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Pulled motor in woods - warped crankshaft


Bryan
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Think when I stuck the wood block in the #3 cylinder to keep the crank from turning, to get the crank nut off (old post), I warped the crank.

I know I bent # 3 rod, but replaced it.

I know the top of the D46 block is perfectly flat, I measured it.  Thought it might not be parallel to crank, but after checking, think crank is warped.

 

Been storing crank horizontal on trunk of my 58 Dodge. Varying opinions on internet whether this will warp a crank.

 

I took a # 1 rod (odd), put a piston on it without rings, and installed it on # 1, 3 and 5 journals. Measured piston to deck clearance, center, front & back of piston.

Then I took the same piston, took same bearing inserts, and put them on a #2 rod and checked 2, 4 and 6.

 

I used my dial gauge to get TDC on each piston. Kept creeping crank back and forth several times looking where dial didn't move, across about .002-3 on gauge.

 

Here's what I got.

# 1 - .012" below deck, center and front (pretty even).

#2 - .010" ABOVE DECK on front, flush at rear.

#3 - .009" bd, center & front (even).

#4 - .000" flush front and rear.

#5 - .003" bd center & rear,

#6 - .006" Above Deck at front, flush at rear.

 

Got another car in the woods at my father's house an hour away..oh well.

 

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Was checking other sites.  Discussion on a V8.  TheSamba.com :: View topic - bent crank? deck height differences

 

One thing I noted, the crank turns easily in the mains with them torqued down. You would think if it was badly bent (by me) it would have affected that.  The crank has been turned .020.  One guy suggesting that if you turn a bent crank it can rotate easily but have different strokes.

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Odds are more likely that it was machined like that from the factory.  Racers have spent decades coughing up money to have their cranks indexed and the strokes equalized.

 

Wait till you try to sort out if the crank is indexed properly.

 

 

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1 hour ago, Sniper said:

Odds are more likely that it was machined like that from the factory.  Racers have spent decades coughing up money to have their cranks indexed and the strokes equalized.

 

Wait till you try to sort out if the crank is indexed properly.

 

 

Agree with that.    I'd think it almost impossible to bend a crank and yet have the main journals perfectly aligned so that it rotated freely.   Since it has been turned .020 under, I'd bet the crank grinder didn't center or align properly.

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1 hour ago, Sniper said:

Odds are more likely that it was machined like that from the factory.  Racers have spent decades coughing up money to have their cranks indexed and the strokes equalized.

 

Wait till you try to sort out if the crank is indexed properly.

 

 

😲 😉 Probably can't with my experience (lack) and lack of tooling.

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All you need is a degree wheel, a dial indicator and attention to detail.  You got the last two for sure, not sure if you have a degree wheel though, lol.

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38 minutes ago, Sniper said:

All you need is a degree wheel, a dial indicator and attention to detail.  You got the last two for sure, not sure if you have a degree wheel though, lol.

Does the degree wheel need to be specific for our engines? Know which one?  

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Just curious for my own educational purposes.

4 hours ago, Bryan said:

Here's what I got.

# 1 - .012" below deck, center and front (pretty even).

#2 - .010" ABOVE DECK on front, flush at rear.

#3 - .009" bd, center & front (even).

#4 - .000" flush front and rear.

#5 - .003" bd center & rear,

#6 - .006" Above Deck at front, flush at rear.

 

 

These #'s seem disturbing to me ...... Then I wonder what type of #'s would be expected from a good running used engine torn down just to measure?

 

I can see where a engine builder could spend a lot of time/money trying to achieve the perfect compression ratio for their build. Gain 10 horse power, smoother running engine.

 

Guess my question is, would a new flathead 6 engine have even measurements across the cylinders?

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Well, specific in the sense that you can bolt it to the end of the crank, but other than that, no.  It's just a 360 degree protractor.

 

Bolt it to the crank snout, zero it out on your pointer on cylinder one.  Put a TDC tool atop the piston, rotate the engine clockwise, record the degree, rotate it CCW, record the degree, average the two and you have the degrre at which that cylinder is at TDC.  Carry on for 3 thru 6 and you'll have them all. 

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Posted (edited)
16 minutes ago, Los_Control said:

Just curious for my own educational purposes.

 

These #'s seem disturbing to me ...... Then I wonder what type of #'s would be expected from a good running used engine torn down just to measure?

 

I can see where a engine builder could spend a lot of time/money trying to achieve the perfect compression ratio for their build. Gain 10 horse power, smoother running engine.

 

Guess my question is, would a new flathead 6 engine have even measurements across the cylinders?

That's my question, how much tolerance is there between all cylinders/pistons on this type engine and maybe on modern 6 cylinder engines.  Seen one site say .001 usual, worst .005 on some imports.   Someone else told me what he saw from a builder's site  .010" (seems a lot).

Edited by Bryan
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6 minutes ago, Sniper said:

Well, specific in the sense that you can bolt it to the end of the crank, but other than that, no.  It's just a 360 degree protractor.

 

Bolt it to the crank snout, zero it out on your pointer on cylinder one.  Put a TDC tool atop the piston, rotate the engine clockwise, record the degree, rotate it CCW, record the degree, average the two and you have the degree at which that cylinder is at TDC.  Carry on for 3 thru 6 and you'll have them all. 

I was kind of doing it that to find TDC with my dial indicator. Kept going back and forth and watching the point where the needle didn't move. Would find the middle of arc of  where I was turning the crank back and forth about 1/8" with no needle movement.   I'll see how much a degree wheel is.

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1 hour ago, Bryan said:

Does the degree wheel need to be specific for our engines? Know which one?  

 

Lots of templates available for download. Just print and glue to a stiff piece of cardboard or thin plywood.

 

http://garage.grumpysperformance.com/index.php?threads/printable-degree-wheel.974/

 

 

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Got to run to a lunch invite from neighbors, but go to thinking about rotational forces on the crank when I was trying to get the nut off.   The #3 was fixed, front was having force applied. Might have twisted it. It would rotate in mains but be off. Will think about it.

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Agree with you Bryan, seems there would be some amount of tolerance allowed. And all engines would be subject to this.

I dunno maybe it really is a matter for a maser engine builder or a machinist to answer.  Someone who has built 100's of engines and many race engines.

 

What I find odd is the same rod, piston is used for the measurements. It is dead flat on some cylinders while offset on others.

Now if you are certain the deck is flat. I do not see how a crank could cause that. A wrist pin will allow the piston to swivel, but not tilt?

 

Makes me think that goes back to when the block was cast in the mold? Then the cast block is machined ... older engines of the 30's-50's Ford, Chevy, Dodge all of them would be cast/machined with the same level of quality.  Today we have much better level of quality and tighter tolerances.

 

So what I'm starting to wonder .... The piston you are using, is it possible from wrist pin to top, it is off .001" or .003" From one side to the other?  From when it was cast?

Maybe you can use your calipers and measure in some way all your pistons & see if they come out the same?

 

Just thinking something is still awry with the test procedure being used.

With a line bore & the cylinder bore & the deck planed.  I could see a consistent pattern of say the front of the piston higher then the rear on all cylinders ... not 2 cylinders.

 

I would also suggest that with a cast crank that the height tolerances would change between cylinders, but the plane of the top of pistons would be same from front to rear?

 

Is it possible I really should be mowing the grass & looking for excuses?  🤣🤣🤣

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5 hours ago, Los_Control said:

What I find odd is the same rod, piston is used for the measurements. It is dead flat on some cylinders while offset on others.

Now if you are certain the deck is flat. I do not see how a crank could cause that. A wrist pin will allow the piston to swivel, but not tilt?

I know that on some of the rod journals they had more wear on one end than the other.  I'll have to check for taper.

 

Makes me think that goes back to when the block was cast in the mold? Then the cast block is machined ... older engines of the 30's-50's Ford, Chevy, Dodge all of them would be cast/machined with the same level of quality.  Today we have much better level of quality and tighter tolerances.

 

So what I'm starting to wonder .... The piston you are using, is it possible from wrist pin to top, it is off .001" or .003" From one side to the other?  From when it was cast?

Maybe you can use your calipers and measure in some way all your pistons & see if they come out the same?  I used the same piston for 1, 3 & 5 then took it off the rod and used it for the even rod for 2, 4 & 6. Kept the same orientation.

 

Just thinking something is still awry with the test procedure being used.

With a line bore & the cylinder bore & the deck planed.  I could see a consistent pattern of say the front of the piston higher then the rear on all cylinders ... not 2 cylinders.  I'll check for journal taper, and maybe go over how I'm measuring. Make sure at same 2 points.

 

I would also suggest that with a cast crank that the height tolerances would change between cylinders, but the plane of the top of pistons would be same from front to rear?

 

Is it possible I really should be mowing the grass & looking for excuses?  🤣🤣🤣 No, I appreciate all the info and suggestions.

 

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If a crankshaft has been ground there is a trick the machinist’s pull to take the bare minimum off the journals.

On the main bearings they check the crank for straightness, then grind them.

On the rod journals they measure the imperfections then alter the stroke to take the least amount off.

Thus you could end up with a crank with as many different strokes as cylinders.

So if you had a 0.010 deep ding in a rod journal to grind it on the original stroke would make the journal 0.020 undersize.

Alter the stroke and you can have a 0.010 undersize journal.

Not only does this method change the various strokes but it can change the timing as well.

The good news is this is an automotive engine not a watch.

You will never notice the variations.

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7 hours ago, Loren said:

The good news is this is an automotive engine not a watch.

You will never notice the variations.

Until one of the proud pistons taps the head.  Appreciate the info though. Looking for explanations.

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As thick as the stock head gasket is I doubt you could grind the crank far enough off to hit the head.  Unless you are deliberately grinding the crank to increase stroke.

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15 minutes ago, Sniper said:

As thick as the stock head gasket is I doubt you could grind the crank far enough off to hit the head.  Unless you are deliberately grinding the crank to increase stroke.

Yep. I was using .035" as minimum compressed gasket thickness (worst case) after surveying several posts. 

They were ranging from .040-.050 compressed.  Plus there is .02" heat expansion and stretch figured in.

If the pistons varied a little and all were below deck and made sense I'd let it go. But some pistons (#2 & #6) are proud at front and flush at rear (not level).  Difference is just too much for perfectionist me.. #1 .012" BD and 2/6 .010" AD.   Still studying on it.

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Loren’s comments on stroke are correct after regrinding crank. There are many variables that can offset each piston (and tilt). I would think one not discussed is the true position of the pin hole to the outside diameter and ring grooves of the piston that results in one side being proud or effectively “tilt”. This is what the break in period is for during first fire up. As mentioned by sniper, blue printing an engine is done by professional racers and very costly to hold those tighter tolerances. 

  When I was in school learning the machine trade, we had a project to complete, a V4 cylinder engine. starting point was a rough cast block only. We made the crank, cam, heads, pistons, sleeves, valves, ect…. After each engine in the class was completed, they were graded. All 25 engines ran for a 4 hour min. and they were graded on the tolerances achieved. I also remember about a 4K rpm difference between the examples, though hp was not tested. Some had different sounds, some ran smoother and all had specific characteristics for each example.  One of the extra credit points was to install a defective part that would still work for the application with an explanation!
  If your engine is free turning, still has enough piston to head clearance, think you will be fine and you don’t have a bent crank😉.

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12 minutes ago, 47 dodge 1.5 ton said:

Loren’s comments on stroke are correct after regrinding crank. There are many variables that can offset each piston (and tilt). I would think one not discussed is the true position of the pin hole to the outside diameter and ring grooves of the piston that results in one side being proud or effectively “tilt”.   I used the same piston and rod for 1, 3 and 5, then took the same piston & inserts off, put them on a #2 rod and tested 2, 4  & 6.  I'll check this again after holidays.  I'll also check for journal taper. 
  If your engine is free turning, still has enough piston to head clearance, think you will be fine and you don’t have a bent crank😉If I hadn't stuck a wood block in #3 cylinder to stop rotation while trying to get the crank nut off I'd agree. But still the Above Deck/Below Deck variance has me worried.

 

Bent crank guess.jpg

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Pretty sure the force exerted by the ignition of the fuel air charge would have far exceeded anything you could have put on it hanging from a cheater bar trying to loosen the bolt.  Which is, sort of, my way of saying you shouldn't worry about it.

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2 hours ago, 47 dodge 1.5 ton said:

Just to ease your mind, when you installed the caps, did you have to draw them in? Secondly, your machine shop would have noted any excessive run-out on any required machine work to that crank.

I was checking before I give the crank to the machine shop.   Don't understand what "draw in" is. They were tight, but installed easily and I torqued them to about 80 ft/lbs.

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take it to the machine shop, let them measure it.  then you can decide.

 

in my truck, the shop said my crank was just out of spec to machine it straight, but i am running it as-is with all new bearings and no machining.  it’s been 3 years since i put it back together; i use my truck hard (1.5-ton) and load it.  it’s an engine that runs at 3000 to 3200 rpm max for me.   these engines are tough.  as long as the internals are clean, run it.

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  • Bryan changed the title to Pulled motor in woods - warped crankshaft

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