Snapped timing belt at 8500rpm - What do you suspect damage will be?

[Stanley]

My mate was building a VERY high specd Civic VTi. It was going to be a high compression B20B3 engined EG Civic. High comp pistons, knife edge crank, stage 3 race cams, bike carbs, block guard, shorter ratio LSD gearbox, fidanza flywheel, coilovers stripped interior and bucket seats, and huge brakes, but decided to break it in the hope of going for an Evo. Shame really as it was going to be daft!

Anyway, he sourced a standard B16A2 and fitted that. He gave it a bit of treatment with the laptop that saw Vtec raised to 6200rpm and rev limit tes to 8800rpm. It went rather well for a standard B16. He was going to run it with just the B16 and sell it. We were out in it on friday night, and during a bit of lunacy, the belt snapped at 8500rpm. After we stopped crying form laughter, we started thinking about what to expect once we get the head off.

He has a spare head anyway......

I reckon 16 bent/snapped valves and possibly holed pistons. Maybe even duffed valve guides.

What do you reckon?

[craig green]

I reckon 16 bent/snapped valves and possibly holed pistons. Maybe even duffed valve guides.

What do you reckon?

Atthe least. Head will have suffered I reckon. If it weren't such a ball ache I'd potentially want to examine the rods.

[Stanley]

Atthe least. Head will have suffered I reckon. If it weren't such a ball ache I'd potentially want to examine the rods.

I cant wait, its going to be veeeerrrry funny!

[craig green]

Torquey engines FTW. None of this high revving/VTEC nonsense!

[nova_saloon]

yeh basically what you said, and i think that limit was set a bit high for standard! but the only way you can see the damage is taking it apart!

[Stanley]

yeh basically what you said, and i think that limit was set a bit high for standard! but the only way you can see the damage is taking it apart!

Weve ran standard B16's with that limit a few times and had no bother. I think this engine wasnt the best, plus it was fitted in a rush, so didnt change timing belt, which he gets regular stick for!

[nova_saloon]

that would of been a good idea to do while its out, always do the simple things like quick wash, water pump and timing belt and anything else that looks a bit suspicious.

[Count Vaux Alot]

Thats what happens when your VTEC kicks in YO!

[Jack]

vtak snapped my belt y0

Are honda vtec engines not safe? I thought that would be a no brainer considering the chance of a belt snapping at high rpm.

[Stanley]

vtak snapped my belt y0

Are honda vtec engines not safe? I thought that would be a no brainer considering the chance of a belt snapping at high rpm.

It would make sense... but due to the high compression Honda engines run, theres very little room for error.

And judging by the thud it made, id say they are most definatly notlol

[robertdevlin69]

thats real funny

[coombsey]

pics or it didnt happen lol

[Jack]

And judging by the thud it made, id say they are most definatly notlol
THUD
WTF was that?
Its ok mate, Vtak just kicked in y0 lol

[Mike]

Engine right off FTW :D

[Spudly]

Yeah the engine will be fudged imo, do they not have a second set of cams for vtak and a mini timing chain for the second set plus all the hydraulic gubbins to make it 'kick in y0'


Vtec, hmmm more likt vtech lol

[Stanley]

Im not entirely sure how they work, but i know they operate a different set of cam lobes when in Vtec. They are still twin cam.

[Spudly]

Yeah i used to work at a local honda mainstealers and im fairly sure one of the tech's said they have a second set of vtec cams and theyre held off to run as an 8v till vtec time then the other cams come in and its a 16v:thumb:

[Sloth]

it moves something using oil iirc, poss the followers, so that they get longer, hence opening the valves more. imo the full engine is bin fodder, having seen a sieve type r '02 plate do the same, the valve heads dropped into the bores and noshed into the walls. also the stresses onthe rods and pistons means id not trust the bottom end again. drop a cav v6 in it for a giggle...

[Jack]

I'm sure the VVTLi on Toyota engines moves the camshaft to operate different cam lobes. Would have though Vtak y0 would be similar.

[edit] google says yes ^ basically the camshaft has a "low rpm" and "high rpm" lobe for each valve, and at a certain point moves the camshaft slightly so the different lobes are used.

[Stanley]

Heres a B16 Cam.

Notice the BIG cam lobe that is sandwiched between the primary and secondary smaller lobes. That big meaty cam lobe is the VTEC lobe.

Now think about it. Normally, the primary and secondary lobes just rotate and open valves, and there's no middle lobe to complicate things. But now, you have a middle lobe...but how does that lobe take control over the non-vtec lobes?

This is where you hear the term VTEC crossover...the point at which the VTEC lobe is engaged.

This is achieved by the ECU reading a variety of different sensors, most importantly, Oil Pressure, Water Temperature, Engine Speed, Throttle Position, and some others. When all these systems show ready, a PIN is pushed through all three of the Rocker Arms per cylinder, so that it is now in reality one BIG rocker arm. And since the VTEC lobe is much bigger than either the primary or secondary lobes, its like there is only one single cam lobe instead of the previous two.

http://image.hondatuningmagazine.com/f/10839027/htup_0808_02_z+honda_b16_vtec_cam.jpg

[Sloth]

I'm sure the VVTLi on Toyota engines moves the camshaft to operate different cam lobes. Would have though Vtak y0 would be similar.

[edit] google says yes ^ basically the camshaft has a "low rpm" and "high rpm" lobe for each valve, and at a certain point moves the camshaft slightly so the different lobes are used.

indeed, but having had 3-4 2zz-ge's in bts, theres alot more to it than that....
basically there a fookin nightmare! having text my honda nerd and ex-honda techie mate, he says at vtec point the oil is fed into the lifters, and "pumps them up" meanng instead of being, say 10mm thick, they become 15mm thick, which mean the valves open more. the toyota VVTL-i is similar, but it also has other things controlled by oil pressure such as the cam timing......

[Nova_Tek]

anyway, pics of said engine failure? will be more interesting then how the vtec works :p

[Rich]

woopwoop pics please it will break my mates v-tec heart lol

[Stanley]

All in good time folks :D

[burgo]

bahahahahahahaha!!!!! yes its fcuked

[Dod]

Dont Hondas have a mechanism to stop the valves getting damaged when Timing gear fails or am I thinking on Toyota?

Anyway, if I'm wrong, then Valves, Guids will have **** themselves, the head will have been badly damaged due to this and the pistons will be very very sore looking indeed.

So, whats the verdict?

[dj_wudgey]

ohh my my sounds like he will have some damage lol

[Tim-SR]

unlucky mate, hope its not too bad but at 8500 rpm i'd imagine it isnt going to be pretty

[dj_wudgey]

ohh yea sounds like itl be shagged like lol

[blue_peg_16v]

new engine me thinks