[Cliff R]

Couple of things to add.

A stock 3/4" wide Morse chain is considerably stronger than any type of roller timing set. Even better if you get older varieties with the heat treated steel gears, but I would use a currently available cast iron sprocket set WAY before I'd use any double roller chain.

What's missing on any double roller chain set is a tensioner. I've been into GOBS of engines over the years and many used roller chains in them, but they ALWAYS have a spring loaded or hydraulic tensioner of some sort to take up the slack.

I tried the Rollmaster once and it failed in 4 years with pretty hard use. I drove more miles and made more track runs that most reading this and the chain got so loose it starting flopping all over the place the the car started breaking up in high gear at the top end of the track. I just thought I had a bad plus, wire or worst case bent a pushrod or broke a valve spring. Everything appeared OK the next day so I pulled the engine and took it apart only to find the timing chain had about 4" of slop in it. Yes, I could just about walk it right off the gears!

No real reason that happened. I had a .030" hole in the front oil gallery plug to spray extra lube on it. I wasn't running much spring pressure and standard 60psi oil pump so the load on it wasn't all that great. What I think happens is that they start to flop back and forth when they get loose and it amplifies the stretching out/wearing out process. Just a guess and don't really care, I went back to using 3/4 wide Morse chain sets and no more issues.

Even with all that said the way most folks use these vehicles you'll probably never have any issues. Most of these cars are lucky to have 3000 miles put on them in the next 20 years, so you'll never have to worry about your double roller timing set going South on you.

You have to be very careful when installing a Rollmaster 9 keyway set and it's pretty easy to line one up wrong if you deviate from the "zero" keyway on the crankshaft. I love stories so here goes a good one.

A "famous" Pontiac engine "builder" and machinist did an engine for a customer. It was a "high" end build, hefty roller cam and extensively ported heads, etc. It was supposedly "ran in" on a test engine then picked up and installed by the customer. Since it was going to be raced it was a pretty "high end" build and I supplied the carb and distributor for it. The customer gets it installed and it's WAY down on power. Seems to idle OK, and drives OK but when you go to heavy or full throttle it "backfires" up thru the carb. He can't figure it out, so he enlists all his friends, beer drinking buddies, several local "guru's", and even the wife's boyfriend to assist and ALL of them tell him the Q-jet is a POS and holding the engine back.

So I get the carb back, and it's absolutely FLAWLESS everywhere. Send it back and no improvement. So it comes back again after a shop that specializes in building these engines once again tells him the carb is a POS. This time I put it on my car, go to our local track and send it back with a time slip. I thought that would end the "drama", but no, now the owner wants to trailer the car nearly 900 miles for me to look at. LOVELY, but I agreed.

So the car shows up, and he fires it up to back it out of the trailer and it just doesn't sound right to me. Seems to idle OK but just not sounding overly "heathly" like a 600hp 455 should sound. So the customer leaves the car and trailer then heads back home. I couldn't resist working on it so did a test drive and it drives OK, but wouldn t spin the back tires if you dropped it off a floor jack! So I remove the Shaker and air cleaner lid and "blip" the throttle really quick which resulted in burnign off most of my eyebrows when it backfired in my face!

So I removed the drivers side valve cover and rotated the engine until toward #1 TDC on the compression stroke. The #1 intake usually starts coming up slightly before TDC, but this one was WAY, WAY off the mark.

So I pulled the timing cover and noticed the "builder" had used a Rollmaster timing set and advanced the cam. No big deal however they FAILED to count up and back to the left two teeth and establish a new reference point to line up the top sprocket....DUH?

So the cam is WAY out of phase and had been that way since it left the builder. Anyhow, I moved the top sprocket to the correct location, buttoned it back up. The engine fired right up, sounded completely different and making at least 300 more HP than it did with the cam in the wrong place. It was a 4 speed car and any full throttle below about 30 mph in 1st or 2nd and you were all over the road trying to keep it out of the ditch!

The owner picked the car up a few days later and went on to run well into the 11's with it at the track.

Moral of the story and lessons learned. Just because a self proclaimed "guru" and Pontiac engine building expert does your engine don't think for a minute that it was done correctly. Also READ THE DIRECTIONS if you are installing any timing set and DOUBLE CHECK your work after moving it. I'm certain the "builder" checked it "dot to dot", saw it needed advanced a few degrees, moved the bottom sprocket, then lined it up dot to dot and didn't check it again. So don't leave out that step either......FWIW.......