Valve adjustment - Vintage Mustang Forums

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post #1 of 34 (permalink) Old 05-10-2017, 05:36 PM Thread Starter
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Valve adjustment

I think the valves on my 302 on my 69 Mustang needs some adjustment. I'm going to attempt it this weekend and I'm just looking for some tips if you guys have any. I'm trying to research it more before trying something like this.

I'm not sure if they are solid lifters or hydraulic. What's the sure fire way to tell? If it's a stock engine and heads would it more than likely have solid lifters?

I bought a feeler gauge and some new head gaskets. I know you're suppose to find top dead center for adjusting. Assuming it's solid lifters, what lash should I set it at? I have no idea what cam it is. Should I see on average what all the valves are at and use that number?

I think one of the cylinders might be a little off. The engine seems to shake or jolt every few seconds or so. The vacuum needle at idle shakes back and forth fast in a small range.

Any help would be appreciated or links to videos and articles would be awesome!
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post #2 of 34 (permalink) Old 05-10-2017, 07:43 PM
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Tongue valves & lifters

69, if your engine is stock, you have hydraulic lifters, and rockers that are not adjustable. Before you do anything, how about a wet and dry compression test and tell us what are your results ? LSG
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post #3 of 34 (permalink) Old 05-10-2017, 09:07 PM
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The only 302 which had solid lifters from the factory was the Boss 302. And while many people believe they have a Boss 302 in their car, this is almost NEVER the case. Thus, your lifters are hydraulic and not solid.

Your rocker arms are also positive stop which means they cannot be adjusted.

Not sure why you bought new head gaskets? I get why you bought a feeler gauge, but since you don't have solid lifters you won't need it.

As LSG suggested, a compression test is a good idea. You may also have a vacuum leak, but the possibilities are many.

Are the spark plugs in good shape? Are the spark plug wires, distributor cap and rotor in good shape? If you're running points, are those in good shape? On a classic car, all these things make a HUGE difference in how the engine runs. If there's any doubt as to how old these parts are, replace them all with quality examples. Buy Autolite spark plugs. Buy the best plug wires available from NAPA, plug wires from a specialty vendor like NPD, or performance wires like Taylor. Don't buy Chinese plug wires from O'Reilly, Auto Zone or Advance Auto. They arc and spark instead of the plugs.

How is the carburetor? If in doubt, rebuild it. It's a very simple job and a quality rebuild kit is inexpensive.

Unfortunately, it's nearly impossible to troubleshoot engine problems on a classic car unless the spark plugs, plug wires, distributor cap, rotor and vacuum advance are all in good condition. Again, if there's any doubt, replace them with quality examples.

Post up some pictures of your engine. There may be something glaringly obvious going on which we can spot, but with which you are simply not familiar.

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post #4 of 34 (permalink) Old 05-11-2017, 10:22 AM Thread Starter
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Originally Posted by Klutch View Post
The only 302 which had solid lifters from the factory was the Boss 302. And while many people believe they have a Boss 302 in their car, this is almost NEVER the case. Thus, your lifters are hydraulic and not solid.

Your rocker arms are also positive stop which means they cannot be adjusted.

Not sure why you bought new head gaskets? I get why you bought a feeler gauge, but since you don't have solid lifters you won't need it.

As LSG suggested, a compression test is a good idea. You may also have a vacuum leak, but the possibilities are many.

Are the spark plugs in good shape? Are the spark plug wires, distributor cap and rotor in good shape? If you're running points, are those in good shape? On a classic car, all these things make a HUGE difference in how the engine runs. If there's any doubt as to how old these parts are, replace them all with quality examples. Buy Autolite spark plugs. Buy the best plug wires available from NAPA, plug wires from a specialty vendor like NPD, or performance wires like Taylor. Don't buy Chinese plug wires from O'Reilly, Auto Zone or Advance Auto. They arc and spark instead of the plugs.

How is the carburetor? If in doubt, rebuild it. It's a very simple job and a quality rebuild kit is inexpensive.

Unfortunately, it's nearly impossible to troubleshoot engine problems on a classic car unless the spark plugs, plug wires, distributor cap, rotor and vacuum advance are all in good condition. Again, if there's any doubt, replace them with quality examples.

Post up some pictures of your engine. There may be something glaringly obvious going on which we can spot, but with which you are simply not familiar.
Good to know about the rockers. Thanks for the help! I'll probably go ahead and replace the wires, cap and rotor and see if it makes any difference. I'll be getting the stuff to do a compression test as well and post those results.
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post #5 of 34 (permalink) Old 05-11-2017, 10:52 AM
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What is the vac reading? You stated, it drifts back and forwards. Also, If the wires are old, very old, then replace. However, if they appear perform a visual) in good shape, no cracks etc., then do an OHM check, before you replace.
A good 'ole simple tuneup is a good start........

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post #6 of 34 (permalink) Old 05-11-2017, 11:29 AM Thread Starter
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What is the vac reading? You stated, it drifts back and forwards. Also, If the wires are old, very old, then replace. However, if they appear perform a visual) in good shape, no cracks etc., then do an OHM check, before you replace.
A good 'ole simple tuneup is a good start........
In drive, the car is about at 700-800 rpm in drive with about 13-14 vacuum. The needle is very bouncy though. It stays within a 2 pt range in the bounce but it's not steady at all. I tried turning in the screws on the carb all the way and the engine died. If I turn down the idle lower than that the engine acts like it wants to die. I've sprayed carb cleaner everywhere and couldn't find a leak.

The wires don't look too awful. You can still read all the writing and everything on there and they don't appear dry or rotted.

How do you do an OHM check? I have a voltmeter. Thanks for helping!
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post #7 of 34 (permalink) Old 05-11-2017, 12:01 PM
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Originally Posted by 69MustangCoupe View Post
In drive, the car is about at 700-800 rpm in drive with about 13-14 vacuum. The needle is very bouncy though. It stays within a 2 pt range in the bounce but it's not steady at all. I tried turning in the screws on the carb all the way and the engine died. If I turn down the idle lower than that the engine acts like it wants to die. I've sprayed carb cleaner everywhere and couldn't find a leak.

The wires don't look too awful. You can still read all the writing and everything on there and they don't appear dry or rotted.

How do you do an OHM check? I have a voltmeter. Thanks for helping!
Hmmm 13-14 Hgs? Does this engine have a performance cam? If not, this reading is approx. 5-7 points too low. A healthy stock engine has a reading in the high teens, low 20s. A performance cam be in that range depending on it's event specs.

Although there are specs (OHM) for plug wires, consistent readings (values) within each wire tested, should be about the same. If you sense a misfiring plug, pull each plug boot away from it's plug and loosely place back on. The idea is to have it close enough to the plug tip to jump the gap and fire the plug, yet, be loose enough to remove as follows.....

Refire the engine. The engine should be such it's still getting fire by each plug. Using insulated pliers (ask anyone why), pull each plug boot away slowly. Listen for a snapping sound. If you do not hear a "snap" it's an indication that wire is not firing the plug, thus a "dead plug or wire". Another trick, wait until darkness, fire the engine and look for signs of sparks jumping to nearby metal grounds. NOT GOOD etither!
Google OHM testing spark plug wires, there are, numerous articles and YOUTube vids.
Let us know.....

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post #8 of 34 (permalink) Old 05-11-2017, 03:31 PM
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....... Another trick, wait until darkness, fire the engine and look for signs of sparks jumping to nearby metal grounds. NOT GOOD etither!

Let us know.....
I had a similar problem, the #2 plug wire was arcing against the header tube. Somewhere here I have a video of that happening. Replaced the wires and things were much better afterward.

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post #9 of 34 (permalink) Old 05-11-2017, 03:39 PM
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Originally Posted by 69MustangCoupe View Post
The wires don't look too awful. You can still read all the writing and everything on there and they don't appear dry or rotted.
There's a dead easy test for this. Run the engine at night, in complete darkness. Any problems will show as sparks from the wires.
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post #10 of 34 (permalink) Old 05-11-2017, 03:48 PM Thread Starter
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Originally Posted by kenash View Post
Hmmm 13-14 Hgs? Does this engine have a performance cam? If not, this reading is approx. 5-7 points too low. A healthy stock engine has a reading in the high teens, low 20s. A performance cam be in that range depending on it's event specs.

Although there are specs (OHM) for plug wires, consistent readings (values) within each wire tested, should be about the same. If you sense a misfiring plug, pull each plug boot away from it's plug and loosely place back on. The idea is to have it close enough to the plug tip to jump the gap and fire the plug, yet, be loose enough to remove as follows.....

Refire the engine. The engine should be such it's still getting fire by each plug. Using insulated pliers (ask anyone why), pull each plug boot away slowly. Listen for a snapping sound. If you do not hear a "snap" it's an indication that wire is not firing the plug, thus a "dead plug or wire". Another trick, wait until darkness, fire the engine and look for signs of sparks jumping to nearby metal grounds. NOT GOOD etither!
Google OHM testing spark plug wires, there are, numerous articles and YOUTube vids.
Let us know.....
I honestly don't know what cam is on it. Probably not performance but who knows. The previous owner had a 750 edelbrock on it so I don't know what else he went overboard with or did incorrectly. He had the vacuum line to the carb reversed to where it was getting manifold vacuum and the vacuum advance was busted. The car isn't the fastest. It seems slower than the 69 coupe with a 302 I had.

I tried doing something similar. I took each wire off as it was running to see if it made a difference. For each plug, the engine got worse sounding when I took it off. For each one I could hear that popping noise as well. I also did the timing light check for each wire and from what I can tell the light looked consistent.

I'll check out some videos on that and see if anything seems out of the norm. I went ahead and ordered a new cap, rotor and wires. Doesn't hurt to see if they make a difference I guess. At least I can rule those out if it doesn't.
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post #11 of 34 (permalink) Old 05-11-2017, 03:49 PM Thread Starter
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There's a dead easy test for this. Run the engine at night, in complete darkness. Any problems will show as sparks from the wires.
I'll give that a try late tonight and see if notice anything! Thanks!
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post #12 of 34 (permalink) Old 05-11-2017, 03:52 PM Thread Starter
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Hmmm 13-14 Hgs? Does this engine have a performance cam? If not, this reading is approx. 5-7 points too low. A healthy stock engine has a reading in the high teens, low 20s. A performance cam be in that range depending on it's event specs.
Also, does the vacuum correlate with the timing any? Could it be the vacuum is low because the timing is off? I've been meaning to see what the timing is as I just got a timing light but I need to put the timing tape on there and everything to check.
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post #13 of 34 (permalink) Old 05-11-2017, 04:00 PM
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The timing should already be stamped on the balancer.


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post #14 of 34 (permalink) Old 05-11-2017, 07:01 PM
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Yes, timing will affect vacuum #s.
If it fluctuates a small amount with a regular rhythm, you 90% have a burnt/dirty valve.

Examine your exhaust for leaks, they sound a lot like loose rockers or lifters.
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post #15 of 34 (permalink) Old 05-11-2017, 10:13 PM Thread Starter
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Yes, timing will affect vacuum #s.
If it fluctuates a small amount with a regular rhythm, you 90% have a burnt/dirty valve.

Examine your exhaust for leaks, they sound a lot like loose rockers or lifters.
Yeah, I feel like it's the valves. Just really hoping it's not. Is there any way to clean the valves or do something if they are sticking or to maybe possibly help?

What can I do if it's burnt or dirty valves?

The exhaust doesn't look too bad but I'll double check to see.
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