Inliners International Forums General Discussion Engines GM and Silicone?

So go to get my first Inline today I get to the guys house and procedes to show me the engine. He pulled for a guy from a truck he was doing a big block swap. The truck was no longer there but he ended up with the engine.

He show a vid of the truck, the engine running, and then the odometer. The truck was a 1981 C10 with a 250 intgeral.The odometer said 18,000 miles. I told the guy probably 118,000. He said no the truck was an old couples and it was in storage till they passed. Everything like valve cover,oil pan, and stuff looked like it had been sealed with black silicone.I said nah somebody's been in there and they guy swore gm used silicone in the 80s. Your thoughts? I guess I will see more when I tear it down.

Sorry for the long story

My '78 was gaskets when I got it with 42k miles. No silicone.

YES!! There were a number of years in the early middle '80s where GM used black RTV silicone for rocker arm and side covers. Also on some timing covers and other small items. It was NOT used on parts that handled or contained fuel. They abandoned it later in the eighties as more and more electronic sensors came into use.

What about the oil pan they use it on there? I seen it on my 250. Just curious.

I think on some vehicles that they did. I'm certain it was used on the ends. but it's been thirty years since those vehicles were new and I've long since retired.

Again! It was inexpensive. Most of the manufacturers dabbled with silicone. It was found that the use of these products caused sensor failures, particularly O2 sensors, when used in repair situations where the product was not allowed to completely cure before the vehicle was returned to service. A problem that still exists to some extent today.

NOTE: This was not a problem with new vehicles when built because the engines were assembled in separate facilities and shipped to the final assembly plants. The silicone had time to cure before the engine was actually started and run.

I have opened a bunch of these engines and never seen silicon used as the main sealant instead of a gasket. Not saying it was not done, just have not seen it.

I do have one odd oil pan. It has about 1/2 of the normal amount of bolt holes to hold it on. It came bolted to a core 292 but I am sure it did not come on it from the factory.

I've seen a lot of the Mr. Goodwrench crate engines done this way in Small Blocks, Big Blocks and the 6 cylinders also. So it may not have been as much a production or assembly line protocol as much as the over the counter protocol. But i've also seen a bunch of the crate engines with gaskets as well. GM outsourced engine assembly programs, casting foundries and machine shops to many different companies and rebuilders all over the world through the years, so it was probably just whatever that particular rebuilder had on hand at the time as part of their own personal engine building practices.