Bond

iTrader: (6)

It must have been the over-rev, was it mechanical or just free blipping? That harmonic **** is interesting though, I just don't know how you could prove it happened to your valves.

hustler

iTrader: (6)

I think mechanical twice (4th instead of 6th at TWS once, a couple times on the street when learning the 6-speed), the throttle stuck open twice

I can't find anything on harmonics mis-shaping the valves.

Miater

For those of us who don't know, what is your rev limit set at?

hustler

iTrader: (6)

7000

miata2fast

iTrader: (2)

Every time I pull the head and have it inspected, I have at least one bent valve. It is what bp heads do, they have bent valves.

Sometimes I think it is the fact that the harmonics on the bp are not so good. Maybe, maybe not.

falcon

iTrader: (13)

or perhaps your non interference engine is not so non interference anymore? Did you do any shaving to the block or head when you built it? Do you know the history of the block? Could it possibly have been rebuilt before and decked/shaved?

I know my motor is not even close to being non interference anymore... unfortunatley.

Faeflora

iTrader: (2)

OK so why is bent valves bad? Lower power?

Sounds like motor was still running fine.

hustler

iTrader: (6)

According to the machinist who I talked to yesterday, our engine is "non-interference) if the lifter stays on the cam lobe. Capiche? He said when you "zing" the engine, the valve springs go crazy.

curly

iTrader: (25)

My understanding was that non-interference motors means that the piston at it's highest point and the valve at it's lowest point won't touch.

Valves have some leeway for extra travel, so if this space is small, which I'm sure it is, getting rid of that slack (aka: hitting your valve's bump stops) with an over-rev may very well make them connect.

dl;dr: sounds legit.

Seefo

iTrader: (5)

thats silly...first valve clearance between the lifter and the cam is present. so they definitely don't stay all the time. second, that would make no sense, because the cam and lifter touching isn't indicative of if the piston and valve are touching, which would be the real killer.

non-interference is what curly said.

hustler

iTrader: (6)

"Indicative" is a stupid word and requires passive voice verbs. Use "indicates" or I'll ban you.

I don't know what happened, machinist claims the valves most likely hit the piston.

miata2fast

iTrader: (2)

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trickyrix

Interesting... you'd think if the valves were floating, the piston would just knock the valve back into place, but I guess it slaps it so hard that the valve angle comes into play and tweaks it.

So, other than the low compression numbers, the thing ran fine, right? Seemed fine when I rode in it a couple months back.

hustler

iTrader: (6)

It ran fine but I imagine it will run significantly better now that I should have 40% better leak numbers all the way around. It was hard to start and started oscilating at idle. The car has really transformed over the last two months and I'm proud of it again. No more embarassment from zip ties, wires, and rubber hoses.

curly

iTrader: (25)

irregardless, I'm glad you're getting it fixed and back on the track. If all of the sudden you start having a whole nother problem, I'd be suspicious of your clearances.

johnwag

iTrader: (3)

Any pics of the manifold i ported?

hustler

iTrader: (6)

Not yet.

spoolin2bars

iTrader: (1)

wierd thing is from what you said, there is no evidence of piston/valve contact. nothing that's been claimed as the cause makes any kind of sense. problem with that is the possibility of it happening again. if you don't know what caused the problem, how can you prevent it in the future? that would be keeping me up at night. I "zinged" my motor 5 times without ill effect. my compression has been the same the last 4 years. Am i just super lucky, or we just grasping at straws with jfk theories of bent valves. there were 2 shooters in case you wondered. Good luck either way, need to get that beast back out there.

hustler

iTrader: (6)

Yeah JZ, that's why I won't let the problem go away. The only real possibilities are piston to valve contact a while ago, and the valves not dinging the pistons, or strange vibration related happenings. I went with the stronger valve springs and SS valves to essentially eliminate variables over over-spinning and a stronger valve to resist vibration, hopefully it will work because it seriously depleted my bank account. I could have picked-up a van and trailer with the money I spent this time around, but I'm really happy about upgrading the things I did. Some of the upgrades fixed things which were hazardous, others will quell embarrassment on the alignment rack.

Bond

iTrader: (6)

I may have missed it, but the valves were checked to be true before you built this motor, correct?