The Stovebolt Site Forums The Shop Area Engine Shop timing gear fix question

Hi folks
I have a good one...
I drive a 66 chevy ,250 six with a three on the tree.4:11 in back(yup milage sux at the moment)
Driving home last night ..I think I broke my timing gear. As I was coming down a hill, I felt and heard something let go like a bang. at that point I pulle dover the engine died.
I cranked it over and got nothin but freewheeling
meaning that the engine turned over way to easily and not catching.
further investigating..after I had it hauled home..I found the distributer not rotating while turning it over..so I assume timing gear issue.
QUestion can I remove rplace the timing gear wthout pulling the cam??
thanks for any and all help
Tom

Short answer is no. The timing gear is a press on fit. To remove it requires the same thing (a shop press) or a heat torch and a lot of patience.

If your timing gear is broken then to fix it right you have little choice but to pull the engine and disassemble. You won't necessarily need to remove the head, but the timing cover and oil pan have to come off. This means pulling your harmonic balancer and removing the pushrods and lifters. You'll have to check for metal shrapnel in the oil pan. Now would be a great time to replace the oil pump and clean up the oil pickup tube.

Many people recommend replacing the crankshaft gear and timing gear as a matched set. If you do this then you will need to use a crank gear puller to remove the gear. When you re-assemble be sure to line up the timing marks correctly.

If you're lucky you may have only chewed up the gear on the distributor. If so then you'll replace the distributor (or distributor gear) and pull and clean the oil pan. I would pull the camshaft anyways to make sure no damage was done.

-ftyler

Sadly, that is what I feared... I have no Garage to work in at the moment. Hence I may have to go deep and have the engine rebuilt all the way ..in for a penny in for a pound. thanks for your help. One note.
I bought this engine from a junkyard 6 yrs ago..for 300 bucks. Its fair to say I have gotten my moneys worth!
Thanks again

Pull valve cover and spin motor over and see if valves move. If not, the cam gear is likely fragged.
Heck if you just wanna get it running, pull the cam, change the gear, install the cam, change the oil, drive it to Sonic and have a large cherry lime-aid.

Now I know why your handle is Chip.

Tom - As you have just read, most of the guys here take the conservative route on fixing engines, and they have good reasons. Follow their suggestions on diagnosis before tearing things apart. Since you don't have access to a shop, you might want to consider locating another running 250, depending on what you find wrong. Save this engine for rebuilding when you do have a shop available.

Tom,
It has been about 20 years since I have worked on the 250 cu. in. engine but if my memory is correct that is an alluminum gear. If it is, then it can be removed while in the vehicle. First remove the radiator and pan and the front timing cover. You can then see what the damage is. If it is the gear, and all the other parts seem to be in good condition, drill and tap a couple of holes in the gear so a puller can be used to pull the gear off the cam shaft. Once the gear is off the shaft, and you have the new gear, then lay the gear in a shallow pan of oil and heat the oil till it is about to self ignite, remove the gear and align up the key on the cam up with the slot in the gear and the timing marks with crankshaft gear. If you do this quick enough before the gear starts to cool, the gear should slide on the camshaft easy.

Hey
Thank you to all for your advice. It is frustrating to not have a garage otherwise I would have been happily tearin it up the minute it slid off the flatbed.
I am in th eprocess of researching another alternative. Imay have accessto a 350 motor for a good price..but am holding off on that I love the 25o sixbanger for the fact that its darn convinient to work with. I think I will keep it somehow and when I go to rebuild it warm it up a bit.
next question..would I be insane to mate the 350 wiht the 3spd tranny, provided I swap the rears to 3:7.3s??

I don't think so. That combination should work fine, and give decent mpg and relatively long engine life provided you don't do a lot of driving over 60 mph for extended periods of time.

I have a 1966 chevy pickup. I have the shortbed stepside model. It originally came with the 250/3 speed column combo. Mine has 3.73 rear gears. And with that combo I took it on many 50-100+ mile trips driving 60-65 all the way. No problems whatsoever. 65 is the absolute maximum sustained speed that the engine was comfortable with. At that speed the engine was turning just under 3k. 2700 rpms at 60.

I swapped in a mildly built 292 (.060 over, 4 bbl, cam, headers, HEI, etc.) and a 4 speed overdrive trans. Now the truck will hold 75 mph with ease and it absolutely cruises at 70 turning only 2300 rpms.

For engine longevity, higher speed cruising possibilities and better mpg I recommend overdrive or a higher speed rear end (2.73-3.23 rear end ratio). If you go under 3.08 and want to keep a stick shift then I recommend going to a 4 speed.

-ftyler

I saw a neat trick on TV for things like this. They were installing the pinion gear on the shaft and they used a grill, something like a George Forman grill to heat it up. Then they just dropped it on the shaft.

Before you do anything pull the distributor and check the gear,I have run into a couple of 250 motors that the distributor has seized and broke the gear.

I agree, check the dist then do a compression check or watch for valve action. I thought that the aluminum timing sets didnt usually fail?

I once had 64 Chevy 3/4 ton, original 230 engine. Same thing happened, timing gear broke, it was a fiber not aluminum, to my surprise, no valves were bent.Pulled the cam after removing the grille and radiator timing cover, lifter and the oil pan didn't have to be removed. not too bad of a job except it was 15 degrees and snowing.

I once had a '66 that was a factory 327 and Powerglide. It was a nice driving truck, even at speed on the freeway.

I swapped in a mild 350 and when driven the speed limit it got 16 or 17 mpg on the road. And it would comfortably exceed the speed limit.

Probably the most helpful part of this story would be what the rear gears were, but if I ever did know 20-some years later I sure don't remember.

..would I be insane to mate the 350 wiht the 3spd tranny, provided I swap the rears to 3:7.3s??[/QB][/QUOTE]

Hi Tom, I thought that I would let you know that the 350/3 speed combo works fine in my '66 stepside. It is a bit on the low speed side but it will really light up a tire. I am going to put in a 4 speed or late model overdrive 5 speed this winter. Good luck with your truck.

That's what you gotta like about this site. Ol-timers gettin the job done. I would of never of thought of it. Makes me laugh on how things have changed. By the way, is thar OSHA approved??

I just might need to use this method sometime

"Then lay the gear in a shallow pan of oil and heat the oil till it is about to self ignite"

My Father had a 66 GMC with a 250 6 cyl.. he smoked the cam gear at least 3 times.. and fixed it on the side of the road one of those times.. not sure if he pulled the whole cam, or just put on a new cam gear... it was some crappy material, that fails every 120,000 miles or so.