I’m told they are harmless on the 5.7 diesel.So the 4.3 is most likely the same situation.

There is a bulletin about it from what the machinist told me.Your best bet is have a machine shop inspect it and see what they think.

 

Thanks. Yes you are right. my 5.7 also had small cracks on the same spot. but it was just at 2 cylinders and the cracks where somewhat smaller than here. Thats why im asking.

 

Finally got to work on the 4.3 again. i was about to clean the pistons when i found this.
I couldn't see it first with all the carbon on it.
On one piston the groove is broken like this:

it is possible to move the pieces up and down a bit, but they cannot come off the piston.

funny thing to notice is, that the cylinder for this piston is one of the cleanest without scratches.

so im looking for a standard size piston now.

 

Finally got to work on the 4.3 again. i was about to clean the pistons when i found this.
I couldn't see it first with all the carbon on it.
On one piston the groove is broken like this:
View attachment 657432

it is possible to move the pieces up and down a bit, but they cannot come off the piston.
View attachment 657433
View attachment 657434

funny thing to notice is, that the cylinder for this piston is one of the cleanest without scratches.

so im looking for a standard size piston now.

I have one std piston if your interested.I’ll take a few pictures of it and let you have a look at it tomorrow.

 

Wow great!! Thank you. the broken one is piston 6.

this little notch should allways face forward on the engine (i guess)
this is the piston i need to replace

someone rebuilt this engine before. however this person had no idea what he was doing. some piston where installed upside down. all the rod bearing caps where mixed ....
just chaos.
so im not 100% sure which pistons go on the left side and which one on the right side. these do have offset piston pins, so it sould matter.

 

No problem.Glad to help out.I’ll check out my piston this morning and see what the details are.

Your right about the notch being placed toward the front of the engine.

 

Morning doki,

The piston looks to be in good shape.It doesn’t have the flame slot in the Center but a good machine shop should be able to cut a groove into the top no problem.I don’t see any broken ring lands either.This piston should fit cylinder 6 no problem.Also a good shop should be able to make both valve reliefs the same if you want it that way.

Years ago the pistons had to go in certain cylinders in the 5.7 because of the valve reliefs but later years the valve reliefs were all the same size.You just had to ensure the piston notch was pointing in the right direction.The piston I have has no notch for direction.It can go in cylinders 1,3,6 and 8 if you had the 5.7

This piston is from an early 1978 5.7 engine so the piston pin is dead center.Later years of course had the offset piston pin for smoother running but this piston should get you out of a jam no problem.I would use it if you had no other alternative.I hope this helps.

 

awesome info btw.
do you know when offset piston where introduced?
i checked all my pistons, they are all center pin. i pulled those from 1979 to 1980 engines. i still have a 5.7 1981 engine with roller lifter assembled. Could that one have offset pins? I need to disassemble the engine anyway at some point because the block is broken.

//EDIT:
i managed to find v6 pistons with the groove in the middle and offset pins. i bought a LH and RH just to be sure. 👍

 

Good morning,
thank you for the offer!!. I have a lot of 5.7 pistons with center pin myself, im looking for one with offset so it matches the other 5.
alternatively i could use 6 pistons from the 5.7 with center pins. Does this work well? the timing is a bit off then i suppose.

 

The 5.7 pistons should be okay if you have those to work with.I can’t see it being a problem.👍

 

Glad to hear you found the pistons you need👍

I believe it was 1982 into 1983 when they developed the offset piston pins.Most aftermarket 5.7 diesel pistons I’ve seen also have the offset pins.

The clevite brand when it was available had a “F” but no notch next to the piston pin on one side only indicating that side faces forward.I’ve had sealed power pistons with the notch on the piston crown as well.

On another note 1982 and later 5.7 engines also had connecting rods that were much more robust in the beam section than previous years.Those years too had different rod bushings.

 

Doki,

If you have pistons it would be wise to hold onto them.👍

 

So today I was about to drop in the pistons. While installing the piston rings I realized that the side clearance on the second compression ring is very tight, way smaller than the service manual says. First, I thought it was my fault because I use a new piston ring set for the 5.7 and assumed that these are thicker. -- just checked. service manual says the rings are identical in thickness.

So, I grabbed the original piston ring that came of the engine and checked the clearance again. it was just as tight as the new ones. (Maybe a tiny bit looser because of wear) I cannot even fit the smallest plate on the feeler gauge which is .0015" (it should be .0018 to .0038)
but I can freely rotate the new ring in it.

any advice? just install the rings and leave it as it is? I don´t know how critical this clearance is.

 

That is rather odd.Of course having the clearance match GM specification would be ideal and that is what we always aim for.

Are the piston grooves free of all trace of carbon buildup?

 

Yes they are completely free of carbon. I decided to make the groove slightly wider with a fine grade sandpaper so the ring can move freely.

its the same on all pistons. I also checked with an other set of piston rings just to be sure.

 

If you have the clearance you need at this point that’s definitely good news for sure.

 

I changed the title of this thread because its more fitting now since all the major troubles are worked out.

Here's some update on this little machine.

Crank and Pistons. Crank is .010 on main and rods. I reused the pistons and rods except for that broken one. I was able to find a replacement with offset pin.
ARP studs for the main caps.

On one head i had to put in new valve guides on all 3 exhaust ports. Machine shop did a great job. Barely even noticeable.

ARP Studs: Olds V6 has M14 and M10 for head bolts. For the top M10 Bolts I couldn't find such tiny studs, so I used Bolts from ARP. (Not on the picture)
Piston 6 is the replacement piston. Not in perfect shape, it looks much worse on picture than in real life.

 

Heads, valvetrain and intakemanifold.

Yes, it is not a 100% perfect build. There is a noticeable ring ridge on every cylinder. Valves have seen better days too however nothing too bad... Its an old engine mainly rebuilt with the parts it came apart. Except for Piston rings, bearings, pushrods, rocker arms and all seals obviously.

Feel free to ask anything regarding this engine or the parts I used.

 

Looks outstanding doki👍

What brand of piston rings did you end up using?The crank and heads look great!

 

Thanks!!

I used Hasting Piston Rings Set Nr 2M5610 if I remember correctly. I will look it up later to be sure. It's a set for the 5.7 V8 Diesel. I checked specifications in the service manual. The rings should be identical for the V8 and V6, since the pistons are interchangeable as well.


next task is to figure out how to install the bracket for the torque arm since this was bolted to a Headbolt. Some of the original Headbolts do have studs on the top to mount brackets and such.

I will keep posting updates here.

 

Perfect.Yes I have both Hastings and sealed power brand rings here as well but in .030 oversize.2M5610 is corrrect for Hastings.The sealed power part number being E-376K.

Glad to hear your making good progress👍

 

Doki,

when do you plan on installing that engine back into the car?I have a couple projects myself I’d like to get done but simply little time on my hands at the moment.Hopefully sometime soon I’ll be able to achieve what I set out to do regarding these GM engines.

 

Hi dieselolds, today im going to prepare the car for the engine installation. I need to replace the engine and transmission mounts do some wireing, cleaning parts.
The car should be finished next week or so.
I will do another update post when the engine is back in the car.

whenever you do something regarding these engines, keep us posted. I love to see and read stuff about these maschines.

 

That’s great doki👍

Glad to hear it.Absolutely. I’ll keep you informed on how things go on this side of the pond.Still waiting on the machine shop to finish up my block and crankshaft.

 

So today I finished assembling the car to the point where I can start the engine. Here are some pics of the progress. It took me longer than I thought it would.

ready to go into the car.

the fitment is very tight. But I managed to do it with the hood on the car. I was too lazy to remove it.

Bolted to the transmission.

here is a short video of me starting the engine. On the video you can see the very first time I cranked the engine (at the beginning, it makes this buzz sound because the video is 6x). I fast forwarded it to the point where it starts. It took just 8 minutes in total.

Streamable Video

Info: I just ran the engine for 30-40 seconds in this video, because the radiator was not filled at this point.

 

After filling up the radiator I started her again. Starts very good. No funny sounds, No strange smoke from the exhaust, no leaks on the ground. It already fires on all 6 cylinders. But she is very shaky. Actually, more like excessive constant/even vibration on every power stroke. Not sure what's going on.
Any Ideas? She ran smoothly pre rebuild, and i haven't touched the IP since.

I will play with the timing this weekend if this doesn't clear up after the break-in phase.

 

Unless it’s still purging some of the air out of the fuel system.Have you had it running very long so far?Were any of the injector lines separated from the injection pump?

 

I ran out of time yesterday. No, it ran about 5 -6 minutes in total.
The lines and IP where not seperated, in fact its the only IP and lines I have for the V6.
I did change the Injectors because some of them were leaking and had out of spec opening pressure.
Usually, I do rebuild the injectors by myself, but I just had no time for it an ordered a rebuilt set on ebay which is listed as 1982-1983 Injectors for Olds V6. From Redsautomotiv_9 on ebay.

Thank you!
I will run it for little longer with higher rpm and if it's not improving, I will try the things you suggested.