Engine issue

[Jeff G 78]

Great points Zed.  As an easy way of telling if the damper is good or bad, I painted a white line across each surface at the timing notch before installing it.  If the rubber bond fails, I can easily see if the 2nd row pulley has rotated compared to the first row pulley and center hub.  It did not fail as all paint marks are still aligned and they match the timing scale when the keyway is at 12:00.

 

Also agreed on the compression check.  I did use the same gauge as always, so the actual readings could be slightly off but they did drop compared to the last time I checked it.

 

I believe my gear set does have the notch, but I am running a very different setup, so I'm not positive if it still applies.  I modified the cam gear using eccentric bushings like the "How to Modify..." book describes.  My head is shaved 0.050", so to get the timing right, I drilled the cam gear hole and installed offset bushings.  I used a degree wheel and dialed in the timing exactly to my cam specs by choosing the correct offset bushing.  I did check the bushing and it is still intact and properly positioned.  The slack side chain guide as slightly modified to take up the additional slack due to the shorter crank to cam distance.  Until I remove the front cover, I won't know for sure, but all looks good at the top of the slack side guide.  It is possible the bottom guide bolt loosened allowing the guide to slide in the slot and the chain to go slack.

 

Again, very possible that the spark isn't strong enough since the timing light wouldn't fire through the inductive pickup.  I will check the wiring and power to the coil and distributor.

[Zed Head]

Here's another thought.  Related to the loose damper bolt.  That should never happen, and really seems like the most significant thing.  I've seen where other people have reported their distributor drive spindle has slipped down in the drive gear and the tang no longer sticks out far enough to grab the distributor groove properly.  Maybe the vibrations related to that loose bolt, either causing the loose bolt or caused by the loose damper, made other parts move. I would follow that path and see if maybe a woodruff key sheared or moved (there's three of them, right?), or if the quill dropped in the drive gear.  Also, why did the bolt get loose?  Could be that something else is coming loose inside the engine.

 

I would have broke a sweat when I saw that loose bolt.  Just because it seems like a big deal.  But that's me, and I've never rebuilt an engine.

[Jeff G 78]

Yeah.  Even worse is that we didn't know it was the bolt that was loose.  I had a teammate crawl under the car with the 27mm socket and a breaker bar to turn the engine over while I watched the valvetrain.  He started turning the bolt and nothing was moving up top.         I was sure that the crank had snapped or that something was very broken.  I asked him to remove the socket and try turning the bolt by hand.  Sure enough, it was backed way out, but once tightened, all looked fine.

 

I have built about a dozen L series engines over the past 35 years and I've never had a crank bolt loosen.  

[madkaw]

Wow, what a challenge. Sucked that it made your race day short-crapcan race?

Loose damper could lead to sheared keys .

[Patcon]

What are you valve clearances? Could you have lost some adjustment and not be getting good valve sealing? I would think it would be noisy with less lash...I would redegree the cam and see if it meets spec. Also Zed may be onto something with the ignition route. If it won't start with ether I almost always rule out fuel. also your AFR was reading fine, so unless it is bad too?? That would also rule out fuel. Can you verify your afr is reading correctly somehow? Swap to another race car or one of your cars?

[Jeff G 78]

Hey Steve, I was awaiting your reply.  

 

I brought the borescope home from work, so I will at least be able to look down the front cover and in the plug holes.  I'll also do a leakdown.  With those two tests I should know if it will be a big repair bill or not.

[Jeff G 78]

Charles, I checked the valve clearances during the prep for the race.  The engine had about 16 track hours on it since I last adjusted them and 9 of the 12 were right on and the other 3 were only 0.001" loose.  I adjusted them back to spec.

 

The AFR is brand new and worked perfectly throughout the race.  The plug readings also looked perfectly light tan, so I'd guess the AFR is accurate. 

[madkaw]

So did you loosen the crank pulley bolt back up and tried to turn the pulley to see if turns(key gone). I think I would want

to see ALL of the bolt too, to make sure it didn't break in half. That Murphy guy sure has a sense of humor-

[Jeff G 78]

No and yes Steve.  We took the bolt all the way out to inspect it, but we did not remove the damper or try to turn it without the bolt.

[Chickenman]

Had the same thing happen with a damper bolt years ago on my race Z. Creates massive vibrations and ended up damaging the distributor drive spindle gears and bending the crank snout. Same symptoms that you had, only mine failed faster. You may find the spindle teeth chewed up and the dizzy may be skipping. It could be a coincidence that it lined up with #1 when you checked it.

 

Check the run out on the crank snout as well with a Dial indicator. . A loose damper can bent the crank snout.  Regardless if this is your issue, check the gears and snout for damage. I always secure the crank bolt with Red Stud-Lock.

 

BTW... how " sharp " is your spark? Should be a sharp crisp blue or white with a distinctive " Snap " if you hold the coil wire about 1/4" from a ground. Weak or yellowish spark is not gonna cut it. Did you try a different dizzy cap and rotor when you switched distributors, or did you use the same ones?

[Jeff G 78]

Interesting Richard.  Hopefully the crank snout is OK, but at least I have several spare engines to rob parts from if the crank is bad.  My biggest worries are the head and pistons since those are P79 and F54 and I don't have any spares of those.  I have lots of N47 parts.

 

I did swap the cap and rotor both with and without the new distributor.  The spark was pretty sharp and once pitch black outside, I could see it jump over an inch.

 

I will check the crank for runout as you suggest and I will always use red Loctite in the future.

[gundee]

The idea of a badly worn crank drive gear and or distributor spindle gear

sounds like a possible culprit.

I would like to see you drop the oil pump and spindle to inspect both the gears.