I have a late 455 with J heads out of God knows what in my 70 Cutlass right now. Last week it started to sound like I shoved a big race cam in it so I pulled the front off and sure enough, the timing chain is stretched way out and the teeth are all worn on the cam gear. Knowing that it was a later model engine, I ordered a set from a '75 88 from Autozone and I'm just hoping that it will work. What changed from 70-'75 that requires different timing sets? Cam shafts? Crank? I'm pretty sure the block casting in that area would be the same throughout the run of big blocks right? It looks like the part changed between '74 and '75.

 

You're fine. Get a set from a 260-455 and you're good to go. They are all the same. Just make sure to replace the crank gear as that will be worn and you don't want to hurt the new set.

EDIT: Although I'm not sure about the roller 307's and the diesels. I've never had call to mess with them so stick with what you have and you'll be G2G.

 

That's what I thought. But every parts store lists different sets for the 68-74 vs the 75 up 455s. I wonder if it's something like the "Headers on a Supreme" issue.

 

Sealed Power shows their timing set fitting different models from 64-88.
In 1975 400 Pontiacs were available in Oldsmobiles. Check the number on the box that you bought and make sure its not for a Pontiac.

 

The part I got from Autozone was part # 73006. I'd say the top gear is about twice as heavy as the one I took off. Also, the one I took off feels like it may be made of aluminum. The teeth were so worn that they were super sharp and pointy. I was worried that the el cheapo part would have the plastic teeth and would be total junk. Not bad for $22 bucks.

 

The teeth are sharp like that because they used to be covered in plastic to make the chain quiet. I had one look like that about 22 years ago. I was shocked to say the least.
Now I know you don't want to hear this, but you're going to have to drop the pan to get the plastic chunks out of there and make sure none of them get sucked up in the oil pump pickup.

 

Thanks for the heads up. Not what I was wanting to hear. How hard is it to drop the stock pan without pulling the engine up? It looks like it will be a pain to get it out past the crossmember.

 

You have to pull one of the motor mounts, maybe both of them, there is no way around it.

 

I just went through this on my '70 Cutlass last fall and I must say its not fun. My timing gear was original like yours and the teeth were even more worn. I only found a few pieces of nylon in the pan and none on the oil pickup screen.Went ahead and changed the oil and filter to be safe. Had to jack up the engine about 6 inches and remove both motor mounts and starter to get the pan out, and I've got the stock 350. The service manual details a lot more work to do a 455 A-body

Good luck.

 

In the recent article "Rocketing the 455 Oldsmobile Engine into the Future Using Today's Gasoline and Oils" by Joe Mondello in Engine Professional magazine, he says,

"The timing chain sets out there aren't very good either. The ones coming from underdeveloped countries have cheap chain material, out-of round-gears, with timing marks and keyways that are in the wrong location. Be especially cautious of the True Roller Chain set for $19.95. I spent three days checking all the chain sets I could get my hands on, and some, like the one mentioned above, were 9° to 11° off the timing specs. I only use Cloyes True Roller chain sets... so far, the Cloyes has been within ¼ of a degree in total timing events."

Does anyone else have any specific information on this subject?
Does this sound exaggerated?
Prices of timing sets vary wildly, and all of us would rather pay $20 than $60 or $100 for any given part, but it seems to me that if these things were so badly made, they'd have trouble selling them.
Looks like I'll be buying the Cloyes True Roller set when the time comes, unless I hear something reliable and specific to the contrary, but the way Mondello's statement was worded, I just can't help wondering if it was a shameless product placement.

- Eric

 

MDchanic, Bill Trovato (BTR Performance) says the same thing in his book. In fact he found so many that were off he makes his own now. He recommends Rollmaster, Cloyes and ProGear billet sets although he does say that ProGear had holes drilled wrong. Seems like he's a big fan of Rollmaster as they are the lightest and highest quality of the billet sets. I use an old Pete Jackson gear drive which is accurate but has straight cut teeth and is noisy.

 

Something seemingly overooked;
In the early '70's, GM was grinding cams retarded to help with the 'federal emissions' BS.
I don't know exactly when that started, but I would think advancing a stock cam 4 degrees, [w/a Cloyes type chain] would be to your advantage.
Even down the road, as the chain stretches, you're back to stock - -

 

People say they sound like a supercharger, true?

 

What will last longer? What gives you less problem?

 

Yes it does sound like a supercharger or a bad front pump on the tranny, hehe.

 

I went looking for them, found 2 types, noisy and quiet, which one is your's

 

It's noisy, straight cut gears