[FC] Engine Top Cover Replacement

[Ken Hand]

 For those of you contemplating replacing the top cover gaskets on your engine I think I have a couple of tricks to help keep that leak stopped. I may miss a couple of steps here and there but if you get it apart then you should remember how it goes together. OH, there is always the shop manual to help out also which is not a bad idea to have if you don't already have one.

There is several steps to this and will probably take you 4-5 hrs working steady with no problems cropping up, plan accordingly. As with any thing like this always disconnect the ground wire on the battery before you do anything else. Not just at the engine because there should also be a secondary ground from the battery to the chassis. This can provide a pretty good ground to burn most any tool you have, including you, if you are holding the tool near where the arc is. There are several places you could start  but I generally start by taking the belt off. Then the gas lines at the carbs and the inlet fuel line at the fuel pump. Remove the fuel pump and lines then the carbs and cross shaft as a unit. Be sure and put the WD-40 caps in the carb holes in the head. Next is the plug wires, gen/alternator, oil cooler cover, and the clamp around the crank case vent tube. The fresh air tube at the front right of the engine will need come off also. If the hose has been there for a while it probably won't come off in one piece. The adapter on for the fresh air hose will need to come off and is held on by only three screws. Next is to start removing the turkey roaster screws. You will need a 5/16, 3/8 and a 9/16 socket. there is a 3/8 bolt in the back center that is hard to see and probably covered with dirt, everything else is easily seen. If everything is loose you should be able to lift up on the top cover and the right side should be able to come up and then slide out from under the throttle rod and the fuel line on the left. This exposes the top of the engine.

This is a good time to clean all the years of debris out of there and to also deflash the head as best you can. You thought this was going to be a simple job didn't you? Once you are done with that then you are ready to start on the top cover of the engine. This is pretty straight forward just as it looks. remove the fan, then pull the vent tube out and then all the bolts. You will probably have to tap on the fan and or pulley to get that started and then with a block of wood as a cushion you will probably have to tap on the bearing some to get the top cover to come loose. If it was stuck that good, how did it leak? After the top cover is off stuff rags around in the engine so dirt stays out as you will need to clean the gasket surface on the block. You may have to separate the baffle and the top cover. You can use whatever but I use a sharpened putty knife to get it started and work around. I have had to tap the putty knife better than half way around before the baffle would come loose without bending it. If you have a wire wheel on a bench grinder that will get the gasket material off of everything you have in your hands. On the block you can scrape most of the gasket off but an air grinder with a  scotchbrite pad does very well and the preferred method of cleaning. If you do use the scotchbrite pad don't linger in one place as you can make a divot that will never seal. Now you see why the rags were put in the engine, be sure and remove them! With everything clean, now comes the easy part.

Make sure you pre-fit the gaskets as they will only fit two ways, they are not a universal fit. Lay the gaskets in the way that they fit on the block just off to the side so you don't have to try and figure out how they fit. I do use RTV silicone here but keep in mind that a thin film is all you need. Don't be afraid to use your fingers. Apply a thin film to the block and then set the gasket in place, another thin film on the gasket. Put a thin film on the top cover and set the gasket in place and do another thin film. There should be enough RTV to hold the gasket in place as long as you don't rub to hard. As a side note the baffle will only go one way. The easy way to determine which way to set it is to look at the little vents that go towards the crank. Think of which way the crank turns and they sort of point the direction the crank turns. I also forgot to mention about getting some 5/16 flat washers, these are for the top cover bolts. With all this ready start all the top cover bolts then tighten them down until the lock washers are just compressed. Make a couple of passes around to make sure everything is evenly snugged. Leave everything set over night and come back and finish tightening the top cover bolts. Then reinstall everything you took off. Be sure and put the fan and the vent tube on right after you do the finish tightening. I have set the turkey roaster on and had to take it back off! After reassembly you should be leak free for a long time to come.

 

Ken Hand
248-613-8586
www.corvairmechanic.com