Valve Adjustment Details Pontiac 400 - Pontiac GTO Forum
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post #1 of 12 (permalink) Old 04-19-2018, 06:16 PM Thread Starter
 
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Valve Adjustment Details Pontiac 400

Patient: 1967 GTO Convertible with 400ci, hydraulic flat tappet lifters (assuming this because car is stock) & TH400

At idle the vacuum swings quickly between 10 and 15. At higher RPMs it is more stable. I'm also chasing a rattle that I thought was in the distributor but now I'm sure it is not. It is pobably a valve rattling.

Who has instructions on how to correctly adjust the valves? I understand the process but need the details.

Thank you,
Andrew

Are these good instructions? I printed this for review.
http://www.pontiacstreetperformance....p/rockers.html
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post #2 of 12 (permalink) Old 04-20-2018, 12:29 AM
 
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The link you added does not work or open
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post #3 of 12 (permalink) Old 04-20-2018, 06:57 AM Thread Starter
 
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It worked for me this morning.

Here is the text from the link:

Whether you have decided to stay with the stock type stamped rocker arms or Competition Cams Magnum Rollers Rockers as pictured here, or something far more exotic, you will need to adjust valve lash. Torquing the adjusting nut per the old Chilton's to 20-25 ft pounds won't work on any heads that have been milled. This is especially true with the high lift cams of today. The valve train needs to be adjustable. Some form of lock nut must be used. I prefer Mr. Gasket's poly lock nuts.

In the past, I've adjusted hydraulic lifters with the engine running, backing off the nut until the rocker clattered, and then turning the nut slowly until the noise dissipated. That process sure works but is just too messy for me. No matter how hard I tried, oil got past the restrictor clips, and my fabricated valve cover oil catchers--oil went everywhere. Nobody should endure that nonsense. I 've found that adjusting valve lash can really be performed while the engine is cold. The adjustment, when done accurately will preclude further adjustment with the engine running.

An important point to remember in adjusting valve lash is that the adjustment must be performed while the lifter is sitting on the base circle of the cam lobe you will adjust. Below is the technique I use. The sequence works on all V8's with the Pontiac firing order--

Firing Order
The firing order on all Pontiac motors is 1-8-4-3-6-5-7-2. The best place to start the adjustment process is to begin with the #1 cylinder. Whether you are building a new motor, swapping in a cam, or adding other upper valve train components, start with the #1 cylinder. Silly as this may seem to some, the #1 cylinder is on the driver's side cylinder bank. The driver's side has the odd number cylinders: 1-3-5-7. The passenger side has the even numbered cylinders: 2-4-6-8. [Number's 7 and 8 are closest to the firewall. (There will be a test on this later.)]

Identify Intake and Exhaust Valves/ Springs
You can't adjust anything until you know where everything is located. This sounds really basic, but you must accurately identify each valve. If you must, use a small piece of masking tape and stick it on the head with each corresponding valve identified. For example, 1X and 1I. Believe me, doing this will save some time. Preparation makes things go smoothly. Besides, who like to do things over. You won't do the wrong valve doing it this way.

Locate TDC on #1 Cylinder
Numerous valves will be adjusted at one time in this process. You must locate top dead center (TDC) of #1 cylinder. I prefer turning the crank by hand because I know exactly where TDC is on my motor. Remove all the plugs if you haven't already done so; it makes life easier on you or your starter. Locate TDC on #1 by locating the '0' on the timing tab with the harmonic balancer line. You can determine whether it's really the #1 cylinder a couple of ways. One way is too look at the hydraulic lifters. If the hydraulic lifters are down and level you're on # 1 TDC. Another way is the old "thumb in the dike" method. Place your thumb in the number one spark plug hole while the engine is being turned by the starter. When TDC is near, your finger will be pushed out by the compression. ( I know this is basic stuff.) When that happens, align the harmonic balancer that fraction or so to get TDC. Remember, the lifters must be on the base circle of the cam lobe for the adjustment to work.

Adjustment Begins
With the engine at TDC on #1 cylinder you can properly adjust the following valves after lubricating the rocker ball, valve stem, and pushrod contact point:

INTAKE 1 2 5 7
EXHAUST 1 3 4 8

The Adjustment Procedure
Remove all of the slack out of the pushrod and rocker arm by slowly tightening the adjusting nut. You must use your sense of touch here. Lightly turn the rod with your fingers while tightening the nut. As you do so, you will begin to feel resistance. When the resistance reaches a point where it requires more grip (torque) to turn the rod, stop! At this point you have removed all of the play out of the pushrod and are at "zero lash." Now you may make the final adjustment. With wrench or socket in hand, tighten the nut 180 degrees (a 1/2 turn). If you are using poly lock nuts, tighten the set screw against the rocker arm stud after the 1/2 turn. Be sure the adjusting nut does not move. (Hold it stationary with a wrench while you use the allen wrench to tighten the set screw.) Thereafter, for added insurance, add a tad more turn to the poly lock nut...just a tad. This will set the screw tightly against the stud so it won't back off.

Do all intakes valves (1-2-5-7) first and then proceed with the exhaust valves (1-3-4-8). Since you are using "feel" take your time. Run through each valve twice, if you must, before proceeding to the next group of valves.

Locate TDC on #6 Cylinder
The next step is to rotate the engine 360 crank degrees to get the #6 piston at TDC. Use the same technique for locating TDC on #1 .

Adjustment Resumes
With the engine at TDC on #6 cylinder you can adjust the following valves after lubricating the rocker ball, valve stem, and pushrod contact point:

INTAKE 3 4 6 8
EXHAUST 2 5 6 7

Adjustment Procedure Reiterated
Remove all of the slack out of the pushrod and rocker arms by slowly tightening the adjusting nut. You must use your sense of touch here. Lightly turn the rod with your fingers while tightening the nut. As you do so, you will begin to feel resistance. When the resistance makes it difficult for you to turn the rod without more grip (torque), stop! At this point you have removed all of the play out of the pushrod. You're now at "zero lash." Now make the final adjustment. With wrench or socket in hand, tighten the nut 180 degrees (a 1/2 turn). If you are using poly lock nuts, tighten the set screw against the rocker arm stud. Be sure the adjusting nut does not move. Hold it stationary with a wrench while you use the allen wrench to tighten the set screw.

Do intake valves (3-4-6-8) first then proceed with the exhaust valves (2-5-6-7). Since you are using "feel" take your time. Run through each valve twice to be certain everything looks and "feels" right to you.

Final Step
Re-lubricate the rocker assembly before installing the valve covers. If you've taken your time to be accurate no further adjustment is necessary.
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post #4 of 12 (permalink) Old 04-20-2018, 08:28 AM
 
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This should help you, notice post #4 written by a noted Pontiac engine builder.

VALVE ADJUSTMENT - PY Online Forums

Ask more questions if any is unclear.
Best of luck.
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post #5 of 12 (permalink) Old 04-20-2018, 10:48 AM
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That is it, from front to back 1,3,5 and 7 are on the driver's side 2,4,6 and 8 are on the passenger side in that order.
Look on the intake, the numbers are there and you can follow them down to the in and ex valves.
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post #6 of 12 (permalink) Old 04-20-2018, 11:04 AM
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link to a head, CTRL and + will blow it up.
You can see the two valves in the center of the head as well as the ones on each end are the exhaust, the others are the intake.

https://www.google.com/search?q=inta...4aATxujEZIM-M:
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post #7 of 12 (permalink) Old 04-20-2018, 06:33 PM
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Please don't miss the point that unless you have some sort of locking/poly-lock rocker nuts, Pontiac factory valve trains (using the bottleneck studs) are *not* adjustable. If you try to use any of these procedures with the factory rocker nuts, they -will- come loose and you won't be happy with "what happens next".

Bear

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post #8 of 12 (permalink) Old 04-21-2018, 03:44 PM Thread Starter
 
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Quote:
Originally Posted by BearGFR View Post
Please don't miss the point that unless you have some sort of locking/poly-lock rocker nuts, Pontiac factory valve trains (using the bottleneck studs) are *not* adjustable. If you try to use any of these procedures with the factory rocker nuts, they -will- come loose and you won't be happy with "what happens next".

Bear
Okay, it seems this is factory valve train. If I back off the rocker nut it then spins freely on the threads. There seems to be no locking mechanism. There seems to be no adjustment except all are to be tightened to the shoulder. I'll attach photos. The one pushrod I removed is 9.125" long.

If true then I should just make sure all the nuts are tight with the valve closed and reinstall the valve covers with fresh gaskets. Is there a torque spec for these rocker arm nuts?

Secondly the driver's side has a sheet metal shield above the rockers below the valve covers. None on the passenger side. Is this correct? A photo of this is attached.

Thirdly, I purchased new cork gaskets. What is my method of installation? Some gasket sealant or install dry?
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Last edited by Andrew69; 04-23-2018 at 08:39 PM.
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post #9 of 12 (permalink) Old 04-21-2018, 04:47 PM
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Quote:
Originally Posted by Andrew69 View Post
If true then I should just make sure all the nuts are tight with the valve closed and reinstall the valve covers with fresh gaskets. Is there a torque spec for these rocker arm nuts?
Yepper - that would be 20 lb. ft.

Quote:
Secondly the driver's side has a sheet metal shield above the rockers below the valve covers. None on the passenger side. Is this correct? A photo of this is attached.
That's an oil dripper - intended to help get oil to the rockers. Not all engines had them depending on which valve covers were used, but my 69 originally had them on both sides. Sounds like you've got one missing.

Quote:
Thirdly, I purchased new cork gaskets. What is my method of installation? Some gasket sealant or install dry?
This is a 'whatever works for you' proposition. I personally tend to use sealant on just one side of the gasket to glue it to one of the surfaces (like the valve cover for instance) and leave the other side dry so that I can R&R the valve covers without (hopefully) having to replace the gaskets every time. However I'm running a solid roller valve train in my car so I need to adjust valve lash every so often. Just make sure the gaskets don't get squeezed out of place and don't tighten the bolts so much that you dimple the valve covers. That tends to cause leaks. Adding some thicker metal spacers under the bolts to spread the load out helps too.

Bear

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post #10 of 12 (permalink) Old 04-21-2018, 05:05 PM
 
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The shields are "oil drippers" which capture the oil splashed by the rocker arms and directs it to "drip" back into the rocker arm to aid in lubricating the rocker arm ball. You are missing one or someone left it off. Ebay typically has these. The other, and later method is the valve covers will have "oil drippers" spot welded to the tops and serve the same purpose. They will look like little fingers protruding from the top of the valve cover.

Your valve train is factory screw-in "bottle neck" studs - a 7/16" base tapering up to a 3/8" neck to which the rocker arm nut fits. Your rocker arm nuts must be matching Pontiac nuts as they have a matching shoulder that fits the bottle neck taper. If not, and they are aftermarket or Chevy replacements, they can back off. With what you have, they simply get torqued down to 20-25 ft pounds, no adjustment. Get both rockers at the point where the valves are closed, then torque. You also want to make sure that your rocker arm balls have the small oil grooves cut into them for best oiling. Some rocker arm balls are perfectly smooth and oil cannot get under them as well to ensure a good supply of oil to the rocker arm cup to prevent premature wear and excessive heat at higher RPM's. Can't quite tell from your pics.

Here is the problem, if you (or someone else) has ever done any work to the heads, ie milled them down, your pushrods could be too long, but not always. What many of us do is to remove the factory bottle neck studs and replace them with the better and stronger ARP brand Big Block Chevy rocker arm studs. They are 7/16" all the way and not necked down to 3/8". Then you use the 7/16" poly locks to make your valve train adjustable, rather than the factory non-adjustable/torque method. This allows for some slight changes in rocker arm geometry due to light milling of the heads and/or "zero lashing" your lifters for best performance and pre-load. You may not be able to use the "oil drippers" as the poly locks may be to tall and hit. Oil drippers are not a big deal in my book if you have the grooved rocker arm balls - which is my opinion on this. If you want, you can get the factory chrome valve covers with the oil drippers spot welded onto them. If you plan on running high RPM's for extended periods of time, have a high lift cam, or use oil restrictors in the lifter galley, then I might do the oil drippers.

If you want to keep the factory set-up, you might want to test exactly where your rocker arm strikes the top of the valve stem. It has to be in the middle of the stem, not more on either outside edge of the valve stem. You have to apply/mark (like a sharpie marker/white paint) the top of the valve stem and then cycle the engine so the rocker arm rubs/wears the marker off the top of the valve stem to get this pattern. Very easy to do and just try it with one rocker arm. This will tell you if you have any issues with rocker arm geometry such as pushrods are not the correct length.

Cork valve cover gaskets don't need any sealer. Just put 'em on and don't over tighten them and crush the valve cover or gasket.
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