justnspace

iTrader: (1)

About a month ago, I let a friend drive my car because I was incapacitated at the time.

this led to Tom Foolery and the hooning began as I was egging it on from the passenger seat.

The friend being unfamiliar with the 6MT gearing, not knowing which RPM at which speed to be in at the perfect gear and most likely over-revv'd the engine.

we woke up the next morning to a funny idle. sounded like the car was cammed.

"lope lope lope lope lope"

Sounded coool!!!! but I knew what happened.
performance was lost and the car just wasnt as smooth any more.

since I knew I had lost compression somewhere; i skipped the leak down and compression test.

I then got in contact with Yungone501 to score J37 heads from the 07-09 MDX coupled with the 07-08 TL-S cams.



After securing the parts; I started to tear down the engine.






I got this far by myself and then I was stuck.

I was stuck on the crank pulley bolt...



I was stuck for maybe a week and a half.

last night, I decided to try my luck with it.
I pried and pried with all my might.

the breaker bar ended up kicking back on me and I decided I was done for the night.




I invited a friend over this morning to help tackle the crank bolt.

as he reached for the breaker bar attached to the crank bolt, he let out a little laugh.

"its already loosened fool"

apparently, I had broken the bolt loose last night when it kicked back at me.





heads are off!!







you can see where the piston hit the exhaust valves.
it's like this for all six pistons.






J32 heads.

this is where I ended for today.

NBP04TL4ME

For me the job isn't complete, until I draw blood. Usually its a knuckle or somewhere on one of my hands.

Hope yours doesn't bruise. Chest bruising blows....

nfnsquared

Let's see the valves...

TacoBello

So how does that happen? If the valves and pistons are all timed by the timing belt, how would they ever touch, regardless of how fast the internals were spinning? That doesn't make sense to me. Timing wise, nothing changes on those honda engines that rev to 9 or 10k rpm. I thought if the engine goes too fast, you end up burning the valves out or you break a connecting rod or bearings give out, no? Hence why you put lighter, stronger components in to handle the rpm. Pistons still shouldn't ever contact the valves unless your timing belt snaps or slips, but again, that shouldn't happen...

...or am I missing something??

paperboy42190

iTrader: (7)

thanks for these pics justin, its always fun to see engine internals. take as many pics as you can on the way please

bauermd

iTrader: (1)

lol Your all like fk it, lets start tearing the engine apart on day 1.

I have had an O2 sensor sitting on my kitchen table for a week trying to figure out which one i'm supposed to replace with it.

paperboy42190

iTrader: (7)

Valve Float - A high-rpm engine condition in which the valve lifters lose contact with the cam lobes because the valve springs are not strong enough to overcome the momentum of the various valve train components.

Think of it like this. During "normal operation"., the cam lobes essentially "push" the valves open. But at extreme RPM the high point of the lobe is almost "throwing" the valves. It is happening so fast that the spring is not strong/quick enough to return the valve to it's seat before the piston reaches the top of it's stroke, thus, the two will collide with each other.

Grand_hustle17

Subscribed... I have a similar issue... At 1st i thought build but im more on the just fix it side now... I kinda want to go with J37 heads also.. but in all honesty, upon reading most of these builds i cant say im any more sure on whats needed... So far ive got.. valves, 3.7 heads, springs n retainers.. and debating on just keeping the 3.2 cams

nfnsquared

Maybe it's just the picture angle, but I'm not seeing valve strikes on the pistons...

Jesstzn

Did he dump it down a gear instead of up? Isn't that the only way to over rev it?

justnspace

iTrader: (1)

piston showing exhaust valve strike.






Front head; showing exhaust valves are white instead of the nice carbon coated intake valves.



rear head shows the same symptoms.
white exhaust valves.

TacoBello

Ah that does make sense! So I guess that's where different valve springs would come into play.

Justnspace:
I can see the impact marks on top of the pistons, but the valves don't look damaged. You're right, you can see they've been exposed to high heat and they've been cooked, but I thought they would be a little mangled around the edges. Any idea what's causing the engine to make those weird sounds when running at idle? Also, are you concerned about the pistons being impacted? Any bottom end damage beyond the minor impact markings?

tihomirbg

iTrader: (1)

Subscribed! This is good info in case I decide to go same route

erdoc48

Geez, that's going to be like a new engine in the car- new heads, new cams, and I assume a new TB/ water pump while you're in there. I'm interested in how much HP/torque it makes with all the upgraded parts. Will you dyno run it after it's all done?

Best of luck with this. Don't let your friend drive it when it's all done.

justnspace

iTrader: (1)

I dont think you can see the valve bent. it damages the valve rod(dont know if i have that terminology correct) more so than the flat part of the valve.




I am not worried about the pistons having a slight scar on them. the cylinder walls have no scaring and I will run it as is.


and yes, replacement water pump, tensioners and pulleys are already on the car.
will put replacement heads on then new timing belt.

I bought brand new head bolts. just to be safe.
and I bought a gasket kit and new spark plugs all from Rockauto.com
the timing belt kit was purchased from rockauto as well.

nfnsquared

I'm still not seeing anything that could definitely be called a valve strike...

Where in that picture are you saying the valve strike/s is/are?

Jesstzn

Still trying to figure out how he over revved it. Thought there was a rev limiter.

Hi speed

iTrader: (3)

You are right the valve stem bends from the contact with the piston in a minor collision of the two.

screaminz28

iTrader: (1)

On an accidental downshift. If you are going to fast and downshift, it will exceed the rev limiter due to mechanical gearing. I forget specifics, but let's say you can normally do 65 in second gear - and you are in 5th going 100 and downshift to 4th and hit second instead - you are now doing (trying) to go 100mph in second gear, i.e much high rpm than possible with the rev limiter.

Basically the wheels turned the motor in this example.

screaminz28

iTrader: (1)

Looks to me like right here:

nfnsquared

^^^^ Just looks like carbon build up to me....

TacoBello

It's subtle, but if you look at the deepest part of the indentations on top of the piston, you'll notice an additional "groove" line as compared to the opposite side of the piston.

The carbon is baked on real good. It's chipping because of the repeated impact between valve top and piston top.

nfnsquared

Hmmm... I can't bring myself to believe that is the case... Just saying. I don't see any valve strikes on the piston metal....

Aman

Sorry about the luck Justn, butt rebuilding is always fun! Thanks for sharing.

What I'm curious about is why there isn't any damage on the intake side? Because VTEC? Or different (smaller) lobes for intake valves?

justnspace

iTrader: (1)

The pictures above are showing cylinder 5.

here's cylinder 1


again, only the exhaust side of the valves.



here's the million dollar question;
I know I said I was running it as is.... should I pull out the whole engine and replace the pistons?

yungone501

iTrader: (4)

Justin, decarbonize the piston crowns with any cleaning solution (such as brake cleaner) that will leave no residue and is highly evaporative. Oreilly Auto, IMO, seems to carry the best brake cleaner that's very good at doing this due to not leaving moisture behind from the evaporation process. Do each piston one at a time and make sure when you spray them off, the piston is at TDC and you spray the cleaner towards the exhaust side to prevent blasting any remnants or debri into the engine/other cylinders. Chances are, you will notice that the interference is minimal to the crowns. And yes, it's generally only the exhaust valves that hit. They typical get their stems bent towards the valve head and this of course causes them to bind on the valve guide which will cause them not to fully seat once the cam lobe has rolled past that particular rocker.

Anyways, clean the pistons and before installing the other heads and new gaskets make sure you also go over the gasket mating surface with a high grit 3M sanding pad. Its easy to do each bank at once so what I normally do is turn the crank until you see all three pistons at least 1-2" below TDC. This is done so you can stuff LINT FREE rags/cloth in each of the cylinders for obvious cleanliness reasons. You will notice a dull finish on the gaskets mating surface and this is what you want to get rid of before laying down new gaskets. It only takes a few swipes back and fourth before the shiny aluminum finish is restored on the block. It's very important that you don't stay in one area too long and also that you ONLY remove this dull finish and then go to the next area. Once the mating surfaces on both banks are cleaned, make sure you clean the piston crowns again the same way as described earlier just in case anything feel into the cylinder while cleaning. One piston at a time. And at TDC.

Many may argue against this (I once did) but it's very critical that both mating surfaces on the heads and the block be brought back down to bare metal again because of the way the oem head gaskets ensure a positive seal. Generally this process is done by a machinist before engine assembly but this is the only solution in your circumstance. Cleanliness is the critical factor here. I myself usually go the extra mile after restoring the mating surfaces by spraying the brake cleaner down through each cylinder to "flush" the area between the piston and cylinder walls. This of course means you should follow the procedure by doing a flush/oil change afterwards.

Don't cheap out here and reuse the original head bolts. The service manual says you can only if they are within a certain "stretch range" but it's more of a hassle than its worth considering the outcome if the measurement is performed incorrectly. Lastly, judging by carbon buildup on the domes of your pistons, chambers and valves...USE SHELL GAS. Haha, kidding. But seriously, not sure what's going on here (could be lots of things such as old oxygen sensors, etc...) but try and run Sea Foam through the tank every other oil change or so. Carbon buildup is such a silent killer when it comes to engines. Carbon is mostly responsible for causing preignition even on NA engines and though the j-series has a responsive knock control system, the increased knock retard percentage from excessive knock detection will MURDER power by killing advance on the ignition system. Bad thing is....you will never even know it.

pbook4g5

From someone who was in this SAME exact boat 4 years ago in my Accord V6 6MT.... no.

I just got a new set of heads (that were ported, polished, and decked in my case) and called it a day. Car was noticeably peppier.

You'll be fine with new heads, and as someone else mentioned in the ramblings thread, the improvements with new pistons won't be that noticeable.

Jesstzn

That I know ...
Just the way he stated it

The friend being unfamiliar with the 6MT gearing, not knowing which RPM at which speed to be in at the perfect gear and most likely over-revv'd the engine.

YeuEmMaiMai

he forgot how to shift and put it in a lower gear and mechanically over-rev'd the engine

justnspace

iTrader: (1)

Since, I really don't know what happened and the accused won't fess up, I can only guess.
I remember him trying to find the sweet spot in 3rd.

So, we're in third at 80 or 90mph at like 6800-7000 rpm. If he accelerated into fourth but dropped back down in third trying to find that sweet spot, he over did the rpm's.

justnspace

iTrader: (1)

Thanks Robert, I really needed that kick of motivation/advice for the heads.

EvilVirus

iTrader: (8)

Vlad_Type_S

iTrader: (3)

too

yungone501

iTrader: (4)

Let's see them pics of the heads installed Justin!

paperboy42190

iTrader: (7)

just to be clear, you are getting j37 heads right? theres no other damage in the engine? what kind of power can you gain with j37 heads?

justnspace

iTrader: (1)

oh man, I'm taking my time.

I might have time to work on it tonight.

justnspace

iTrader: (1)

yes, I bought a used set of 07-09 MDX J37 heads.

you're seeing the damages of the engine laid out in this thread, as I tear it down.
So far, I took the J32 heads off and saw the exhaust valves white. compared to the nice carbon coated intake valves, something is wrong. the valve stems are bent.
Next, we take a look at the pistons and can see valve strikes on the pistons.

as others have stated, it's fine to run the pistons like this. I'll clean up the piston crowns, clean up the gasket mating surface and install the new J37 heads.

the J37 heads are made for more torque, as it's used to push a big ole SUV.
I also chose the TL type-s cams, because they have a higher lift in vtec than the MDX cams.

So, I'm expecting a pretty good jump in power all throughout the tach

Sonnick

Good luck, Justin! Keep us updated. Sometimes blowing the heads or trans is a "good" thing, because you may have never done this otherwise! Same thing happened to me with my trans ha.

pbook4g5

Just so everyone is on the same page...

The colors of those valves seems normal to me.

Are you saying you can tell there is an issue because of the color of the valves?

justnspace

iTrader: (1)

<---inexperienced.
so, the exhaust valves are supposed to be white????

usually, I play the game of "spot the difference" if one side doesnt look like the other...

but, if you're telling me that the exhaust side is supposed to be white...