Was this Motor Rebuilt? Bored & Sleeved? Advice Needed.

[Dan O]

Good morning and happy Mother's Day to all! - I pulled the head from my 1949 76S (warped and cracked from heat) and my mechanic remarked that it looks like the cylinders have been previously bored and sleeved during a rebuild - that or they came from the factory like that..  I really don't know much about engine rebuilding and he doesn't know much about old Buicks SO, could y'all look at this photo and tell me what you think?  The previous and first owner would have had the dough to rebuild the engine without thinking about it and I imagine it was done in the early 60's if it was done.  The engine does not smoke when running and has been run up to 70 mph without any issues so a rebuild was not on the agenda but I stupidly blew the headgasket due to no water in the radiator on a first of spring start up.

 

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Edited May 8, 2016 by Dan O (see edit history)

[JohnD1956]

I'm thinking that in the early 60's, someone would have replaced a bad 1949 motor, rather than rebore and sleeve it.  The ring I see in the picture looks like a mark from the head gasket.  I imagine scraping a small bit with a new single blade razor scraper would help determine if the ring is indeed the mark for an insert.

[NTX5467]

If the engine was rebuilt, that might have more likely meant new "rings and bearings" than a "rebore".  Especially considering that piston rings didn't have the life span they currently can.  If the engine needed a valve job at about 80K miles, some went ahead and did the rest of the "bottom end".  In-chassis "overhauls" were generally done, due to vehicle architecture, what it took to get the engine out, and capabilities of the particular repair shop/dealership.

 

My machine shop operative commented once that it was much easier to remove the complete front end sheet metal (the front clip) from the car to work on the engine rather than trying to lean over the fenders.  With the body panels removed, it also made it easier to get the engine out of the chassis, too, if desired.

 

Back then, as I recall, a "sleeved" engine was a "last resort" of sorts and not very desirable.  Reason was you didn't know how good a job of getting that new sleeve installed was done.  A used salvage yard engine was much more-desired, as long as it didn't knock and had good oil pressure.

 

I rather doubt "the factory" would have sleeved an engine.  The block would have gone to the scrap pile if it needed THAT much work to fix.  Cylinders which have been bored will have pistons stamped with the oversize amount on them, which checking the cylinder bore can also confirm.  About the only thing I've known of "the factory" to try to save, at the engine plant level, is crankshafts.  The famous ".008" Undersize" crankshaft bearings, usually identified by a particular color of paint stripe on the crankshaft, somewhere.  As my machine shop operative explained . . . they cut the journal to .008" undersize with the orientation that when the engine does need to be rebuilt, the wear on the journal will make it about .010" and can accept normal .010" undersize bearings, as the other journals will probably end up with anyway.  The .008" bearings don't exist outside of the factory walls, I believe.  Of course, the bearing size and such are stamped on the backside of the bearing shell, in the locating tang area.

 

There were also "high limit" pistons for those cylinder bore sizes which were worn, but not enough to need an overbore to .010" or .030".  ALL factory-supplied pistons were the SAME WEIGHT, so using a high-limit piston on a slightly-worn cylinder was a viable warranty alternative, but one which was NOT supported in the aftermarket (which did not have replacement pistons of the same exact weight of the OEM pistons, by observation.

 

IF the cylinders have been sleeved, which will be verified when looking inside of the crankcase itself, probably not a significant issue as the engine has survived well all of this time.  But until you look at the innards of the crankcase, about all you can do is scrape the cylinder head surface (as mentioned) or use something as red Scotchbrite for a gentle surface cleaning of the block's deck surface (being CAREFUL not to let the grit/debris get into the cylinders).

 

Please keep us posted on your progress.

 

NTX5467

[Ben Bruce aka First Born]

Whatever, and I tend to agree with the general consensus that it is marks from the head gasket,  if the block is fairly square, install a new head gasket and go. The worst you have lost will be the labor to remove the head a second time.

 

  Ben

[old-tank]

1 hour ago, First Born said:

Whatever, and I tend to agree with the general consensus that it is marks from the head gasket,  if the block is fairly square, install a new head gasket and go. The worst you have lost will be the labor to remove the head a second time.

 

  Ben

Replace all the head bolts too.  When an engine gets that hot everything expands and the head bolts stretch, but they don't shrink when it cools down and your head gasket will leak.

[Dan O]

Thanks to all.  I am going to tackle it again this week after some delay.  I imagine it's just marks from the gasket.

 

  The head bolts idea is good advice.  Do they need to be anything special, like hardened steel?  Or just a hardware store replacement?

 

My mechanic said we'd need to run a die in the bolt holes for a good seal plus clean the block surface with a type of pnematic plastic brush tool. 

Edited May 11, 2016 by Dan O (see edit history)

[Alfa]

You need bolts of the correct tensile strength (not hardware store stock). These might be sourced from another engine, or can be made, of course.

 

New bolts are definitely advisable but to be honest, I would doubt if a cooked head gasket would stretch the bolts beyond their elastic limit. I would be tempted to clean and re-use, but be mindful that they need torqueing down with care. Replace if they have become corroded along their length.

 

The bolt holes definitely need to be cleaned with the correct thread cleaning tap, preferably a parallel rather than tapered shape. It is also very, very advisable to have the cylinder head face cleaned up on a milling machine. Just a few thou removed to ensure that there is at least one flat surface for the head gasket to seal against. Otherwise you may have a leak on the new gasket too. Any local engine re-manufacturers should be able to do it for not much money. 

 

It is difficult to see from the photos if the bores have sleeves (dry liners) fitted. You need to clean up the face of the block to tell that. But sleeves are a valid form of repair and if the bores are good then they are just as good as the original engine set-up.

Edited May 11, 2016 by Alfa (see edit history)

[Ttotired]

I have to say that the head bolt question scares me a bit.

 

I am a bit of a classic car lover and try hard to preserve these cars and a question asking if head bolts are special kind of makes me think that you shouldnt be sticking your fingers into that engine, You cant ring up and order a crate one, its not a 350 chev

 

Nothing wrong with learning, no one here was born with their knowledge, so leave it to your mechanic to fix (if he knows what he is doing and isnt a first year apprentice or something of the like). You can help your mechanic out by offering a workshop manual (you have one right?) so he can have all the specifications he needs.

 

He is not going to know all the ins and outs of that engine because its rare, rare equals expensive and if you stuff something up, expensive could

happen twice

 

On the head bolts themselves, in a true engineering world, all stress bolts (like head bolts) should not be reused as when they are tentioned down, they stretch, thats what your supposed to do, I have never replaced a head bolt that was visibly ok, just cleaned and reused and I cant remember ever seeing a broken head bolt (that was being used to hold a head down)

 

Mick

[Dan O]

TtoTired - I'm not doing this myself and am not inquiring for the mechanic, just for me.  Yes, I have a manual and use it but these threads start out one way and lead to other questions that are easy to ask here and draw on a world of wisdom.  I said I'm no motor mechanic so layoff.a little, OK?

[buick5563]

Dan,

I had this issue on the first engine I rebuilt. I kept tightening with the torque wrench and it wasn't ever clicking. I knew something was up, so I stopped and reversed the bolt. It had stretched and was about to snap. I ended up using a Grade 8 bolt of the same length. Ok, the same original length... Not the stretched "new" length.

[buick man]

 … even in head bolts size does matter ….

[Guest]

On 5/12/2016 at 8:12 AM, buick5563 said:

Dan,

I had this issue on the first engine I rebuilt. I kept tightening with the torque wrench and it wasn't ever clicking. I knew something was up, so I stopped and reversed the bolt. It had stretched and was about to snap. I ended up using a Grade 8 bolt of the same length. Ok, the same original length... Not the stretched "new" length.

Stretched bolt threads can sometimes  be found by using a new nut and bolt of the correct size and putting the new nut on the new bolt, should spin easy, try new nut on old bolt, if it turns hard and the old bolt is sufficiently clean, it's a good call to condem the old bolt. The threads are a different "pitch" if bolt has been stretched. Hope that reads right! Good luck. Have used head bolts. The other test is to use a stretch gauge, used when torque for bolts is measured by how much the bolt is stretched for torque instead of turn force required, measure known good bolt for reference, then measure used ones to diagnose if stretched or not. Critiques of this post welcome! Thanx!

[NTX5467]

The "marks" on the head of the head bolt will denote the hardness of the bolt.  As I recall, ALL were Grade 5 bolts?  Never did see a Grade 8 bolt from the factory.  What DOES make them specific is the "flange head" head (looks like a built-in flat washer) on the bolt.  This helps spread the clamping force of the torqued bolt better to surrounding surfaces.  Many can have a light oxide coating, too, which is where the "black" color comes from.

 

As 5563 mentioned, if a bolt doesn't "feel" right as it is being torqued (in torque sequence AND location sequence!), stop and see what's going on!   Typically, all head bolts on the older motors were readily re-used rather than replaced.  The current production head bolts are "torque to yield" and MUST be replaced each time they are removed.

 

The "torque to yield" bolts have a different tensile spec and sound different when dropped, as I recall.  You take them down to a specified torque, they add a certain number of degrees past that point.  Not sure why, but that's what they say to do.  To me, it sounds like the old shadetree method . . . 1/2 turn past as tight as you can get it.

 

In ANY fastener situation, ONE piece is designed to be the "sacrificial" item.  In this case, it's the head bolt itself RATHER than the threads it screws into.  Hence, no "hard" bolts per se.  Using the tap to clean the threads is a good idea, too, so that the bolt torque is reached smoothly and correctly.

 

NTX5467

[Dan O]

Thanks again for all the great insight and advice.  What looked like sleeve inserts were just marks from the head gasket afterall - some photos attached show the marks before and during the polishing process.

 

 Without going into all the details, the original head bolts were all cleaned (as were the threaded holes in the block) and the head torqued down on a new gasket with no problems.  The cylinder walls were still nice and smooth according to my mechanic.  I know it will probably blow oil but I'm not in a position to do a full engine rebuild - the head was warped and cracked so it had to be replaced inorder to be able to drive/move this car around for the time being.  The project got sidelined due to more important matters but should be all back together next week if we don't flood again here in Texas.  I feel bad about neglecting this old car but perhaps this will get the project going again.

 

 

Edited June 1, 2016 by Dan O (see edit history)

[NTX5467]

Thanks for the update and pictures.  It might take a while for things to get back to normal, but I suspect any real oil control issues might not be too bad.  If the oil rings were already bad, there'd be a washed area on the top of the piston (from oil comping up past them), around the edge.  Just run it with fresh fluids and see how it goes.

 

NTX5467

[s_hilmoe]

On 5/31/2016 at 6:53 PM, NTX5467 said:

The "torque to yield" bolts have a different tensile spec and sound different when dropped, as I recall.  You take them down to a specified torque, they add a certain number of degrees past that point.  Not sure why, but that's what they say to do.  To me, it sounds like the old shadetree method . . . 1/2 turn past as tight as you can get it.

 

NTX5467

 

Here is a very simple explanation about using "torque angle" to tighten bolts. 

 

 

Dan O, Nice Roady!!!  Love them sedanettes..

[NTX5467]

Thanks for that illustration.  Seems like the factory torque specs were for "clean threads, lightly oiled"?  Certainly, as we all know when removing fasteners which have unclean threads, it takes more effort to move them.  It would be the same for installing them on dirty/corroded threads, too.

 

As I recall reading somewhere, on bolt/fastener torques, it's also related to a certain amount of "stretch" in the bolt/stud, too.  It might only be measured with a micrometer, but everything stretches or contracts no matter how hard we might perceive it to be.

 

NTX5467

[Alfa]

Hi Dan O

 

You may have the engine built up by now, in which case this is irrelevant, but if the bores were 'de-glazed' with a glaze-busting hone and new rings fitted, it probably would not burn oil. The critical factor is wear in the piston ring grooves, which if present, allows the rings to move in the grooves with a pumping action, which moves the oil up the bore. But otherwise, it should be fine.

 

Adam..

[Glassesguy]

If you still have the head off probe the cooling system passages at the rear to check for built up crud. These straight eights were mounted with the rear lower than the front and that's where the crud builds up. Could be a possible overheating problem from before?

[Dan O]

All good ideas but let's close this thread as in my more recent, separate post I noted the water jacket has creacked and I will replace at least the block now.