Valve Touched Piston When Crank Turned by Hand.. Insight?

[grimreaper]

Motors on the stand.
Heads on and Tqed down.
Cams in and Tqed down.
Valve clearances within stock specs. .10-.11mm on this particular valve
Stock cams.
Stock valves.
Stock springs.
Timing belt NOT on.
No spark plugs.

I was filling the oil passages with oil to ward off rust while it sits and spun the crank pulley with my bare HAND while doing so. After the first revolution I noticed a hang up in one spot. Took 3-4 more revolutions to realize #2 exhaust valves are open and when #2 piston hit TDC I could feel the contact through the valve stems. The impact never got "lighter" over the 4-5 total revs. Turning the crank was done slowly with a single hand on the crank pulley.
I'm trying to think of how to describe the amount of resistance I felt. Reminds me of a key pushing up on a lock tumbler... Felt slightly notchy in an other wise seamlessly smooth crank revolution and never got harder or easier.

Will a leak down test work on rings that have not been ran yet? (to test valve leakage)
Likely hood of bending a valve given such a minor load, engine speed, and amount of crank turning resistance?

 

[IJ.]

Something is VERY wrong, shouldn't even come close to touching.

Leakdown will show if it's bent or not as it will have massive leakage into the Intake or Exhaust

"If" it touched it's bent, it takes almost nothing to bend a 7M valve.

 

[Another MkIII]

Something is VERY wrong, shouldn't even come close to touching.

Leakdown will show if it's bent or not as it will have massive leakage into the Intake or Exhaust

"If" it touched it's bent, it takes almost nothing to bend a 7M valve.

Would it be possible to touch if the block and head had been machined? I'm guessing not since you know what you're talking about and you say it shouldn't be close.
-AM3

 

[IJ.]

You have to remove a LOT of material before it becomes interference, what HG is in it?

 

[grimreaper]

Indeed something is off. Block had a lot taken off and pistons where fly cut to reduce the protrusion.
Head has been decked 3 times. Minimal amounts on the 2 that where done by me. the head still measured 40cc's. Sorry cant recall the amounts. I'll dig through my notes and see if I wrote it all down.

Only the exhaust side hits. I didn't try any other pistons with the valves open. Intake side does not, But a different set of valves where open.

Deck height is .014" with a 1.6mm HG. Piston to head clearance should be 1.25mm unless I'm doing it wrong.
With all the spec put into a calculator, Its right at 8.95XX : 1 compression with weisco pistons. They are supposed to be 9:1 pistons. The dish is a little shallower at 16cc.

I'll give a leak down test a shot before tearing the head back off..

 

[grimreaper]

Thought this over a bit. I'm going to pull the cams back out and see if maybe the HG is rubbing the piston.

On initial install the bores cleared perfectly. (83.5mm pistons, 84mm bore on the HG) I did remove all the rivets to clean the HG so maybe something didnt line up like it should have. The dowel pins where in the block and I used 3-4 head studs as well to line things up.

 

[Another MkIII]

You have to remove a LOT of material before it becomes interference, what HG is in it?

That's what I figured, but wanted to hear from someone with more motor building experience.
-AM3

 

[grimreaper]

UPDATE:
I hit the cylinder with air. I couldnt feel anything at 100psi so i filled the cavity behind the valve with some wd-40 like spray lube. Both valves bubble like boiling water. Tried the #5 cylinder, both vavles on the exhaust also bubbles, but near impossible to feel or hear the air when dry as well.

Its about 50* out side.. should I expect this type of leakage with a cold head?
Valve job has about 15-20,000 miles on it.

 

[grimreaper]

spoke to the shop, its expected to have some leakage given the miles on the valve job. (closer to 28,000 miles after looking at the receipts). all the valves retained the spray silicon lube for 5+ minutes with out any noticeable amount leaking through.

Lots of theories on why the valve may be touching the piston. The measurements seem sound. I'm taking a guess that the previous valve job + unknown amounts removed at that time may very well have the head on the shallow side. Carbon build up on the valve face may be a possibility as well. No issues with the timing belt on though. Smooth as butter. I'll measure the head next time I'm in the garage.. Hopefully that will solve this.

My quench clearance is a bit tighter then stock.
mine= .048"
stock = .05" (based off .2mm deck height and 1.47mm stock HG compressed)

 

[grimreaper]

Final UPDATE: found the issue about 20 minutes before I pulled the head back off. At some point I manage to drop an o ring into the cylinder. After careful inspection of the piston through the sparkplug hole I found an o ring flattened half way into the valve relief on the valve in question. Not sure where it came from but all the other holes are clear and no more issues at this point. This was resolved back in December but been to busy with work to work on the car until now. Almost done at this point, just need fluids and the radiator installed.

 

[IJ.]

Stock HG is 1.37mm compressed.

 

[bioskyline]

Final UPDATE: found the issue about 20 minutes before I pulled the head back off. At some point I manage to drop an o ring into the cylinder. After careful inspection of the piston through the sparkplug hole I found an o ring flattened half way into the valve relief on the valve in question. Not sure where it came from but all the other holes are clear and no more issues at this point. This was resolved back in December but been to busy with work to work on the car until now. Almost done at this point, just need fluids and the radiator installed.

injector o ring perhaps?

 

[grimreaper]

Stock HG is 1.37mm compressed.

good catch, so my math has stock quench clearance at .046". I'm just a hair larger..

Oddly this o ring was blue. Im almost positive it came from a "plug" I fashioned from an old compression tester fitting. Couldnt find my old set of plugs at the time.

 

[Blackdawg]

well glad ya figured that out. I was seriously scared to learn how you made a noninterference motor and interference motor lol

 

[northwestsupra]

i kinda lulz'd at the beginning then really lulz'd at the end, happy to hear it was just an o-ring, some things are just un-explainable.

 

[Nick M]

Indeed something is off. Block had a lot taken off and pistons where fly cut to reduce the protrusion.
Head has been decked 3 times. ..

On a side note, regardless of headgasket thickness, you are probably way out of spec, and deck thickness is compromised. Not that money grows on trees, but you should *consider* a less worn long block.

 

[grimreaper]

^ if/when this motor has to come back out i have a "virgin" head and will let rich sort out the "new" block. Basically I agree, the block and head are on there last run. Sad huh? I've already got another build planned...

 

[Nick M]

Toyota didn't set a max spec at .001" warpage on the block to sell parts. That would be embarassing to a Japanese company. While GM, Ford, and Chrysler would have went out of their way up through the 70's to do just that. Them and their 5 digit odometers. Sorry for the derail. Back to o-ring.

 

[CT26smoker]

Good to hear it was only an O-ring, as I have seen several engines destroyed by fantom nuts being left/lost into intake manifolds.


Engine assembly requires 100% concentration, and watching all openings, all the time.
Kids playing near by, buddies wanting to come over & suck down a brew, etc., while engine is going together is a no-no.