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

Teacher, from the kid down under, i was taught by a previous teacher from another school to never reuse the Old head bolts, if new ones are easily obtainable.(like you have done on your motor)
Step (1) starting in a clockwise direction from the from the front of the cylinder head, lightly nip the bolts and work in an ever deminishing circle. (ie) from the outside edge to the inside bolts.
Step (2) set the tension wrench for 30ft pounds, and repeat step1.
Step (3) seset tension wrench to 40ft pounds.
and repeat step1.
Step (4) reset t/w to 45ft pounds, and repeat step1
Step (5) reset t/w to 50ft pounds, and repeat step1
Step (6) reset t/w to 55ft pounds, and repeat step1
Step (7) reset t/w to 60ft pounds and repeat step1.
Step (8) check work again, leave wrench at 60ft pounds and repeat step1 and recheck all bolts.
Step (9) Recheck again after finishing assembling motor and before you are ready to fire up the engine.
Step (10) Start the engine and let warm up to running temperature, stop the engine and retension at 60ft pounds again repeating step 1.

The workshop manual however prefers the head bolts tensioning pattern, front to rear in diagonal opposites, and reverse the process on the inner 4 bolts, see pg 14 of the manual.


As a note, i manufacture head studs with 1/2" x 20 tpi unf thread on the top of the stud and 1/2" x 12 on the base of the stud on all of my engines this gives a much more even tension when pulling the head down.

I basically agree with ozjim but would add a bit. When installing head bolts first lubricate the threads with a bit of oil. If the bolts penetrate into the water jacket then add a sealer like Permatex 33 designed for the job. Also check for straight threads without nicks, burrs or other deformations. If the threads are not regular and even don't use the bolt. Check the length of the threads with a gage if there is any doubt. When tightening the bolts always back off about a 1/4 turn then tighten to torque desired. Then back off 1/4 turn and re torque. Note the position of the wrench when torqued the first time and second. If they differ by more than a few degrees then repeat the loosening and tightening. What you are doing is mating the threads on the bolt and block giving more of a complete contact. It eliminates loosening of the bolts during operation and most retorquing.

Also make sure that both the top of the block, gasket and the head are flat and clean. It is suprising how small a piece of dirt can cause a leak or cracked head if in a critical place.

I believe it makes more sense to ignore the Repair Manual in this one specific situation, and tighten in an alternating "X" pattern starting with the INNER bolts, then the outer bolts. It defies everything I have ever learned or believed to tighten starting with the outer bolts, and work inward.

When reusing the old bolts, a wise man told me not to exceed 50 Ft Lbs normally, maybe up yo 55 if absolutely needed to seal. I would also take the extra time to torque down in 5 ft. lb. increments, not 10.

I also like the copper spray gasket sealer, given the low compression, and the likelihood of leaks.

Old216 ,

The only head gasket that can be reused are the metal clad type which may be steel or copper. The reproduction composite gaskets are not worth the shipping charge. I would much rather reuse a good gasket that risk a re-do on a job by using the composite.

Page 13, in the Series AA-AB Repair Manual effective Feb 1st, 1928, gives instructions for reusing the head gasket and also describes the use of grease as a sealer. Other repair manuals in my library contain similar instructions on the subject.

Ozjim ,

I do not have a problem with your solution to the torque settings nor the method employed. I just find it interesting that Chevrolet started on the outside (ends) and worked into the middle bolts. I have never seen the torque specifications printed in any of the old service manuals. If it is there I would appreciate someone directing me to it.

I know several members who work on the 4-cylinder engines and use the studs as you mention. As they are building race engines I can see the need for the studs. In doing a restoration with the studs it leaves the stud sticking up with a nut, which is easily seen on the driver’s side. If you were producing the studs it would be just as easy to make replacement HEAD BOLTS. The markings on the head bolt would give away the fact that it was a replacement head bolt, but would not be as obvious as the stud.

ChevyChip ,

Very good input on the technique of how to torque the bolts. Also your comments on cleanliness are very timely. Assembly time is when we wipe, blow, inspect, and clean again. Good points.

ChevyGuru ,

Your point on the procedure is well taken. After the job is completed it would be very difficult if not impossible to find which method a mechanic used. Again, if you had a failure I don’t know how you would make the determination that it was caused by the procedure.

Although not desirable, reusing the head bolts is a common practice. I have done it for years and never experienced a problem. As you indicated, I drop the final torque figures down some and am very conscious of the feel when tightening the bolts. You can easily feel a bolt stretch and know to stop.

If we could get ozjim to make head bolts for us we would use them.

I have had extremely good luck with the copper spray sealant on head gaskets and any other place I need to make a good seal.



To compensate for worn valve stems and guides, Chevrolet provided valves with oversize stems. The heads did not originally have guides installed. The hole bored through the head was the guide. Years ago when these special valves were available that was an acceptable solution. The accepted solution now is to install valve guides and use standard valves. Guides can be knurled once and if worn out can easily be replaced again. From the picture it is obvious that this head has had guides installed. Notice also that the boss is split on one of these installations. This should not pose a problem and will be used as you see it.

HOMEWORK :

At what point is a valve stem or guide worn out?

I've always used the rule that if there's any perceptable side play, they should be replaced. Probably OK to use them with .002" - .003" side play (wear).

-Bob

The 1928 engine was way ahead of its time.The cast -in- heads guides reappeared in 1955 on the V-8s.Oversized valves were also the repair option.

This is a tough one as there is nothing definitive written on the subject as far as I know. Therefore, let’s run this thing through the computer and see what comes up.

We start with the exhaust valve. On the POWER stroke the valve is closed so no problem. On the EXHAUST stroke the valve is open. If there is extreme wear in either the guide or stem or both some exhaust gas will be discharged along side the valve stem. Not a big problem, perhaps some unwanted noise. On the SUCTION stroke the valve is closed and again no problem. On the COMPRESSION stroke the valve is still closed and again no problem.

Now for the intake valve. On the POWER stroke the valve is closed and no problem. On the EXHAUST stroke valve is still closed and no problem. On the SUCTION stroke the valve is open. Again assuming considerable wear air could be drawn down the valve guide to mix with the incoming charge from the intake manifold. This would dilute the charge and reduce power, and the lean mixture could cause overheating. On the COMPRESSION stroke the valve is closed and again no problems.

So it would appear that the only time we could have a problem with worn guides/stems would be with the intake valves. In my opinion this would require considerable wear to pose a problem. As to an exact measurement, I don’t have one. It just doesn’t appear to be a big problem. However, if the valves are to be ground as I have done on this job, the 4 best fitting valves were designated as intake valves and fitted to that position. The worst 4 were designated as exhaust and placed there. Then, all valves were ground to fit the assigned hole.




On the left is the face of one rocker that is as removed from the engine. The mark you see is the wear pattern. Let’s assume for the sake of discussion that the wear mark is in fact .010 inches deep. This valve would be noisy and we may decide to gage it and readjust. Assuming that we wanted to set this valve to a value of .010 inches and place the flat feeler gage between the top of the valve and the end of the valve stem. We make this adjustment and to our amazement the valve is now much more noisier. Why, because the combined value of the assumed correct setting and the addition gouge in the lifter has in fact become an actual .020 setting. The point of this discussion is to point out the necessity of grinding the rocker arm faces when a head is rebuilt. The rocker arm face on the right has been ground so that now a feeler gage placed under the arm and on top of the stem would result in an actual setting of .010.

Hey teach, hey teach?
Kid in back takes finger from nose to raise hand up.

Teach, My grandpop taught me different. He said that if a valve guide gets too worn then it is more likely to have carbon build up on the valve stem. And the guide tends to wear unevenly which makes an oblong hole. When the valve stem with carbon on it moves up and down and rotates a teeny bit or cocks a little in the guide it will stick. Then something bends or breaks. When that happens it ruins your day.

Chip, I will have to agree with your grand pa a little.I believe that a loose intake guide will lead to carbon formation on the valve stem.This would be caused by excessive oil running down the stem, causing valve sticking.The only thing is this can't or won't happen intil 1929.In the later years )Modern) its found best to have guides dry of oil.Guess it all 4s would natrually run dry.

Gene,
I have found carbon build up on the valve stems for both intake and exhaust valves. Most of the time it is the exhaust valves that has the hard tan deposits and they are limited to the head area. But I have seen it creap up the stem if the guides are worn. I recently took a two '31 heads apart and both intake and exhaust valves were stuck. There was carbon build up on stems of both. Now I realize the sixes had oil fed to the valve train and likely more chance of carbonization of oil on the stems. But oiling of the four bangers will put some oil on the valve stems. That said I personally feel that the majority of the carbon comes from the combustion chamber and not the oil on the head.

Comments by ChevyChip and Chev Nut are so noted. However, the teacher will stick by the comments in my previous post. Although possible, I have never heard of a 4-cylinder valve sticking which resulted in a bent pushrod or broken rocker arm. The worst case scenario is for a piece of carbon to lodge between the lip of the valve and the valve seat. This would hold the valve open and cause the valve to be ’burned’.

In defense of ChevyChip and Chev Nut , there comments are pertinent to the 6-cylinder and later engines. The major difference is the later engines are submitted to an oil environment. In fact we must use valve stem seals to prevent the oil from entering the engine by way of the valve guides.

Back to the assembly of the head. In the following picture note the felt rings on the top of the pushrods and under the rocker arms.



If there is a question about these felt rings, rest at ease. They are part number 327647 and are in fact OE. With the valve cover off, each of these rings are oiled with engine oil. Each rocker arm has an oil hole located over the shaft and this position must be oiled also. Before replacing the valve cover a felt pad is saturated in engine oil and placed over the length of the rocker arm shafts. The part number of the pad is 345468. And yes, there are valve cover gaskets, two of them, part number 348561. They are “L” shaped and placed at each end. While on the valve cover, note that it has 4 small holes, two at each end. These holes match up with channels on the underside of the valve cover. The purpose of the holes is to allow oiling of the felt pad without removing the valve cover.




I cringe at posting the above picture as it is intended to show the engine color. Depending upon many variables each of you will probably see a different color, but the correct engine color is “olive-green”.




In preparation to adjusting the valves we must move the flywheel into position. This is the view we see looking through the cutout provided and the marking arrow. Next class will cover the procedure for initial valve adjustment.




Note the two major depressions in the head. One on each end with 4 valves and associated valve springs and rocker arms. These depressions are the subject of your home work.

HOMEWORK: How much and what type lubrication is placed in these two depressions .

The side cover view shows a very nice green color on my screen but the next two, because of being shot close up?? are 6 cyl. gray.

I'll be bold, and answer the Homework Question-

NONE!

You have already outlined all the top-end oiling points in the text above.

According to the August 1927 CSN "these pockets are filled on every new car before delivery" with engine oil.

What is the reason for them to be filled with oil?...looks as if it would serve no purpose :confused: :confused: :confused:

my guess is that, upon initial start up after it left the factory, the pockets full of oil would provide a splash of oil to all of the rocker contact points and refresh the felt pads, until the regular oil came up to pressure?..

epi

Bt the "regular" oil dosen't get up there-the rocker arms are oiled with an oil can by the the owner-

chevgene,

uh, that's probably why your forum number is 252 and mine is 1723... :)

my next guess is that "I guess I don't know"...

epi

Chevrolet- Don't feel bad.When I made an earlier post in this thread about oil causing carbon on the valve stems on a 4 cyl. it was necessary for me to erase what I wrote and reword it.We just have 6 cylinder minds.

There is no forced oil to the head of the 28 engine.
As far as the "wells" around the valve guides, maybe there to catch oil run off from the felt pad. I still cannot get use to the head bolts. Original bolt have a higher head and no top markings. Did we ever find out what the one contraption is in place of the headbolt?

About the two holes to oil the felt pad without taking off the valve cover!!!! I have a hard time believing that one. First those holes are very small. It would take days. Also, the oil would not be distributed evenly over the surface of the felt pad that is on top of the rocker arms. I am open to dialogue.

later
mromano

Perhaps the way to attack this series of Q&A is to start at the end and work backward.

mromano

First, you are still concerned about the head bolts. The head bolts that I used came with the engine. They are a very good quality bolt obviously made by either the prior engine rebuilder or by a machinist for his use. That is why you see the shallow head and with visible markings. The threads were cut to match the original TPI. Perhaps I confused the students by putting the information on the odd head bolt in a different thread Head Bolt

Lastly, you have doubts about the oiling of the felt pad over the rocker arms.



There are a total of 4 holes provided to replenish the oil in the felt pad. Remember, that on assembly, the pad is saturated with engine oil before being placed under the valve cover. The holes are provided so additional oil can be placed on the pad without removing the cover.



If oil is placed in the 4 holes on the top it will be discharged below at each point I have marked with the chalk arrow. This would provide very good coverage of the felt pad.

Now for the homework assignment. What type of lubricant if any is to be placed in the two depressions?



This is a very interesting instruction located in the August 1927 CSN on page 31. This instruction says ”˜filled’ not just replenish the oil.



The bosses that the valves operate in are equal to if not higher than the surrounding area. For any oil to get to the valve stems it would have to be splashed(?) by the valve springs. I would think that if the valves were squeaking a shot from the on board oil can would be sufficient.



Every vehicle delivered by the dealer to the original owner came with an envelope that contained the owner’s manual and a lubrication chart. This chart was the same as contained in the center of the owner’s manual except it was 18 ½ X 24 inches. This chart was to be placed on the garage wall as a reference for the owner. I have several of these charts, many different owners manuals, and repair manuals for many different years. I have combed every reference I own looking for instructions about servicing the oil in these two depressions. Results: NONE , other than the small notice in the Aug ’27 CSN.

This forum is still open for your comments, with references, on this puzzle.

Just one comment for Mromano, there is a oil can and holder that goes on the firewall so that motor oil can be squirted into the four holes in the valve cover, every few hundred miles.

Chevygene: I liked your class on the flywheel last December. But, what is the answer on the cotter key. Is it so that the oil doesn't build up, and it keeps it cleaned out?

Also, I didn't see the answer to the repositioning of the flywheel to avoid the bad areas. Can this be done? I have a flywheel on a 6-cylinder engine, and it has three worn areas. Please help me. Thanks, :confused:

Concerning - Oil in the valve pockets
I was reading Jim Farris copy of Chevrolet Sales Speeder for October 1922 at the San Diego Swapmeet this pass weekend, when I spotted the notice that the factory was now adding oil in the valve pockets. The reason mentioned was to prevent loss of power caused by sticky valves. It claimed that with the tight clearance between the stem and the valve bore in head on a new 'motor' that the valves could stick during the break-in period if the engine got hot. Therefore the factory would add the oil in the valve pockets so some splash oil would lube the valve stems. This fact was not mentioned in the Owners Instruction Book or the Lube Charts because after break end period it would not be required to maintain oil in these pockets.

KenK

L6farmer@aol.com : The answer to the cotter key question was answered by MrMack on 12/17 @ 07:30am. His answer is printed below:

- Bob