The Stovebolt Site Forums The Shop Area Engine Shop crankshaft removal

Hello.

If I unbolt the crankshaft from the block, will it lift out of the assembly with the timing gear?

For putting it back together, do I need to mark anything or remember its relationship to the camshaft or anything else?

(my engine is already on the stand with everything else off)

Thanks,

Judson

if you are asking these questions, what you really need is a shop manual. As a general rule, always mark anything, and everything pretty much as you are taking it apart. However the timing gears already have marks. Yes you can take the crank out with the gear attached, I sent mine off to get drilled for full pressure with the gear still on it. Basically, just look at what you are doing, there isn't really any magic involved. (this is from the other post) the pushrods probably won't be affected too much, it isn't the adjustment you need to worry about, it is the wear pattern created by the individual parts. But since you don't know which end is which, you don't have a lot of choice, but it should be OK. Just look for any obvious signs of impending doom before you assemble them. (this includes the little sockets that the pushrods fit into (rocker and lifter))Pictures are good too. I don't do it because I have no idea how to save them anywhere, but if you know how to deal with the electronic portion of the pictures, I would recommend that as well.

Which engine are we talking about? A stovebolt six has a big plate sandwiched between the timing gear and the crankshaft which will make it very awkward to handle, and the camshaft MUST be removed first. V8's- - - -no problem- - - -just remove the timing chain and unbolt the main bearings.
Jerry

Is this what you are working on?
http://chevy.oldcarmanualproject.com/parts/1929_54/089.htm

The cam gear and crank gear are marked, they must be lined back up when assembling. Rotate the crank till the gears line up so you know what you are looking at. It should be two little dots on the gear teeth. Once clean, paint a bright color dot on each for easy alignment.
See here;
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0607.html


Unbolt the main caps, be sure to keep the bearings with each cap and keep any shims that might be with them. Keep each bolt in the cap incase there is a different. Keep the caps in order, THEY WILL NOT FIT OTHER POSITIONS.

Cam will come out after removing the two small retaining bolts behind the cam gear. You have to rotate the gear to get to them. Pull cam first.

Go here and get a copy of a shop manual for your truck, most all inlines are the same so get close if your year is not listed.
http://www.oldirononline.com/
http://chevy.oldcarmanualproject.com/index.htm

Here is a good link to a 250 cu in inline six, http://oldcarmanualproject.com/manuals/Olds/1966/Chassis/06-Engine.pdf

Joe

Thanks, guys. This is all very helpful and I appreciate all the work with all the links. Im working on a 216 out of a 41. Ive been posting on and off for several months, but now I finally have the engine out and on the stand. It all started because it would not start due to low compression. It definately needed a valve job, but in looking at the rings I also noticed they had to much gap.

The reason Im thinking of taking out the crankshaft is to blow out the oil lines before putting it all together. Ill have to print out the links you gave me. I have a shop manual, but it doesnt seem to give me much. These will be good resources.

Thanks again,

Judson

The reason for the wide ring gap is cylinder wear, and it won't be equal from top to bottom. The major amount of cylinder wear happens in the top 1 1/2" or so of piston travel, resulting in constant flexing of the rings trying to maintain contact with the cylinder walls. Even if you hone and re-ring the cylinders, the new rings will lose their tension in a very short time due to excessive flexing. If the cylinder taper exceeds .005", do not attempt to re-ring the engine- - - -rebore it and install oversized pistons and rings. There is a very simple way to measure cylinder taper using an old ring and a feeler gauge, if you're interested in finding out how much taper your cylinders have.
Jerry

Jerry,

I was thinking of simply taking an old ring and moving it up and down the cylinder using the flat part of the piston head. I will measure it at varying points to see if the ring gap is the same/different.

I know what you mean about the wear on the cylinders. I tried to replace the rings with a stock size from Napa, and the gap was too big. I bought an oversize set, and there was to much overlap. There is a stamp .010 on the first piston head, so I thought they were possibly oversized by 10 thousandths, but when I took it to the machine shop they measured it and said they were actually stock size.

To be honest, I was going to buy a set of oversize rings and file them down to specs, but it sounds like you are saying that wont work. You are saying it wont work. I have to rebore it and get oversized pistons.

Judson

Rings are sized to a specific cylinder bore. They MUST stay round. File-fitting an oversize ring to get the gap right will cause it to get egg-shaped and lose contact with the cylinder wall around most of its circumference. Here's how to check cylinder taper with nothing but an old ring, a feeler gauge, and a calculator:

Place an old ring in the cylinder and square it up against the ridge at the top of the ring travel. Stack up feeler gauge blades to fill the gap and add them up to give you the gap thickness in thousandths of an inch. (For instance, 65 thousandths- - -.065")

Push the ring near the bottom of the cylinder with an inverted piston so it stays square with the bore and measure the gap again. Example: .020"

Subtract bottom gap from top; .065 - .020 = .045"

Divide the difference by 3.14: .045 divided by 3.14 = 14.3

That's a cylinder taper from top to bottom of just under 15 thousandths- - - -three times the allowable taper to get a good re-ring job. The cylinder would need to be rebored at least .020" oversize to get the cylinder wall straight again, and .020" oversize pistons and rings would need to be installed.

Running new piston rings in a tapered bore causes them to flex in and out twice each turn of the crankshaft to maintain contact with the cylinders. At 2500 RPM (normal highway cruise speed) the rings are flexing 5,000 times a minute, or 83 times a second! No wonder they lose tension in a hurry. Reboring the cylinders straight eliminates the ring flex until the cylinders wear tapered again in another 40,000 miles or so.

To make it even more interesting, most cylinder wear happens in the first couple of inches at the top of the piston travel so the rings are flexing very rapidly at the top of the stroke in a tapered cylinder.
Jerry

Thats very helpful, Jerry. Thank you. I appreciate the formula and will use it asap. Judson

Jerry,

I want to respond to your question, because today I was out looking at the crank and studying it and taking it apart.

I have a 216 straight 6 in a 1941 sedan.

You are right. At the end of the crankshaft is the timing gear, but that is seperated from the crankshaft by a metal plate. The gears for the crankshaft and camshaft are covered by a timing gear cover, but on the outside of that is the harmonic balancer. So from outside in, it goes balancer, cover, gears, metal plate, then crankshaft.

I took off the first bearing cap today and noticed the shims. The shim which holds the cranshaft from moving front to back is totally ground out except for the remains of the shim on one side. On one side it had two shims in between lower and upper cap. The upper bearing had several deep groves/pits.

I couldnt figure out, however, how to get the crankshaft out of the block. The harmonic balancer will not let me remove the timing cover. I removed all the screws and bolts that hold the plate and cover to the block. Thinking ahead, there still is a problem. Even if I take all of the bearing caps off and remove the crankshaft with the harmonic balancer and plate attached, how will I mark the gears so that it lines up correctly with the camshaft when I put it back together? I cant access the gears with the cover on. And I cannot get the cover off with the harmonic balancer there.

I read the manual, and it looks like there is a special tool to remove the balancer. The manual is helpful in some ways-especially in understanding how it works. Is there another way to get this engines crankshaft out with the balancer and seperating plate?

Judson

You will not be able to get where you want to be without removing the harmonic balancer first. There is no shortcut around this with a Stovebolt, so you need to buy or rent the correct tools for the job or you can't go any farther with your removal.

First question- - - -is the engine still in the vehicle? If it is, why are you trying to remove the crankshaft? If the engine is removed, take it apart one piece at a time- - - -remove the balancer, timing cover, camshaft, crankshaft timing gear, and separator plate, in that order. There are NO shortcuts! Be sure to keep the shims between the main bearing caps and the block in order- - - -they determine the oil clearance for the main bearings. If you've got scored bearings, you'll also need to get the crankshaft reground, buy the proper undersize bearings, and adjust the oil clearance with the proper shims. We are literally splitting hairs here- - - - -there is no way to guesstimate or take shortcuts!

With damaged rod or main bearings, you're looking at a complete engine overhaul. The debris from the worn bearings will be all through the engine with no way to clean it up short of a complete teardown to a bare block and a detail cleaning- - - -oil passages and all!
Jerry

thanks. yes-the engine is out. any leads on where to buy or rent the puller?

Just about any local parts store will rent you a puller, but search Ebay for "harmonic balancer puller" and you'll find several dozen of them offered for sale. I use one with a "crow foot" shape that works with either 2 or 3 bolt holes. Stovebolt Chevy 6 balancers have 2 holes, while lots of V8's use 3 holes spaced at a 120 degree angle to each other.
Jerry