The Stovebolt Site Forums The Shop Area Engine Shop timing gear removal

i finally found a wiindow in my schedule to tear into the engine to find out what all broke. the fiber timing gear shed about a quarter of the teeth off and that is where the engine stopped.

i am now trying to get the timing gear off and was wondering if there a way to remove the timing gear from the cam without taking the cam out of the engine, and i suppose if it is possible to get the new gear back on while the cam stays in the engine as well.

any input is appreciated!

Someone in a backyard somewhere has probably done it. The correct method is to remove the cam and use a press.

PJ, The common way to remove the old gear when I was hanging out at local shops and stripped timing gears were very common was to: break off the old gear to expose the hub at the keyway, then with a sharp chisel cut in toward the key.The hub is soft and will split with just a few blows then you can easily remove it.I would have a helper with a second heavy hammer resting it opposite your cut to make the chisel more effective.

Once the timing cover is removed, pulling the camshaft is not that much additional work. I do not see how the gear could be installed correctly with the camshaft in the engine. Has anyone ever performed this operation.

What engine do you have? Here is the Shop manual for the 1954 Chevy truck.

Hoyt

Yes, I have changed them, and it's a pretty simple operation. Like it was described in a previous post, break the damaged gear away with a big pry bar, and split the hub over the Woodruff key with a BFH and a sharp chisel. Turn the crank and cam so the timing marks align(Be sure to remember the teeth spiral together.) Heat the hub of the new gear with a Propane torch until it's too hot to touch, and quickly tap it onto the cam snout. Be sure to file or sand any burrs off the cam snout to prevent the gear from seizing up partway onto the cam. I used a big 3/4" drive socket the size of the gear hub to serve as a driver to prevent damaging the fiber part of the gear. If a CO2 fire extinguisher or a can of Freon is handy, freeze the cam hub just before driving the hot gear into place. I've also used an air chisel with a large flat bit to drive the gear on after heating it. It's not the best method, but when you're working for flat rate labor pay, taking the cam out of the engine is not an option!
Jerry

Usually removing the cam from the engine involves removing the radiator,grille,and radiator support housing.
Ive seen it done with the cam still in the truck/car,just be sure not to drive the cam back out the end of the motor.
It wont slide all the way out but it will move back abt. 1/2 inch or so. And mess a few things up.

thanks for the feedback everyone.

i am fabricating a puller to get the old timing gear off. it's essentially a micro hydrolic press that does the same thing as the technique used in the shop manual and the best part is it won't require the use of a hammer. i would like to avoid pounding on the cam too much but if the puller doesn't work, i may have to resort to that.

i assume that the camshaft is hardened?! i was looking at the end of the cam shaft and was wondering if drilling and tapping threads into the end would enable using a bolt to "press" the new gear back onto the shaft end, that, and i could imploy the heat option to assist with getting the new gear back on.

i have most of the front exposed (grill, rad, etc.) is off already, but i really don't want to disturb any more engine parts than i have to. i pulled the pan off to get to those two bolts that hold the timing cover on and was overwhelmed by how nice the condition of the bottom end was in. clean and beautiful. like jewelry. minimal sludge in the pan and shining a flashlight into the bottom end of the cylinder bores revealed absolutely gorgeous cylinder walls. no scoring or play as far as i can tell right now. just amazing when you consider this truck has over 100,000 miles on it and it is has never been apart before.

again, thanks for the feedback. i will let you know how things work out.

a possible new discovery...

i had just assumed that the fiber timing gear had a weak tooth that failed and led to the chain of catostrophic events that brought the truck to a halt, but after getting the timing gear off, i started to wonder if it wasn't a result of a camshaft bearing seizing up and thus locking the gear and stripping the teeth off. the shaft turns but not easily.

so i guess my new question is, how easily should the camshaft turn with the entire valve train still in place? the fuel pump is not on but the distributor gear is still in place.

as i have said before...any advice is welcomed!

PJ, With the valve train intact the cam will be difficult to turn and it will not be smooth in turning as the spring effect changes from resisting turning to turning the cam forward.The cam bearings usually are a soft babbit like metal overlaying a steel backing for strength.If the soft metal fails (lack of lube)it quickly goes away making clearance between shaft and what ever is left so it usually doesn't seize.The cam bearing failure and sticking in these engines, in my opinion, would be a very unusual failure mode.
If the pan is removed, there are several opportunites to use a pry bar to support the cam outward while driving the gear on.
In my opinion there is no need to rush a project we are enjoying--like eating a good meal.Why hurry when we are enjoying the trip?Now if we are doing it for a living like Jerry said time is money and we are looking for ways to be more efficient.
A stub of GOOD hacksaw blade could split the hub over the key with a few minutes and a little patience or a bearing splitter might be worked behind the naked hub to allow use of a steering wheel type puller.

Guys, you're over-thinking this one! Just because the methods were crude, they were effective, and thousands of us oldtimers changed timing gears without going to heroic methods. If you're worried about driving the cam out the back of the engine (very rare happening) take the fuel pump off and have a helper use a big pry bar to hold the cam forward while you drive the gear on. Heat the hub, use a big socket as a driver, and pound it on there with a BFH. Trust me, it works!

No, the cam is not hardened, and it would be possible to drill & tap for a push tool. Maybe I'll make a drill/tap guide and a pusher for cam gears like I did for drilling crankshafts!
Jerry

I agree with Hotrod. These engines came from simple times. Most were repaired either independent mechanics or the owner under a shade tree. Very few mechanics had ever seen a shop manual. There were no reprints around and no eBay where many are sold that look almost new. They survived 50 years because dealerships were required to have them, but no one ever looked at them. Just break the old gear off and put on an aluminum one. Aluminum expands a lot when heated.

success!

got the old gear off cleanly. the end of the shaft is flawless so the new gear should go on pretty good with the appropriate amount of heat.

still thinking about drilling and tapping the end of the shaft to utilize a pusher to seat the new gear.

i did discover late last night that one of the push rods is bent. will have to pull it out and do some further inspection to make sure that the valve didn't suffer any damage. guess i should look at the piston as well...

post hoc ergo propter hoc

The pushrods usually bend because of sticky valve guides. I've polished the end of the cam with fine-grit emery cloth and used a little Never-Seez on the cam snout to ease the gear back on once the hub is heated. Just don't get it hot enough to damage the phenolic material if you choose to use the fiber gear, or better yet, use the aluminum gear. It can be heated in an oven enough (300 degrees or so) that it can be slipped on without hammering much at all. It's a slight bit more noisy, but it lasts forever!
Jerry

I found a great bearing/small part heater to be my wife's old electric skillet.Mine won't go beyond 430 degF and can be dialed down to suit the occasion.Will heat several bearings at a time and if preheated will top one out in 2-4 min.
And if you play your cards right you can get her a new one as a gift and claim the old one.

I think you probably had 2 separate problems. A bad fiber gear which has a life expectancy of less than 50 years and stale gas that caused a valve to stick. I would put the new gear on whichever way you choose to do it, pull all the push rods, inspect them and replace the bent ones. I would then squirt something like Marvel Mystery oil in each cylinder and let it set about a week to dissolve the varnish. Chances are very good that will fix your vehicle. If your head gasket is good, why risk something going wrong by pulling the head.

i would prefer to put the fiber gear back on instead of the aluminum one (noise issue). probably not the smartest move but i figure i will be long dead by the time the new gear hits the 50 year mark and potentially fails. then it will be up to my daughter to figure out how to fix it. if the fiber gears are only expected to last 50 years, i got by pretty good given that it was almost 60 years before it failed.

i was already planning on utilizing an oven to warm the part prior to installation since it has the best chance of being heated evenly and under controlled circumstances.

if by stale you mean old gas, that would not be possible. until the time of the engine failure, this truck was my daily driver so it always had fresh gas in it. the last time this truck potentially had any stale gas in it was when i bought it off of my grandparents farm sale in 95.

more as it developes...