interference engines

[D1SR240]

ok, my friend said that he read somewhere that some Toyota engies close all the vavles when the timing chain/belt breaks. I'm not sure how this is possible but if anyone knows anything about this please help me out.

thnx in advance?

[Hijacker]

they probably close the valves by having the piston beat beack up

seriously, though. i don't think toyota, or any company for that matter, has anything like that.

[elbles]

Well, if you are referring to non-interference engines, Toyota has at the very least the 5SFE, 3SGE, and 3GSTE, all of which are non-interference, meaning if the timing belt breaks (all of those engines have belts rated for 60K miles), the valves will not meet their death by hitting the pistons, or vice-versa; most, if not all, Nissan engines are interference, meaning that if the timing belt or chain breaks/jumps teeth, et cetra, the valves will hit the pistons (or vice-versa), and you'll have a much more expensive repair bill. ;-)

Interestingly enough, quite a few people tout chains as being better simply because less maintenance is "required", but in at least 3 Nissan engines that I'm aware of, there have been some pretty interesting problems related to timing chains, with the KA24E, KA24DE, and VH45DE (or whatever engine was in the 1990-early 1993 Q45's) all having problems with chain guides, et cetra. Because of stuff like that, I'll take a non-interference belt engine anyday, hehe.

[D1SR240]

Well, if you are referring to non-interference engines, Toyota has at the very least the 5SFE, 3SGE, and 3GSTE, all of which are non-interference, meaning if the timing belt breaks (all of those engines have belts rated for 60K miles), the valves will not meet their death by hitting the pistons, or vice-versa; most, if not all, Nissan engines are interference, meaning that if the timing belt or chain breaks/jumps teeth, et cetra, the valves will hit the pistons (or vice-versa), and you'll have a much more expensive repair bill. ;-)

Interestingly enough, quite a few people tout chains as being better simply because less maintenance is "required", but in at least 3 Nissan engines that I'm aware of, there have been some pretty interesting problems related to timing chains, with the KA24E, KA24DE, and VH45DE (or whatever engine was in the 1990-early 1993 Q45's) all having problems with chain guides, et cetra. Because of stuff like that, I'll take a non-interference belt engine anyday, hehe.

in non interference engines how will the valves not hit the pistons?

[elbles]

Good question. :-) The valves won't hit the pistons, simply because when the valves are fully open, the pistons at their respective TDCs won't hit them. Nothing more than dimensions of engine design, I guess . . .

[Hijacker]

TDC is short of the valves at full open. Interference engines were introduced as a way to get more power by allowing higher compression. correct me on that if i'm wrong though

[elbles]

Exactly right. :-) Forgot to mention that compression ratios are higher with interference engines, because the piston is allowed more distance to compress the gas/air mixture before ignition. Good call. :-)

[lessthanjakejohn]

so good for turbo

how is that chopped to hell MR2 coming??

[BuudWeizErr]

Can you give a definitive answer about whether the redtop SR is interference? I'm sure you know the info already... 8.5:1 compression, turbo, timing chain, dohc, blah blah

[lessthanjakejohn]

Its probaly definitely not

Is that definitive enough?

[ride4lame]

i am pretty positive that it is interference.

[krazy skwerel]

I want to say the old ca20 was noninterference but I can't say for certain.

[180fan]

I'd guess sr's are interference since you close up all the valves when doing a timing chain job via pulling the cam bolts out.

[lessthanjakejohn]

oops

I meant to say that SRs are interference... not that they were not interference

fu ck...

[D1SR240]

so all 4 stroke engines are either interference or non interference engines?

[DAEDALUS]

You could say that, but the distinction only matters to overhead valve engines, since L-head engines are always non-interference. Also, rotary engines are 4-cycle, but don't have valves so are always non-interference as well.

[D1SR240]

ya good point