The Teardown

For those that have been following...

I had some metal show up on my drain plug, some clunky buzzy sounds and somewhat less than great oil pressure. I'd never had the bottom end apart and didn't know what condition it was in. Further, as evidenced by the oil pump gears, some crap had been through it. Sooooo...

I pulled it apart and found the following

Timing Side:


Primary Side:


And the Crank - Timing Side:


Primary Side:


Sludge Trap:


When I measured the journals I got:
1.7500 - 1.7505 on the primary side and
1.7485 - 1.7495 on the timing side.

The manual indicates they should be 1.7504-1.7509

I should also add the rods seemed pretty loose on the crank when I pulled it apart.

From the collective consciousness of the group, what say you as to what to pay attention to? I'm sorta thinking that it don't look that bad and a set of bearing shells, new con rod nuts and crank studs and nuts and I'm outta here. Except for maybe the cam. I need to pull together some pics, it's not too bad, but looks a bit worn.

--- David

Depends on the ' clearances ' and rpm's intended .Ovality is more an issue .
With a really fancy micrometer , you measure at differant locations, if all
measurements are near identical , the Big End Jouranals are ROUND .
Which is what is nessesary.
Ordinarilly youd see errosion at the outer face of the Journals if worn eccentric .
So she looks O.K.

Std. Practise is to POLISH the Journals .

'One ' measures the ROD Big Ends , bolted and tourqued ( use the old rod bolts & nuts )
for ovality allso.

( The dreaded Falcon Ive thrown new .001 under shells in , as it Ran a Bearing ( Spun the shell )
going danga danga etc, tecnically has rooted the rod , Made it go Oval with the Hammering . :x
The things r00ted anyway , given up on oil changes , as a fresh engines going in. I rev to a taggering 2.000
as a Hyd. lifters out to lunch and the timing chain is ' a bit of a worry ' . :shock:
The riges you can feel with your thumb nail , at 50 Yds , after youve hit it with a hammer :cry: )


INSPECT the Main Bearings , with a Eye Glass , for any pitting or uneven appearance.under a bright light .

Those shells are std. ' babbit metal / white metal ' ??


The worn bit looks Coppery . COPPER LEAD bearings , ( lead backed copper) have a higher melting temperature.
and are harder on the crank .They lap it away, where the white metal tend to erode, leaving the crank healthy.


She all looks pretty clean , but looks like youve ' caught it in time ' as far as excess clearances starting .(see 'Hammering ')

I figure it was youre timng chain / sprockets produceing the ' scrap metal ' , How do they look , please .
and is the camshaft History .

Nothing in those rod bearings and basically unmolested crank will show on the magnet.

Stilll need to find out where that stuff came from!

Matt - how does one "polish" the journals correctly?

GP - I'm still looking, but things look remarkably reasonable. Even the mains.

-- David

From the collective consciousness of the group, what say you as to what to pay attention to? I'm sorta thinking that it don't look that bad and a set of bearing shells, new con rod nuts and crank studs and nuts and I'm outta here. Except for maybe the cam. I need to pull together some pics, it's not too bad, but looks a bit worn.

While you have the engine apart, split the crankshaft and clean out the ‘centre oil filter’’
There may be a lot of crud inside there. Use new bolts on assembly.

How many miles on that bottom end? Here's my sump trap and shells after 13K miles and no oil filter. That scratch on the right shell happened in the junk box.





Dave
69S

DogT said:

How many miles on that bottom end? Here's my sump trap and shells after 13K miles and no oil filter. That scratch on the right shell happened in the junk box.
Dave
69S

Click to expand...

Yep, that's pretty clean - why did you tear it down?

mitchp said:

Yep, that's pretty clean - why did you tear it down?

Click to expand...

Because it was 41 years old, I didn't know it was so clean, it was leaking oil, it needed new non-slotted pistons, I wanted to change the bearings, I needed something to do and it looked like crap. Actually Nelson pushed me into it.

Dave
69S

Here's the cam - It really doesn't look too bad to me.



GP - I have no idea where all that metal came from. How do you check the cam chain?

--David

napanorton said:

Here's the cam - It really doesn't look too bad to me.

GP - I have no idea where all that metal came from. How do you check the cam chain?

--David

Click to expand...

It would be the cam chain tensioner to check for wear-in (grooves from the chain). This could be excessive if the cam chain was too tight.

Do you still have the material from the magnet? This may take some analysis to determine its origin.

You are right, that cam looks very good, nicely broke in. Be sure not to mix up the followers. Keep them oriented just as they are.

I was running the RMA tensioner, which looked brand new - very little wear. I may go back to the stock set up as there are more than a couple of folks on this forum that think they are just waiting to blow up or wear out your engine. Frankly, it seems to work as designed and I've had no problems - yet. But piece of mind you know.

--D

A lot of metal can come off the cam chain/tensioner, especially if it has just been adjusted, is new, and doesn't have the rubber shoe. I was amazed at the wear on my cam chain and metal shoe, but apparently after they wear grooves in them, they settle down (according to hobot). I was thinking about the rubber shoe one, but used my original steel shoe and a new chain. Looks to me though like you have a lot of metal in the engine, I hope you have a filter. I put one on, the WIX 51032 has a 10 micron rating, most are double that. I'm sure everyone has their own opinion on that though.

Dave
69S

Sorry, realized I didn't post the important info - it's a 73 850 with about 19K miles on it. It has a stock oil filter. I have no idea if the engine has ever been rebuilt, but I did do the head a few thousand ago.

DogT wrote "Actually Nelson pushed me into it." Gee DogT you can't give Nelson all the credit, LOL, just made me chuckle Dog. Cj

cjandme said:

DogT wrote "Actually Nelson pushed me into it." Gee DogT you can't give Nelson all the credit, LOL, just made me chuckle Dog. Cj

Click to expand...

No, I can't give him all the credit because I did it, but he certainly made some arguments to push me in that direction, and actually I'm glad I did it.

Dave
69S

Polishingski , Bear in mind ; the old tri pointed skewer things you found at garage sales in the 60s 70s ,
with a curved end that looked like the end for a pike , or for reaming mangos , were Bearing Scrapers .
From the days of poured white metal bearings , like a 50 T-bird etc.
Used in conjunction with engineers blue to get the fit refined . A bloke did a set of .010 under Trident bearings to
std size , as std non avaliable in the dim dark ages around 80 in NZ , he wasnt amused , but tecnically sound .

POLISHING .(starting at worst case )

Stick of machined lime wood with 600 ( !? ) grit glued to it , to dress nasty rides felt with fingernail,
wood & wet & dry / Garrnet Paper the width of journal , constantly rotateing crank on bench , and
holding tounge in cnr of mout with one eye squinting.

Going down to 800 & 1000 grade in doing a flash job as the cranks not really scrap .

The Dreaded Twine METHOD .to ' merely ' POLISH , the old brown hemp? Twine for parcel tying,
(I think there was actually specific machine shop polishing string ) or the solid woven White cord,
about 1/16 in + Dia.

Crank secured ( one foot ea eand . :shock: ) the string is put a turn and a half around the journal
and grasped in Ea Hand , and judisiously pulled Indian Fire Strter style , working across back & Forward.

On an undamadged journal , two or three minutes should start having it shiney and smooth . Getting entusiastic you can use a bit of metal polish.IF you clean it off throughly afterward.If the 50000 year old crank was dulled and gungey ,you might
put a strip of wet & dry Under the string to Linish .

Engine shops sometimes ' Linish ' a crank , with a belt or garnet paper , with the crank between centres rotateing.
It removes metal. Usually used to clean slightly marred bearing surfaces , AND fitting the , .001 , .002, or .0025
under bearing shells.

Brings us to ' Clearance ' . Normally a specified radial clearance is required.

Some people dont like 'Plasti Gauge ' but it comes in a thing like a cord, is placed between parts on trial assembly. The width on dissasembly is measured, the chart checked and hey presto , clearance ascertained .

ANYWHERE a OIL SEAL runs , should be inspected for burnt on gunge , pitting , and nasties.
Ordinarrily , a brass wire brush , in the bench grider or whatever, or hand wire brush ,is used to clean and polish that journal , carefully,The wet & Dry resorted to to smooth if nessesary.
More usual to get trouble in these spots on something thats been derilict for a few decades , or dumped.
Though baked on deposits arnt unusual , or some erosion if not kept clean. F.O.D. forign object damadge .

Zen and the art of healing hands . Hide the Hammer in the cupoard if youre in a bad mood . :lol: :mrgreen:

Camchains:

ANY perceptible "droop" when held out on it's side means REPLACE.

Any flattened, shiny link edges from wearing down the adjuster shoe means REPLACE. (easy to spot - they are typically equally worn/trashed).

Heck, they're cheap enough, JUST REPLACE!

I'm making slow progress. I'm not really that good at, nor do I much enjoy the cleaning portion of a rebuild. So it's going slowly. I decided to try to polish the crank journals myself as they looked reasonable. In other words it shouldn't take much and if it does, I should send them out. So how does one polish a journal? I looked around the internet and basically came upon the string/twine method or using a wood block. I then came across this image:


And realized I could something like that. So I made a quick and dirty mount for the crank half, chucked it up in the lathe and applied some crocus cloth and oil whilst turning the crank slowly.



A minute or so yielded fairly good results.



Same thing for the cam



Hopefully this doesn't screw anything up. It looks like one of the journals is a bit worn on the underside, so I need to do some more measuring and plastigage, etc. before I'll know just how bad it is. Other than that, everything looks pretty good.

What measurements did you take from the bearing journals before polishing them? Very often journals will appear to be perfectly ok, but will either be oval or getting very close to upper wear limit.

OK, I've managed to measure the crank and here's the numbers

Timing Side Journal
1.7482-1.7495
Delta = 0.0013

Primary Side Journal
1.7498-1.7501
Delta = 0.0003

Workshop manual indicates correct STD size should be 1.7509 - 1.7504 So it looks like both are a bit small, with the Timing side the worst.

Then I test fit with new Big End Bearings and some plastigage.

Timing side I get about 0.002 -0.0025" clearance
Primary side I get about 0.0015" clearance

Workshop indicates it should be less than 0.001.

So my conclusion is the primary side is OK (not perfect, but probably OK). The timing side is more dicey. It's out of spec, but I wonder just how bad is this? Can I run it this way or should I have the crank ground? From some of you more experienced engine builder, what do you think? I don't plan on hot rodding this thing, but I would like it to be reliable and not blow up on me.