Consequences of Incorrect Valve Timings on Your Engine

[FishmanGeertz]

What would happen if an amateur mechanic decided he wanted to adjust his valve timings outside the factory specifications and screwed up? What would happen? What can incorrect valve timings do to an engine?

 

[Ranger Mike]

by valve timing i assume you mean camshaft timing relative to crankshaft rotation. worst case is bent valves if you advanced the opening event too much.

 

[xxChrisxx]

Bent valves + broken engine is worst case.

Also would this 'amateur mechanic' happen to be you? A light ribbing is in order to whoever decided messing with that would be a good idea. I suppose the next logical question is, does the engine still start? and did it at any point make a horrid 'something's broken' noise.

 

[FishmanGeertz]

Can't the valves collide with the piston and basically blow up your engine?

 

[xxChrisxx]

Can't the valves collide with the piston and basically blow up your engine?

Won't blow it up, but would certainly wreck the valves, and possibly wreck the pistons.

If that had happened you know about it, you'd hear a juddery bang and then you'd never get it started again.

 

[Jobrag]

Lots of unburnt petrol / air mix in the exhaust, fireball, painful death and Darwin Award

 

[turbo]

Many engines are "interference" designs these days. That means that the valves intrude into the space that is occupied by the pistons when they are near the top of their stokes. Not a good thing, especially if a timing belt breaks because that means you need a new engine when the valves and pistons collide.

 

[Ranger Mike]

Can't the valves collide with the piston and basically blow up your engine?

in the case of the mild grocery getter..you bend a valve(s)

This is what you see in Nascar..the scenarios are much more dynamic..like 9000 rpm..
worst case is the piston smacks the valve, the poppet itself separates and cracks the piston ( very rare ) now you have combustion gases mixing with crank case fumes and oil fire starts when oil is sucked out thru the headers , mega smoke,,sometimes flames..

scenario two - valve hammers piston and cracks off piston ring lands piston seizes in the cylinder bore, breaking connecting rod that spins wildly and shears oil pan causing oil to ignite on exhaust headers..fire ball ensues...

oh the death of a high precision engine is a sight to be seen,,as is the sight of owner hysterically sobbing when accessing his check book on line

 

[turbo]

oh the death of a high precision engine is a sight to be seen,,as is the sight of owner hysterically sobbing when accessing his check book on line

Yep. There was a Canadian drag-racer that used to frequent US strips in the 80's with his Camaro. He'd leave the line at 10K and pull hellacious wheelies. I talked to his pit crew one day while I was waiting for my friend to make a run so I could take pictures, and the chief mechanic told me that the engines were professionally-built and cost $25K each. Not a lot in NASCAR circles, but pretty steep for drag-tracks dominated by weekenders.

 

[Ranger Mike]

how right your are Turbo1..drag racing is king of the engine hand grenade contests..as h.p. went up crankshaft main bearing caps would literally walk and shear studs. cam shafts would break due to excessive valve spring loading...engine blocks would get ventilated by broken con rods...oil pans frequently got emptied by stray engine components exiting thur the thin sheet metal...then you add in blowers ,,,,,entire engine blocks separated when the clutch blew and sheared off the flywheel/pplate and mounts ..spectacular and dangerous..

 

[turbo]

how right your are Turbo1..drag racing is king of the engine hand grenade contests..as h.p. went up crankshaft main bearing caps would literally walk and shear studs. cam shafts would break due to excessive valve spring loading...engine blocks would get ventilated by broken con rods...oil pans frequently got emptied by stray engine components exiting thur the thin sheet metal...then you add in blowers ,,,,,entire engine blocks separated when the clutch blew and sheared off the flywheel/pplate and mounts ..spectacular and dangerous..

My friend was on the cusp of the semi-finals in the Winston Cup races at Epping, and when he left the line I knew something was terribly wrong. He managed to slow down and hit the first pit entrance, and the Brut funny-car team rolled into action. They had been rooting for him until he broke, and they tore down the top end of that Duster in minutes. An intake valve had shattered and distributed itself to most of the other cylinders. They buttoned the engine back up and helped us roll the car onto the trailer for the long sad ride home.

Steve looked for old used (seasoned) 340 engines and rebuilt them to his own specs. He wanted blocks that had been very hot and very cold for years so they were stable enough to machine reliably. He could spot a Li'l Red Wagon at a thousand paces - high-performance heads on that limited edition truck.

 

[turbo]

BTW, so many people came to the pits to see what kind of big-block Hemi Steve had under the hood, only to see a 340. It was pretty comical.

 

[Averagesupernova]

Many engines are "interference" designs these days. That means that the valves intrude into the space that is occupied by the pistons when they are near the top of their stokes. Not a good thing, especially if a timing belt breaks because that means you need a new engine when the valves and pistons collide.

Not necessarily. I just finished putting together a Deutz 1011 diesel in a skid-steer loader. The timing belt broke which of course caused a valve-piston collision. It bent the push rod, that's it. The push rods are made to give in this instance just for the sole reason of timing belt issues.

 

[AlephZero]

entire engine blocks separated when the clutch blew and sheared off the flywheel/pplate and mounts ..spectacular and dangerous..

Even "better" when it happens on a really big motor. There was an accident at a local railway engineering works, where somebody wrongly torqued up the flywheel bolts on a big diesel, and it came loose when running in one of the testbeds.

The flywheel went straight through the brick wall of the test building, rolled across about half a mile of railway sidings, through the wooden boundary fence, across somebody's garden, and through a glass-panelled door into a house.

After trashing a few pieces of furniture it finally ran out of kinetic energy. Luckily nobody was in the house at the time, but they got quite a surprise when they returned.

 

[Ranger Mike]

Turbo1..nice video..btw..being a huge MOPAR fan, the biggest mechanical design problem with the original 340 engine block was the cylinder head was held by 4 mead bolts per cylinder vs the 5 bolts per cylinder like the small block ford and chevy..to run any cylinder compression ration over 11 to one you just about had to machine copper O-rings to seal the head gaskets..
the engine was a very good HP maker if you plumbed the oil passages properly.

AlephZero - nice ...btw the drag race pioneer Don Garlits suffered a terrible accident when he was racing a front engine AA/FD dragster...the clutch blew when everyone was running slipper clutches. The accident cut off half his foot and while he was in t he hospital recovering ( months) he dreamed up the rear engine dragster that is so common today..a testimony of a real fighter..he did not feel sorry for him self but fought his way back to win numerous championships with this revolutionary concept..

slipper clutch- the first dragster to run a 6 second quarter mile time did this when the clutch was set up to "slip" instead of locking up solid..back then the dragsters smoked the tires big time and this clutch slippage permitted more tire hook up..it was super dangerous and many clutch explosions injured a lot of people until the clutch manufactures developed a slipper clutch package capable of handling the tremendous friction and heat