Pistons in a 1928 Master Buick

[gward1211]

Hello from lockdown in Australia.  I wonder if someone could kindly give me some advice about 1928 Buick Master pistons.  I purchased a 1928 Model 58 a little while ago.  Its history is unknown but it seems to have been restored about 25 years ago.  Little was known about the engine except that I could see hone marks in the bores through spark plug holes and it had some prodigious oils leaks.  I have removed the engine with a view to replacing the rear main seal.  Having got that far I decided to completely disassemble it to see what was inside.  The engine has new cast iron pistons 60 thou oversize.  There is inadequate clearance in the bearings and one center main bearing in the cap has been slightly damaged in the 100 odd miles that I have driven it.  I intend to shim the bearings for a little more clearance.

The pistons are a mystery to me.  They have no offset and they have a second oil ring below the gudgeon pin - see photos.  My questions are:

1. Does the lack of offset matter?

2. Is the lower oil ring a good thing?  It seems to me that it would cause extra drag and might cause the swept area above the lower oil ring to be inadequately lubricated.  A couple of the upper oil rings were gummed up with an enamel-type substance which might mean inadequate flushing with oil.  However, the car has been sitting around for the past 20 years and had a lot of grease-like sludge in the sump, I guess from a lot of cold running trying to get it to run properly.  The carburetor was a mess.

3. Would it be acceptable to remove all the lower oil rings and leave them out?

4. Would a small amount of scoring on one side in a center main bearing cap (about 20% of the surface area in the cap is deeply scored) be cause for concern once proper clearances are established?  The crankshaft is not scored.

5. To which side of the engine should the heads of the gudgeon pin retaining bolts point?

 

I would greatly appreciate any opinions on these matters.

Kind regards

 

Geoff Ward

 

[Hubert_25-25]

Geoff, 

    Not unusual for a piston manufacturer to use 4 rings and I have even seen 5 rings.  In my opinion, I would leave the rings alone.  Regarding oil control rings I have always felt that they were lubricated from the oil entering from the ring internal side, and they held excess oil between the upper and lower faces of the oil ring.  When I see them on the skirt, I always thought that was a way to hold lubrication near the piston skirt.  

When I rebuilt my 1925 Buick engine, I had been reading that it is not uncommon to go back in with 0 offset pistons.  That is what I did.  I have not noticed any problems.  

A picture would help for #4 but scoring on 20% of a main bearing cap does not seem like the end of the world.  I noticed that one of my babbit castings had imperfections from the babbitting process.  Attached is a picture.  To send it back as a redo would have been a lot of effort so I just went with it.  Oil pressure is great, so a non issue.  I would plastigauge and shim as necessary.

From the shop manual.  "Piston and rod should be so assembled that the offset of the piston pin will be toward the camshaft when rod is replaced on crankshaft.  There is a pointed projection on the cap of connecting rod and a pointed boss in the channel of rod.  These must point to rear of engine."       

Consider replacing wrist pin bolts with drilled head bolts and wiring them.   Replace lock washers with quality metallurgy.  Observe in my first photo the accident waiting to happen.

Good for you for pulling the engine down as you have done.

While in there, inspect the oil pump screen quality and the integrity of oil pump drive pin.  

Hugh 

[Terry Wiegand]

Geoff,

In reading your posting you said that you found the pistons to be cast iron.  I am wondering why whoever rebuilt the engine did not go with Aluminum pistons.  Going that route cuts down on the reciprocating weight and in turn is much easier on the rod and main bearings.  Since these engines had poured bearings that is a serious consideration to keep in mind.  Just my 2 cents here.

 

Terry Wiegand

South Hutchinson, Kansas

AACA Life Member #947918

[Rock10]

14 minutes ago, Terry Wiegand said:

Geoff,

In reading your posting you said that you found the pistons to be cast iron.  I am wondering why whoever rebuilt the engine did not go with Aluminum pistons.  Going that route cuts down on the reciprocating weight and in turn is much easier on the rod and main bearings.  Since these engines had poured bearings that is a serious consideration to keep in mind.  Just my 2 cents here.

 

Terry Wiegand

South Hutchinson, Kansas

AACA Life Member #947918

They really had cast iron pistons?!?! I thought that was a typo. Holy Mackerel  😳

[Oldtech]

Those are strange looking pistons. Don't think they are Buick.  Should be 3 rings on top, and a longer skirt. The pin is close to the bottom of your pistons going by your pictures. Perhaps the deck height is higher to get more compression.?? 

The offset or lack of it wouldn't matter. 

If it were me... and I could afford it - because they are expensive, I would order a nice  new set of proper aluminum pistons from Egge Machine. 

Many engines used 4 ring pistons to control oil consumption. With modern rings, as you would get with new pistons, that is not an issue. 

Edited August 1, 2021 by Oldtech (see edit history)

[gward1211]

Hugh, many thanks for the comments.  I have now attached some photos of the damaged main bearing.  What do you think? The fine scratches are from a small amount of rubbing I did with some 280 wet and dry paper.  The deeper scratches are the damage from lack of clearance.  Thanks for the suggestion for the aircraft bolts.  Looks like a good idea.  I don't know what the last photo in your group is.  Could you explain it please.

 

12 hours ago, Hubert_25-25 said:

Geoff, 

    Not unusual for a piston manufacturer to use 4 rings and I have even seen 5 rings.  In my opinion, I would leave the rings alone.  Regarding oil control rings I have always felt that they were lubricated from the oil entering from the ring internal side, and they held excess oil between the upper and lower faces of the oil ring.  When I see them on the skirt, I always thought that was a way to hold lubrication near the piston skirt.  

When I rebuilt my 1925 Buick engine, I had been reading that it is not uncommon to go back in with 0 offset pistons.  That is what I did.  I have not noticed any problems.  

A picture would help for #4 but scoring on 20% of a main bearing cap does not seem like the end of the world.  I noticed that one of my babbit castings had imperfections from the babbitting process.  Attached is a picture.  To send it back as a redo would have been a lot of effort so I just went with it.  Oil pressure is great, so a non issue.  I would plastigauge and shim as necessary.

From the shop manual.  "Piston and rod should be so assembled that the offset of the piston pin will be toward the camshaft when rod is replaced on crankshaft.  There is a pointed projection on the cap of connecting rod and a pointed boss in the channel of rod.  These must point to rear of engine."       

Consider replacing wrist pin bolts with drilled head bolts and wiring them.   Replace lock washers with quality metallurgy.  Observe in my first photo the accident waiting to happen.

Good for you for pulling the engine down as you have done.

While in there, inspect the oil pump screen quality and the integrity of oil pump drive pin.  

Hugh 

 

[gward1211]

Thanks Terry and OldTech.  Yes, I don't know where new cast iron pistons came from.  Maybe they were readily available 25 years ago.  It would be nice to get some aluminium pistons.  Would the crankshaft and Al pistons have to be re-balanced?

[Hubert_25-25]

These are what the steel pistons in my Buick looked like.  I believe these are originals, but they could be .010 oversized, so not sure if someone did that from a rebuild or if the factory put any oversized pistons in?? Notice the lack of an oil control ring on the right piston.  Someone slept through their engine basics class.   Lots of reasons that I was glad that I pulled the engine apart.

 

I see your babbitting had a porosity issue as well like mine did.  So the reason I left mine alone and went with it is because I would have needed to have the babbit repoured, and I would also need to have the engine line pored again.  Only my opinion, but it looks like you have cleaned the babbit surface well, and babbit is fairly soft.  I would plastigauge it and use it.  Whatever hard thing was in there, is no longer there.  Clean the oil pan well.  

 

The crankshaft and flywheel are balanced separately.  The difficulty with balancing the connecting rods and pistons is that unlike a modern connecting rod, there is no boss to grind on for balancing.  Then you get into balancing the big end and the little end of the connecting rods.  I believe all the aluminum pistons were already of equal weight.  Attached is a write up on what I went thru to balance my connecting rods.  My machinist was going to just leave it alone under the feeling that this motor would never see greater than 3,000 rpm.   

 

https://forums.aaca.org/topic/316231-balancing-connecting-rods/?tab=comments#comment-1796787

 

The last 2 photos are my oil pump drive.  That is where the photo of the pin in my last posting came from.  

Hugh

 

[hidden_hunter]

Could be Holden pistons, not sure if they ever crossed over in size with buick

[gward1211]

Thanks everyone.

Kind regards

Geoff

 

[Oldtech]

I would run that bearing  unless you need a 100,000 mile engine. It's not burned and you're not racing it.  Smooth it off and shim it correctly. 

No you don't need to rebalance. It should run a little smoother with the Aluminum Pistons.

Edited August 3, 2021 by Oldtech (see edit history)

[32buick67]

Thanks for the tip about lockwiring the wrist pin cap screw, I wish that was done on my 32, 272 engine so the piston wouldnt have been damaged.

 

Anyone know where I can get a new piston?

3.0625" standard bore, cast iron

 

Anyone know if I can buy an old cast iron piston that is close in size, turn it down, ensure size and weight to match original?