Setting The End Play. AIR-TECH

In this article I will be talking about setting end play with the three shims behind the flywheel. I cannot stress how important this is and what I have learned with the new main bearings we are getting these days. So first things first, you will need a flywheel lock (Please don’t use a big screwdriver against one of the bottom main studs), a 36mm socket, a torque wrench that will go to 250ft lbs, micrometer or calipers for measuring the shims, and a dial indicator. You can buy a cheap one at harbor freight if you don’t have one. Parts you will need include a flywheel seal, flywheel o-ring or gasket depending on what engine you are working on, and a some different thickness flywheel shims. Let’s get started.

Let’s say we are checking a motor that already has some miles on it. If the motor is in the car, grab the front pulley and push and pull it with your hands. If you can see it move, then you will need to pull the motor and fix the endplay. The movement is supposed to be .003 to .005. That’s really not enough to see. You might be able to feel it but not see it. So go ahead and pull the motor out and get the clutch off. Before you take the gland bolt off take your magnetic base dial indicator and attach the base to the flywheel where the clutch rode. Position the arm so that the dial stem is hitting the case. Make sure you have travel on the indicator stem. Grab the flywheel and push it in. Set your dial to “0”. Now with your two large screwdrivers, gently pry the flywheel out. Look at your indicator. If it is over .005 you need to reset. I’m sure it will be because this is why we are taking the motor out in the first place. Whatever the measurement, is write it down somewhere.

Now take off the gland bolt. This is where you need the 36mm socket and flywheel lock. You can take the gland bolt off with an impact gun, but please don’t put it on with a gun. With two large screwdrivers pry the flywheel off. If you work the screw drivers side to side it should come right off. If you have a buddy handy have them catch the flywheel as you pry it off. Now, using one large screwdriver, pry the flywheel seal out. Save it, we will use it to install the new seal if you don’t have the correct flywheel seal installer. Pull out the three shims and set them on the bench.

Now the biggy. Grab your buddy so they can give you a hand. They will need both hands so they will have to put down the beer. What I want you to do is place both thumbs on the rear main bearing. Have your buddy push and pull the front crank pulley. Can you feel the rear main bearing moving? Hell can you see it moving? If it is, you’re so done. This motor needs to come apart and get that fixed. Yeah, I know, that’s not what you wanted to hear so grab another six pack and some tissues for your tears. There is no magic fix here, it has to come apart.

Let’s say it’s not moving. Grab your shims that you took out. Wipe the oil off of them and see if they are cupped. Flex them in your hands, and if they make a popping sound yeah they are cupped and need to be tossed in the neighbors yard. You will want to start with three new or non cupped shims that measure out .010 each.

If they are not cupped, then measure each one with your mic or calipers. Now comes the math so I'm hoping by now the majority of that six pack is still left unopened. Take the number you wrote down earlier then subtract the total of the three shims you took out. Ex: the number was .039 and you had .030 in total with the three shims. That means you had .009 endplay. We need to take up at least .004. That means you will have to come up with a shim combo that equals .034 to .036. That will give us the .003 to .005 endplay that we need. Once you think you have it put them over the crank.

If your flywheel is a non o-ring then install a new gasket over the dowel pins. If you have an o-ring flywheel do not use the gasket. Gaskets come in metal or paper. I prefer the paper but when doing your math you might have to use the metal to get the math to come out right. I would start with the paper gasket. Again only use the gasket with non o-ring flywheels. Install the flywheel and run the gland bolt down by hand. Once snug turn the motor over by hand. Does it move? If yes then install the flywheel lock and torque the bolt to 217 to 250 ft lbs. Take the lock off and put your dial indicator back on and check and see what you have. If the motor doesn’t turn you have one of few problems. One, the bearing was moving in the case and you didn’t catch it. The main bearings that are in it are not chamfered enough and the crank is bottoming out in the chaffer. Or, you had too many beers and did your math wrong. If you’re correct and the endplay is correct then remove the flywheel again and we will start to install the seal and o-ring (if your flywheel takes one). If it didn’t come out right, then play with your shims until it’s right.  

Now we need to put the flywheel on with the o-ring if your using an o-ring flywheel. If you look inside your flywheel and see a groove with a black o-ring then you have an o-ring flywheel. If you just see a step then that flywheel doesn’t take an o-ring. Use a small screwdriver and pull the old o-ring out. Clean the groove well and with your fingers smear some light oil on the new o-ring and install in the groove. Now install the flywheel one more time without the flywheel seal. Torque it down and then pull it off again. What we are doing is seeing if the o-ring gets pinched between the two mating surfaces. If you see it did then take a razor blade and trim off the part that got pinched. Once you have checked that then your good to go on installing the seal. If you have a seal installer great. If not, then with a hammer gently install the seal until it's flush with the case. Now take the old seal and turn it upside down and place it against the new seal. Hammer against the old seal which will drive the new seal deeper into the case until it stops. You cannot leave it flush with the case or it will leak. Once done, use a little oil or white grease on the surface that the seal rides on, on the flywheel. Place the flywheel over the dowel pins. With a clean gland bolt use a little blue locktite on the threads. Install the bolt and torque it down to 217 to 250 ft lbs. That’s it done.

Notes here: I set most of my street engines to .004 to .005. On drag car motors I am setting the endplay to .007 to .010. What I have found is the new main bearing material expands more then the old bavet bearing and they expand more.  .005 I have found is too tight for hotrods and the rear main bearing will grab the flywheel.

I have also found that torquing the bolt over 250 can crack or roll the threads over on the bolt. Not good. That is why we torque the bolt and not use an impact. It really sucks when a flywheel comes loose. Not only do you have to replace the flywheel but you will also be replacing the crank. If you don’t have a way to torque it find a way. Rent a tool, borrow a tool, but a tool. Don’t use an impact.