nm9stheham
Well-Known Member
Good point RRR. Maybe that is why trannie input shafts are always a bit 'wobbly', and use a roller ball bearing, and not a needle bearing.... bell housing faces are gonna have a tolerance too.
Block out of square
- Thread starter Jason Wenger
- Start date
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Treblig
Well-Known Member
Being a machinist I would think that the factory, or any company making engine blocks, would have fixtures that held the blocks in the exact correct orientation for each machining process, there's no other way to mass produce factory engine blocks. If one block was off .040" on the back face they should all be off (which doesn't make any sense). Also, "Wenger" wrote that the block had been align bored and that is where things could have gone wrong (depending on the machine shop). It might run fine just the way it is, there's no way to know unless he completes the project and puts many miles on the drive train. I'm surprised that no one has checked their block (in the last few days) to verify how square a regular block should be. I have one I might be able to check......I bet it's square!!! Lastly, I wonder how much end play there is in the crank. If the crank in walking front to back as Wenger is checking for square it might make a difference in the reading??? treblig
nm9stheham
Well-Known Member
Dang.. Just when I thought I was going to get something useful done for real paying work; you are an enabler, Treblig LOL. I have a 273 block/crank in process right now that is at the stage to be checked; never has been bored or lined bored or anything, with a new SCAT crank (which I hope has a straight flange!). Maybe this evening...
As for reliable machining... let's remember that Chrysler underwent a bankruptcy and reorganization while these engine were being built and went through 5-7 years of harsh cost cutting. If something went through the cracks in QC, no surprise. QC was going downhill at Chrysler even prior to the bankruptcy... you could see it in the fit and finish in the mid 70's cars, and I can clearly recall it was a source of public comment even at that time.
Every dimension has a tolerance. Gear blanks for transmission are measured in .001 of a mm, not inch. Yet no matter how precise, there is still a tolerance even if it's 10 microns. My point to your point is "Amen", there is a tolerance.
I have never seen that spec in question measured. Ever.
Treblig
Well-Known Member
"Dang.. Just when I thought I was going to get something useful done for real paying work; you are an enabler, Treblig LOL. I have a 273 block/crank in process right now that is at the stage to be checked; never has been bored or lined bored or anything, with a new SCAT crank (which I hope has a straight flange!). Maybe this evening..."
I bet it's within .005" of being square, I would expect it to be closer. As far a QA/QC.... Even if QC didn't check the back face of the blocks it would take some real poor machining (set up) to install the block incorrectly in the fixture to get it that far off?? That's why they have fixtures in mass production....REPEATABILITY!! But again, the block was align bored, so that's hard to ignore. Let us know what you find on your block and make sure you put a slight bind on your crank (front to back, or check for end play) so that you don't get any "walking". You can easily check the crank flange for straightness by mounting an indicator on the rear of the block and checking the crank flange for straightness (flatness) ....as long as there is no front to back "walking".
One can argue with the machinist doing the work.....but if you piss him off he won't care as much about the work he does for you...LOL. With a machinist, you have to show him, talk is cheap!! Treblig
I bet it's within .005" of being square, I would expect it to be closer. As far a QA/QC.... Even if QC didn't check the back face of the blocks it would take some real poor machining (set up) to install the block incorrectly in the fixture to get it that far off?? That's why they have fixtures in mass production....REPEATABILITY!! But again, the block was align bored, so that's hard to ignore. Let us know what you find on your block and make sure you put a slight bind on your crank (front to back, or check for end play) so that you don't get any "walking". You can easily check the crank flange for straightness by mounting an indicator on the rear of the block and checking the crank flange for straightness (flatness) ....as long as there is no front to back "walking".
One can argue with the machinist doing the work.....but if you piss him off he won't care as much about the work he does for you...LOL. With a machinist, you have to show him, talk is cheap!! Treblig
nm9stheham
Well-Known Member
The block will be on its front face on blocks (timing cover face) so gravity ought to prevent crank walking. But I will check for crank runout 1st as a very good suggestion... this one is a new cast stroker crank, and has .001" total runout in the #3 main, so it might have a bit in the flange. As an observation, any runout in the crank flange could translate to many times that at the bell housing face, so the crank flange runout seems pretty important to know here. (Edit: Actually this is not so; see my next post.) But the OP reports getting consistent results with the dial indicator turned at various angles on the flange, so he seems to have eliminated that part.
So what do you do with a machinist (or anyone for that matter) when you walk in with a well-organized, easy-to-read printed sheet with detailed and carefully taken data, and the first thing he says "I'm not even going to look at your data". (That's what actually happened in my 'sloped deck' incident.....) I guess ultimately the right answer is to go elsewhere.
So what do you do with a machinist (or anyone for that matter) when you walk in with a well-organized, easy-to-read printed sheet with detailed and carefully taken data, and the first thing he says "I'm not even going to look at your data". (That's what actually happened in my 'sloped deck' incident.....) I guess ultimately the right answer is to go elsewhere.
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Treblig
Well-Known Member
Every good machinist loves the customer to put what he/she wants on paper. That way after it's machined (finished) the machinist can show that the machining he did matches what you asked for. I no longer work in the machine shop (retired) but I've had plenty of stuff made by machine shops. The machinists I've worked with are always thrilled when I walk in with a home made blue print of what I want want. They might have a few questions and make some notes on the blue print but they always appreciate a picture of what they have to make. A good machinist is always more than happy to prove that what he/she did was correct, most of us have a ton of pride in what we do. Treblig
PRH
Well-Known Member
All that “shoulda, coulda, woulda” stuff is great, since there’s fixtures and such, and the blocks should all be basically the same.
Then you measure the deck heights on one where they vary .030” from one end to another...... and that theory goes out the window.
Then you deck the block to even/square it up....... and when you’ve got it to where the lowest corner cleans up, it’s still about .015”-.020” taller than spec.
Or the cam bore that’s .012” too big, and .004” out of round.
There are countless examples of things that shouldn’t be possible to have happened...... and still made it past QC.
Like the one stage 6 I had here where one whole chamber was sunk about .125”.
14cc’s bigger than the one next to it....... valve tip heights off .100” plus from the adjacent chamber.
I’ve seen enough screwed up factory stuff to the point where I’m rarely surprised anymore.
Then you measure the deck heights on one where they vary .030” from one end to another...... and that theory goes out the window.
Then you deck the block to even/square it up....... and when you’ve got it to where the lowest corner cleans up, it’s still about .015”-.020” taller than spec.
Or the cam bore that’s .012” too big, and .004” out of round.
There are countless examples of things that shouldn’t be possible to have happened...... and still made it past QC.
Like the one stage 6 I had here where one whole chamber was sunk about .125”.
14cc’s bigger than the one next to it....... valve tip heights off .100” plus from the adjacent chamber.
I’ve seen enough screwed up factory stuff to the point where I’m rarely surprised anymore.
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Check the parallel of the camshaft tunnel to the alignment of the main caps.
That will tell you if the alignment job is what threw everything off.
Or will tell you if the rear face of the block is off in relationship to the crankshaft.
That will tell you if the alignment job is what threw everything off.
Or will tell you if the rear face of the block is off in relationship to the crankshaft.
Treblig
Well-Known Member
There are many things that can be wrong on a block or even on heads. Deck height will not make an engine fail, deck "squareness" will not make an engine fail. The back face of the block not being square to the mains can cause big problems once you bolt the trans to the engine. It's insidious because although the car (drive train) might work fine for 5 or 10 thousand miles (if that long), when the trans input shaft bearing (or crank bushing) starts failing you won't know why?? I know a full blown drag racer wouldn't continue building an engine with those "out of square" issues. We just don't know how much out of square it can be before it causes a problem. treblig
PRH
Well-Known Member
I’m still going with it’s been like that since day one.
RAMM
Well-Known Member
nm9stheham
Well-Known Member
273 block measurements are done. '68 273, never rebuilt.
One thing I realized is that, as long as the dial indicator and its base are stable on the crank flange, then any crank flange runout does not matter. As long as all is stable, then the dial indicator body is going to move in a level circle perfectly perpendicular to the axis of rotation. So this is why the OP saw no difference regardless of the orientation of the dial indicator base on the flange.
FWIW, this particular crank flange has a total of .0015" runout. I found the + and - spots and put the dial indicator arm 90 degrees to that before I realized the above. I had to use a length of thick metal (an old heavy duty extension shackle) bolted rigidly to the crank flange to extend the dial indicator short arm far enough.
Working in a CW direction around the bell flange of the block, and looking from the back, with a + indication being towards the trannie:
Left dowel +.001
10 o'clock hole +.002
11 o'clock hole -.002
12 o'clock hole .000" (Reference)
1 o'clock hole +.000"
2 o'clock hole +.003"
Right dowel +.004
There were +/- .001-.002 " variations around the holes and in various spots. The dial indicator is marked in .001" increments so is nothing super special.
Looks like this was not a Monday block....and Treblig wins a prize! LOL But, this does not prove that all blocks were this good or that the OP's could not have been so far off from the factory. All we know is that it is now.
FWIW, the decks on this block have been measured on this block using the new 4" stroker crank and a single piston & rod assembly. You can see that the crank bore is generally straight with the decks, except for the big drop off at the back on the left bank.
One thing I realized is that, as long as the dial indicator and its base are stable on the crank flange, then any crank flange runout does not matter. As long as all is stable, then the dial indicator body is going to move in a level circle perfectly perpendicular to the axis of rotation. So this is why the OP saw no difference regardless of the orientation of the dial indicator base on the flange.
FWIW, this particular crank flange has a total of .0015" runout. I found the + and - spots and put the dial indicator arm 90 degrees to that before I realized the above. I had to use a length of thick metal (an old heavy duty extension shackle) bolted rigidly to the crank flange to extend the dial indicator short arm far enough.
Working in a CW direction around the bell flange of the block, and looking from the back, with a + indication being towards the trannie:
Left dowel +.001
10 o'clock hole +.002
11 o'clock hole -.002
12 o'clock hole .000" (Reference)
1 o'clock hole +.000"
2 o'clock hole +.003"
Right dowel +.004
There were +/- .001-.002 " variations around the holes and in various spots. The dial indicator is marked in .001" increments so is nothing super special.
Looks like this was not a Monday block....and Treblig wins a prize! LOL But, this does not prove that all blocks were this good or that the OP's could not have been so far off from the factory. All we know is that it is now.
FWIW, the decks on this block have been measured on this block using the new 4" stroker crank and a single piston & rod assembly. You can see that the crank bore is generally straight with the decks, except for the big drop off at the back on the left bank.
nm9stheham
Well-Known Member
That would be another interesting check. (Just make sure the cam bore housing diameter differences are accounted for.)
Treblig
Well-Known Member
Thanks for taking the time to do a good check on your block. I would expect some out of squareness, no one expects it to be perfect. treblig
Jason Wenger
Active Member
Absolutely, yes... Assuming that every single block through that machine is fixtured and clamped properly. There's never a single block that someone clamped only at one end, and never a block that got set down in the fixture with a metal chip under it, lifting one end... A 60 thou piece of debris trapped under the nose of the block while the rear face is machined would produce rhis amount of error, right?
Yes, there's about 5 thou of end to end play. When I dialed the flange, I gave a bit of persuasion to the front end of the crank with a plastic mallet each time I turned the crank, to ensure that play is not in the measurements.
PRH
Well-Known Member
Going by what’s been posted so far, if some shop lined bored the block and created this situation.......the result is a crank that’s pointed nose up/down at .4°.
How far off is that in .000 at a distance of about 22”?
Using an on line calculator, .4* is .083775 in/ft.
So, over the length of the crank, one end would have to be off about .150”(which would also translate to the deck clearance).
I don’t see how any machine shop would make that big of a screw up........ not to mention..... try finding a timing set to fit that situation.
How far off is that in .000 at a distance of about 22”?
Using an on line calculator, .4* is .083775 in/ft.
So, over the length of the crank, one end would have to be off about .150”(which would also translate to the deck clearance).
I don’t see how any machine shop would make that big of a screw up........ not to mention..... try finding a timing set to fit that situation.
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@krazykuda , do know the sequence the block surfaces are machined? If a un-machined casting is set in a jig, what surface is machined first? Is the block removed from the jig and set up in another machine for other operations. My point being, If something was wrong from the start, all the dimensions would be off if the block remained in the same fixture during the process. If the machine shop line bored, square decked and bored the block to correct issues the bellhousing surface was left untouched. Bores and decks are dependent on the pan rails being correct. also the main saddles are used. I am just trying to see where in the process something could have gone wrong.
Treblig
Well-Known Member
PRH
Well-Known Member
I don’t have easy access to a SB block, but I checked a BB....... it’s about 8.5” from the crank c/l to the top of the bell housing flange.
If that were off .046”, it would be about .32*, which works out to .067 in/ft, so over the length of the crank it would be in the .122” neighborhood.
Still so far off nothing would fit right.
You’d really have to work at it to screw up the line bore that much.
And then there’s still no timing set that would fit.
I still believe the actual “issue” is the way the back of the block is machined, relative to the decks, main bore, cam bores.
And I think it’s always been that way.
Just get another block and start over.
If that were off .046”, it would be about .32*, which works out to .067 in/ft, so over the length of the crank it would be in the .122” neighborhood.
Still so far off nothing would fit right.
You’d really have to work at it to screw up the line bore that much.
And then there’s still no timing set that would fit.
I still believe the actual “issue” is the way the back of the block is machined, relative to the decks, main bore, cam bores.
And I think it’s always been that way.
Just get another block and start over.
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PRH
Well-Known Member
So, hypothetically...... the machine shop screws up the line bore to the tune of .32*(so the result is the .046” out of square condition at the bell housing mounting flange).
(Keep in mind, when performing the line boring operation, and screwing it up to this degree, on one end of the block you’d be cutting nearly an 1/8” out of one side of the main bore........ and zero on the other. So now the main bore is like .125” out of round...... how do we fix that before continuing on to the next step?
Oh btw....... if we’re not installing aftermarket caps with a way undersized bore, and just truing up the main bore using the existing caps, we’re expecting to only be making like a .005” deep cut........ not .125”.)
The normal way to go about it is, main bore first, then deck the block.
You have your freshly line bored block that’s now off .32*...... you mount it on your surfacing machine with the centering rings and check it end for end.
The deck surface is 19” long....... which would now require .106”(.067 in/ft x 1.583ft) being removed from one end of the deck to get it parallel to the main line.
Does this really seem like a plausible scenario?
(Keep in mind, when performing the line boring operation, and screwing it up to this degree, on one end of the block you’d be cutting nearly an 1/8” out of one side of the main bore........ and zero on the other. So now the main bore is like .125” out of round...... how do we fix that before continuing on to the next step?
Oh btw....... if we’re not installing aftermarket caps with a way undersized bore, and just truing up the main bore using the existing caps, we’re expecting to only be making like a .005” deep cut........ not .125”.)
The normal way to go about it is, main bore first, then deck the block.
You have your freshly line bored block that’s now off .32*...... you mount it on your surfacing machine with the centering rings and check it end for end.
The deck surface is 19” long....... which would now require .106”(.067 in/ft x 1.583ft) being removed from one end of the deck to get it parallel to the main line.
Does this really seem like a plausible scenario?
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Treblig
Well-Known Member
To make things worse if the crank is not perpendicular to the rear face of the block you'll have the clutch assemble (which is bolted to the flywheel) rotating on a different plane than disc, which is connected to the trans input shaft. In theory the disc will make contact with the top front of the clutch and bottom rear before anywhere else. I'm not sure how this would effect the smoothness or lifespan of the clutch?? Treblig
The bellhousing surface should be 90° from the pan rail as well as the deck surfaces. A precision square should show if it is mis-machined.
stixx
Well-Known Member
Jason Wenger
Active Member
Feeling the same -- If they didn't re-deck it, then displacement and compression would be all over the place from the front cylinders to the back, and it would run like ****. If they re-decked it, but didn't start wondering why there there was over 100 thou of error needing fixed, then they're completely insane or completely clueless. And, even if they did redeck it that way, I still think the mains and the connecting rod journals would bind like hell with so much angular problem in them. It seems very unlikely.
But if it's the other case -- that the back of the block is machined out of square and has been since the factory, then I come to the opposite solution. Shim it back up to perpendicular, and call it all good. If it's jsut the rear flange then the crank and the rest of the engine can plausibly be presumed to be fine which is consistent with the dyno results that show it performing. Once it's shimmed perpendicular, then the clutch and input shaft are back in angular and linear alignment, so I don't need to worry about clutch wear or input shaft bearing problems. So there's no problem. I can live with having a couple pieces of shim stock between the block and the block plate.
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