Interference Engine?

[Kilroy]

My wife's 99 LX -cyl Accord has 85K miles. The owner's manual states the timing belt is good for 7 years or 105K miles. The car is now 7 years old and I was planning to wait on the timing belt if the engine is a non-interference motor. If not, I guess I need to go ahead and get the timing belt changed.

A local dealer has a special to replace the timing belt and balancer belt, replace cam seal, balancer seal and crankshaft seal, water pump and antifreeze and drive belts for $630. That seems like a fair price to me, can any experts comment?

Thanks,

Don

[RTexasF]

No expert by any means.......Interference engine or not (which I think it is) why risk the better half being stranded?

The price for the work sounds reasonable to me, especially considering the seals, water pump, and drive belts. It appears to me like they would prefer to do it right the first time instead of having to go back in again later.

[princess]

what's non interference???

[dragoncoach]

I've never heard of a interference (or non) engine. Does it have to do with electrical interference? I would like to know exactly what it is and what it does if someone can provide and explanation. Thanks.

[jermy4]

I think I know what it means. If the engine is an interference engine and the timing belt breaks the engine will have permanent damage (bent valves, etc.).

[Kilroy]

Yes, in a non-interference engine, the valves at maximum lift would not touch the piston at TDC. I had a Toyota Supra Turbo that was a non-interference engine and guessed the Accord may be as it has a fairly low compression ratio.

We'll probably just go ahead and get everything changed. I'd like to get another year out of it, but I don't want to chance buying a new engine.

Cheers,

Don

[princess]

Well, if THAT'S what it means, then if Hondas timing belt breaks theres usually internal damage.... bent valves being the norm. Some years are worse than others. So I would guess by the explanation Hondas ARE interference.

[stiller fan]

let me take a stab at this one.....

non-interference: if timing belt breaks, no damage

interference: if timing belt breaks, and not shut off in time, then major work needs to be done....

correct me if i'm wrong....

[stevencrosbie]

I am gonna beat the dead horse more

Interference: When the egine is running, the valves open and close as the piston moves through its cycles. These open and closing are carefully timed so the valve is not fully open when the piston is top dead center. When the belt/chain breaks, the valves quit moving, but the pistons continue to move. If a valve is stuck in the open position, the piston will impact the valve. Now you will have bent valves and the need for a new piston.

non interference: Nothing happends. Just get a new belt.

[greg-ster]

Why would anyone use an interference engine design, if there are so many potential sources of damage?

[princess]

So with most Hondas....timing belt breaks...horses are dead!!

[04EXNavi]

This month's Road & Track had a reader question about which companies make non-interference engines, vs. those that do not. Suprisingly, only a handful make the non-interference ones...I'll post the list tomorrow to add to our library of semi-useless knowledge

I don't get why more makers don't design them to be non-interfering, the only difference as far as I know is little half-circle depressions in the piston tops to allow valve clearance.

[stevencrosbie]

I'm sure that little dimple makes a huge difference in the fluid dynamics of the cylinder. I am sure there is a really good logical reason why they use an interference engine...I just haven't learned that one yet.


Maybe Ben knows?

[Conundrum]

I guess from reading all this then the J30A4 must be an interference engine unforuntely

Anyhow I'll wait for 04EXNavi to post with the company/model names...although I still cannot figure out why companies design engines this way (so that if the belt snaps you need essentially an engine rebuild).

Also just to shoot this out there...when the belt goes...is there any way to tell that its about to happen? Does the engine run oddly for a number of miles/kilometres first, or is it just BANG and your screwed?

[stevencrosbie]

Originally Posted by Conundrum

Also just to shoot this out there...when the belt goes...is there any way to tell that its about to happen? Does the engine run oddly for a number of miles/kilometres first, or is it just BANG and your screwed?

I am almost positive that its that one.

I have not heard of anyone who has had a Honda belt break before the 105k change. Since the belt is covered from the elements, they are usually in good condition even when they are changed.