all 7m's are non interference correct?
under what circumstances would a valve hit a piston on a 7mge? ever?
under what circumstances would a valve hit a piston on a 7mge? ever?
7mge non interference
- Thread starter suprra_girl
- Start date
if enough material has been removed from the block and/or head then the motor could become interferance.
I would think if the timing were way off...but the timing belt was still intact, that could cause a valve to be down when the piston is comming up.
On a stock setup, the valves and pistons should never come in contact with each other unless, as Lagged said, you have removed material from the block or head and didn't compensate for it with a thicker headgasket. The only way otherwise is if you have replaced the pistons with ones that don't have the indentations to clear the valves or if you have squeezed larger valves in there somehow. You can check this when the timing belt is off by setting the cams so the valves are open on one cylinder and rotating the crank. If it you can do a full revolution without it stopping then they don't hit.
Also, spinning the engine too fast or seriously tired valve springs could cause valve 'float' - where the valves open further than they should from inertia.
High compression pistons, material removed from block/head, higher lift cams, or like Grim said, inertia moving the valves past where the lobe is touching them.
I think that's about it.
I think that's about it.
ok.. this is a very very stock 7mge
intelligent brother tried doing a hg LOL
had timing off as well
#4 piston has a chip out of the exhaust valve pocket (only one chip) #3 is not effected
valve faces at a quick look are ok... yet to open valves and get a better look
very odd
edit: had a look at the #4 valves, first ex valve in #4 is bent... so obviously valve hit piston..... somehow (suspecting broken spark plug in bore or similar)
intelligent brother tried doing a hg LOL
had timing off as well
#4 piston has a chip out of the exhaust valve pocket (only one chip) #3 is not effected
valve faces at a quick look are ok... yet to open valves and get a better look
very odd
edit: had a look at the #4 valves, first ex valve in #4 is bent... so obviously valve hit piston..... somehow (suspecting broken spark plug in bore or similar)
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ahh, well if that is the case I guess the 7MGE isnt a non-interference motor. Like limequat said, even if the timing belt were to snap in a non-interference motor piston and valve should never meet. Unless a good chunk of material had been removed when decking the head or block.
1TuffSupra said:
no, the 7m is a NON interferance motor.
either the valve was bent before hand, or some debris entered the combustion chamber.
I had a valve come in contact with the piston when a shim came out of the lifter and acted like a lever to open the valve further than it normally would (see link). But under "normal" circumstances, the engine is non-interference. I suppose higher than stock lift cams could cause contact if the T-belt breaks.
http://www.supramania.com/forums/showthread.php?t=2542
http://www.supramania.com/forums/showthread.php?t=2542
thats basically what I said. Non-interference motors will never allow the valves to contact the pistons. She stated that there are marks on the piston and the valve is bent. If the valve did in fact come in contact with the piston there should be a circular indentation on the piston face. Ive seen it before quit a few times from working on dsms with my buddy. If the valve was bent previously it should have definitely been noticed. A bent valve would make the car sound and perform like ass, a bent valve will not seat properly and allow exhaust gas to mix with fresh air and vise versa, and in a na motor it would have caused a nice power decrease. If the car was running normally before the BHG, then no some foreign material shouldnt have made it past both the filter, intake piping, tb, and the runners on the intake manifold. There should have been some sort of indication that there was a problem before the car was down for the bhg. So if the valve were to contact the piston it would have had to been because so much material was removed from either the block or head that the engine became an interference motor. If it was never opened, that is an entirely different ballgame, but she said it is a very very stock motor. I think we need some answers about how the car was running previously to completely answer her question. Besides a turbo motor and a NA motor are completely different beasts, the na has a higher compression ratio and since the block, hg and head of the turbo and na's are the same, the compression bump had to come from dome pistons. I dont know for sure whether these motors are interference or non-interference, but based on what she said, I came to a conclusion. Sorry for not wording it better.
Troyota said:
No, in a non-interference motor the valves and the pistons can not meet, ever. Thats why I and limequat said, even if the timing belt snaps, and the timing is doing its own thing independently, even if the half of the valves are down, while the pistons are still moving up and down the valve and piston will never come in contact with one another.
On a side note, what does troyota mean?
I had a different image in my head of what Non-Interference actually meant...I have been enlightened. I'm sorry.
On the other note...I have had this nickname since I was young (back when Toyota had the slogan "I love what you do for me!") Since my name is Troy, my cousins just started singing the song "I love what you do for me...Troyota!" I grew up around Toyota's and loved them...then when I grew up and got my MKIII it was just natural to get that on my personalized plate. Now everybody calls me Troyota.
On the other note...I have had this nickname since I was young (back when Toyota had the slogan "I love what you do for me!") Since my name is Troy, my cousins just started singing the song "I love what you do for me...Troyota!" I grew up around Toyota's and loved them...then when I grew up and got my MKIII it was just natural to get that on my personalized plate. Now everybody calls me Troyota.
ahhh, dont apologize, its a great thing to learn something. Hell I learn something new everyday, lol. I like the name, and the fact that your name is troy just makes it that much better. :icon_razz
I bet you had some debris in the engine (check the spark plug). You'd have to remove over .060" from the head and block (combined) to make the engine interference. Valve float would keep the valve from coming back down with the cam, but unless you had extraordinarily weak springs it wouldn't make the valve open more than with the cam all the way down... In order to rev the stock engine high enough to make this occur, you'd likely see a rodknock and it would only happen from a mis-shift. Plus both valves would have contacted the piston...
NON means timing belt breaks and you get towed.
Other than NON means you do work on the engine.
Please don't ask me how I know.
Other than NON means you do work on the engine.
Please don't ask me how I know.
speaking of timing belts, i just pulled the turbo on my friends mr2 and i was just imagining what new curse words i would invent if that was my car and the timing belt broke.........
read: mr2s are almost impossible to work on with the motor in the car.
read: mr2s are almost impossible to work on with the motor in the car.