Timing chain on 1984 Corvette

[Walter F.]

I have been told that if the timing chain breaks on a 350 small block the valves will bend because they are interference engines. I thought only cars with a timing belt breakage caused belt valves ?

[Michael W.]

Re: Timing chain on 1984 Corvette

Belt or chain drive has no relevance. I can show you lots of scary pictures of 8 and 12 cylinder engines with bent valves from jumped chains, usually due to bad tensioners.

[Duke W.]

Re: Timing chain on 1984 Corvette

I am not sure if Chevrolet engines are "free running" i.e the valves won't hit the pistons if the timing chain breaks, but they rarely do and there is no tensioner to fail. The only "problem" was the nylon tooth cam sprocket back in the late sixties. A number of OHC engines over the years have had tensioner failure issues, which can cause valve-piston interference. Late seventies Porsche 911s come to mind.

[Joe L.]

Re: Timing chain on 1984 Corvette

I am not sure if Chevrolet engines are "free running" i.e the valves won't hit the pistons if the timing chain breaks, but they rarely do and there is no tensioner to fail. The only "problem" was the nylon tooth cam sprocket back in the late sixties. A number of OHC engines over the years have had tensioner failure issues, which can cause valve-piston interference. Late seventies Porsche 911s come to mind.

Duke------


The nylon toothed, aluminum cam sprocket was used in PRODUCTION for all 1966-91 (and, possibly later) small blocks. That design was also used for all 1965-74 big blocks.

[Mark E.]

Re: Timing chain on 1984 Corvette

Are SB (or BB) Chevys interference engines? Great question.

I know a stock 9:1 CR 283ci 195hp passenger car engine is not (my first car).

And I've heard some of the high-compression, high-lift cam engines are interference.

But I've never seen a list of available SB/BB engines designating which are interference. That would be interesting.

[Darryl D.]

Re: Timing chain on 1984 Corvette

Duke------


The nylon toothed, aluminum cam sprocket was used in PRODUCTION for all 1966-91 (and, possibly later) small blocks. That design was also used for all 1965-74 big blocks.

Supposedly the reason for the nylon toothed gear was to make a quite engine but I would think it was cost. Rebuilding an engine of course everyone uses the stronger metal gear. However that won't prevent the possibility of the chain jumping off of the gear with a worn high mileage engine.