# RB26DETT- Interference or Non-Interference Engine?



## Renith182 (Oct 29, 2006)

Hi everyone

Is the RB26DETT- Interference or Non-Interference Engine? I tried searching the boards and no one asked and i cant seem to find an answer online. 

Any help will be appreciated
Thanks
Ren


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## iceager (Dec 23, 2004)

Did a search on google ( RB26DETT interference engine ) and came up with this:

wat interference? ..
There are two types of engines that use timing belts. They are described as: "Interference Engines" and "Non-interference Engines" The difference lies in the proximity between the valves and the pistons. On an interference engine, if the timing belt slips even one notch, the piston can crash into an open valve causing serious engine damage by bending valves and breaking pistons. Non-interference engines will usually not self destruct, but in either case if the belt fails, the engine will immediately shut down leaving you stranded. :shades_smile: 

Well I just found out that all RBs are interference engine..sigh.. Unlike my other engines 4AGE and 4G92 mivec.


regards
Jan


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## Renith182 (Oct 29, 2006)

Hey thanks for the help.

That sucks. I noticed that all Honda engines (I think all VTEC's at least) are inteference aswell. 

Im curious as to why they dont make all engines non- interference. I guess the mechanic has to make some money from rebuilding a poor guys engine 

Thanks again.
Ren


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## GarethK (Aug 29, 2004)

It comes down to compression, chamber design inc piston top and valve lift. A lot of low compression turbo engines are non interference but most others are interference.


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## hodgie (Oct 23, 2003)

I think they are more economical,precise engines(maybe wrong). I used to have a Ford Cortina a few years ago 1.6ltr and it used to do about 26 - 27mpg.
We just used to drive them until the belt broke and then put a new one on:clap:
5 minute job, even for someone like myself.


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## Marky_GTSt (Dec 31, 2005)

I have found that a number of 8 valve small engines (less than 1.2)are non interference, and generally speaking all engines with 3 or more valves per cylinder are...

I had a vectra 16v in that completely wrecked 10 valves IIRC, But several small fiat and peugeot engines that did no damage, Its safest to assume its interference if your not sure. The RB series engines most certainly are, And I would guess the SR20 is too...

All Diesels are, And some even smash the camshaft to bits when they go...

From what I can tell its to do with high valve lift and the fact that the valves open at an angle that does it for the multivalves, Whereas in the 8 valve engines they seem to have tamer valve lift and the valves are at a much lesser angle to the piston... In diesels its because the piston has to allmost touch the head to get the compression it needs, And as a result the valves are allmost flat to the piston with the cam on top, Hence the cam breaking rather than the valves bending so much.

Im guessing they use multivalves in order to be able to get more lift, as each valve being lighter will be less prone to bounce, IIRC they valve is most efficient if it opens to a height of one quarter its diameter, Easier to do if the valves are smaller on a multivalve too, Then they just cram two of them in there for better volumetric efficiency...

/Ramble


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## hodgie (Oct 23, 2003)

That makes more sense than my mumbling on.


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## Renith182 (Oct 29, 2006)

Yeah i guess designers figured that having a more efficient engine over a longer period of time (providing there are regular timing belt changes) was better than sacrificing efficiency for reliability in the event a belt breaks (which is quite rare if you follow the service intervals).

Ren


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## SteveN (Aug 6, 2002)

VERY few engines, regardless of compression ratio, will be non-interferance these days.

Most engines even with compressions in the low 7s or even 6s would never be non interferance.

Infact i cant think of a single engine used in modern times that isnt.

That is IF non-internferance is the pistons never being able to touch fully open valves even at TDC...


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## GarethK (Aug 29, 2004)

Depending on how modern you're talking about, if i remember correctly quite a lot of even the most recent toyota engines are non-interference - the 3S-GTE from MR2 turbos and Celica GT-Fours were non-interference, and i think the 2JZ-GTE is non interference if it is the non-VVTi motor.


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## Marky_GTSt (Dec 31, 2005)

From what I can tell the small fiat and small peugeot petrol engines are freewheeling, This is based on my experience of seeing several of them with broken belts and no damage being done, even when turning the crank to reset the timing...


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## kismetcapitan (Nov 25, 2005)

The SR20DE may be interference but it also has some kind of "timing chain", never really got what it was but I never had to change it - supposedly it could last "forever" without maintenance. SR20DET I imagine is the same deal.

Anyone know the difference between timing belt and timing chain?


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## iceager (Dec 23, 2004)

Chain up to 200k miles
Belt 60k miles.

well thats what i have been told.

regards
Jan


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## Marky_GTSt (Dec 31, 2005)

The difference is, A belt, is made from rubber with fibres woven in, They are strong, Quiet and cheap to make and replace they dont like being contaminated with oil, diesel or coolant, The chain is just that, Its like a big pushbike chain, It usually uses friction type tensioners, they are noisy, and not allways easy to swap they also need oil going to them, But the service interval is much longer. Oh yes, A chain is mechanically more complex too.

There are some horror stories about the V6 volkswagen engine chain drive as used in the galaxy, I will tell you later 


If either breaks it causes just the same damage.


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## Andy W (Dec 31, 2005)

Marky_GTSt said:


> The difference is, A belt, is made from rubber with fibres woven in, They are strong, Quiet and cheap to make and replace they dont like being contaminated with oil, diesel or coolant, The chain is just that, Its like a big pushbike chain, It usually uses friction type tensioners, they are noisy, and not allways easy to swap they also need oil going to them, But the service interval is much longer. Oh yes, A chain is mechanically more complex too.
> 
> There are some horror stories about the V6 volkswagen engine chain drive as used in the galaxy, I will tell you later
> 
> ...


the chain on the twin cam sierra was good fun when the tensioner went :chuckle: 

the worst bloody thing i ever tried to time up was that V6 in the golf


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## dan0h (Jul 26, 2002)

Timing chains, awesome, much nicer than a belt, as long as they are maintained...

SAAB's B204/205/234/235 engines have counter-rotating balancer shafts (an attempt at making up for the fundamental natural wrongness of the inline-4) and these bad boys were chain driven, not a nice big chain like the timing gear, but a weedy little chain with a messy tensioner arrangement. Well, they used to break eventually (and often without warning or prior noise) and often when they did they would get tangled up in the timing chain too...

You can imagine the mess, it used to look like a hand-grenade had detonated in the front cover  Saw a few that had literally smashed the front cover to pieces, one customer of ours (back when I was a SAAB'er) had one fail at seriously high speed, he couldnt quite place the noise as he decelerated with his foot still flat on the floor as the tunez were on too loud - it was only the panic of the oil fire under the car that caused him to lift off a few seconds later. The mess was so catastrophic I think it ended up with a new short-engine, we never found the front cover (or even pieces) as most of it was vaporized by the remains of the flailing timing chain rotating at a good few thousand revs lol.

That said, if they are maintained and oil changed, they are usually no trouble


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