A couple days ago on the Edmund 4Runner board someone asked what the difference between a timing chain and a timing belt. I believe the new V6 has a timing chain and the V8 has a timing belt. I wrote my two cents worth plus I said "More important question to ask is whether the engine is a interference engine or a non-interference engine". I think the V8 is a interference and I am un-sure of the new V6. Someone asked for a explanation of a interference engine was and I responded. Thai like my answer and asked me to repost here.

Basically, what we are talking about here with timing chains and belts and interference engines is something that will affect you in the long run, if you don't keep cars long, then no need to worry. Now onto what a interference engine is. A piston in the engine goes up and down, on the down stroke the valves (either exhaust or intake) open and let in fuel and air or release exhaust. Sometimes engineers like to put a little more clearance on the valves to get more air and fuel in. Also engineers like higher compression ratios. As a result sometimes the valves go below the line where the piston goes on its powerstroke. This is not a problem until the timing chain or belt breaks. When that happens you lose all compression, the valves come to a stop, but the pistons keep moving until you come to a stop. Some valves will be open and when the piston goes up, ouch. Bent valves or worse.

The big point being, if you have a interference engine, as I do in my Honda and Acura, when it comes time to change the timing belt or chain, YOU BETTER DO IT.

The other point for 4Runners is do we have a interference or non-interference engine. I know the old 3.4 V6 is a non-interference engine, meaning if I break the timing belt, no ouch. Does anyone know what the new engines are. That may help to make up peoples mind on what to get.

In case you didn't like my explanation, here is a link to two other explanations and one picture.

http://cartalk.cars.com/Columns/Arch...00/May/09.html

http://www.cartrackers.com/Buyers_Gu...1113101.1.html

http://www.gates.com/brochure.cfm?br...ocation_id=524

This question came up on another Board and I did some investigation on the V8. I checked with my service manager who said it was indeed a NON Interference engine. I checked with the Gates Rubber company, maker of timing belts and sent an e-amil for a clarification. They too told me that it is a NON Interference engine. I never asked about the V6 as a chain driven engine is not a prone to failure though the same problem would occur if the chain failed.
Subject to some new information to the contrary the V8 4.7 engine is a NON INTERFERENCE ENGINE!!!!!!!!

Thanks for the information. I was basing my knowledge from another post on the Edmund board. I think that is excellent news for the V8. Is the replacement for the timing belt 90,000 miles, like it is for my 3.4 V6? If so, that would be even better news.

Oh, one more thing, I noticed this is your first post. Welcome to the board.

Yep, LTC really kicked butt with this one! The Gates site lists the change interval at 90K, BUT, as LTC said, they also list the 4.7 V8 from 2-3 years ago as interference. But they now say Toyota made changes and it now is not. So who knows if they are up to date on the change interval. Toyota would be the best source for this.

Does anyone know if 4 cylinder engine in a 1990 4runner is an interference engine?

The 22re is a chain driven interference engine.

This explains why I need to change the timing belt in my V8 soon! I don't want an "ouch!"