1924 Buick 24-6-49 - Cylinder head and block permitted distortion

[TomN]

Dear all,

I would like to ask you for some help regarding the overhaul of the 6-cylinder engine of the 1924 Buick 24-6-49. It is the car I presented here about year ago.

My principal question is: What is maximum permitted warp (flatness specification) of the cylinder head and cylinder block of this engine, please? Does exist some manufacturer recommendation, please? I didn´t find this information in the workshop manual. Or do you have some experience from your repairs, please?

To explain my concern – We bought the car with the cracked engine block (probably due to the frozen water). We started it for a while, and except the leaking water from the cracks, a lot of the bubbling water was forced out of the radiator then.

The cracks were welded and engine started again. Most of the coolant was again expelled from the radiator in few tens of the seconds. Seems the pressure from the cylinder(s) was leaking to the cooling system, so we removed the head. We found the engine has been already disassembled before (three bolts were replaced by studs). Hard to say if the head was torqued properly, a lot of force was needed to loosen the bolts, but it could be by the corrosion of their threads, reaching into the water.

Having in mind how fast was the water expelled, I expected visibly damaged head gasket. There are signs, but nothing extreme. Anyway, the gasket is branded Victor No.480. I don’t know how long it was available at aftermarket, but I have suspicion it wasn´t replaced during the previous repair.

I was also afraid the cylinder head and/or block could be deformed, either by overheating when running without water (I know nothing about the engine history), or by welding (the welder was very experienced, was doing short welds to avoid extensive heat accumulation, but nevertheless it could cause some tension).

Measured maximum head distortion is less than 0,25 mm (one area, the rest is less than 0,15/0,20 mm), for the block is less than 0,25 mm too but on more places. Regarding to known faults it seems to me quite good condition of both parts and not far away from limit for the current engines (usually 0,20 mm). Anyway, I have no idea what should be the maximum distortion for this engine.

I am going to test the head and block for leaks and can let them also grind, but I don’t want to do it if not necessary, because I don’t know, if this wasn’t done also before. There are some signs stamped on the head and block surface, maybe suggesting they weren´t machined yet. Signs &, L, A, S, K, F and sign B11 are at block, D, F and X are at head. Do you know their meaning, please?

I am in doubt, if the root cause of the leaking pressure to cooling system was the re-used head gasket, improperly torqued head, or too rough surface of head and/or block. If you have any experience or idea, I will be very grateful.

Regarding the overhaul I would also like to ask for your opinion about following:
1.    I am considering to use studs instead of original bolts, do you have some good/bad experience with studs, please?
2.    If using bolts, where to buy them, please?
3.    Which thread is used on the head studs for intake/exhaust manifold, please?
4.    1924 6-cylinder has quite strange prescribed sequence for the head torqueing, later models have more common sequence, even though they are almost the same. Do you know the reason and do you recommend to strictly follow 1924 instructions for 1924 model, please?

Many thanks in advance
Kind Regards
Tomas
 

[Oldtech]

You are correct to be checking for leaks / rust outs. If it's  chucking coolant that fast you may have a rusted out exhaust passage in the head, It looks like it has never been resurfaced.  With the amount of uneveness it shows I would get the head surfaced.  You can likely get away without doing the block, but it should be .2 mm or less.  The studs are original equipment, at least the 2 end ones.  That's how you line it up when you put the head on.  I would stick with bolts. It can be impossible to get the head off after several years with studs.  Tightening pattern is starting in center then working to both ends evenly. do it in 3 stages. 40 lbs the first time, then 50, then 60.  Check the spec. Memory says 60 but memory is sometimes wrong. 

I think the manifold studs are coarse thread in the block, fine on the nut end. 

Edited March 4, 2022 by Oldtech (see edit history)

[Oregon Desert model 45]

Bolts are 7/16-14 x 5-1/4" length.  I found 5-1/2" length bolts from some online source and trimmed 1/4" off the end.  I don't recall what grade these are. 

Source for gaskets : Bobs Automobilia or Olson's gaskets.  Prices for head gaskets have gone up since I purchased mine.  

https://bobsautomobilia.com/shop/engine1628937744/headgasket-1924-28-master-or-std-metal-cladstate-year-and-series-hg-260m/

https://www.olsonsgaskets.com/

I have wondered about those various stampings on the head and block, and my best guess is inspection quality control record identifiers. 

A possible source of coolant leaking is around the head bolt threads.  The head bolts penetrate into the coolant passages and pipe sealant should be applied to the bolt threads before installing. Traces of this sealant is visible in your photos.  It looks like red RTV sealant to me.  If the head bolts were retorqued after RTV sealant has cured, it could fail.  I think that might be the source of the leak. 

Kevin 

[Robert Engle]

For your head bolts, you want a grade 1 or at most grade 3 bolts.  You only need about 40 ft-lbs of torque. Higher grade bolts will have no stretch at that torque level so will not maintain the proper torque. I like to use Permatex  FormaGasket On the threads.  

 

Usually, there are only two studs and the remainder are bolts.  The 2 studs align the head for installation. 

 

 

Bob Engle

Edited March 5, 2022 by Robert Engle
Added info (see edit history)

[Hubert_25-25]

Head bolts were used originally, but that is not how a proper head is installed today.  Today they would all be studs.  Grade 3 or Grade 5.  No need for grade 8 as the original bolts were not high strength.  Clean the holes well and use thread sealant wiped into the threads in both the head and on the studs.  Double nut the stud when installing them to make them a little snug and where the shoulder hits the deck, you can expect a better seal than with just a bolt thread.  Remove the double nuts.  The length of the stud should be from the base of the stud shoulder, plus the gasket, head, washer and the nut, then add 1/8".  The reason I say this is the old studs have 1/2" of coarse threads, and most modern studs, it is 3/4".  The extra length is just in the water jacket.  

 

If you are concerned about the the flatness of either the head of the block, have a quality machine shop check it and make the recommended corrections.  

 

The torque order is a little strange in that between the cylinders there is 1 bolt on one side and 2 on the other.        Hugh

 

[Fred Rawling]

You already have most of the engine apart.  Why would you take a chance on a warped block when only a bit more work you can send it out to have it milled.  The cost of a new head gasket is much more than the cost oif milking the block.

 

The other part is that if you have a problem after you assemble the engine,, you have to take all that stuff off again to mill the block.

You have a kot of time and money in it now.  This is not the time to take a short cut.

Fred Rawling

[TomN]

Dear “Oldtech”, Kevin, Bob, Hugh and Fred,

Thank you very much for all replies and comments, I appreciate them very much.

Based on your advice looks that the head, neither the block haven´t been machined yet, so they can be resurfaced without worry to reach the distortion no more than 0,2 mm.

The main reason why I hesitated was that I didn´t know whether it wasn´t done before, thus whether it is still safe to remove some material. Also I wasn´t sure if that surface quality, equal to modern engines with significantly higher pressures is necessary. I will follow your recommendations.

 

I already bought the complete set from Olsons recently, the head gasket looks pretty old school with thickness 3 mm, which I believe is much better for these applications then modern thinner gaskets.

Many thanks for precise specification for the cylinder head bolts/studs, either regarding the size and the grade. The fact the bolts penetrate to the coolant is the main reason why I would prefer studs over bolts, even thought it is not original design. There is always risk the sealant will fail during bolts are re-torqued and I would like to avoid it

Oldtech: Do you mean the manifold studs are fine thread UNF, or UNEF, please? None of multiple thread patterns I have (UNF, Withworth…) match it, but I don´t have the complete range probably.

Hugh: Thank you for more detailed descriptions, the sequence you added I like much more. The one shown in the 1924 workshop manual is different and seems strange to me – number one is at the front of the engine. I have no idea why, because as far as I know, both 1924 and 1925 engines has virtually same block and head. I will probably follow the later sequence you posted.

Thank you very much again
Kind Regards
Tomas
 

[TomN]

The tightening diagram I posted is from the book "Buick Six Cylinder Models Their operation and Care - 1924", page 64.

[Oldtech]

I Think the studs will be SAE   NF. I have a '28 engine. I can check this weekend. 

[Robert Engle]

Buick used head bolts through at least 1933 and they went through to the water jacket on most bolts.  You will have the same potential of the studs turning when you retorque the head.  If you ever need to remove the head, you will find getting the head off of all the studs will not be fun.  It's true that modern aluminum engines use studs, but I believe most cast iron blocks and heads had bolts.

Just my opinion, but I don't like to overthink the process and stay with simple is best.

 

Bob Engle

 

[Oldtech]

23 hours ago, Oldtech said:

I Think the studs will be SAE   NF. I have a '28 engine. I can check this weekend. 

Yes. 3/8 in, 2 inches long with national fine for the nut 24 tpi and nat coarse in the block 16 tpi.  The heavy washer crosses the gap. 

[TomN]

Oldtech, thank you very much for your kind help. I´m much calmer now - our front stud has slightly damaged thread and I was afraid about it, but NF / NC fortunately will be not problem. Many thanks!

 

Bob, I agree with you, but if the stud is fixed in the block properly it should´t turn there while retorquing, only the nut on the upper end should do. I think this reduces the risk of later leaks. That is why I considered them. On the other side is truth that the factory used bolts going through the water jacket many years, sealants were not at the level known today, and those engines were running many decades without any problem. And sure some of them are still running without any repair. Anyway, thank you for your opinion, I will think about it.

 

Kind Regards

Tomas

Edited March 13, 2022 by TomN (see edit history)

[Fred Rawling]

I had some head bolts that were badly rustedon on the threads.  I bought new Dorman head bolts to put into the part of the heaed that is covered by the rocker cover.  Then I used the best of the original bolts on ther outside of the rocker cover where they show.

 

Fred Rawling