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rebuilding a 425

Started by "Cadillac Kid" Greg Surfas 15364, April 03, 2020, 01:32:00 PM

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"Cadillac Kid" Greg Surfas 15364

You talk about being bored?  While I am waiting for my 1970 "binocular piston” 472 block to come back from the machine shop (being zero decked and cylinders honed) I started clearing out my garage and the low mileage 425 I pulled out of my '79 to replace with a large chamber 9:1 472 "jumped out" at me.  Soooo, I am rebuilding it for something to do.  Cylinders have been honed (stock bore with VERY little taper, new cam bearings installed and Moly rings ordered.  I will post the progress, again this is to keep me from going stir crazy, so any conversation on this is welcomed.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

carlhungness

       Well, it was some of your advice that convinced me to get a late model Cad engine for my '37 LaSalle rather than one of the 50's model. I did get a brand spanking newly rebuilt 500" incher with ported and polished heads and a gigantic intake manifold and
valve covers that look like gun-boats, all in aluminum.
      Actually I hope I don't ever have to take the thing apart Greg as I plan to treat the new engine and Tremec 5 speed very gently.
      Meanwhile I'm whacking away on straightening hubcaps which is task enough for me.

"Cadillac Kid" Greg Surfas 15364

Carl So that we don't get this thread too far off center, could you start a new thread describing how you adapted the Cad crank for the manual transmission?
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

savemy67

Hello Greg,

I am curious.

One can look at the surface condition of cylinder walls and have a good idea whether or not honing or boring is needed, but in some cases it is not always easy to determine wear/taper by a visual inspection.

What measuring tools did you use to determine that wear/taper were within tolerance - an inside micrometer, a telescoping gauge, a bore gauge, a piston ring, or something else?

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

"Cadillac Kid" Greg Surfas 15364

Chris
Both the machine shop and I measured the cylinders and the pistons.  The cylinders were measured with an inside micrometer and measured out at less than 0.001" taper which is under the 0.002 limit and about right according to Cadillac engineering.  The Blocks were intended to wear at the rate of 0.001" per 100,000 miles up to .003" at 300,000 miles. 
It's too cold (for me) to work outside today, but the next thing I will be doing is installing the crank and main bearings.  I'll show the bore condition then.  The hone "job" was to help the rings seat .
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

carlhungness

   Can't give you specifics on the back of the crank and front of the Tremec yet but initial measurements seem to show back of the crank may not need modification. At worst the Tremec shaft may have to be shortened slightly. Will be precise with a report soon, but can't work in that shop as it is closed for the virus.
    The flywheel has a bearing that can be inserted either direction so waiting to see what I need. The guys at Cad Co. say there should not be a problem with back of crank interference.
   

"Cadillac Kid" Greg Surfas 15364

Well, Sunday seemed secial so I did a bit more on the 425.  The block is prepped.    I have the crank that I was going to use in rebuilding the 425 before I decided to go to the 472.  It was machined by MTS and the mains were turned 0.010 under, mikeing out at 2.490”.  Installed the rear seal and laid the crank on the new bearings using GM Engine Assembly lube. Torqued the mains to 90ft/lb. with a piece of 0.001-.003” plastigage between the bearing and the crank.  Results show a clearance of 0.001”.
Enough for one day.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

"Cadillac Kid" Greg Surfas 15364

A couple more shots
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

The Tassie Devil(le)

Got to love Plastigauge.   Takes out the guesswork.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Scot Minesinger

Greg,

What are going to do with the 425 engine once it is rebuilt?  Is it a just in case spare, or are you selling it? 
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

Caddyholic

Ring gap? Looks excessive. Is the block going to be bored?
I got myself a Cadillac but I can't afford the gasoline (AC/DC Down Payment Blues)

1961 Series 62 Convertible Coupe http://bit.ly/1RCYsVZ
1962 Coupe Deville

"Cadillac Kid" Greg Surfas 15364

#11
The ring you see is not straight in the bore, in fact I do not know where it came from. Bore itself measures 4.081"

Scott,
Aside from my cousin's roadster this has no definite destination.  It is just something to do to keep some semblance of sanity during these weeks of "social separation.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

"Cadillac Kid" Greg Surfas 15364

Just been thinking about it and 0.001 is just a bit to tight for my liking so the crank came back out and to the machine shop to polish .0005 more off the main journals.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

The Tassie Devil(le)

Did you take into account the oil that was on the shaft?

Your Gauge is reading about .00125.

One of the problems with what you are doing is that really, there needs to be a piece of Plastigage on both the top and bottom of the journal, and the shaft placed on the bearings exactly parallel, and with plastigage on all the top and bottoms of the journals, then the main caps torqued down.

When the shaft is removed, then look at the results, and it will indicate if the shaft is bent, as the strength of the shaft itself will give an uneven reading in just using one cap.

Not a problem with connecting rods big end bearings as they are individual, and cannot be altered by any other bearing or journal anywhere along the crankshaft.

Food for thought.

Plus, a Dial Gauge will show any out of round or bending if the shaft is turned without the main caps on.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

"Cadillac Kid" Greg Surfas 15364

Plastigage was on all 5 mains.  It just "felt" a little tight.  The machine shop will check the crank to be sure it is straight.  I did not think I needed to worry because this is something I bought from MTS several years ago when Marty was overseeing all machine work that went out of their shop.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

"Cadillac Kid" Greg Surfas 15364

crank is at the machine shop for polishing.  I'll have to find some carburetors or something else to keep my brain from turning into mush for the rest of the week.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Cadman-iac

When I rebuilt the 472 I'm going to use, which was 30 or so years ago,  I used plasti-gage on it. The engine had just over 100K on the clock, and the machine shop sent the crank out to be checked, and it came back with just a polishing.
When I installed it,  all but the number 4 main was at .002 thousands,  and number 4 was at .0015 thousands.
The number 6 and 8 rods were at .0015, and the rest were at .001 thousands. I thought that was pretty good,  considering how many miles it had and had been polished as well.
These are really great engines, and I hope to get at least another 200K out of it before I expect any issues with wear.
That's not unreasonable to expect that is it?

I'm going to recheck it when I reassemble it just to make sure nothing has happened to it since then. I don't expect to find anything different, but I want to be sure.
Good luck on your build. Are you going to dyno it to see what it will do,  or do you care?

Rick
CLC# 32373
1956 Coupe Deville A/C car "Norma Jean"

"Cadillac Kid" Greg Surfas 15364

Rick
You are getting ahead of my story. I've got a 118K 1970 472 that I pulled down and after hot tanking, checking cylinders and crank journals the motor is going back together with just a hone job, new rings and bearings.  But that is ANOTHER story.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

savemy67

Hello Greg,

I am glad to see you reconsidering the crank/main clearance.  If I am interpreting the photo with the Plastigage correctly, the Plastigage is measuring less than .001.  The wider the strip, the less the clearance.  The strip in the photo appears to be wider than the green bar indicating .001 clearance, hence my observation that the photo indicates clearance of less than .001.

I agree with Bruce that Plastigage should be used on a spotless journal - no oil or lube of any sort.  Whether or not you want to use Plastigage on both the top and bottom of a journal is up to you.  You may want to look at that issue in the following manner.

Assuming a perfectly straight crank and crank bore saddles and caps - when you place the crank into position in the block, the crank journals will rest on the bearing inserts with no clearance because the diameter of the journal is slightly less than the diameter of the insert.  If Plastigage is used only on the cap side of the journal, when the cap is torqued, the saddle side of the journal is still resting on the insert with no clearance.  This would imply that using a strip of Plastigage on both sides of the journal might give a more realistic/accurate reading.

Another consideration is that virtually all engines are assembled upside-down.  When the engine is running, the caps are below the crank, not above the crank as when the engine is being assembled.  Until the journals/bearings are fully pressurized, the crank will actually fall from top to bottom within the bearing every time the block is rotated to facilitate assembly.  This can be somewhat mitigated by using a quality assembly lube.  The issue of accurately measuring the clearance remains because the measurement is usually taken only on one side of the journal.

Assuming a perfectly round bearing insert, and a perfectly round journal, if Plastigage is used only on one side of the journal, the Plastigage reading should probably be divided by 2.  In your photo, the Plastigage looks like it measures less than .001 - probably closer to .0007, which if divined by 2 gives a clearance of .00035 when the journal is centered in the bearing insert.  The crank my have felt tight because it was.

The most accurate way to measure bearing clearance is to install the bearing inserts in the saddle and caps, and torque the caps to spec.  Then use a bore gauge to measure the inside diameter of the inserts.  Then use a micrometer that reads to the ten thousandths of an inch, and "mic" the journals.  The difference will be the actual clearance.

Of course the accuracy of the measurements depends on the quality of the tools, and the skill of the mechanic.  As with most things, there is a trade-off.  A good bore gauge costs in the neighborhood of $1000.  You can buy a lot of bearing inserts for $1000.  Ultimately, the decision is up to the engine builder or owner of the engine.

Quote from: "Cadillac Kid"  Greg Surfas 15364 on April 08, 2020, 12:12:28 PM
crank is at the machine shop for polishing.  I'll have to find some carburetors or something else to keep my brain from turning into mush for the rest of the week.
Greg Surfas

Maybe chewing on this will help.  Good luck with the rebuild.

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

"Cadillac Kid" Greg Surfas 15364

FWIW Plastigage was intended to measure clearances of assembled, in car motors.  The idea was to drop the pan, drop the main cap and then retorqe the cap.  Yes I was a bit concerned about the plastigage showing a bit less than .001 clearance but I was a bit more concerned by the fact that I couldn't turn the crank over once all 5 caps were torqued.
The crank came from MTS a few years back and Marty said it had been turned .010 under on the mains and .020 under on the rod throws, so without checking I just started installation.  Silly me.When I get the crank back I have no doubt it will be correct, and the installation can continue.
Meanwhile today I had a chance to inventory my shelf full (14) or rebuilt carburetors. Oh boy what's next?
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-