I take it you meant to type "non-interference".
This means that the valves have no chance to hit (or interfere) with the top of the piston should something bad happen to the valve train like a broken cam chain or like when you mechanically over rev the engine and "float" the valves.
The S2000 engine is an "interference" engine. If the valve movement (opening) doesn't coordinate precisely with the piston movement, it can strike the top of the piston and do considerable damage.

 

At the risk of sounding ignorant, why would you de-stroke an engine? I think you were actually asking the same question, Wisconsin, but you must've had something in mind when you posted? Please, do tell.

The only reason I can guess for reducing an engine's displacement would be if you intended to add forced injection of some sort... Even so, I'm still stymied.

That non-interference issue was a good point, XV. I suppose if you changed the stroke so the piston didn't get as close to the values, you could do what you described... But, as lurker said, you'd end up changing the shape of the combustion chamber. Again, why???

Thanks (and sorry if that's a stupid question)!

 

There are many reasons to de-stroke an engine. The most popular one is to fit the engine into a class for racing purposes. If you want to be in the 1.5 litre class with a certain block, you must make sure you have the right bore and stroke. Manufactureres use the same block for a number of different applications by changing bore and stroke. So can you.

De-stroking, with nothing more, reduces both displacement and piston speed, so while you lose the diplacement, you can usually increase rpms somewhat without worrying about rod, piston and to some extent, crank failure (until you reach higher piston speeds yet). Of course, you must now spend considerable time on the valves and cylinder head to make up compression and to allow the engine to reach higher RPMs. A higher dome piston is one way to regain compression, the other is to reduce the volume in the dish of the cylinder head, by either skimming the head, or finding a new head with less displacement. New, stiffer valve springs will allow the valves to open and close properly at higher RPM.

You don't have to change rods. It is possible with some engines to change the crank and then cut the top of the block to lower the deck height down to the new, lower reach of the pistons. This has the dual (or triple) advantage of saving money on rods and saving weight off the block and making sure the block surface is flat before rebuilding, but you need to make sure the deck of your block can be cut that far before you start.

As far a interference, there are better ways to deal with it than de-stroking. Typically you get pistons that are relieved where the valves come close to the piston face. Of course, you want to time the engine so the two don't meet if you have an interference design as XV discussed.

Hope this helps.
What are you thinking about doing anyway?

Regards.

Bill

 

Bill, thanks for the info!

 

Ah yes.

I could lie and say I'd have known that if I wasn't dislecix.

I did float my valves about to years ago. That sucks.

Thanks for explaining.

edit: that's two years ago.

 

[QUOTE]Originally posted by Chazmo
[B]Bill, thanks for the info!

 

Yes, destriking allows for higher revs generally. longer stroke equals more torque and less revs. bigger bore equals more horsepower and more revs but less torque. all of that is of course a generalization. good example, and i know i'm going old school here, is the chevy 327. if i'm not mistaken it was made by destroking a 350 in order to make race specs and chevy came up with a great revving engine(for its time of course) that made decent power and met specs for the race. i'm personally fond of big bores and high revs but it depends on your taste.

 

ok so somebody already explained, my page wasn't loaded yet so disregard my redundant reply. apologies