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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
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