smoke and then it will clear up!!! Don't you just love old Chevys

 

You do not understand "mechanical advantage".

 

Please explain then.

 

Risk of breaking the rings is high .Yes you may be able to free it up but plan on it smoking and having a short lived life....unless youre merely trying to get it to start and sell.

 

To those who are saying "do it right, take it apart", I say huh?

If I have an original engine (assumption on my part) '70 LT-1, that's a pretty valuable engine in there, yes? If I want to retain the value of the car, even if I want to rebuild the thing, I want to rebuild with at very least the original block, so those stuck pistons are going to have to get unstuck one way or another, correct? Say I pull the motor and put it in my engine stand, take off the heads, drop the pan, unbolt the rods and crank, hey, I'm doing a great job of taking the thing apart, but I still have to unstick those pistons. If there is a way to do this on an engine stand that is any gentler than rocking the car or GENTLY using a breaker bar, I don't know what it is, but would be REALLY happy to be educated here.

 

Think of a first class lever with one end 3 times as long as the other. If I put 100 pounds on the short side, I can lift it with 33.3 pounds of force on the other side. The work is the same, but the force is multiplied. The work is the same because for each inch I raise the 100 pound weight, I move the other side of the lever 3 inches. What the differential in your example is doing is making you turn your "breaker bar" the tire, 3 times to turn the engine over once, as opposed to one time with the breaker bar. The differential has effectively lengthened your lever, and multiplied your force at the crank by a factor of three.

 

Sorry, wrong, and probably what the other guy is thinking also. In this case the 'tail is wagging the dog'. Torque is DECREASED by a factor of three when the axles are driving the input pinion. Rotational speed, not torque is the factor to multiply.

 

Actually, you are correct. I got my lever backwards on this one. Turning the tire once around will rotate the driveshaft three times, which is like pulling on the short end of the first class lever. Sorry 'bout that one.

 

No prob.

 

Yes you are correct but I can control the amount of torque way better than by pushing the car. I have read al your other posts and you are correct in your math and physics but try to control your torque once you get a 3400 pound car moving then by your arm. I know you will disagree but I'll stick to my way. I'd probably take it apart anyway for fear of breaking a ring.

 

If the engine is on the stand and the heads are off, I can rotate the engine so that the decks are level to ensure I'm getting penetrating lube all the way around the bore. I can make sure the crank is as wet as I can get it with a penetrating lube. I can remove the cam, lifters and timing gear to reduce the rotational effort requried. I can see what I'm working with. If the bores above the pistons are rotted junk, I'd rather find out before I start trying to turn the thing over by hand. I certainly have more options in terms of tapping here and there on the piston crown. I have more options for a careful application of heat or cold. I can use a crank socket vs. the crank bolt (sure to strip) or trying to pry on the flywheel.

IMHO, it's a gentler approach with more options and a higher possibility of success based on my experience

Correct me if I'm wrong, but this is one of about 1, 200 '70 LT-1s and one of the most legendary engines of all time. Can you see the Smithsonian just cracking away at it until it turns? It ain't about getting it to turn, because regardless it's going to have to come out...unless you guys all think he's going to put a little gas in it and take it for a drive...?

 

Can we see a pic off this LT1 ?

 

No amount of chemicals will loosen the frozen cylinders. All you will do is fill them up and still not turn over because of some cylinders will hydraulic lock....Just yesterday we took my 66 Bonneville that had been soaking for months with every concuction you could think of....Persons from all over the webb had the suggestions. Nothing worked and with only two cylinders seized, now can you figure several? {a LT1} We took it apart yesterday... It wasn`t as bad as it appeared and finally pried the cylinders off the pistons. In your situation I would first try pulling the car slowly in high gear. The tires will probably slip as did the Triumph but it may be worth the chance...If it dont work you will have to rebuild it anyway...about my Bonnie? A set of rings and a few gaskets will put it back on the road as soon as the parts arrive... good luck,.....maybe lots of these....

 

X2 I'D LOVE to see some photos of your Vette!

 

Mike, why are you such a dick? Seems ur always looking for an argument......

 

I tried this trick on a 20 year storage Ford Falcon and it worked. First, remove spark plugs and spray PB Blaster penetrant into cylinders (the more the better), then also spray top of valve stems with same. If valve stems have umbrella seals (rubber), take a syringe with needle and squirt PB Blaster through the seal to let it drain down the top of the valve stem to the valve guide. Let this sit a few days and then try to turn motor over by hand. This worked for me and now the car is running fine and has 150 psi compression in all cylinders. Just don't forget the valve stems because if you do it could bend a bunch of pushrods.

 

i would use a breaker bar on crankshaft,however you do it any way you like,i dont care its not my car.

 

I think the Op has plenty of good suggestions to work with here. No need to turn this into a match of whos smarter