VCCA Home Forums TECHNICAL - GENERAL Radios, Tools, Accessories School is in session (Contd)

I replaced the first one I ever saw when I tore down a 52 PG engine back in the 50's and said" What is this Mickey Mouse thang?" even tho it was in fine shape, I replaced it with a aftermarket aluminum one from a local Speed shop. It was a little noisy, but I was a teenager with a lead foot and didn't mind a little noise ( split manifold and glasspacs). Now I just go with the flow and replace them with new fibre ones. I suppose metal replacements are available somewhere on the swap meet circuit.

The fiber gears were not all that bad.The important thing is their lubrication.Chevrolet constantly tweeked the oil flow to the gears but the passage tended to sludge up-causing the timimg gear To wear. The problem was less when they went to full pressure oiling because the oil flow was better.Fiber gears were used on the 194--230--250 engines right up to the last years that they were produced and they were much more dependable than the chain drives on the V8s in those years.When ever a timing gear goes (you can usually hear it rattle) the oil pasage behind the front mounting plate should always be cleaned out.

Chev Nut good advise, I have a extra block here from a 56 truck that was overhauled in 1988 and threw a rod because the shade-tree didn't line up a rod insert, or got it stopped up and the fiber gear is new, so I guess they are ok,

I have had a 400, a 305 and a 350 long milage engines that had to have the chain and gears replaced on. They are a bear to troubleshoot when they just jump one notch.

Yes its strange.On the Pontiac Iron Duke engine they changed from a timing gear to a chain in the last years of production.The fiber gears were always extreemly noisy in them but seldom went out.When they went to the chain they were not as noisy but had more failures......If you read the introduction info. in 1954 they described a new stronger and quieter timing gear for just the Power Glide engine.the gear has a cast iron inner hub and an aluminum outter gear separated by a synthetic rubber insulator .It was supposed to be stronger & quieter.It never was used in production-sounded like a good idea but???

Cost was prohibitive?? and not more durable? That was about the time Chevrolet radios were really becomeing common so you needed a quiet engine???

Chev Nut,

As a matter of fact, I did not replace the timing gear. Admittedly, it has more backlash than recommended, prior experience tells me it will be okay. When you install a new fiber gear and run it for several hours/miles and inspect it you will find that the “hair” has been worn off and the gear will have approximately as much backlash as I have from using the old gear.

Barring additional questions, we will lay the timing gears to rest.

Time now to assemble the pistons, rods, and rings.

First step is to measure the ring gap. The ideal situation is for the ring to make a perfect continuous circle in the bore to prevent compression from escaping. This is not possible, as the ring will expand when heated. Therefore the ring gap must be established to account for this expansion and not seize when heated. To determine this spacing follow the instructions packaged with the rings. In this case the manufacturer specified a factor of .004” per 1” of bore. Or in our case .004 X 3 11/16 (3.6875)=. 01475 or .015. To measure this ring gap, place the piston, without any rings installed, in the bore. Place a ring on top of the piston and square it away with the bore. Measure the ring gap and assure that it exceeds the .015.



EVERY ring must be measured except the oil control rings.

Next is to hang the piston.



Insure you have identified the front of the piston. This one is clearly marked near the piston pin boss. Inspect the rod and insure that the installed rod will have the piston pin bolt and the open oil hole on the big end facing the cam. Insert the rod into the piston, place the piston pin in place and center the pin and rod.



The last action to the block was the honing of the cylinders. Therefore each bore must be completely cleaned to insure none of the grit is embedded in the cylinder walls. Follow the piston ring manufacturers instruction as to lubrication of the cylinder walls. Perfect Circle recommends the walls be lubricated with light oil before the piston is installed.

Note the instructions as to which side is UP on each ring and install in the appropriate grove on the piston. A ring installation tool is recommended.

Using a ring compressor, install each assembled unit into the holes as marked when the engine block was bored and with the correct pre-fitted rod. It is advisable to rotate the crank at least one revolution as each piston is installed to insure there are no binds. When all units have been installed and the crank turns without binding, install the cotter pins to insure the cap bolts will not loosen.

Ray, I've been following your instructions with interest and agree with all you've taught. Just thought I'd add one small item which was overlooked (unless I missed it): When installing the rings, make sure to stagger the ring gaps from each other. I remember one neophyte dummy mechanic :(

I am at the back of the class so you probably didn't notice my hand up. Anyhow, recently, on the disassembly of my 216, I noticed that the oil ring gaps were almost together, not staggered. Is this not unusual, even for oil rings ?

Your aluminum pistons look great.I see they even have off-set piston pins ( the "big" improvement Chevrolet introduced in 1954 to eleminate piston slap)

Shouldn't the ring gaps be staggered 120°. (12óclock,4´oclock, 8´ oclock).

To check ring gap: On latter Chevy Six cylinders I usually just take both Compression rings for a given cylinder, stack them together with the gap lined up, and shove them ¼ of the way into the cylinder bore using the piston as a plunger. It works real fast cause you are just looking for a ring with the least clearance. (takes 6 "feeler" readings instead of 12 on a Chevy Six).

Ps. Did you micrometer your piston skirts; or do a skirt-to-sidewall clearance with the long feeler gauge?

"Stepping into class here, a walk in..... if you will". An apple to the teacher if I may,......but wait a minute. Reefer Service charges being what they are. The paperwork for it..... being silly. But on the other hand....he would get it in 2 days....... Naaaaa.......it will be the thought that counts and I'll have to leave it at that. I'll repeat myself here, don't understand a single sylable with regard to what has been said thusfare. Sure is interesting though !

Now I need to know what the offset is. Darn, I thought I knew it all! Is the pin actually offset to favour one side ?

Just look close at the front view of the piston.Notice that the pin is left to center.This reduces the force with which the skirt hits the cylinder wall .This is a rather simple answer but the full description with illustrations is in the 1954 Chevrolet Engineering manual.The 1953 Power Glide piston looked exactly like that only the pin was centered,There were a lot of complaints of cold piston slap.Chevrolet insisted that this wouldnt happen when the '53s were new due to the steel struts (which were also used back in the original 28 pistons).Well in the quieter hydralic lifter engine the piston noise could be heard and the "big improvement" in 1954 was the off set pins.That is still used to day on GM engines but piston noise is worse than ever due to the short skirt pistons in use today.Back in 54 we replaced many ofthe 53 pistons with the 54's and also used the standard high limit which were a .001" or so larger.

Hey teach,
Is the offset piston pin the reason that the locating the "front" of the piston is so critical? Thought so! (thumbing nose at Wacky, Macky).

Q&A

Bowtie Bob,

Excellent observation Bob. I did in fact forget to point out the procedure for aligning the gaps in the compression rings. The procedure is to stagger them in any pattern that does not have them all located at the same point on the clock.

Old216,

Yes, it is even more important that the three components of the oil rings are staggered. The two outside rings hold the interior spacer together.

Chev Nut,

I am really pleased with the selection of these pistons for my project for several reasons.

Lil' johnny,

I have no problem with your system of aligning the gaps as you suggested. Good plan. Excellent suggestion of gapping all the rings in one bore in one step for that specific bore. Saves time.

When we bored the block we made very precise measurements of EACH piston and insured that each piston was assigned a bore and the bore honed to the specified clearance for that piston.

DduceMan,

It is very obvious that I should have paid more attention to your comfort in the back of my ”˜28 touring during the week we spent together on the National 4-cylinder tour in Canada. I think you must have gotten too cold. This is the engine from that touring that we are working on.

Old216,

Chev Nut answers your question very ably in the post immediately following your question. An excellent explanation.

Chevy Chip,

Right on. A lot of good it does to have state of the art hardware in your hands if you don’t employ it to the maximum advantage.

Somehow we overlooked the picture of securing the bolts on the big ends of the rods. So here it is.



Thanks for your interest, comments and questions.

Ray,
One of the most common areas of general confusion when rebuilding an engine is the difference in numbers that a mechanic uses, and the numbers that a machinist uses.
Your example of the ring makers .004" per 1 inch of bore is a good example of a confusing specification. A mechanic uses the nominal 3-11/16" for the bore. A machinist uses an actual measurement to the degree of his measuring tools (ten thousanths). Both numbers will give a "ballpark"number for the ring gap due to the "wiggely" spec given by the ring maker.
>>>There sometimes arise problems with precision, significant digits, and especially accuracy when so many numbers get specified and converted that actual "clearances" may drift from factory specs.
>>>Your doing a great job on this project and you really know what your doing!
>>>I just have a tip for the more "novice" engine builders. So many guys have complained of problems like piston slap, piston collapse, oil clearances, etc. that the beginner should use extra caution. For instance measure twice; double check a micrometer reading with a dial caliper to see if your reading the mic' OK; and use stuff like plastigage and feeler gauges on the "finished" engine part to ensure "accuracy". It will keep the quality up, and the blame down.
>>>New parts, old numbers, and a smaller pool of experienced craftsmen make Ray's posting very important for future reference.
>>>Nuff said...keep up the great worK, and thanks for the pictures!!!!

Ray....."NO".....did not at all feel neglected, ( am a rather somber chap anyway ), and did not by any stretch of the imagination get cold back there. It was really neat. Got to "WAVE" at a bunch of strangers all day / week. I did however get a real "wrist workout" on the Banff Downtown Day. LOL......Felt like Prince Phillip or somethi'n. ( honest ).

lil' johnny,

Head lowered and blushing. Thanks for your comments.

Before we progress further I think it would be wise to re-emphasize some points that were made earlier in some of the postings.

In the posting Nov 30, 2002, 00:46 considerable discussion was devoted to the checking, and in some cases remarking, timing gears. It was pointed out that an error existed in the Chevrolet Repair Manual in reference to a figure in the manual. The wrong tooth is marked on the Series-AB figure 42 on page 42. That post also describes how to mark or check a new cam gear if you do not have an OEM gear as a reference to transfer the mark.

Both of these subjects are addressed in the May 28 Chevrolet Service News on page 30. By the use of drawings and text, specific instructions are given on both of these operations.

The same page also describes how to mate the flywheel to the crank. There are 6 holes in the crank and flywheel, which give us too many combinations. This tells how to make the selection. Additionally, this subject will be covered in the next class session.

In a posting elsewhere, in Chevy Chat, some snide remarks were made about a 1928 Chevrolet on ebay that had a side mount. Eat your words as you go to page 42, August 1928 Chevrolet Service News. Question: Does anyone have this complete set-up for sale?



This is the last time we will see the innards, as the next step is to button up. Best we blow out the cavity real well with compressed air and most of all check to see that we have not left any tools inside. (Don’t laugh. I took a door apart on a new car to locate a rattle and found a tool inside from the assembly plant).

Class dismissed.

Take you seats and get out your notebook.

We need to install the flywheel now because it is the right time in the sequence of assembly, and because we can use it to turn the crankshaft much easier. After a good cleaning and inspection it was determined that there were two locations around the ring-gear teeth that were damaged. When a 4-cylinder engine is switched off it comes to rest in either of two locations. It can stop with #1 & #4 pistons up of with #2 & #3 pistons up. When the starter is engaged then one or the other of these locations on the ring-gear meet with the starter Bendix drive gear. That is why we have two specific locations for wear and not uniform wear around the circumference. Ideally, we would replace the ring-gear as this is an easy fix, but they are relatively hard to come by. Therefore, we will try to improve the worn locations. Either a hand file, or if you are proficient with an angle grinder and thin stone, can be used to smooth down the damaged teeth. The idea is to remove any sharp projections and blunt spots that prohibit the gears from meshing smoothly. Caution must be exercised to prevent too much material from being removed.



While the flywheel is off and cleaned up is also a good time to examine some other characteristics. Looking at the markings we note that the casting number is 344100. The casting date is K117, or November 11, 1927, and there is the official logo of the Chevrolet Bow Tie. This is consistent with the dates on the block, head, and seat-side data plate. The company that did the casting was GMRL (Yield to KK to enlighten us on that one).

As mentioned in a previous post the flywheel can be mounted in any of 6 different positions. Any of which would not affect the running of the engine, however, there is a correct position out of the 6. To find this location the support must be assembled to the back of the block. In this support is a window, visible from the front of the engine, equipped with a pointer.



The large hole on the right is the opening for the starter. Across from that hole is the window with the pointer. Insure that the crankshaft is located with the #1 piston at TDC and by looking inside at the cam lobes for number 1 piston, insure that both valves would be closed (compression stroke). Now very carefully place the flywheel on the end of the crankshaft. While looking in the viewing window on the support, turn the flywheel until the pointer is aliened on the U I C mark (Upper/Center) on the flywheel. You may install the flywheel at this position, or if not ready, mark the location with chalk so you know where it goes when you do install it. The chalk line on my flywheel indicates this location. Notice that the line does NOT go through the position marked U I C on the flywheel and that is the point to be made.



Now you can see where the U I C line is located. To the right of this line is the 25-degree mark. Now that the location of the flywheel has been established and installed these two marks are of no further concern at this stage of assembly, but will be of major importance later as we install the distributor and perform final timing.

When final installation of the flywheel is made, insure that each bolt has the special flywheel bolt gasket, part #346800, installed on the BOLT end. This is a special copper washer.

The flywheel under pan is the next item to be assembled. It is held with a single bolt screwed into the support on each side. Insure that the under pan still has the large cotter pin installed in the drain hole.



It has been brought to my attention that the students are getting by with very little study and NO homework. Therefore, here is your homework assignment for the next class. In the above picture is a cotter key installed in the drain hole. As long as I can remember sliding under a Chevrolet I have observed that cotter key. It is even pictured in the parts book preinstalled in the under pan. Your assignment:

What is the purpose of this cotter key and state your reference?

Class dismissed.

It looks like an oil dripper.

Oh! Oh! Teacher!!! (hand waving furiously) - The cotter key, I believe, is to ensure that the hole doesn't get plugged up and allow oil to build up in the housing, which would comtaminate the clutch plate. At least, that's what I was told a long time ago by an old mechanic.

Ok, If you think I am not paying attention, You were wrong. It does not make any difference where the camshaft is oriented in order that the flywheel is installed correctly, in fact the camshaft does not even need to be in the engine in order to aline the flywheel with the crank, UC is Uc whether the engine is on intake , or what, number one piston must be at the uppermost position in the cylinder. The timeing mark is in the window any time the # 1 piston is at upper center.

I do,however, agree with Rays instructions for this reason, you need to get in the habit of having all your ducks in a row!

Oops....

I took that cotter key out, and tossed it!

I'm gonna flunk for sure.......

MrMack,

Just wanted to give you some time to think about your post before I comment.

Hint: You must follow the discussion in sequence.

AntiqueMechanic...Would it be possible to bolt the fly wheel in a different location on the crank and restamp the timing marks?This would rotate the worn teeth to an unused location.