I had a revelation!(thats what you get when the "senior moment" ends and you remember what you should have remembered two months ago) My '65 B'cuda with 225 has been running a little rough and mileage is down. Went through the carb and that helped a little. ECU died and I replaced it and it is still a little rough. The engine has been making a tinny rattly noise that I haven't been able to find the source of. Then I finally remembered, that is the noise it made when the timing set was worn out and the broken chain links were slapping the timing cover.

I installed a TRW timing set in 1998 and the engine has run about 70,000 miles since. The previous timing set had about the same mileage on it. Both sets had the link belt chain and steel or iron gears. On the last set the chain was very tight. I knew it wouldn't last. The engine rebuilder installed the first set so I don't know how tight it was. I assumed it was also to tight and that is why the chain wore out so fast. The best explanation I can think of for the tight chain is that the cam bore was machined a little to far from the crank.

So, I am wondering if there is a different timing set that will work better with my engine. I wonder if a roller chain timing set would better tolerate the crank to cam distance being to large. Maybe a timing belt but I don't know if there is one for a slant. Maybe Doc has an idea. Anybody know what the crank center to cam center should measure?

I would hate to bury this slant early. It is only on its first rebuild and only has one crack in the block and a couple in the head. It hasn't turned its first million miles yet! I will probably try to get the parts this week and change it next weekend.

I would think that once the chain wears a little bit it will no longer be tight.

I've had those iron gear sets wear out in short time too. I think they are JUNK! Running a steel chain on a cast iron cam gear? Cast iron is rather soft. That ol' steel chain just pounds away on that soft cast.
Studying my factory service manuals, 1975 or so states something special about one half of the front main bearing having a chamfer for timing chain oiling. A couple years later the manuals change to saying something about the front cam gear having something for timing chain oiling. Not enough info there to know exactly what it is for either bearing.

I've posted here a couple years ago about these bearing mods and timing chain oiling but never got any definite answers about the subject.

The factory front main bearing had a chamfer on one edge of one shell, to allow oil leakage to lube the timing chain. At one time, after market mains had a different part number for the front main, these had the chamfer. Since I have gotten back into slants, I have found this is no longer done. The main bearing sets I have gotten, do not have a different front main. I take a file and file a chamfer on the shell, to insure chain oiling. I also use a crankshaft oil slinger. I have found slants both with and with out slingers.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The chamfer on the bearings would explain why the original engine ran so long. The rebuilder probably didn't use the chamfered bearings.

I am not going to pull the engine in order to chamfer the main bearing. I just don't have time to fool with it right now. Maybe I will try a roller chain this time. The problem with the chain being to tight is that the initial wear in and loosening destroys the tooth geometry and its all down hill from there.

What kind of chain are you fellows running? Do you know who makes a roller set for the slant? I haven't found one in the parts catalogs that I have.

I have one engine with a roller chain set. I usually use the silent chain with a metal cam sprocke instead of the plastic. The roller timing set is available from the Cox Bros. in Columbus, Ohio. You can use the search function on this site, for their contact info. They have the largest supply of slant six speed parts, of anyone.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I would also suggest using a factory type "double row, roller" gear and chain set.

Chain oiling is also something to pay attention to, some SL6 engine do nothing to get oil onto the chain set.

Oil slinger is a "must" and the chamfered front main bearing is also nice.

One other "trick" I have used is to drill a small hole in the front oil gallery plug in order to provide a stream of pressurized oil right onto the chain and gears. Keep this hole small, .020 is all you need. I use a larger drill to go most of the way thru the plug from the back side the "poke thru" at an angle with the small drill, from the front.
DD

Could someone post photos of these modifications (the bearing chamfer and the plug drilling)?

Hopefully Doc can do that. I'll be dammed if I can get any pics to post.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225