Changing the chains without splitting the case is not a easy thing to do but its much easier than I thought it would be.
What had happened to mine ( 69` r/s clone with a 77` 2.7 ) was that the previous owner of my motor had the chain guides in backwards and this caused the chains to flop around and caused the chains to stretch resulting in my right side tensioner wheel to rub the cam housing.
After pulling off the exhaust I found that it looked near impossible to get the new chains around the crank gears since the gears are nearly impossible to see even with a mirror.
After looking in every shop manual printed I could not find a procedure to change the chains without splitting the case. Although there was a few that said you could but just plainly said remove chains and reinstall new ones, and that did not help me figure out how to get them around the crank.
Here's what I did:
First thing is to remove the oil drain pan to have inside access to the left chain gear. Next was to remove the left side (driver) tensioner,wheels,cam gears,and guides. Oh yea make sure the engine is at TDC (Z1). Next step was to remove the chain by either grinding a random link or open the master link (if your chain was already replaced).I had one of each since my left side chain had been changed already.
After opening the chain I used the master link from the new chain and connected it to the old one.
Next step was to make a tool to slip in between the chain and the top side of the crank gear (I cut a piece of plastic 1-1/4" by 10" flat) My homemade tool looked like a ruler but was thinner and more flexible.
I worked the plastic tool between the top of the crank gear and the old chain.Once the tool is inserted far enough I pulled the chain from the old end and with ease I pulled the old chain out while pulling the new one in place. Next was to disconnect the link which held the new and old chain together and connect the chain as intended making sure the center link of the double roller was in place and that the locking clip had the closed side facing engine rotation. The chain did however slip off the tool and fall behind the gear but without much difficulty I was able to put the chain back on the gear by using the oil drain pan passage for access to the gear from the inside, making sure the chain was on both sets of teeth.
Next step was to put the left side together using new guides and putting in new hydraulic tensioners (which is a whole different animal). The correct way the guides go is to have the long end of the guide facing its nearest gear. When installing the ones that are in the case which use the through bolts make sure the little plastic clips lock in place or the guide will not be inline with the chain. Also remember that the right side inner lower guide is different from the rest but looks very similar. After putting it all together on the left side without the pin in the cam gear, I installed the tensioner wheel and tensioner by pushing up on the tensioner wheel letting the cam gear freewheel on the cam (no pin ) while I took up the slack in the chain. I had the cam timing right in the ballpark since I never rotated the crank or the cam.
The right side was done the same way and I didn't have to worry about the chain falling off the homemade plastic tool since the chain has no room to fall off in this side.
After setting the cam timing I was ready to button it up.
All this took about 7 hours but if I had this info I could have done it in 5 hours or less.
Also my camshafts don't have the dot which is supposed to face up at TDC which is noted in the cam timing procedure in most manuals. I found that the #911 stamped on the face is what is supposed to face up. I hope my experience with this helps someone out.