Compression and Vibration Questions

[RRoller123]

Trying to isolate the source of an engine vibration that is constant at all rpms, although it eventually smoothes out around 3500 to 4000. It is disturbing and I have ignored it for way too long. I am praying that it is not something down in the block, because I don't have the funds to address that right now. 2 possibilities?

1.) Compression figures: (#1-#4):

9/23/13: 145, 150, 145, 150

3/14/16: 154, 152, 145, 158

+9 +2 0 +8

Could these changes cause or explain engine vibration? I obviously expect to see a lot of carbon when the head comes off.

2.) Could the exhaust cam timing being a little off cause a vibration? It seems like it is off 1 tooth, opening early. But if I set it back the other way, by a tooth, it will be off as well, opening a little late. Sanity checking that I set the TDC correctly: Pics:

Crank at TDC, #4:



Lobes up (compression stroke):



Intake Cam Gear Hole is spot on:



But Exhaust is off:



Plugs are all excellent (thank you FI):

[131]

Adjust your exhaust cam timing. It's going to be closer than it currently is.

[RRoller123]

Thanks. Yes, I think you are right, will do that. Hopefully it makes things better.

[RRoller123]

Well the head is off now, and I am looking for your opinions on how it looks inside there:

Pictures below.

Considerations:

1.) Compression was very good prior, 154, 152, 145, 158.
2.) Head Gasket looks fine (no surprise given the Compression numbers.)
3.) I could NOT get intake cam box off without removing intake manifold, due to a support bracket interfering with it, so it all came off together. Not too bad, with the exhaust cam box removed, my son and I easily lifted the whole assembly out on the driver's side.
4.) The valve cup on Intake #4 is quite sticky, does not slide well in the cam box guide. Could this be a source of the constant vibration I have been seeing? All the other cups fell right out as the cam boxes were lifted away from the head.
5.) How do I clean up the carbon on the pistons?
6.) How do I clean up the carbon on the head mating surface?
7.) Head Locating pins are fine.
8.) Head bolts: re-install completely dry? no RTV sealant, or RTV sealant on some of them?
9.) If I don't rotate the crank, does the Computronics block-mounted Ignition have to be re-setup prior to restart?



Even with this support bracket (Intake Cam Box-to-Intake Manifold) removed, I couldn't get the Intake Cam box off. Should have not even tried. Removed it loose as a set.



Is this ground wire on the backside of the Exhaust Cam Box factory? Almost missed it, caused some trouble.





Head Mounting Surface and Carbon: Is this normal? Bad? Ok? I don't have the experience to judge this:

[So Cal Mark]

why did you remove the head?

[RRoller123]

Sorry, I have a couple of related posts going at once and they are getting mixed up. I haven't been as clear as I could on these.

Putting in new large valve ported head and adjustable cam wheels, new aluminum radiator, 274FI camshafts, engine cosmetics and re-plumbed everything. Don't have the funds to do the lower end, so doing this part now and hopefully things will improve and next winter I can do the HC pistons, etc.

But I also have had a constant slight vibration in this engine, at pretty much all speeds that I am trying to isolate. Can't be tuned out. Hoping that it has something to do with the head, and not the lower end. Compression good, runs great, good power, starts right up, etc. Motor mounts good, but vibration is there and constant. No knocking, no thuds, just a mild vibration.

Found the Intake #4 valve cup was sticking pretty well in the Cam Box, so I am hoping that this may be the cause?

Plus all the carbon questions below, etc.

Thanks for any help you folks can provide. I am not highly experienced at engine internals. Taking this one nice and slow step at a time.

Pete

[124JOE]

you could have ran slick50 in it to clear up the carbon before you pulled it apart
of premium fuel cleans good too

carb cleaner will break it down also.but tape off all the passages and use a few rags to catch the crud

hope this helps.joe

[narfire]

How did you isolate the fact it is an engine vibration? Any chance it might be further down in the drive train?
A case history here...I swapped out a set of u-joints and had a hellish vibration after a spin around the block. Jacked up and blocked the rear end with wheels off the around and ran the car in second and had a look- see. The drive shaft was bouncing up and down.
What ended up happening was I had not seated the u-joint clips properly.
Just a thought that it might not be the engine if things were running just fine and this was a sudden issue. Was it a progressive issue?
Chris

[RRoller123]

It does it in neutral, at idle, at rest, with the engine at pretty much any rev, although it tends to smooth out around 3500-4000. It has been there for longer than I want to admit that I have been ignoring it! Engine mounts are very good. I have used Seafoam regularly in the gas, as well as their spray treatment process into the intake manifold once. Apparently it didn't do very much, or else the carbon was much worse. But my question is: Does this look normal for a 74K mile engine? I doubt that it has been pulled apart before, although I suppose it is possible.

Pete

[wizard124]

Inspect cam lobes and fuel injectors.

[RRoller123]

Thanks, good ideas. I too suspect maybe a clogged injector. The fuel tank is very clean and I replaced the filter and had the injectors professionally serviced, but the vibration did show up sometime (months) after this was one. I measured fuel pressure at the CSI and it is good. I suppose one of the injectors could have failed or become blocked. They all are clearly firing, as evidenced by the stethoscope. I have a second fuel rail with regulator and injectors that I think I will send out and have fully refurbished, and use that one in the engine reassembly.

That is a good idea about checking the cam lobes. I have a shop manual and all the critical dimensions are surely contained in there.

There has to be a reasonable explanation for the vibration that requires me not to have to pull the engine and examine the lower end, right?

Does that carbon look normal for ~75K miles?
Sticking Valve Cup do it?

Pete

[micbrody]

I had vibration that become very loud around 3000 rpm. Turns out it was alternator because bolts holding it were not tightened

[RRoller123]

will check, thanks!

[djape1977]

i've had several case over the years where vibration was coming from exaust.

all sorts of problems. missing bracket that holds exaust to gearbox, missing rubber exaust hangers, too tight rubber hangers, exaust hanging on handbrake cable, exaust touching the floor, touching the crossmember, touching the central tie rod, or just plain bad design of aftermarket system that makes vibrations because of angles of bends, mufflers that resonate and produce vibrations...

way to test this is to have engine working in neutral, at RPM where it produces most vibration, and push down or pull up on exaust to see if anything changes. you can do this by just pushing down on exaust pipe with your foot.
you can also completely disconnect exaust from manifold and run the engine like that.

[RRoller123]

Thanks, will check that out!