Got a question for a friend.

[mathd]

I have a friend who was working on a sbc. he was checking the accuracy of the balancer/pointer using a PISTON STOP. He removed all the spark plug but he kept the rocker arm on.

He say piston stop came out slightly bent(it was NOT screw all the way in) and he did not use much force and did not feel much resistance, so he is surprized this happened.
Now he is worryed about a hole in the piston(wich i said prolly just a scratch).. or many a bent valve??
I honestly don't think he bent a valve, (its straight plug heads with under 500 lift), and looking at the instruction the piston stop is made to be used with head/rocker arm on.

tool look soft to me, i dont think it could damage any engine internal, kind of a fail safe.

EDIT: i forgot to tell, he did feel a little resistance but only at tdc, so to me, for it to hit a valve it has to be about 45 degree not tdc. I also told him to check for bent pushrod and make a lead down test.

 

[87vette81big]

Without a Video Boroscope Tool Camera, The Best thing to do Mathiue is pull the Cylinder head.
More than likely damaged occured.
Bad Deal for your friend.

 

[grumpyvette]

EVERYONE screws up at times!,
I have!, you have! and everyone else has and will continue to do so, its a fact of life!
the secret is to learn from previous mistakes and not repeat them, and to learn from the mistakes other people have made.
tell your friend too take a deep breath and think logically,better to be safe and test things out than guess and trust to luck, Id suggest he do a compression,test ,(and in the future always remove the rockers on the cylinder you use that piston stop on as its much less likely to cause a problem used that way) if it shows any indication that cylinders running lower compression,than the other cylinders, after the compression test, that could be an indication of a bent valve or other damage that warrants closer inspection, and if it was my engine I,d invest the time and the cost of an intake and head gasket and the couple hours labor it might take, to pull and inspect the head just to be 100% sure,your not dealing with more than cosmetic damage, but the chances are good no serious damage was done if the valves were closed on the compression stroke at tdc, when he bent the piston stop, if it was on tdc on the exhaust stroke it could be a problem.
this is one of the reasons I suggest use of a damper with a degree marking on the surface , owning a degree wheel and dial indicator, piston bridge and degree wheel that you use to degree in the cam with the heads off the engine.
an engine , with an automatic or manual transmission out of gear or in neutral, up on jack stands with all the spark plugs removed should be able to be rotated manually with less than 50 ft lbs of force even with accessory's belts connected, but remember the crank exerts compound leverage thru the connecting rod and piston on the piston stop so 50 lbs on the crank is far higher force exerted against the piston stop

YEAH! I KNOW SOUNDS LIKE A LOT OF WORK! if the compression test shows a lower reading on that cylinder, you could just run it and you might be fine.....but then, you might not..., better to be safe and out $50-$70 for gaskets and a couple hours work... , and know where you stand rather ....than guess in my opinion.

viewtopic.php?f=52&t=966&p=13811&hilit=dead+center+finding#p13811

viewtopic.php?f=50&t=455&p=559&hilit=crank+turning#p559

viewtopic.php?f=70&t=1015&p=39847&hilit=degree+wheel#p39847

viewtopic.php?f=52&t=90&p=114&hilit=degree+wheel#p114

viewtopic.php?f=32&t=27&p=35&hilit=degree+wheel#p35

viewtopic.php?f=52&t=399&p=1499&hilit=degree+wheel#p1499

viewtopic.php?f=52&t=974&p=1699&hilit=degree+wheel#p1699

 

[DorianL]

Mathieu - I did the EXACT same thing. I could not feel positively the bump stop, and it came out bent.

I just drove it. There was no damage, Tho it did scare me. Those stops are weak.

 

[mathd]

Mathieu - I did the EXACT same thing. I could not feel positively the bump stop, and it came out bent.

I just drove it. There was no damage, Tho it did scare me. Those stops are weak.

I think thats going to make him feel alot better .

Anyway, am going this afternoon to make a leakdown and compression test and checking for bent pushrods with him. will try to look thru the spark plug hole too.
But am pretty sure it will come out fine(he did NOt use the starter, just a 2 foot breaker bar with very little force)..

I think it bent because it was not all the way in(piston/crank have more force near tdc)

 

[mathd]

Leak down test was positive. all cylinder between 3 and 6%.
Did a compression test to compare with a few other cylinder, result where the same.

Did run the engine and got that sweet chevy v8 music .

 

[Indycars]

Good news for your friend Matieu!

I made my own piston stop from an old spark plug. Forgot to check for
accuracy of my timing marks before I put the heads on.... oops!

 

[mathd]

Good news for your friend Matieu!

I made my own piston stop from an old spark plug. Forgot to check for
accuracy of my timing marks before I put the heads on.... oops!

Be VERY GENTLE, when your going to use it, a little force on the crank = lots of force on that piston. it look alot stronger that the one in my picture

 

[grumpyvette]

if you care to get into the math and engineering,of why the piston, nearing TDC has the leverage and force to bend the bolt, heres some linked info

I went thru years of this in college and still get head aches thinking about the math

https://www.forging.org/system/files/fi ... alysis.pdf

http://emweb.unl.edu/Mechanics-Pages/Lu ... s%20VI.htm

http://www.iosrjournals.org/iosr-jmce/p ... df?id=7622

http://www.ijsrp.org/research-paper-021 ... -p1479.pdf

http://www.eng.utoledo.edu/mime/faculty ... 15-624.pdf

http://victorylibrary.com/mopar/rod-tech-c.htm

 

[DorianL]

Leak down test was positive. all cylinder between 3 and 6%.
Did a compression test to compare with a few other cylinder, result where the same.

Did run the engine and got that sweet chevy v8 music .

 

[DorianL]

Leak down test was positive. all cylinder between 3 and 6%.
Did a compression test to compare with a few other cylinder, result where the same.

Did run the engine and got that sweet chevy v8 music .

I have this "friend" see… :mrgreen:

And he (not me, a friend mind you :roll: ) nearly punched a hole in his piston with a bump-stop. How silly of me… No, HIM!!! :mrgreen: :mrgreen: :mrgreen:

 

[mathd]

Leak down test was positive. all cylinder between 3 and 6%.
Did a compression test to compare with a few other cylinder, result where the same.

Did run the engine and got that sweet chevy v8 music .

I have this "friend" see… :mrgreen:

And he (not me, a friend mind you :roll: ) nearly punched a hole in his piston with a bump-stop. How silly of me… No, HIM!!! :mrgreen: :mrgreen: :mrgreen:

Oups i just got unmasked :mrgreen:
Sometime its soo easy to make a mistake.
Take note to myself: must be more carefull to what am doing.