Lemme process a few pics…. be right back..
OK, hot off my cell phone, I wanted to show you how important a timing chain is on any original Olds motor with over 80,000 miles.
As you may know or not, Olds motors turn their distributer backwards. Yes, so be sure to tell your Chevy mechanic to turn the dist. clockwise looking down to advance.
Beyond that though, this fact causes more valve train internal friction than the other GM motors so…… at @ 70-90,000 miles the single row chain with it’s original plastic gear causes issues. Follow me while we dig into John’s 120K mile motor to give it a lease on it’s performance life…
In the final restoration of this early 1972, 23′ GMC….. John brought it to us to make it reliable after so much he had done himself to his coach. Some things you can do, others we can help with.
This is renewing the “front” of the motor. We are removing and replacing his timing chain but to get to it we will touch and thus suspect if not just down right replace everything we touch.
Radiator is first and being original…….it’s getting recored. Would stink having this awesome looking coach on the side of the road with a rotted radiator.
Next it the fan and clutch… a new Hayden 2747 is in order, his belts look new so we’ll keep those. Now removing the water pump means the power steering pump needs to move and the front motor mount comes off. Support the motor from inside to do this. 
Hitting the timing cover, removing that and there it is… an original, plastic tooth, single row timing chain and it has @ 1/2″ play in the chain…. good call doing this 
Forgot to have Jr. show the slack.. trust me it was there. Pulling out the chain you wonder the logic in having a plastic gear on this part… hey, they tell me it was done to make the motor quiet… I thought Midas muffler did that! 
Ans a littlr more work you can see the steel gear double row true roller design chain and a new double row chain in place 
. Seriously guys, if you are running an original motor and you have 80,000 miles or more on an original timing chain…. it only stands to reason having the crank and cam run true and together can only be a good thing. Chain is @ $100, gasket set is cheap but it will take some or your or some mechanics time …. and unless you wanna take a pile of time to make sure you get this right you may wanna have a local mechanic.. or us… do this for you. Stay tuned for finals on this project. Hey and if you have a basic rebuilt motor, chanes are you have a single roller chain. Pull out the mechanical fuel pump and take a look. No restoration goes outa here unless this issue has been addressed…
Tomorrow we’ll have a looksee on our paint process and where we are… see ya then….
