nylon timing gears in 72 307

[mike16]

i was doing some work on the 72 today and noticed alot of slop in the timing chain. It has 88000 miles on it. I experienced nylon timing gear failure at this many miles on two other 307's but they were cars. Its going to need a new chain and gear set but I was curious if the trk 307's had that *&%$ nylon gear set?

[bhoeger70]

I think they were used in the light duty trucks also.

[Huck]

Definitely in trucks--had a 68 that thru the timing chain when the plastic coating on the gears gave out. Piston and valves slapped.
Before it goes kaka, replace with a new super quiet gears set eliminating the chain.
fyi---when the plastic covering on the gears lets go, the chain gets way too much play and eventually will come off. If you just wait for that to happen---and then throw rebuilt heads on the block, you create much higher compression then before which tends to create oil blow by at the rings ---. It's like an ugly snow ball going down hill towards a tree.

[mike16]

yea I seen that tree up close and personal

[Sammy]

Yes seen a few nylon timing gears. Your just lucky if the chain gets loose enough to wear hole in the cover before it goes completely.

[mike16]

Did you say gears? like a gear drive set up? not a good quality chain? I want everything to stay put under a factory timing cover. I can get at least as good a life out of a new quality chain set? gears are noisy. Its only a 2bbl 307?

[Arad68]

Yes,
GM put nylon tooth timing chain and gear sets on trucks and just about everything else they could. Buy a good Cloyes set and be done with it. Whats really cool is the pieces in th oil pan from this mess.

[mike16]

which is cooler, the big pieces that clog the pick up screen or the little pieces that get sucked into the pump?

its not the catostophic failure that worries me. its pulling the engine to pull the pan...to pull the timing chain cover to replace the gearset. No doubt when I thread the course bolts of the balancer puller into the fine thread holes and get the balancer off I'll notice that the seal has worn a groove in its sealing surface too...and what else...Oh Yea trying to start the truck and discovering that the timing chain is one tooth off.

[Wrenchbender Ret]

If it hasn't sheared off the plastic teeth you will not need to pull the pan if you are careful & take your time with the cover. Sounds like you are familiar with the fine thread bolts to pull the damper & you can get a sleeve to go on the damper to repair the grooves.

[factorystock]

Timing gears were only installed on 6 cylinder engines, V8's used timing chains. Gears may be noiser, but they are more durable and reliable. The number one reason a V8 engine gets rebuilt, regardless of size, is when the timing chain slips.

[mike16]

picked up a gasket set, oil pump and timing set (cloyes) today. I see the oil pump and pickup are separate. Seems to me last time I bought a pump the screen was attached already. does it ever stop?

[57larry]

go with a gear drive, they sound good

[special-K]

Just slap a double roller chain set in and be done with it.You won`t see the torsional vibrations a gear drive gives that risks breakage of other parts way before you`ll ever wear that double roller out.That was good enough for a 375 hp 327.You should hear the chain slap the cover,mostly when letting off a rev,way before any problems.If not,you`ll jump time and bend pushrods and maybe valve stems.Which leads to a head job,which is the number one reason for an overhaul...along with wiped cam lobes at about the same mileage.Small blocks were known for early top end wear.If you don`t go into the bottom end you`re peeing into the wind.Sounds like you caught it in time.You don`t need to pull the motor or heads,but it`s easier IMO.I`d want to pull the pan and install a new oil pump.

[mike16]

I dread pulling the motor and trans. the service manual says to drop the exuaste. undo the mounts and stick a 2x4 between the motor mounts and the engine. I'm pulling the pan as well and putting a new higher volume oil pump in it as well.

not to hijack my own thread but I bought a new oil pump and the pick up is separate. My experience with pontiacs is that this is always a pain. some suggest a few spot welds around to keep it in.

any input on installing the pickup screen.

and does it really need to be primed by pulling out the distributor and putting some sort of drill atachment on to pump it up?

I've always pulled out the plugs and cranked her over untill the guage strts to read pressure.

wont that work considering I dont have a drill attachment and it seems there really is no space inside the engine compartment for a drill rig

[77chris03]

I have a 70 model 350 that had the nylon timing gears. And it's a 4 bolt main.

[mike16]

I know and others will agree its agood idea to replace it. one of my engine failures due to a failed timing chain damaged the engine irrepairably. It would be a shame to loose a 4 bolt main 350 to that

[bigsnookmaster]

Go with a good timing chain set, a gear drive will drive you crazy in about two weeks.IMO

[mike16]

I already picked up a cloyes double roller timing chain. gears never made the short list

[CCCC]

I have replaced three of these before disaster (JUST before disaster once, by the look of the gear) and know I NEED to go ahead and do the same on a two or three other original unopened SB/BB engines that are over 90K - just a matter of time.

It does not seem too tough - rad out, fan assembly off, pull balancer, off with the pan - new seal and gasket going back together. I have used steel wheel and new chain (I think double) and love the peace of mind when done.

Have never felt need to drop oil pan and look for debris, and oil pressure has stayed good - but did high pressure spray some kerosene up all around in the pan to try a flushout and got a few little pieces of stuff. Maybe was worth it.
Best wishes, CCCC

[mike16]

Disaster averted. The gear teeth were factory GM. They were steel but they had alot of play like over 3/4 inch of slop either way. Truck has only 88000 miles on it and its soooo clean under the timing chain cover.

when i pulled off the pan.....same deal very clean. installing a new hi volume oil pomp and callin it good.