Rattling wasn't Octane, or Timing....

[Sean]

It is the Pistons. My buddy Rod, the guy I bought the Motor from, told me to bring it out to his shop so he could listen to it. I took him out on the road and right off the bat he said, "Thats the Piston noise I was telling you about."

The Pistons were used in late 80's, early 90's factory Roller Cam 350's. Rod said most of them were in Vettes and Police Cars. He has six complete, low mileage 350's with these pistons setting in his Barn, not counting the three he has already beefed up(mine included).

When he was working as a Goodwrench Mechanic, the cars were coming back to the Dealership because of the rattling noise in the engine. The dealership didn't even try to do anything with the engines, they just pulled them out and replaced them. Rod and the other mechanics were taking them home as fast as they could get their hands on them.

He said the problem is that the area above the Compression Ring is almost full bore size, while from the compression ring down, the piston is smaller. This allows the Piston to rock back and forth in the bore at certain times, like when you first start to accelerate, or when you let off the gas. He has built three engines using those shortblocks, and he said all three of them continued to make the same noise. One of them is in his Dad's truck and has about 70,000 miles on it with no problems, so I don't think its worth worrying about.

While he was there, I had him check out the timing and advance. He ended up setting it at 10 degrees initial, and took out the heavy curve springs I installed, and used the medium set instead. At 4000rpm I think he said total timing was 34 degrees. He also suggested that I put AC 43 plugs in it instead of the 44's that I am running. He pulled all the Plugs and looked at them though and they were all light tan, so he figured the Carb was set pretty close to where it needs to be.

I have a new problem now. After all the holeshots we pulled while messing with the timing, the Rearend started feeling loose and making a clanking noise at 1-2 shift. We pulled it in the shop and the front leaf spring bushings were non-existant. I guess after nearly 40 years, they didn't like the new engine and decided to self destruct...

[jaybee]

The Pistons were used in late 80's, early 90's factory Roller Cam 350's. Rod said most of them were in Vettes and Police Cars. He has six complete, low mileage 350's with these pistons setting in his Barn, not counting the three he has already beefed up(mine included).

When he was working as a Goodwrench Mechanic, the cars were coming back to the Dealership because of the rattling noise in the engine. The dealership didn't even try to do anything with the engines, they just pulled them out and replaced them. Rod and the other mechanics were taking them home as fast as they could get their hands on them.

I think I remember those engines.  One of the Sheriffs up here went to the local officials and asked to have his entire fleet of Chevys replaced with Fords because he felt they were of poor quality.  The department had replaced 18 engines at low mileage due to "bad pistons."  Never heard the rest of the story, though.

[Sean]

According to Rod, it doesn't seem to affect durability of the engine, just makes enough of a noise to make everybody nervous. He's not afraid of them, he's putting another motor together right now using one of those shortblocks with Iron Bowtie Heads and Iron Bowtie intake for the "Street Stock" class at the local Dirt Track.

He wasn't very happy with GM yesterday though. Gave $180 for that Iron intake and two of the boltholes had cracks coming off them...