V8 SHO Catastrophic Shim Failure

[gamefanatic]

You are definitely fighting the tensioner when putting the CAM gear back in place. I don't have experience with doing it this way. I have seen others do 4 cylinder Honda's in this manor. Are you only fighting the rear head exhaust CAM or another one? If another, you will want to get it in place first then do the rear exhaust.

However if you don't have a way to leverage the tension, you might be better off pulling the cover.

 

[E1]

It is a one way ratchet down by the oil pump.
It only clicks out. If you let it click even one click you won't get the sprocket back on unless you take off the front cover, take off the tensioner, SPIN the head of the tensioner so the ratchet teeth disengage from the lock. Only then can you re-compress the tensioner to get the main timing chain back on.
Once you compress the tensioner all the way, you can fit a small allen wrench into it and capture the ratchet so the tensioner stays compressed during reassembly.
After all is back together, you pull out the wrench and the ratchet arms itself.

 

[Stan Phillips]

That is what I thought....I heard a "click" when I took some tension off of the cam gear....almost sounded like something fell in that area. Going to tackle the timing cover tomorrow....got the back valve cover off Sunday.

Good thing I had just replace COP's on the back last summer....bolts on the back were relatively easy. Anything specific I need to know about the cover removal\installation. Been reading about the pulley bolts not being able to come off with a ratchet. TY for the info so far...

 

[E1]

14 mm ratcheting wrench for the front cover big bolts.
One of those bolts, goes through a pulley, needs to thread BETWEEN the frame and an AC line. Very tight but doable.
Don't miss the 3 buried 8 mm bolts.

a 12mm MEDIUM depth socket is a huge help on the front cover bolts.

Good luck.

Change the front crank seal while you are in there.

 

[Stan Phillips]

I am having an issue with the crank bolt. I have the pulley (power steering) at the top of the motor wedged with a bar so that it can't move, & the cam gear so it can't move. Thought this would enable me to "break" the bolt loose. My Craftsman 125psi compressor does not want to budge it. Tried a breaker bar, but the crank turns. I applied quite a bit of pressure before it gave loud click. Sounds like the chain is clicking (jumping teeth) on the inside of the cover....don't want to keep turning due to the cam gear not turning with the crank. Afraid I might bend a valve or something worse.

Any way to keep the crank from turning while I try to remove the bolt ??

 

[E1]

there are two threaded holes in the crank pulley for attaching a puller.

I took a steel plate I had laying around and put an edge against the frame rail, figured out where the jack screw holes were on the pulley and made a couple holes in the plate.
Drill out a big enough hole in the plate center between the bolt holes to get a socket through.
Bolt plate to pulley with edge against frame.

It wont turn now...

 

[NoSlo]

A strap wrench is not enough, so belts certainly aren't. You need 8+ CFM compressor with big hoses to run a 1000ft/lb nut-busting torque impact to ensure success with impact tools.

19" impact deep socket + 2' breaker bar with the car on high jack stands should be enough if you can lock the engine. Tusk engine lockup tool. Since the spark plug is so deep, to use it, you may need to tap the back for a long bolt and locking nut.

Don't get a cheap tool. The all plastic version has failed before.

Another way to make a lockup tool is to just get a very long hardened ("11") bolt the same threading as spark plugs and screw it in. Round off the edges of the end with a grinder. The most mechanical advantage over the crank, the least pressure on the bolt and piston, will be contact at mid-piston stroke.d

You can also feed rope into the cylinder "rope trick". This should be done when you can determine that the cylinder you'll use is on the compression stroke, so the valves will be closed. Note that you are turning the engine backwards to loosen, so go past cylinder TDC 90 degrees of tightening crank turn, and then lock up the cylinder with rope and turn backwards.

 

[E1]

Tusk engine lockup tool.

NOT enthusiastic about this option.

Maybe with Iron heads. Do this with Aluminum heads and you better have a Helicoil kit handy because that is what I believe one will be doing next.

 

[NoSlo]

NOT enthusiastic about this option.

Maybe with Iron heads. Do this with Aluminum heads and you better have a Helicoil kit handy because that is what I believe one will be doing next.

I haven't heard anything about these engines ejecting spark plugs, which hold back near 2000 PSI of combustion pressure when you run them up to 500HP on boost. I'd be more worried about the piston top myself. That the nub is made out of plastic shows how small the force is vs what you might think.

 

[E1]

I haven't heard anything about these engines ejecting spark plugs, which hold back near 2000 PSI of combustion pressure when you run them up to 500HP on boost. I'd be more worried about the piston top myself. That the nub is made out of plastic shows how small the force is vs what you might think.

Respectfully, I don't think a V8 SHO has EVER been dyno'd at +500 hp.
This is the 3.4L V8, I think you might be mistaking it for the 3.5L V6?

Blown out plug and stripped threads on a 3.4L V8 SHO motor? happens too often -
http://v8sho.com/SHO/Blown Spark Plug.htm

http://www.v8sho.com/SHO/StrippedSparkPlugThread.htm

 

[NoSlo]

Some information to help you figure out why threads get damaged, and ponder the lock up tool:

Spark plug torque specification: 7-15 lb-ft, dry (180 in-lb max)
Spark plug thread 14mm x 1.25 (.551 inches)
Coefficient of friction steel 0.2
= axial clamp force 1640 lbs

If the threads are lubricated with oil, as might be found in a plug well, then the reduction in friction coefficient to ~.16 means the same 15lb-ft could increase the clamping force - upward pull on the threads - to 2000+ lbs. That's without adding the 1000psi of a non-detonating normally-aspirated engine. They just need to not back out, not be tightened beyond the equivalent of picking up the front end of your car by one spark plug.

A blue Yamaha V6 has been making 1000hp without shooting engine parts all over the place (yet).

Now, compare to the lock-up tool: The stroke on the V8 is 3.13 inches, a 1.56 inch, or 0.13 foot, crank radius. At just above the center of the stroke, this moment arm magnifies the foot-lb by approximately x7.7, so 200ft/lb at the crank bolt = 1540 lbs of upward force, without subtracting friction losses.

10 foot-pounds, as one should be using to install plugs (after turning backwards to feel they drop into the existing threads, and installing straight), is a very small amount of torque; "by feel", a mechanic may apply significantly more, explaining why threads are easily damaged on many cars or why resulting clamping force plus later combustion exceeds the limit of materials.

I do like the idea of a pulley wrench, a circle with bolt holes for the harmonic balancer's puller threads and a long handle, cut from thick steel stock. However, one must clamp such a tool tightly to the pulley with hardened bolts, as you don't want to bend, twist, break bolts off in the pulley; instead, clamping friction with the pulley face must stop the tool from turning. Bolts must be the correct length to fully engage all the pulley threads without hitting the engine cover behind.

The strength of the rubber ring inside the harmonic balancer is enough to drive accessories, but using a strap wrench may be enough to break the bond between metal and rubber.

 

[luigisho]

Blown out plug and stripped threads on a 3.4L V8 SHO motor? happens too often -

Mine puked one out in the front bank. I thought I blew the motor when it happened.

 

[Stan Phillips]

Got a chance to get back to this....was able to get the crankshaft bolt out....used E1's suggestion & created a tool out of angle iron. Then had to "tap" out the puller bolt holes in the pulley. Wanted to wait to get the service manual in the mail...had an older cd manual...but recall it would not work with the new windows....could not find it anyway. Put it in a "safe" place ..ha. The manual speaks of a special tool to remove the front crankshaft seal (Crankshaft Seal Replacer/Cover Aligner T88T-6701-A). Is this required, or can I just pry off the cover ??...Anxious to get the cover off to see what is next.

 

[Stan Phillips]

Actually dug deeper into the cd...had to go to engine removal section. Maybe the tool (different tool in this section) is not required.
From the cd: If required, use Locknut Pin Remover T78P-3504-N to remove crankshaft front seal (6700) from engine front cover.
See what happens...

 

[E1]

If you are replacing the seal, any means necessary - Screwdriver, woodscrew and slide hammer, prybar - just don't damage the cover.
I usually leave them in during removal and beat them out from the backside on a bench. Just make sure the reinstalled new seal is perfectly flat with the cover face.

Rip that old sucker out and pitch it out.

 

[Stan Phillips]

Question on the main timing chain (black link) in reference to the crankshaft keyway. Because I had cam sprocket off...I was not at TDC. When trying to take off the crank bolt...it seemed to have "jumped" main chain. I can see where the black link was about 3 links further along. I lined the black link up with the keyway on the crank....but would like verification that this is the way that it is supposed to be..before covering it up. I will take the cams off & do the lining up described in the manual....if need be. Trying to save a couple of steps.

I could try rotating the crank to get it to TDC (toverify timing)....but with everything setup...afraid it might bend something if it isn't correct.

 

[Stan Phillips]

I decided to pull the cams & try to do it correctly. Ran into an issue. Was trying to turn the crank to TDC (all cams out & spark plugs out), but it gets "stuck" at 1 spot. I can get to TDC, but it won't rotate a complete 360 degrees. If I turn it backward, and it gets stuck in about the same spot. Does this mean bent valve\valves ?? With the cams out...all valves should be "out"\closed....correct ?? If there is a bent valve...can I do a leak-down test to see if the valves (on the cylinder that threw the shim) are bent\not closing ??

 

[NoSlo]

You can carefully measure the height of each valve bucket, from the same point at the edge to the top of the shim, or better, to a ruler laid across the cam journals, or even check gap like normal with a cam partially bolted back in, after pressing down the shim holders if needed. Intake and exhaust should all be the same height. Valves would likely bend from piston contact so they don't close right.

Any other debris, like broken spark plug electrode or random screws dropped in plug wells by vandals could do the same thing.

 

[E1]

I screw in my compression tester and apply air pressure to the hose.

Imperfectly sealed valves will at the very least make a hissing sound as air escapes into intake or exhaust manifold.

 

[Stan Phillips]

Unfortunately...not good news....bent valve\valves. What kind of project is having the heads done ??
Seems like I am 3/4 of the way there now....might as well try to tackle it. Should I do both heads, or if I can just get the gasket for the front (LH) head...just do the one ?? Again, any advice welcome. I do have a spare head with all the parts that I might need.
Thinking gasket(s), head bolts...anything else recommended ??