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Discussion Starter #1
The following is long and I apologize beforehand for taking up your time. But on the other hand I think it's pretty interesting stuff, so read away!

If you have been following the ongoing saga of my lash pads popping out this will make sense. Basically, I thought I had bent valves, so I was preparing to take the head off and back to the machine shop that did the rebuild work...

I started taking apart my engine, so as to take the head to the machine shop. But before I got too far, i thought to myself... Self, why not turn the engine over one more time before pulling this shithead of a head off the car? So I checked all the valve clearances and they were almost all perfect except for two intake valves which were .007 instead of .008 (I left them that way) and with the plugs out I turned the engine over, fully expecting the #6 intake valve to stick open, but it DIDN'T!!! I kept cranking the engine over, hoping, expecting the valve to stick open, but it didn't. Not at all. So I put the engine back together again. That was 1:00am this morning. I woke up at 7:00 and went out to the garage and with the plugs still out I cranked the engine again. It still didn't stick open. So I put the plugs in, and with my video camera on, I cranked the engine over.... It started right up! @!#% And I mean instantly. turn the key and vrooom. What the **** is going on?! I asked myself. I ran the engine for 15 minutes. Considering I havent adjusted the timing and didn't adjust the valves hot yet, It ran admirably well. I kept the revs between 800 and 2500 rpm the whole time. Here's the kicker: After those 15 minutes I decided to rev the engine up to 3000 rpm. 30 seconds after running at 3000 I heard a LOT more valvetrain noise and the engine started to misfire a lot so I shut it down right away.

The problem only occurs when I rev the engine over 3000 rpm. I DID have a sticking valve earlier that I thought was the problem. But the valves are not sticking anymore and I don't know why.

I have several theories, but they are all flawed so maybe some of you can help shed some light:

Theory 1- The timing is so far off that the spark ignites mixture before the valve closes (but that would cause backfire and anyways the engine does run pretty smoothly at low rpms.)

Theory 2- After 15 minutes of low rpm the engine heats up and since I haven't adjusted valve clearances hot, this somehow causes the rockers to bind on the cam lobes, causing the engine to run rough and something or other else happening... blah, blah (Highly unlikely)

Theory 3- the machine shop did not install the valves properly and they are binding in the guides.

Theory 4- The machine shop did not install the springs correctly by possibly forgetting the shims and they are not creating enough force to close the valves at higher rpms.

Do any of these theories hold water? Any better ideas?

Steve Graber
 

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> The following is long and I apologize
> beforehand for taking up your time. But on
> the other hand I think it's pretty
> interesting stuff, so read away!

> If you have been following the ongoing saga
> of my lash pads popping out this will make
> sense. Basically, I thought I had bent
> valves, so I was preparing to take the head
> off and back to the machine shop that did
> the rebuild work...

> I started taking apart my engine, so as to
> take the head to the machine shop. But
> before I got too far, i thought to myself...
> Self, why not turn the engine over one more
> time before pulling this shithead of a head
> off the car? So I checked all the valve
> clearances and they were almost all perfect
> except for two intake valves which were .007
> instead of .008 (I left them that way) and
> with the plugs out I turned the engine over,
> fully expecting the #6 intake valve to stick
> open, but it DIDN'T!!! I kept cranking the
> engine over, hoping, expecting the valve to
> stick open, but it didn't. Not at all. So I
> put the engine back together again. That was
> 1:00am this morning. I woke up at 7:00 and
> went out to the garage and with the plugs
> still out I cranked the engine again. It
> still didn't stick open. So I put the plugs
> in, and with my video camera on, I cranked
> the engine over.... It started right up!
> @!#% And I mean instantly. turn the key and
> vrooom. What the **** is going on?! I asked
> myself. I ran the engine for 15 minutes.
> Considering I havent adjusted the timing and
> didn't adjust the valves hot yet, It ran
> admirably well. I kept the revs between 800
> and 2500 rpm the whole time. Here's the
> kicker: After those 15 minutes I decided to
> rev the engine up to 3000 rpm. 30 seconds
> after running at 3000 I heard a LOT more
> valvetrain noise and the engine started to
> misfire a lot so I shut it down right away.

> The problem only occurs when I rev the
> engine over 3000 rpm. I DID have a sticking
> valve earlier that I thought was the
> problem. But the valves are not sticking
> anymore and I don't know why.

> I have several theories, but they are all
> flawed so maybe some of you can help shed
> some light:

> Theory 1- The timing is so far off that the
> spark ignites mixture before the valve
> closes (but that would cause backfire and
> anyways the engine does run pretty smoothly
> at low rpms.)

> Theory 2- After 15 minutes of low rpm the
> engine heats up and since I haven't adjusted
> valve clearances hot, this somehow causes
> the rockers to bind on the cam lobes,
> causing the engine to run rough and
> something or other else happening... blah,
> blah (Highly unlikely)

> Theory 3- the machine shop did not install
> the valves properly and they are binding in
> the guides.

> Theory 4- The machine shop did not install
> the springs correctly by possibly forgetting
> the shims and they are not creating enough
> force to close the valves at higher rpms.

> Do any of these theories hold water? Any
> better ideas?

> Steve Graber
Steve I believe Theory #4 is the culprit.I dont know if you read my post a week ago,but in it i told of having same problem.It was on one valve only and at high RPM but lash pad would pop out.it turned out to be low spring tension caused by a sunken spring retainer.I installed shim under spring and have not had problem since. Good luck, Norm
 

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Discussion Starter #3
> Steve I believe Theory #4 is the culprit.I
> dont know if you read my post a week ago,but
> in it i told of having same problem.It was
> on one valve only and at high RPM but lash
> pad would pop out.it turned out to be low
> spring tension caused by a sunken spring
> retainer.I installed shim under spring and
> have not had problem since. Good luck, Norm
I give #3 and #4 both a thumbs up. I'm leaning more towards #3.
 

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Discussion Starter #4
> The following is long and I apologize
> beforehand for taking up your time. But on
> the other hand I think it's pretty
> interesting stuff, so read away!

> If you have been following the ongoing saga
> of my lash pads popping out this will make
> sense. Basically, I thought I had bent
> valves, so I was preparing to take the head
> off and back to the machine shop that did
> the rebuild work...

> I started taking apart my engine, so as to
> take the head to the machine shop. But
> before I got too far, i thought to myself...
> Self, why not turn the engine over one more
> time before pulling this shithead of a head
> off the car? So I checked all the valve
> clearances and they were almost all perfect
> except for two intake valves which were .007
> instead of .008 (I left them that way) and
> with the plugs out I turned the engine over,
> fully expecting the #6 intake valve to stick
> open, but it DIDN'T!!! I kept cranking the
> engine over, hoping, expecting the valve to
> stick open, but it didn't. Not at all. So I
> put the engine back together again. That was
> 1:00am this morning. I woke up at 7:00 and
> went out to the garage and with the plugs
> still out I cranked the engine again. It
> still didn't stick open. So I put the plugs
> in, and with my video camera on, I cranked
> the engine over.... It started right up!
> @!#% And I mean instantly. turn the key and
> vrooom. What the **** is going on?! I asked
> myself. I ran the engine for 15 minutes.
> Considering I havent adjusted the timing and
> didn't adjust the valves hot yet, It ran
> admirably well. I kept the revs between 800
> and 2500 rpm the whole time. Here's the
> kicker: After those 15 minutes I decided to
> rev the engine up to 3000 rpm. 30 seconds
> after running at 3000 I heard a LOT more
> valvetrain noise and the engine started to
> misfire a lot so I shut it down right away.

> The problem only occurs when I rev the
> engine over 3000 rpm. I DID have a sticking
> valve earlier that I thought was the
> problem. But the valves are not sticking
> anymore and I don't know why.

> I have several theories, but they are all
> flawed so maybe some of you can help shed
> some light:

> Theory 1- The timing is so far off that the
> spark ignites mixture before the valve
> closes (but that would cause backfire and
> anyways the engine does run pretty smoothly
> at low rpms.)

> Theory 2- After 15 minutes of low rpm the
> engine heats up and since I haven't adjusted
> valve clearances hot, this somehow causes
> the rockers to bind on the cam lobes,
> causing the engine to run rough and
> something or other else happening... blah,
> blah (Highly unlikely)

> Theory 3- the machine shop did not install
> the valves properly and they are binding in
> the guides.

> Theory 4- The machine shop did not install
> the springs correctly by possibly forgetting
> the shims and they are not creating enough
> force to close the valves at higher rpms.

> Do any of these theories hold water? Any
> better ideas?

> Steve Graber
I give three and four a thumbs up.
 

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53 Posts
> The following is long and I apologize
> beforehand for taking up your time. But on
> the other hand I think it's pretty
> interesting stuff, so read away!

> If you have been following the ongoing saga
> of my lash pads popping out this will make
> sense. Basically, I thought I had bent
> valves, so I was preparing to take the head
> off and back to the machine shop that did
> the rebuild work...

> I started taking apart my engine, so as to
> take the head to the machine shop. But
> before I got too far, i thought to myself...
> Self, why not turn the engine over one more
> time before pulling this shithead of a head
> off the car? So I checked all the valve
> clearances and they were almost all perfect
> except for two intake valves which were .007
> instead of .008 (I left them that way) and
> with the plugs out I turned the engine over,
> fully expecting the #6 intake valve to stick
> open, but it DIDN'T!!! I kept cranking the
> engine over, hoping, expecting the valve to
> stick open, but it didn't. Not at all. So I
> put the engine back together again. That was
> 1:00am this morning. I woke up at 7:00 and
> went out to the garage and with the plugs
> still out I cranked the engine again. It
> still didn't stick open. So I put the plugs
> in, and with my video camera on, I cranked
> the engine over.... It started right up!
> @!#% And I mean instantly. turn the key and
> vrooom. What the **** is going on?! I asked
> myself. I ran the engine for 15 minutes.
> Considering I havent adjusted the timing and
> didn't adjust the valves hot yet, It ran
> admirably well. I kept the revs between 800
> and 2500 rpm the whole time. Here's the
> kicker: After those 15 minutes I decided to
> rev the engine up to 3000 rpm. 30 seconds
> after running at 3000 I heard a LOT more
> valvetrain noise and the engine started to
> misfire a lot so I shut it down right away.

> The problem only occurs when I rev the
> engine over 3000 rpm. I DID have a sticking
> valve earlier that I thought was the
> problem. But the valves are not sticking
> anymore and I don't know why.

> I have several theories, but they are all
> flawed so maybe some of you can help shed
> some light:

> Theory 1- The timing is so far off that the
> spark ignites mixture before the valve
> closes (but that would cause backfire and
> anyways the engine does run pretty smoothly
> at low rpms.)

> Theory 2- After 15 minutes of low rpm the
> engine heats up and since I haven't adjusted
> valve clearances hot, this somehow causes
> the rockers to bind on the cam lobes,
> causing the engine to run rough and
> something or other else happening... blah,
> blah (Highly unlikely)

> Theory 3- the machine shop did not install
> the valves properly and they are binding in
> the guides.

> Theory 4- The machine shop did not install
> the springs correctly by possibly forgetting
> the shims and they are not creating enough
> force to close the valves at higher rpms.

> Do any of these theories hold water? Any
> better ideas?

> Steve Graber

Do you Know if the machine shop knurled your valve guides or were they replaced or maybe the did nothing at all to them. Also possibly your valve geometry is screwed up if they did a valve job and didnt check seat height (to make sure the valves all stick up out of the top of the head at the same height).

It would probably be worth finding out if you dont already know
good luck

BTW I think you can see the shims that go under the valve springs just by looking at them. That would at least tell you if they are there, They are just flat washers between the between the spring and top of the head.

good luck
 

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Discussion Starter #6
The Mystery continues!

The Machine Shop did a valve job. This I am sure of. The reason the engine died the first time (previous owner) was... a Sticking Valve!!! When I bought the car I thought it was a bent valve, but the machine shop told me it wasn't bent so we decided to re-use it. I don't really know any details of the procedures the machine shop took. But I will ask on Monday for sure.

I see any shims (washers) sitting underneath the springs.

I messed around some more with the valves this afternoon and I have other valves now sticking as well. They all seem to be intake:

But why would the valves not be sticking yesterday, when I ran the car for 15 minutes? Then I rev to 3000 rpms and it starts to run really rough, So I pull the valve cover off and it's not #6 intake sticking anymore. Now it's #2 intake. Then I go back the this morning and it's not #2 anymore, it's #3, #4 and #6 intakes! I even tried depressing the valves with a large screwdriver and I can barely budge them! I am 6'3 215lbs and I was **** near standing on that screwdriver!

So I'm convinced that the machine shop neglected to ream out the valve guides. But then again, if they didn't replace the valve guides, and these are the original valves, why would they have to ream the valve guides in the first place? wouldn't you just put new oil seals on and slide the valve back in? Is there any other reason for binding valves? Other than Bent stems?

It's a big job pulling the head off. (For me it is.) I don't really feel like doing it. If it IS the machine shops' fault, should I tow the car over to them and make them take it apart?

Steve G
 

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Discussion Starter #7
Re: The Mystery continues!

> The Machine Shop did a valve job. This I am
> sure of. The reason the engine died the
> first time (previous owner) was... a
> Sticking Valve!!! When I bought the car I
> thought it was a bent valve, but the machine
> shop told me it wasn't bent so we decided to
> re-use it. I don't really know any details
> of the procedures the machine shop took. But
> I will ask on Monday for sure.

> I see any shims (washers) sitting underneath
> the springs.

> I messed around some more with the valves
> this afternoon and I have other valves now
> sticking as well. They all seem to be
> intake:

> But why would the valves not be sticking
> yesterday, when I ran the car for 15
> minutes? Then I rev to 3000 rpms and it
> starts to run really rough, So I pull the
> valve cover off and it's not #6 intake
> sticking anymore. Now it's #2 intake. Then I
> go back the this morning and it's not #2
> anymore, it's #3, #4 and #6 intakes! I even
> tried depressing the valves with a large
> screwdriver and I can barely budge them! I
> am 6'3 215lbs and I was **** near standing
> on that screwdriver!

> So I'm convinced that the machine shop
> neglected to ream out the valve guides. But
> then again, if they didn't replace the valve
> guides, and these are the original valves,
> why would they have to ream the valve guides
> in the first place? wouldn't you just put
> new oil seals on and slide the valve back
> in? Is there any other reason for binding
> valves? Other than Bent stems?

> It's a big job pulling the head off. (For me
> it is.) I don't really feel like doing it.
> If it IS the machine shops' fault, should I
> tow the car over to them and make them take
> it apart?

> Steve G
Wow this is getting good,
the random cylinder with the sticking valve is a nice touch.
What did you do to mr. murphy
(murphy's law) to get him so pissed off at you?
No seriously, at this point if it were me (thank god it isn't)
I'd pull the head off and take it to another machine shop and explain what has been going on.
Then see what they can find.
I'm not sure how the cooling passages circulate around the valve stems but when I got my head back there was wads of paper towels in the cooling passages. had to use compressed air, dental picks,bailing wire, and solvent to get them cleaned out.
The shops out here flush a colored dye through the head to check for cracks under high pressure. Can't use magna flux since aluminum is non ferrous.
Anyway is there a possibility that you have some crap in the cooling passages working it's way though and allowing the guides/stems to overheat and stick?
That's about the last thing I can think of except for the shop not machining enough clearance between the stems/guides or not enough seat(spring) pressure.
One last cheery thought, how about a bad casting, warping when warm, and puttng a little twist on your guides?
Wish you luck, and merry Christmas.

Jeff
 

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Re: The Mystery continues!

Just my 2 cents........

But it sounds to me like a the timing chain is a tooth or 2 off, and revving the motor is advancing the spark WAY off base. Or there's a problem in the distributor.

Maybe I misread, but your valves can't stick closed. They are forced open when the cam lob hits it, otherwise the motor would lock up.
And if they are sticking open, you would be seeing it pretty constantly, not just at 3,000.

So just a thought, but since all the clearances look fine, I think you may be looking in the wrong place.

Bryan
The Datsun Z garage
 

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Re: The Mystery continues!

Just my 2 cents........

But it sounds to me like a the timing chain is a tooth or 2 off, and revving the motor is advancing the spark WAY off base. Or there's a problem in the distributor.

Maybe I misread, but your valves can't stick closed. They are forced open when the cam lobe hits it, otherwise the motor would lock up.
And if they are sticking open, you would be seeing it pretty constantly, not just at 3,000.

So just a thought, but since all the clearances look fine, I think you may be looking in the wrong place.

Bryan
The Datsun Z garage
 

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Discussion Starter #10
Re: The Mystery continues!

> Just my 2 cents........

> But it sounds to me like a the timing chain
> is a tooth or 2 off, and revving the motor
> is advancing the spark WAY off base. Or
> there's a problem in the distributor.

> Maybe I misread, but your valves can't stick
> closed. They are forced open when the cam
> lobe hits it, otherwise the motor would lock
> up.
> And if they are sticking open, you would be
> seeing it pretty constantly, not just at
> 3,000.

> So just a thought, but since all the
> clearances look fine, I think you may be
> looking in the wrong place.

> Bryan
> The Datsun Z garage
I've been talking back and forth with him and how I understand it is that they don't stick open until the engine gets warm.
It runs fine until that point and then they are stuck open to where he can't even move them by prying on them. He comes back later when it's cold and they aren't stuck open anymore.
 

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Discussion Starter #11
Re: The Mystery continues!

Bryan,

> Bryan
> The Datsun Z garage
Before I get started let me just say that I have read your website (many times) and consider it to be one of the most informative and well executed sites regarding Z engines I have seen. I want to thank you for the work you put into it. It's obvious to me that you are an expert in your field. Thanks for your input on my problem.

I meant to say that the valves were sticking open.

Although I have not verified the timing with a gun, I did check #1 TDC and bright chain link with sprocket marks and everything is by the book. The engine starts and runs magnificently when the valves aren't sticking. The problem is definitely in the valve action itself.
When I first got the rebuilt head back from the machine shop, bolted it on the block and put the rocker arms on I remember how easily I pushed down on the springs with a screwdriver to slip the rockers onto the lash pads. Now when I push on the springs with a screwdriver, the springs go down fine but the valve doesn't budge, but if I push the tip of the screwdriver on the end of the valve stem, the valve barely budges unless I put my 215 Lbs of body on the screwdriver. It does move, but it feels like it is completely binding.

Again, the strangest thing is that I can push down on that same valve two days later and it will move fine, but then a different valve, or two, or three, might be binding.

It seems to clear up after a few days and then I can start and idle the engine at low rpms again for 15 min or so, but when I try to go over 3000 rpms they start to stick again and don't release for another few days.

That just CAN'T be a timing problem. I know that the cam is getting lubricated because there is plenty of oil all over the valves and rockers and cam when I open it up.

Steve G
 
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