Author Topic: My 427/452 autopsy results are in  (Read 2030 times)

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blykins

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Re: My 427/452 autopsy results are in
« Reply #15 on: September 21, 2020, 11:12:38 AM »
I've never needed to add oil to the rear sump pans in an actual vehicle.  On the dyno, I'll add another quart just to help with the oil that won't find its way back from the front sump.

I'd also check bearing clearances again and adjust as needed.  .0015" is definitely too tight and I don't like .0020" either on a factory, narrow, FE bearing.  I'm usually at around the .0030" mark for non-BBC journal FE stuff. 

My guess, however, is that your converter took the crank out and probably pushed the crank so far forward that it began to take the rod side clearance out. 
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cjshaker

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Re: My 427/452 autopsy results are in
« Reply #16 on: September 21, 2020, 02:15:17 PM »
My guess, however, is that your converter took the crank out and probably pushed the crank so far forward that it began to take the rod side clearance out.

If that is the case, I wonder if the other rods would show signs of wear on the rearward face (big end), where the clearances closed up? Maybe on the crank throw rear radius' also?  Although the crank may have moved far enough forward from the thrust wear that they may have come into contact post-damage. Just trying to think of tell-tale signs for Alan to look for.

Alan, I'm sure you checked crank end play, and given the amount of damage on the crank thrust, I wouldn't think that it was from racing only (since you've only made a few passes), so that would seem to point to something creating a constant forward thrust. The only thing that comes to mind is the transmission. Any chance the rear of the block had been faced before, which would close up distances? I've heard of guys in racing circles doing that, just to verify the trans mounting is perpendicular to the crank centerline. Not sure how you'd measure that though.
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AlanCasida

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Re: My 427/452 autopsy results are in
« Reply #17 on: September 21, 2020, 04:42:55 PM »
My guess, however, is that your converter took the crank out and probably pushed the crank so far forward that it began to take the rod side clearance out.

If that is the case, I wonder if the other rods would show signs of wear on the rearward face (big end), where the clearances closed up? Maybe on the crank throw rear radius' also?  Although the crank may have moved far enough forward from the thrust wear that they may have come into contact post-damage. Just trying to think of tell-tale signs for Alan to look for.

Alan, I'm sure you checked crank end play, and given the amount of damage on the crank thrust, I wouldn't think that it was from racing only (since you've only made a few passes), so that would seem to point to something creating a constant forward thrust. The only thing that comes to mind is the transmission. Any chance the rear of the block had been faced before, which would close up distances? I've heard of guys in racing circles doing that, just to verify the trans mounting is perpendicular to the crank centerline. Not sure how you'd measure that though.
I have started wondering if the dimension on the rear of the block is correct. This is an agricultural block that at some point was not deemed worthy of getting crossbolt main caps so I thought maybe that dimension could be off but it would not make any difference on an irrigation pump. I had my 428 in the car for a couple hundred miles and the thrust bearing is ok on it. When I put the engine back in the car I am sure I measured the clearance between the converter and the flexplate at .125" before I bolted them together but maybe I got it wrong. I'll dummy the transmission up to my 428 and check the clearance but I am definitely getting another converter.

frnkeore

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Re: My 427/452 autopsy results are in
« Reply #18 on: September 21, 2020, 04:44:59 PM »
The rods can follow the crank, for as much clearance the small end, has inside the piston bosses. I'd look inside the pistons for signs of that.

But, if the limit of axial travel was exceeded, I think all the rods would show it and be discolored, at the big end.

If the rod clearance was in spec, for the load range, I'd follow that crank passage back to the main bearing.

Could it be that that the crank pushed far enough forward, that it covered up most of the feed hole to the pin?

No matter what, the end play issue, has to be fixed before it's put back together. I'd suggest mounting the face of the block to a eng stand, put in a good used thrust bearing, crank and FW on, then put the trans on a table at the same height and push them together to find, when and where they bind. Start with 1/8" thick washers and reduce the space, until ii binds.

My guess is it the shank that drives the pump having no end play. Nothing can give between the converter mounting pads and the end of the pump drive.

You can also put a indicator on the flex plate as you tighten the bell housing bolts, to know when it starts pushing the crank.
Frank

frnkeore

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Re: My 427/452 autopsy results are in
« Reply #19 on: September 21, 2020, 04:49:35 PM »
One other thing, when you bolt a trans to the block, after it's bolted, there should be enough clearance between the flex plate and the converter to be able to turn the converter, to line up the holes.

Are you using a block plate, between the bell housing and the block?
Frank

AlanCasida

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Re: My 427/452 autopsy results are in
« Reply #20 on: September 21, 2020, 05:33:13 PM »
One other thing, when you bolt a trans to the block, after it's bolted, there should be enough clearance between the flex plate and the converter to be able to turn the converter, to line up the holes.

Are you using a block plate, between the bell housing and the block?
Yes I am using the OEM block plate. When I put it motor in the car I checked and thought I had .125" clearance. This same thing happened to me last year causing me to have to get a new crankshaft. I found the tail end of the pump snout had not been beveled on the converter causing it to be too close and pushing the crankshaft forward...or so I thought. I put the bevel in the converter and reused it. In hind sight I probably should have gotten a new converter.     

frnkeore

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Re: My 427/452 autopsy results are in
« Reply #21 on: September 21, 2020, 06:51:59 PM »
So, if there was clearance between the flex plate and the converter, when they were installed, then, maybe the converter ballooned and pushed the crank forward?
Frank

AlanCasida

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Re: My 427/452 autopsy results are in
« Reply #22 on: September 21, 2020, 07:11:00 PM »
So, if there was clearance between the flex plate and the converter, when they were installed, then, maybe the converter ballooned and pushed the crank forward?
That's a possibility. I haven't gotten that far in my investigation.

runthatjunk

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Re: My 427/452 autopsy results are in
« Reply #23 on: September 21, 2020, 08:18:15 PM »
One other thing, when you bolt a trans to the block, after it's bolted, there should be enough clearance between the flex plate and the converter to be able to turn the converter, to line up the holes.

Are you using a block plate, between the bell housing and the block?

Don't think I've had any trannys that you could turn converter with block bolted together,  I think I would be worried about enough pump engagement at that point
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AlanCasida

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Re: My 427/452 autopsy results are in
« Reply #24 on: September 21, 2020, 09:57:22 PM »
One other thing, when you bolt a trans to the block, after it's bolted, there should be enough clearance between the flex plate and the converter to be able to turn the converter, to line up the holes.

Are you using a block plate, between the bell housing and the block?

Don't think I've had any trannys that you could turn converter with block bolted together,  I think I would be worried about enough pump engagement at that point
The converter I am using does not have studs. It has threaded holes and uses bolts to mount it to the flexplate so you can spin it around.

RJP

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Re: My 427/452 autopsy results are in
« Reply #25 on: September 22, 2020, 09:57:31 AM »
Alan, Did you check the crank pilot bore for clearance including depth of the bore? I've heard of aftermarket cranks that the bore diameter could be correct but the depth is too shallow and/or have a secondary bore for the 385 series converter pilot [1.375"?] Just another thought.

My427stang

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Re: My 427/452 autopsy results are in
« Reply #26 on: September 22, 2020, 10:20:50 AM »
If it could spin with bolts out during assembly, you had clearance, could it spin when you pulled the engine this time? If not could have ballooned

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jayb

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Re: My 427/452 autopsy results are in
« Reply #27 on: September 22, 2020, 11:13:10 AM »
To check for proper clearance you should be able to spin the converter, but also push it forward so that the mounting pads are in contact with the flexplate.  If you can't do that, then you are bending the flexplate to conform to the converter location when you bolt them together, and that will put pressure on the crank.  There have been many cases where I've had to put spacers between the converter mounting points and the flexplate in order to ensure correct installation.
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AlanCasida

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Re: My 427/452 autopsy results are in
« Reply #28 on: September 22, 2020, 12:26:20 PM »
To check for proper clearance you should be able to spin the converter, but also push it forward so that the mounting pads are in contact with the flexplate.  If you can't do that, then you are bending the flexplate to conform to the converter location when you bolt them together, and that will put pressure on the crank.  There have been many cases where I've had to put spacers between the converter mounting points and the flexplate in order to ensure correct installation.
Now that I finally have everything out on the floor that is something I am going to check.  I did notice my flexplate when laying on the concrete floor was not flat so there may have been something like what you mentioned going on. At some point I am going to mock it all up to my 428 and see what it looks like.

AlanCasida

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Re: My 427/452 autopsy results are in
« Reply #29 on: September 22, 2020, 09:06:51 PM »
I took another look at the thrust bearing and it looks like the front side of the bearing has not been touching at all...it looks brand new. So, I bolted the transmission to the block/crankshaft with the crankshaft pushed back as far as it would go. Since the front side of the bearing looked new I felt this would be accurate. I put a dial indicator on the front of the crank to check for movement. I took a measurement from the flexplate to the converter with the converter pushed all the way back and then another with it pushed up against the flexplate then subtracted one from the other and I got 0.125". Then I put one bolt in the converter and tightened it down and checked for movement on  the dial indicator...there was none. So either something is causing the converter to push forward or something in the motor is causing it. I didn't put anymore bolts in the converter as I didn't see it was necessary for what I was doing. I sure wish I had found something obvious.
« Last Edit: September 22, 2020, 09:09:02 PM by AlanCasida »