Timing chain and sprockets

[71FuryGC]

I'd welcome any opinions on replacing the timing chain and sprockets on my 71 Fury. I believe, but can't be sure, that it has it's original 360 with 87,450 on the odometer which seems plausible based on pedal wear, steering wheel condition etc. It runs great with no odd noises and I don't thrash it. Leaks a bit of oil, mostly around the intake manifold bolts. I put about 1 pint of oil in it between oil changes (a little over 1000 miles) and use Driven GP-1 10w 30. It does smoke slightly from the left cylinder bank on cold start but not once up to operating temp. I think it has the fragile nylon/plastic sprocket teeth. I don't want to rebuild the whole engine yet as it doesn't seem to warrant it.
Thanks in advance for any advice.

 

[volksworld]

been about 30 years since i had a smallblock apart but iirc you can pull the fuel pump and check the slack in the chain?

 

[Toolmanmike]

Take the distributor cap off and watch the rotor as you turn the crankshaft back and forth by hand or with a socket and ratchet on the crank bolt. If it is quite sloppy you will know it. If it is good there will be a almost immediate rotor movement. Here's a little vid on one I replaced a few years ago.

 

[Davea Lux]

At that mileage, given the age of the car, the chain and sprockets should be replaced. Cloyes makes really good all metal replacement units and that is what i would recommend. Smoke on start up is usually an indication of leaking valve seals. Those can be replaced without tearing down the engine. Usual proceedure is to screw an air chuck into the spark plug hole. This will push the piston on that cylinder down to where both valves are closed and they will stay in place as the springs are removed due to air pressure in the cylinder. This will take a shop grade air compressor, at least 3hp. At one pint every 1000 miles your seals are not leaking enough to bother with replacing them at this time. Let that go until it starts to use a lot more oil.

You can check for slop in the timing chain by rotating the crank by hand to TDC, remove the distributor cap. Now have a helper rock the crank shaft back and forth by placing a socket on the large bolt that holds the damper in place. Note how many degrees it takes to make the distributor shaft move. 15 degrees or more the chain has excess play and needs to be replaced. Note the plastic gear gets more brittle with time and at 50 years old it is very brittle.

Dave

 

[71FuryGC]

At that mileage, given the age of the car, the chain and sprockets should be replaced. Cloyes makes really good all metal replacement units and that is what i would recommend. Smoke on start up is usually an indication of leaking valve seals. Those can be replaced without tearing down the engine. Usual proceedure is to screw an air chuck into the spark plug hole. This will push the piston on that cylinder down to where both valves are closed and they will stay in place as the springs are removed due to air pressure in the cylinder. This will take a shop grade air compressor, at least 3hp. At one pint every 1000 miles your seals are not leaking enough to bother with replacing them at this time. Let that go until it starts to use a lot more oil.

You can check for slop in the timing chain by rotating the crank by hand to TDC, remove the distributor cap. Now have a helper rock the crank shaft back and forth by placing a socket on the large bolt that holds the damper in place. ote how many degrees it takes to make the distributor shaft move. 15 degrees or more the chaing has excess play and needs to be replaced. Note the plastic gear gets more brittle with time and at 50 years old it is very brittle.

Dave

I'll check for slop in the chain first. It is possible that the chain/sprockets have been replaced in the past but not all that likely, based on as far back as I can trace it's history. I'll hold off on the valve seals for now but good to know the procedure. I think some of the oil replaced leaked rather than being burned! I've replaced valve guides on one of my motorcyles twice in the last 40 years.
Thank you for the advice.

 

[71FuryGC]

Take the distributor cap off and watch the rotor as you turn the crankshaft back and forth by hand or with a socket and ratchet on the crank bolt. If it is quite sloppy you will know it. If it is good there will be a almost immediate rotor movement. Here's a little vid on one I replaced a few years ago.

Perfect. Thanks for the advice and the video!

 

[CBODY67]

As LOT of those nylon-coated cam sprockets didn't last much past 80K miles, back then. You can do all of the checks and such, but considering the time and mileage (as Dave mentions), consider it INSURANCE to go ahead and change it as soon as you can. THEN worry about other things. Cloyes is the preferred brand, with one of their basic roller chain sets (you don't need the multi-keyway models for a stock motor). Do cover everything in motor oil and assy lube when you change it and before re-starting the motor. Do NOT wait for failure before you change it!!

The slight smoke at start-up is usually from the valve guide seals, as Dave mentioned. Replacing just the seals usually is a shorter-term fix (and a decent one!) to reconditioning the worn valve guides . . . in the long term. Wait until you have a burnt valve to pull the heads. No need to change the oil as often as you are, even with short trip driving. 3K mile changes should work out well, or wait for it to get to 1qt low and then change it.

Just some thoughts,
CBODY67

 

[ayilar]

@71FuryGT -- you may find this post useful in the thread I maintain for Medina, my similarly-engined 1971 Monaco.

 

[71FuryGC]

As LOT of those nylon-coated cam sprockets didn't last much past 80K miles, back then. You can do all of the checks and such, but considering the time and mileage (as Dave mentions), consider it INSURANCE to go ahead and change it as soon as you can. THEN worry about other things. Cloyes is the preferred brand, with one of their basic roller chain sets (you don't need the multi-keyway models for a stock motor). Do cover everything in motor oil and assy lube when you change it and before re-starting the motor. Do NOT wait for failure before you change it!!

The slight smoke at start-up is usually from the valve guide seals, as Dave mentioned. Replacing just the seals usually is a shorter-term fix (and a decent one!) to reconditioning the worn valve guides . . . in the long term. Wait until you have a burnt valve to pull the heads. No need to change the oil as often as you are, even with short trip driving. 3K mile changes should work out well, or wait for it to get to 1qt low and then change it.

Just some thoughts,
CBODY67

Thanks for the response. The reason I asked about the chain set is because I feel like it probably is ready for changing if a previous owner hadn't done it before it's last 10 years or so. As you say good insurance!

 

[71FuryGC]

@71FuryGT -- you may find this post useful in the thread I maintain for Medina, my similarly-engined 1971 Monaco.

Thanks @ayilar but as soon as I saw the photo of Medina's engine bay I realized we are apples and oranges. Medina is T code whereas my 71 Gran Coupe is K. I'd be happy to shoe horn a big block into mine but the budget would be eye popping compared with a timing chain replacement! Perhaps the avatar name confused you.