nylon timing gears in 72 307 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mike16 · 01-08-2010, 08:24 PM

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 · 01-08-2010, 08:30 PM

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

Huck · 01-08-2010, 08:39 PM

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 · 01-08-2010, 08:43 PM

yea I seen that tree up close and personal

Sammy · 01-08-2010, 08:45 PM

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 · 01-08-2010, 08:46 PM

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 · 01-08-2010, 10:18 PM

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 · 01-08-2010, 10:44 PM

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 · 01-09-2010, 11:43 AM

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 · 01-09-2010, 12:57 PM

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 · 01-09-2010, 05:14 PM

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 · 01-09-2010, 06:25 PM

go with a gear drive, they sound good

**special-K** · 01-09-2010, 09:11 PM

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 · 01-09-2010, 09:24 PM

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 · 01-09-2010, 09:31 PM

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

mike16 · 01-09-2010, 09:46 PM

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 · 01-09-2010, 09:55 PM

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

mike16 · 01-09-2010, 09:59 PM

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

CCCC · 01-09-2010, 10:01 PM

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 · 01-13-2010, 08:12 PM

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.

01-08-2010, 08:24 PM	#1
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	nylon timing gears in 72 307 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?

01-08-2010, 08:30 PM	#2
bhoeger70 Registered User Join Date: Sep 2007 Location: Grand Forks ND Posts: 434	Re: nylon timing gears in 72 307 I think they were used in the light duty trucks also. __________________ "Beer is proof that God loves us and wants us to be happy" Ben Franklin 67 Chevy 1/2 lwb, 67 GMC 1/2 lwb (parts)

01-08-2010, 08:39 PM	#3
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,261	Re: nylon timing gears in 72 307 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.

01-08-2010, 08:43 PM	#4
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 yea I seen that tree up close and personal

01-08-2010, 08:45 PM	#5
Sammy Registered User Join Date: Apr 2000 Location: Bonne Terre, Mo Posts: 3,005	Re: nylon timing gears in 72 307 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. __________________ '69 Chevy Long Fleet & '71 GMC Short Step & Project "ODD BALL" "You can wash a pig, soak it in most expensive perfume. In the end it is still just a pig." ODD BALL build thread http://67-72chevytrucks.com/vboard/s...d.php?t=478629"

01-08-2010, 08:46 PM	#6
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 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?

01-08-2010, 10:18 PM	#7
Arad68 Trucks N Tranzams Join Date: Dec 2002 Location: North Las Vegas, Nevada Posts: 816	Re: nylon timing gears in 72 307 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. __________________ Don '68 Chevy LB 383 TH400/GV/373 posi '56 Chevy 4WD SWB '64 Chevy short stepside '79 Trans Am 455/TH2004R/12blt/4whldisc 95 Kia (Wifes car) 2002 S-10 extended cab pickup "God punishes small sins immediately" Last edited by Arad68; 01-08-2010 at 10:19 PM.

01-08-2010, 10:44 PM	#8
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 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. Last edited by mike16; 01-08-2010 at 10:51 PM.

01-09-2010, 11:43 AM	#9
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,229	Re: nylon timing gears in 72 307 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.

01-09-2010, 12:57 PM	#10
factorystock Registered User Join Date: Feb 2007 Location: west coast Posts: 3,396	Re: nylon timing gears in 72 307 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.

01-09-2010, 05:14 PM	#11
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 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?

01-09-2010, 06:25 PM	#12
57larry Registered User Join Date: Nov 2007 Location: Indianapolis Posts: 1,161	Re: nylon timing gears in 72 307 go with a gear drive, they sound good

01-09-2010, 09:11 PM	#13
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,851	Re: nylon timing gears in 72 307 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. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

01-09-2010, 09:24 PM	#14
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 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

01-09-2010, 09:31 PM	#15
77chris03 Registered User Join Date: Jun 2009 Location: CoNrOe Tx Posts: 1,343	Re: nylon timing gears in 72 307 I have a 70 model 350 that had the nylon timing gears. And it's a 4 bolt main. __________________ 68 C10 Stepper #1- GONE 68 C10 Stepper #2 1977 Chevy Cheyenne...gone...was my first Chevy 04 Tahoe Z71, 04 Silverado 2500HD, 04 Sierra 2500HD 99 Sierra Stepside, 17 Denali HD, 84 K10 My 1st build-- http://67-72chevytrucks.com/vboard/s...d.php?t=379333 My 2nd build-- http://67-72chevytrucks.com/vboard/s...d.php?t=700310



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01-09-2010, 09:46 PM	#16
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 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

01-09-2010, 09:55 PM	#17
bigsnookmaster Registered User Join Date: Jan 2008 Location: St.Petersburg,Fl Posts: 1,267	Re: nylon timing gears in 72 307 Go with a good timing chain set, a gear drive will drive you crazy in about two weeks.IMO __________________ greg http://community.webshots.com/user/68406Stepside

01-09-2010, 09:59 PM	#18
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 I already picked up a cloyes double roller timing chain. gears never made the short list

01-09-2010, 10:01 PM	#19
CCCC Registered User Join Date: Mar 2007 Location: San Pedro River, SE Arizona Posts: 734	Re: nylon timing gears in 72 307 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 __________________ CCCC 67 Sting Ray Coupe 327 4sp; 68 K10 Suburban 327 4sp; 69 K20 Lifted 383 4sp; 69 C80 Fire Truck 478 V6 5sp/2sp; 69 C20 Longhorn 327 4sp; 70 C30 Wrecker 350 4sp; 70 C30 Flat Bed 350 4sp; 71 C20 LWB 350 4sp; 72 K5 Blazer 350 4sp; 72 C30 Flat Bed Gooseneck Hauler with sleeper 350/TH400; 72 C20 Longhorn 402 4sp; 52 Mack LTL Supercharged Cummins 5sp x 3sp; 01 Dodge 5.9 HO Cummins 6spd; 02 Safari Trek 2430 8.1 Vortec on Workhorse Chassis; 03 Silverado 2500 HD 4wd Duramax/Allison Moved but still in the family 70 C20 Custom Camper 350/TH350; 72 K5 Blazer CST Highlander 350/TH350 Recently sent to new homes 72 C30 MoHome 402 4sp; 72 K5 Blazer Conv 350 4sp; 75 GMC 6000 Aerial 350 w Allison; 72 GMC 3500 Utility 350 4sp; 70 GMC 3500, 350 4sp

01-13-2010, 08:12 PM	#20
mike16 Registered User Join Date: Dec 2009 Location: bisbee, arizona Posts: 1,529	Re: nylon timing gears in 72 307 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.

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