kneeslide

Basically, on a B16a in my car,
Mechanic lined up marks on pulleys,
removed timing belt,
asked assistants to move car,
assistants pushed it with gears engaged.

I dont think he heard anything untoward, and he reckons no damage may have occured once the marks were lined up.
But he asked me to run it by somebody who's familiar with the engine,
What do ye think?

Searching has only brought up different issues of timing/breaking belts while driving etc,
but can you turn the crank safely when the cam pulley marks are aligned and timing belt removed?
Any help appreciated, thanks

f20b jones

unless he rolled it down a hill and poped the clutch you should be fine . If the valves touch the pistons he couldnt have pushed it . As long as the timing was set at top dead center when he took the timing belt off all the valves are closed any way so doesnt matter weither you pushed the car or spun it over with the battery nothing is going to happen. I have also heard you cant bend a valve with a battery im not sure if thats true or not but like i said as long as it was at top dead center when the timing belt was removed the valves were closed so no way to hurt anything.

PyroProblem

Even with the cam gears lined up, there will still be valves that are open. (There is never a time when all 16 valves are closed with the cams installed)

So yes, IMO, there is a chance the pistons could have touched the valves.

If the engine is far enough out of time, even cranking the engine with the battery will bend valves. If the starter is strong enough to move a car (think starting while in gear w/o clutch safety switch), it is definately strong enough to bend a measely little 5mm valvestem.

Id suggest taking the cams out and doing a leakdown test. Good luck!

kneeslide

Oh gosh, half of that sounds ok, the other half terrible!

I dont know did the mech say something like some valves might have been only half open, so was hoping we'd escape damage.
He could turn the crank by hand afterwards without issue/noise,
and when he turned each cam, the valves all seemed to go down and come back up without a hitch, and relatively straight looking.
I might have a look again tomorrow.
Anyway, it's his bad, he'll have to make good if it's damaged
I blame the fool that left it in gear!

Thanks for your help on it.

I was considering doing the valve clearances while it's open,
there's around 70k miles up and I get a noticeable amount of chatter on decceleration, and/or when cornering I think?.
Am I right in thinking it might need adjusting right now, or is the chatter unrelated/normal?

hoffmanb16

I think the first response makes scence, chances are very slim any piston to V contact even happened and if it did the car would have stopped and could not be pushed any more...

Do a leakdown test and you will get your definitive answer.

N/A

X2

pr0honda

Unless you had the VTEC lobes locked, I doubt you hit anything. The stock small lobes on that engine do not have enough overlap to hit the pistons.

kneeslide

Well call me biased, but I like these answers the most!!
It was good just there, I had the mechanic on the phone and I read your replies out to him.
Thats a good point about the VTEC,
I have yet to sit down and fully understand the lobe locking operation (the valves open further, and for a longer duration with VTEC, right?),
but I doubt they would have been in operation with engine switched off, valve cover/timing belt removed.

Anyway, I dont think he was worried from the start, I was the one who got worried! (worst case was just head gasket and a few valves + loads of labour for the mechanic!)

The guy doesnt have a leakdown tester, but could a rough comparison be drawn against the other cylinders from a compression tester?
Or if he was more familiar with the compression tester he might have an idea of what values to expect? I know they're crude, but would they be useless in my case?

A huge thanks for all the replies and sharing knowledge,
I thought I'd be flamed for posting in the wrong section or asking a silly question!
Cheers

Natural Aspirations

Super easy way to check for bent valves is to check the valve lash clearance. If you bend a valve it will not allow the valve to fully seat and will greatly increase your valve lash.

kneeslide

Sounds good, thanks man.
I'm planning on getting him to adjust the clearances, so will let him know this.
The only problem I can see is that I havent measured them recently for a comparison,
and I did already have quite a bit of rattling on decceleration/cornering,
but I suppose if a valve is bent, they're going to be hella out!!
like a mm or two?
Thanks for the tip

Natural Aspirations

Yes significantly

94eg!

iTrader: (2)

With the cams set at TDC, each cylinder is as follows:

TDC all valves closed
BDC intake valves still closing
BDC exhaust valves already opening
TDC intake already opening and exhaust still closing (overlap)

Moral: None of the valves are fully opened with the cams on the TDC marks, so you should be safe. The thing you do NOT want to do is rotate the cam with the crank set at TDC. This can/will bend all valves in cylinders 1 and 4 since the pistons are all the way up.

Hopefully your cam really was set to the TDC mark when the car was moved.

N/A

/thread

Wow I forgot all about that......

hoffmanb16

So when you driving down the road and your t-belt snap and as long as you are out of vtec your good to go....?

I seriously bet not.....

If the valve is at it's lowest point and the piston is at it's highest point they are going to hit...... valve relief or not.

N/A

No but it would be less likely to have damage, especially being pushed

Natural Aspirations

WOW misinformation overload............................

With the cams at TDC you have 2 intakes and 2 exhaust at full lift (on the small lobes) and it has NOTHING to do with how much valve overlap is going on in ANY WAY. Being pushed wile slightly better than at 9k makes really little difference either. Common guys do you need to see the animation of how an engine works, I thought we were all beyond the basics......

If the mechanic made the mistake he is responsible.....

andyz

I snapped a timing belt while decelerating and at idle. Didn't do any valve damage. So just don't think 'belt snapped=valve damage'.

Seems to me, you won't bend anything if you turn it by hand, because the piston will push the valve up *slowly*.

If the belt breaks while the piston is running 5k RPMs and has a ton of momentum, when it hits that valve the valve can't move out of the way fast enough and it's goodbye to that valve.

As far as while in gear, kinda in the middle, I mean, if they really got it rolling it could've bent a valve and the overwhelming force of the car weight...

I'm not sure leakdown is indicated in this case. Isn't leakdown more for the oil leaking past the rings? I'd say just do a straight compression test, turn the engine over by hand and listen/feel for any binding. The result of those two should give you enough insight to put the time/money in to just get it running and see if it is giving good power. If not,...well you know.

Also, once that belt is off, most anything can happen to the alignment of of cam and crank. Just because it was at 'TDC' doesn't mean nothing. As it was rolling, surely the CAM found a nice spot and sat there, totally off-time with the crank and as soon as the crank came around, there was a chance for contact. THAT WHAT THE BELT IS THERE FOR!

Natural Aspirations

Once again someone who has no idea in hell how a Honda engine works.

How the **** can you push a valve up when the cam is pushing it down.

Over welling force of the cars weight? Jesus Christ......

Natural Aspirations

And for the record I'm not saying any valves were certainly bent, just that everyones reasons are completely iacurrate. If anything saved you it was the relatively low lift of the stock b16 cams and the generous valve reliefs in the pistons.

andyz

Piston will push on the valve, not enough to bend it, and *the cam will rotate*, without the belt!

Natural Aspirations

The valve is not strong enough to turn the cam in that way especially at TDC.

The cam doesn't rotate with the belt?

PyroProblem

This is why their called "interferance" engines. The pistons can hit the valves if its outta time. Hopefully you got lucky.

N/A

Think he is trying to say with the belt off the valves can be pushed back up and move the cam freely, which if he knew how the piston hits the valve he would know its highly unlikely.

OP what's this issue just throw your **** back together and see if its ok why waste you time bullshiting on honda tech find out on your own if its ok

andyz

I know personally that I sat there for 15 mins trying to start a D15B7 with a snapped timing belt and never had valve damage AFAIK (10000mi later no problems). My personal theory is that although this is an interference engine, if you are just turning it by hand, or with the starter, with the belt off, the valves will rotate the cam around, just enough to keep them from getting bent.

Maybe not. Maybe on D15B7 there is quite a bit of clearance. So WHY then is this labeled an interference engine?

SOOOO..help me out here....tell me, WHY oh WHY was I able to sit there and pound pound pound those valves with the starter with a snapped belt and nothing ever happen?

And NO, It's not because it's at "TDC", which for some reason some of you think is some 'absolute' term. Each cylinder has a TDC. And if you are cranking the starter and the CAM is stationary, each cylinder is moving toward and passing through TDC which if there any CAM lobes opening valves,which there will always be AT LEAST ONE, on an interference designed engine will certainly cause piston to valve contact.

My point is piston to valve contact, thru the entire crank cycle, with a snapped belt MAY not cause bent valves.

pr0honda

Basics are good, if you set your cam centerlines to 90 degrees, you would be correct, and you are the only one I have heard of that does that on the small non- VTEC lobes (or the VTEC ones). Even with your settings, that are about 15 degrees off, they will not hit. B16 max lift non-VTEC is .320@90 degree centerline, pr-3 valve relief .280+.030 head gasket +.030 head to valve + .010 deck = .350. Or .030 clearance @ the worst case. EX comes out @ .050 clearance @ the worst or wrong cam timing setting.
Set the engine to TDC and put a belt on it. These numbers do not work with aftermarket cams.