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I need a pass to the principal's office, I left out the special flywheel bolt gaskets, part #346800 on my last rebuild. The ones I removed were not worth saving and no replacements were readily available.

If it's of any redeeming value, I did have the entire flywheel and pressure plate assy. precision balanced along with the crank, rods and pistons.

-R

Yeah, Ray That is what I meant by having your ducks in a row! that is surely the way to go on a complete rebuild. But the uc should be in the window anytime that the #1 piston is up, not just when #1 is on the compression stroke, ( that is the point I was makeing) when you time the camshaft the previous procedure you showed better be followed to the letter. That is the place that an error is likely to occur. Also when the distributor is inserted.

Mr Mack!

You must be talking about a 2 cycle engine! :p Not a Chevy 4! :p :p You sure you don't want to think that one over again? Think really hard this time, because I agree with Ray.

Ok, You think about it We are talking about the flywheel in relation to the crankshaft, doesn't have anything to do with 4 cycle or 2 cycle there is one position where the flywheel will fit on the crank when # 1 piston is at UC, and that is it. the flywheel is fastened to the crank , and therefore when #1 piston is up it is in the correct position.

Now the camshaft and distributor is another story, the flywheel and the crankshaft make TWO revs per one rev of the camshaft and the distributor rotor makes one rev......... That is why you have to have the #1 piston up on compression to set the rotor to fire.

I must ask the unasked question: Why does the engine come to rest in only two positions? Now I was in class the whole time and I didn't here this explained!

"Why does the engine come to rest in only two positions?"

Maybe the reason is that a typical 4 cylinder employs a 180° crankshaft? The "throws" are 180° apart (1 & 4 pistons move up-down together, 2 & 3 pistons move up-down together) therefore when the engine comes to rest the weight of the crankshaft has either 1&4 on the bottom, or 2&3... its gravity.

The Chevy Six has a 120° crankshaft and will have 3 places of normal wear on the flywheel corresponding to pairs of pistons that will come to rest in one of 3 positions.

I guess???

Johnny, do you think it is as much comeing up against compression as well as gravity?...I haven't noticed that kind of wear, I have 3 or 4 used flywheels I need to check them.

Mr. Mack,
I would think that sooner or latter the compression/vacuum won't matter as it will leak out to stabilize to the atmospheric pressure. Gravity seems a bit more constant, but to tell the truth , I really don't know.

Anyway, I have heard the end result will show up in the flywheel teeth and some old-timers used to "turn" the ring gear around the flywheel to even out the wear.

PS...I think I'll spin my old Chevy Six around and mark the flywheel with chalk where it stops. Kinda like one of them crooked roulette wheels at the casino.....

My curiosity is up :confused: - What IS the cotter pin in the drain hole of the flywheel underpan really for ????

The cotter key serves the purpose of assureing that any oil, clutch powder dirt will drain out of the drain hole, it keeps it from being stopped up like Chevy nut said . It is loose enough a fit so that it jiggles around from the motion of the car but is bent over so that it doesn't bounce out.

Ah ha.......

The stopping position of the engine must be determined by compression-depending on which cylinders "stop" the engine as it quits revolving.If you were to remove the spark plugs (no compression) it would slowly come to a halt at any position.............Very intresting.The 4 cyl. cars used six flywheel bolts and and in 1929-up the 6 cyl. engines used only four up thru 1941.[plus a locating dowel]

Gene, does that mean that a six is smoother running than a four? and a V/8 is just really a twin four?

Four is good, six is best, eight is way too many?

In any V type engine there are pistons and rods going up and down in two different directions or planes. Check out the Oakland - Pontiac - Viking series of V8 engines that GM made around 1930-32. Some had a single plane crankshaft and were not as smooth as the ones with a two plane crankshaft. Cadillac V8s had a two plane crank from about 1924 on. It changed the intake manifold design, the firing order and the sound of the exhaust.

Q&A

d2d2

Sorry, can’t give you any credit for your answer, as it is too vague.

Bowtie Bob

A perfect answer. Main purpose is to keep the hole open for drainage.

MrMack

I have reviewed the transcript from the lesson and see no reason for further elaboration. From you later posts it appears you really do understand how it goes together and why.

ChevyGuru

Best you go put the cotter key back in the flywheel cover. After all, there really was a purpose for it being there.

Chev Nut

Excellent solution and frequently used. As long as new registration marks are established it is a very logical fix. The old marks should be painted over or concealed in some manner to prevent confusion by subsequent mechanics/owners.

Rusty Fender

Shame on you. Reminds me of my conversation with a technician at the parts house where I get my bearings. When I specified I wanted sealed bearings he ask what I intended to use them for. I told him axle bearings on a 1925. He advised that the sealed bearing was an inferior bearing to the normal bearing and further advised I could only expect about 50,000 miles under that usage. (If I could only be so lucky).

Anyway, the purpose of the seals was twofold. First, they acted as a lock washer and second they made a seal around the head of the flywheel bolts to prevent oil leaking from the engine penetrating into the clutch housing.

Old216

Why does the 4-cylinder engine come to rest at only two places? Take a look at lil’ Johnny’s comments. I think he covers it quite well.

lil' johnny

For lack of a more technical answer we will go with your explanation.

Bowtie Bob

You have already answered your own question and a good answer at that.

Chev Nut

Combine you answer with that of lil’ johnny and I think the subject has been well covered.



More homework. Now, here is the number that is on the flywheel 344100. When I go to the parts book and find a flywheel for a 1928 (same from 1925-28) I come up with part number 344099. (Look closely at the picture and you can identify the copper washers/seals under each flywheel bolt head.)

Assignment: Do I have the wrong flywheel or is there an explanation?

Nope! - You have the correcto-mundo flywheel !!

As I understand Chevy's numbering system, the number on the flywheel (344100) is a casting / forging number. The part number in the Parts manual (344099) is an "odd" number, one digit below the casting number. I believe that using an "even" number for a casting number and a number one digit less for the part number, was used throughout Chevy's numbering system. <img border="0" alt="" title="" src="graemlins/gift.bmp" />

Bowtie,
You got it almost right. Some casting numbers end in an even number and then the part number is the same. Though not as prevalent others end in either an even or odd number and the casting number has no relation to the part number.
I have not researched to find if any odd numbers are both part and casting numbers but I would not put it past Chevolet trying to confuse us.

I agree that it is the casting number and you do have the right flywheel. But I don't know about the part number always being one number below. I had a 33 Canadian engine and the casting number on it was one number below a 32 manifold.

Food for thought - Chevy's numbering system ("systems", apparently) may have changed depending on who was in charge of Engineering at any particular time. I saw a lot of changes like that happen in the place I worked for 38 years, when management changed. I guess when someone moves into a highy visable position, they have to make SOME kind of change to justify their appointment. "Smoke & mirrors", we used to call it!!

Would like to congratulate all the students as a group for your fine homework project. The confusion exists because a number marked on an item does not provide positive identification. I have always explained the difference as only replacement PARTS have part numbers.

In our last session we took a final look inside the engine, removed all the tools, and blew it out good with an air hose. About time to ’button’ it up.



The pan should be inspected for any deformities and most important the inspection of the oil troughs. If this were a major rebuild, where parts from many sources were combined to assemble the engine, we would make some major tests for rod and trough clearance. This could be accomplished by construction of a “JIG” or by filling the troughs with axle grease, installing the pan with correct gaskets, and turning the crank to send each rod through the troughs. The repair manual refers to these troughs as “small oil pans”. Ideally, the rod will dip into the troughs 1/16 inch to 3/32 inch. As we are reassembling an engine with basically all the original parts we will not make any tests for the “dip”. On the teardown there was no evidence of a problem in this area. We will however, inspect each of the troughs to assure they are firmly affixed at each end and have no visible damage.



I have nothing against gasket sets, but have always preferred to cut all my own gaskets. I usually keep several different gasket sets in stock and use them as patterns if it is not easier to just trace the part from where you intend to use the gasket. If you are not experienced in the proper thickness of various gaskets, then it is better to use the sets.



It is always a challenge to get the pan end gaskets to a) stay in place, or b) fit the pan. The gasket furnished in the kit is too thick to work with. Take a piece of gasket stock approximately ½ the thickness of the piece in the kit. Slice two strips ½ inch by approximately 12 inches. Bend together in the middle, use a very good quick dry glue, glue the two pieces together, place around a coke/beer can and secure with a rubber band. Leave assembled till the glue has set up. Use the same glue to affix the two strips to each end on the bearing caps. Set the pan down on the gaskets and leave till fully set up. In most instances I only glue one side of a gasket. After all we do occasionally make a mistake and have to go back in. I use gasket shellac compound by Indian Head, but any brand will do. Remove the pan, lay each side gasket in place and take a good look at what area it covers, remove the gasket, apply the shellac, then replace the side gasket in place making sure all the holes line up. When the gasket is firmly held in place I use black RTV and place a dollop in each corner where the side gasket meets the bearing shell gasket (ChevyGuru whispering to ChevyChip, “What to hell is a dollop?” ChevyChip whispering to ChevyGuru, “Two or more dabs”. Chevy Guru, “OH!”.) Set the pan back on and start a screw in each corner. The Chevrolet Parts Price List is an invaluable tool. I have the 3 ¼ X 6 inch version dated Apr 1, 1928. Under Oil Pan is listed Round Head Machine Screw ¼”-20X½”. So that is what we will use to secure the pan.



Laying on the side of the engine is the “Special” tool used to install/remove these screws. Note that it has a shield over the bit and is spring loaded. By placing the shield over the screw, pressing down to engage the bit in the screw and then operating like a brace and bit.

After the pan is installed the Gear Cover is installed. Again by looking in the Parts Price List we find that it is secured with Round Head Machine Screw ¼”20X3/8”, ¼”20X7/8” and ¼”20X5/16”. I make the gasket for this application also and glue it to the Gear Cover Plate. As oil sits at the joint at the bottom of the cover you may choose to glue the other side of the gasket also.



Time for more home work.

What is this cover covering and why? Extra bonus points. Find the part number for the cover.

Don't know about that cover. Must be something that appears on these new-fangled '28s that I don't have on my '25. Or else I left it off of my '25, which is definitely possible. I notice lots of other improvements and updates on this '28 job, versus my slightly more primitive '25.

I was pleased to learn that the Teacher uses Indian Head gasket gloop. That's what I've used for years, too.

However, last month when I installed my oil pan, I used BLUE RTV (not the black) at those corners where the crank "humps" meet the flat surface of the pan. And, I'm sorry to say, I inadvertently used 3 dabs, which apparently would equate to 1.5 dollops, of the blue stuff, but it's all on the inside....

Also, I was not able to find a Coors can handy when making the crank hump gaskets as above, but I am happy to report that a Mountain Dew can will work just as well.

That cotter pin device that is not an oil dripper, does it have an official name and part number?

Hi d2d2,

The reason I did not give you full credit on your report card is that you did not also specify that it was for the purpose of keeping the hole open so the oil could "drip".

I don't know the official name for the device. It is already installed in the flywheel under pan both from the factory and if you purchase the pan from the parts department.

Don't worry, you will get additional chances to bring up your grade.

Hi ChevyGuru,

Your quote gives me great concern. I am not a real fan of RTV. I have had some very serious problems using it. Do not EVER use it around any place where it can come in contact with gasoline. Be especially careful with overusing it. As I read your post you allowed a quantity of the RTV to be on the INSIDE. And that of course is where we do NOT want it to be. If a glob of the RTV is allowed to be free in the pan/sump only bad things can happen. The pickup pipe on the '25 engine lies on the bottom of the pan/sump and is UNPROTECTED . Eventually this glob will find the pickup tube and block the entrance. Even if it does not attack the pickup tube, if it is splashed up into any of the 6 reservoirs, it will sink in the oil, and block the drip hole to the bearing.

I will not bore you with details, but I spent several days on the road years ago, with a newly installed oversize gas tank, that RTV had gotten inside of. Blocked the gas pickup and when I switched lines and used the return line as the pickup, eventually it blocked that line. Nothing like removing a full gas tank from a motor home, disassembly and total cleaning. Bad enough in your own garage or shop.

On a National Pre-29 tour at Moab, UT, I experienced low oil pressure and finally no oil pressure in my '25. On teardown it was discovered that a glob of RTV was stuck in the end of the oil pickup tube.

Please do not read anything into this warning on RTV. It has its uses and serves them well if used sparingly and carefully.

It is suggested you place a large fuel strainer "sock" over the intake tube of any 4-cylinder you are rebuilding prior to 1926. Starting with the "in block" oil pump in 1926 a strainer is standard equipment.

Oh, and MERRY CHRISTMAS to all.

Now you have scared me!

I gotta say, though - the dollop was firmly smeared into place at that junction of the crank "hump" gasket, where it meets the flat gasket (all 4 corners). There should not have been any left loose, I smeared it as sort of a back-up film layer over that leak-prone area, no lumps.

But I will consider myself warned and advised, for future applications.