Main causes of dropped valves?
 

What are the main contributing factors that would cause a dropped valve. A friend of mine and I were in a discussion the other day and this topic came up, and I really couldn't give a definite answer. I would appreciate if anyone could shed some light on this topic as I have had friends drop valves with upgraded valves and valve springs under normal conditions, as well as with stock Type R valves and springs under casual driving.

Re: Main causes of dropped valves?
 

over-rev, causing retainers to give, possibly bent valves.

Re: Main causes of dropped valves?
 

Main reason for this, other than over rev, are after market cams.

Take BC3+ for example, everyone on this board calls them "small" cams, until you actually measure what they are.
Type R exh cam is 10.5 mm lift, BC3+ is 11.8mm, BUT primary's on BC3+ exh are 11.5mm.
So you end up with 1mm bigger lift OFF VTEC with BC3+ exh cam(than type R was IN VTEC at 10.5), and people usually consider this as basic small cam upgrade on stock GSR with single VS on exh side and take out 9.6 mm cam putting this in.

Even if you put this on type R setup exh side will get tired as you are ALWAYS 1mm larger than stock Type R was on VTEC.
Now imagine driving this around for year or two, well stock GSR will drop the valve in a month or two and type R with this cam will float the valve or brake the springs and drop the valve in a year or two.
And these love to drop valves around 2000 rpm crusing down the road...

Now this was BC3+, how about Pro1, Pro2, Pro3? Daily driver cams? Sure, if you put high quality VS and replace them once a year, even then you are only addressing part of the issue caused by BIG cams. How many poeple do this anyway?

Regards,

Nino

Re: Main causes of dropped valves?
 

Good stuff. But what if a car drops valves twice on two different heads within a three month period, and all on Type R cams and valve train...what then? It dropped valves twice all with Type R cams and springs with both instances, the valve cutting just before the valve head. He claimed it happened under 3000 rpms just as he drove off from a stop sign, causing a giant hole in the piston and a cracked sleeve two cylinders over from the dropped valve. Does this sound right to you?

Re: Main causes of dropped valves?
 

sounds like a seat issue to me

Re: Main causes of dropped valves?
 

It happened on two different heads with two different sets of valves/springs/retainer...the only thing that was the same was the ITR cams.

Re: Main causes of dropped valves?
 

sounds like supertech valves to me lol

anyway improper v2v will cause valves to snap off as well as v2p interference

could also be a seat issue as well, if the valve is pounding on one side of the seat it will put more stress to the one side. although if a proper vj was cut and checked for seal, the seat shouldnt be an issue.

unless it is being pounded into the head afterwards, which doesnt normally happen unless you have a huge port w/ insufficient material left under the seat.

stiff springs could cause broken valves as well but you said its all oem stuff...

Re: Main causes of dropped valves?
 

I can only speculate, as internet diagnostic is not the most accurate. So take this for what it is, my own opinion and guessing...

If there was seat issue with these heads you would not have compression to begin with, so that would be easy to notice as power would be down or car would not hold idle.

If they state that all this happend at 3000 rpms, I am OK with that, I would like to know what happened within few days of that.

I would suspect valve to piston contact in this kind of scenario. Type R valves are not very forgiving once they "kiss" the pistons (none are, but type R have that valve steam that is tapered)

Long story short, if you think that valve train is stock and cams are stock, and do not have very high milage, I would think that valve piston contact was the reason (if that is the case, why this contact happened is the next question).

Regards,

Nino

Re: Main causes of dropped valves?
 

this is not true

you can pound the seat and still have enough compression to idle smooth and run decent

you can also bend your valves and have enough compression to hold idle and run decent as well....

i have done all of this btw

Re: Main causes of dropped valves?
 

On the stock springs and rets once the valves are float the stock rets will do this crazy dance on the top of the springs and eventually develop a thin hairline crack, so the next time you go drive around the crack gets bigger and flop it's valve drop. I have skunk2 valve spring somehow rusted and snapped in 1/2. There're million other things that can cause valve drops, like loose valve guides, valves that are not concentric to the seats, poor quality valvetrains, piston to valves, valves to valves contact(although this problem mainly exist on head with os valves), bent valves, etc.......

Re: Main causes of dropped valves?
 

NAH2B, I would think that you would need aftermarket VS with high installed height pressure to do that, but if you have done this on stock valve train, point taken, I did not think that motor would go on without this showing up with stock components...

Regards,

Nino

Re: Main causes of dropped valves?
 

The guy said that after installing the new head and valvetrain, the car ran great for 3 weeks before he lent a friend who said the car began smoking at a stop sign after he just started it and drove a few feet. It amazes me that it put a giant hole in the piston and cracked a sleeve after driving a few feet from parking.

Re: Main causes of dropped valves?
 

what about just fatiuge? stock valves have been through countless heat cycles plus alot of the times you dont know if they have been turbo'd or sprayed,and seen extreme temps. just throwing it out there to see what yaw think

Re: Main causes of dropped valves?
 

the friend proble miss shift or something

Re: Main causes of dropped valves?
 

same thing i said lol.

Re: Main causes of dropped valves?
 

like a top of third to second would do it lol

Re: Main causes of dropped valves?
 

over-rev or perhaps jump timing

Re: Main causes of dropped valves?
 

I doubt over-rev as i think he has in a stock ITR ECU.

Re: Main causes of dropped valves?
 

this would do it'lol! fuel cut off in a stock ecu is fine when you are acceleration,but i wrong shift it does nothing

Re: Main causes of dropped valves?
 

doesnt matter what ecu or rev limit you have

you can still over rev the motor

Re: Main causes of dropped valves?
 

gearing doesnt care about the ecu haha

Re: Main causes of dropped valves?
 

the main reasons dropped valves usually occur would be due to brittle or fatigued cotter/ keepers and also can be caused by worn notches that were cut on the valves to keep the cotters in place from the manufacturer. I'd change the cotters every 50k.

Re: Main causes of dropped valves?
 

The guy showed me the valve that dropped and the retainer/keepers were still attached perfectly to the valve.

Re: Main causes of dropped valves?
 

My question is that if it is possible to drop a valve, bore a giant hole in the piston, and still crack another cylinder sleeve, all while driving at 1500-300rpms for 1 minute after starting the car?

Re: Main causes of dropped valves?
 

sure it can, dropping a valve is the worst thing you can do to a motor. doesnt matter what rpm you are at. maximum distruction will occur haha

what dont you understand?

your not gonna figure out what caused it by making useless posts on the internet....

btw did you ever go to the dyno w/ your pro3 setup?