Topic: K8 Engine Damage - cam shaft sprocket in pieces

[bryanj]

Yes the thickness is different as are the pistons

[Jerry Rxman Griffin aka MuthaF'er]

Is there a difference in piston rings between the pre-76 models and the 77-78? Thanks!

1.5mm, 1.5mm, 2.5mm pre 77
1.2mm, 1.2mm, 2.5mm 77/78

[anotherCB]

Thanks gents!

[Alan F.]

That is good info, thanks.

[anotherCB]

Got all my parts back from aqua blasting, everything looks great!

I am going to order new main bearing shells, mine show some minor scars. For the heck of it I can’t seem to find the numbering on the crank that I need to determine which shells to order. Can someone show me a pic where the numbers are located on the crank? Thanks!

[PeWe]

You need a flashlight to illuminate the area close to cam chain sprocket. Look like written with a pencil. Crank bearings + rods. Visible in specific angles only.
I'm sure green shells will work fine!

[anotherCB]

You need a flashlight to illimunate the area close to cam chain sprocket. Look like written with a pencil. Crank bearings + rods. Visible in specific angles only.
I'm sure green shells will work fine!

Ok thanks, I'll take another look. My eyesight isn't what it once was 

[PeWe]

It is on this side. This crank came from a later K or F. I have the trans too.

Numbers visible are
 AAAAA (crank bearings)
To match what stamped on the block. All 5 hopefully same but can be different. Result end up in crank shell of matching thickness.

4444  for rods.

This was extra easy to see. My other cranks much weaker written.

[anotherCB]

Thanks. I just went to the garage and found mine. I see something but can't decipher all of it, need some other light or have my kids try and read it for me later. For sure there is an A and a C in there, so I need to use that table in the manual to figure out the crank shells. Case is all B's.

[PeWe]

Try lamp from different angles.
Take photos you can edit in your computer increasing contrast and play with light.

[anotherCB]

Will do that later, thanks. Trying to figure out how the factory manual comes up with the calculated oil clearances. As an example, if I look at an "A" crank case and a "A" crankshaft, I see the following min/max measurements in the manual

Crank case: 39.000-39.008 mm
Crankshaft: 35.995-36.000 mm
Bearing for this combo is yellow: 1.4990-1.4986 mm

To calculate MAX oil clearance I would do the following (I think):
MAX crankcase radius - MIN crankshaft radius - MIN shell = MAX oil clearance
39.008/2 - 35.995/2 - 1.4986 = 0.0079 mm, which is 7.9 micrometer

Factory manual lists 41 micrometer as MAX clearance for this combo. What am I doing wrong??? 

[Jerry Rxman Griffin aka MuthaF'er]

Most people take the 2 letter readings, match them up in the chart as you have, get those bearings then install/torque down the crank/cases with Plastigauge in a couple places and carefully without allowing the crank to rotate open it up and measure/gauge the flattened Plastigauge. If too tight or loose go to the next size bearings but you will notice the clearances go into the ten thousandths so there is not a lot of differences. 

[anotherCB]

Yes, I ordered the Plastigauge already, and figured out the shells I need from the table, just curious how the manual does the math to calculate the oil clearance....anyways, I guess it doesn't really matter, but if someone knows I'd be interested.

[anotherCB]

Let the fun (assembly) begin!

[anotherCB]

Can anyone tell me why I don’t seem to have the “oil guide” pictured in the factory manual? Neither my 1977 nor my 1978 bottom end seem to have it. Is it 1976 and earlier only? Thanks!

[seanbarney41]

yes, it was only on earlier models that have the automatic chain oiler

[anotherCB]

Great, thanks!

[754]

Yours has no chain oiler, early short shaft does. 

[anotherCB]

Thanks!

Can someone tell me what I need to do with the two small oil metering valves (I think that's what they are called) in the heads? Those that restrict oil flow to the cam. Do I need to take them out and inspect/clean them or can I leave them alone? My heads were bead blasted and I am afraid there may be some blast material stuck in there. Or would blowing out with carb cleaner/compressed air be sufficient? 

[754]

Oh yes..oh yes .oh Hell YES..
 Even on the cleanest of engines , debris can blow in while cleaning.
 Be careful, don't use air near them for removal.. try gripping  gently pliers or something  without hurting them.
Big  unwanted issues  can occur if you miss this step.

[anotherCB]

Thank you for a very easily understandable answer 

[scottly]

Got all my parts back from aqua blasting, everything looks great!

You need to thoroughly clean the oil passages in the crankcase of any blasting media, lest it gets pumped up to the oil jets, plugging them.

[anotherCB]

You need to thoroughly clean the oil passages in the crankcase of any blasting media, lest it gets pumped up to the oil jets, plugging them.
[/quote]

Even though the parts came back very clean from blasting, I spent an hour or so washing everything out. Only then I realized that the valves in the head can be removed, so I will definitely give the top end another good cleaning. Thanks!

[johans]

You can remove the jets  ( highly recommended )  and clean the passages that they go into . I Had painted a motor and had the smallest amount of overspray on the studs that provide the oil  passage to those jets . The overspray and hot oil mixed and clogged the right jet = new cam and towers   (((

[PeWe]

Good info!
A little overspray might be the explanation for other cases that happened soon after restore.
The 2 inner on inlet side goes direct to the top. Even if sealer was used, the o-rings should block it.
Paint on studs another thing.

Threadlocker as Loctite another risk on these studs.