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Interference engines! The sr20det is one you know.

Well I didn't know what that was until I finally asked. Then when I knew about what an interference engine is, I asked myself "well if so much damage can occur to the valves if a valve gets stuck open, why do they design it the way they do?"


Originally Posted by S14240SR
Ive always wondered this......

How does an interference head work compared to a non-interference head?
Where can I find a write up on this? Specifically about the SR20DET
-Thanks

It is not just the head. It is a combination of the head, pistons and camshaft lift and timing. In an interference engine, if a valve is stuck open while the engine is rotating, the piston will strike it. This can happen if the timing chain breaks, or the cam timing is off by several teeth, or the valves float at high rpm.

Lew
Heres some other stuff I found after searching Interference engines.

Dear Tom and Ray:


You've often mentioned that timing belts should be replaced before they break, because on some cars, engine damage can be severe. I own a 1986 Honda Accord LXi. Due to a divorce, I've lost some of my service records, and I don't know how long ago the timing belt was replaced. Do you know if this is one of the engines that would be damaged if the belt breaks while I'm driving? Thanks. -- Jeff

Ray: Well, I've heard of nasty divorces before, but this is the first time I've ever heard of one spouse getting the service records. "He gets the Honda, she gets the house, the kids and the service records."

Tom: Oh, they go for everything. Trust me.

Ray: Unfortunately, your car IS what we affectionately refer to in the shop as a "motor wrecker."

Tom: The technical term is "interference engine," because the valves open so far into the cylinders (they "interfere" in the piston space) that if the valve timing isn't perfect, the valves can be struck by a piston.

Ray: The "interference" design actually increases the engine's efficiency, because the wider the valves open, the more "stuff" you can get in and out of the cylinders. But when the timing belt breaks on an interference engine, the pistons and valves can collide, and then it's "bye-bye valves."

Tom: By the way, most Hondas and Nissans use interference engines. Some other cars do, too, so check with your dealer about your specific year and model.

Ray: Since you have an interference engine, Jeff, unless you can verify that the belt was changed within the past 60,000 miles, you'd be wise to go ahead and change it now. And the easiest way to find the date of the last timing-belt change is to call your ex-wife and ask her to look it up for you.

Tom: If you'd rather sit on a hot fork than do that (hey, I've been there), you can try asking the garage where you take the car for service. It's possible that it will have a record of when you last changed the belt.

Ray: But better safe than sorry here, Jeff. This is probably not the time to be adding a car payment to the monthly bills for alimony, child support and hair plugs. Good luck.



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S14240SR said:
Interference engines! The sr20det is one you know.

Well I didn't know what that was until I finally asked. Then when I knew about what an interference engine is, I asked myself "well if so much damage can occur to the valves if a valve gets stuck open, why do they design it the way they do?"
To get more power:

- The camshaft holds the valves open for more degrees of rotation of the engine to allow more time to fill the cylinders with air/fuel. This means that the valves run closer to the pistons.
-The valve lift of the camshaft is run as high as possible allowing more air/fuel into the cylinders. This brings the valves closer to the pistons.

That a major factor in making an engine that, normally aspirated, can produce more than 1HP per cubic inch as it comes from the factory.

Lew
 

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you just have to remember that timing chains(sr20det) rarely fail, timing belts(hondas use) on the other hand almost always fail.

I had my 'ol Teg's break while on the way to Tijuana from Portland. Sucked, nothing like a plane flight and your car is stuck 1000 miles away.
 

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Well, your KA24DE is also an interference engine. With 2 timing chains.

I prefer chains to belts.
 

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JayLew said:
Well, your KA24DE is also an interference engine. With 2 timing chains.

I prefer chains to belts.
Tensioners on the KA's go out a lot too though. and the chains are kind of loud compared to engines with timing belts...
 

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scafidipro said:
Tensioners on the KA's go out a lot too though.
Easy fix since they are fully mechanical. Take it apart, clean with carb cleaner, fill it back up with oil, and re-install.
 
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