Knock, knock....Knock.....

[Custom Coffin Works]

Friday night, I just got done driving my 25 mile ride home in it with no issues at all. We got back in the Caddy to go to our local bar about a mile down the road I noticed it seemed as if I started to have a vacuum leak. The engine needed more gas just to keep running. I got her home and shut her down to look for a leak. Nothing..no hoses removed no leaks after checking with the WD-40.. So I figured the fuel must have gummed up the carb so I tore it down and cleaned it up. Still ran shitty if at all, and pop through the carb a couple of times so I pulled out the timing light to check the timing. Turns out it was way off! But the hold down bolt was still tight! I had just done the timing last month for emissions and knew it was set right! So I turn it counter clockwise and she smoothed out.. Thats when the idle calmed down enough for me to hear that dreaded knock..I think I have a rod bearing going... I don't get how the timing would move like that with no movement of the distributor? Is this related or just a qunzadence? (spelling)....How hard is it to change out a worn bearing with the engine still in the bay? She runs like a champ now...do I just turn up the radio?

[hotroddwayne]

Sounds like it jumped time. Over time your timing chain will stretch and the longer it goes without being replaced, the more sloppy it will get. Timing chain links the crankshaft with the camshaft. Also GM used a fiber gear on the camshaft... those can wear too (and teeth break off sometimes) so don't get too excited about the knock... yet. An engine that's way out of time will make strange sounds.
First just strip down the front of the engine... remove the fan & shroud, water pump, and you'll probably have to drop the front of the oil pan down some to get the timing chain cover off. Once the timing chain cover is off, pinch the chain with your fingers between the gears, there should be virtually no slack. You'll probably see that one side of the chain appears tight & the other side is VERY loose & has alot of movement. Next... bump the engine over with #1 spark plug removed & bring it up to top dead center so you know the crank is positioned where it needs to be... the dot on the crankshaft timing gear will be at 12 o'clock. Compare that to the dot on the camshaft timing gear (it should be at 6 o'clock)... they should be perfectly alligned. If they aren't... it jumped time. Also check the position of the rotor inside the distributor to make sure it aligns with #1 spark plug wire on the distributor cap. Changing the oil pan gasket & it's main seals with the engine in the coach will prove to be more difficult than the timing chain replacement though. It's hard to clean everything properly & get a good seal with no room to work, Stock up on some good Silicone sealant & be generous in the corners where the main seals meet the pan gasket. I'm not all that up to speed on the big block Caddys, so you may luck out & not have to mess with the oil pan to get the timing chain cover off. The job will be much easier if the timing cover meets the oil pan (Chevy small blocks have the front main seal within the bottom of the timing cover) so the oil pan pinches against the seal in the bottom of the timing cover. What i'm saying is don't drop the oil pan down unless you HAVE to, to get the timing cover off.

[Custom Coffin Works]

So then if thats the case...where is the knocking coming from? Is the knock a valve hitting the piston? That would be worst! Does anyone know if this engine has a interferance fit (Meaning the valves can and will come in contact with the pistons if cam saft is off a bit) on the timing.

[hotroddwayne]

Here's an article I found on the Cadillac/LaSalle technical forums when doing a search for "472 Cadillac knock": http://www.cadillaclasalleclub.org/f...c,69884.0.html
It could be several things... a spun rod bearing, bent pushrod clanking around, but since it jumped time so bad as you described it's probably the timing chain slapping the timing cover. Typically a worn timing chain is loose at both sides when you physically look at it, but one that jumped time will typically be tighter on one side than the other, and the now VERY sloppy side will slap the timing cover. I doubt that with a stock cam you're hitting a valve with a piston. Was just reading you can install a 500 crank in your 472 (i'm assuming that's what you have as my '70 limo had a 472) and the 500 stroke is another 3 tenth's of an inch greater than a 472, so I doubt you're gonna smack a valve. I've bought cars that jumped time & had a very "clattery" sound to them until properly repaired, and yes advancing timing will make it run smoother. But when valves aren't opening just when they're supposed to & full stroke isn't achieved before ignition, strange knocking, tapping, straining for power, "stuffed up" performance, dieseling, pre-ignition... all make their noises. My advice is start with the timing chain & go from there. Maybe others with specific Cadillac expertise will help more, i just wanna help ya get that cool coach on the highway. My background is mainly small-block Chevy so maybe someone else here knows some tricks!

[Custom Coffin Works]

I think your right in the timing...that distributor is not going to rotate on it's own. I will say this...that sucker has some git up and go it didn't have before...Maybe that's a effect of the advanced tooth. I'll pull the front off this week.

[Custom Coffin Works]

Whew~!~!~

Pulled the front off this evening and sure enough its the chain. It is so lose I could pull it off the cam gear without removing the gear. I flapped the chain back and forth and it did hit the case so I'm pretty sure its the cause of the knock. Tomorrow it goes back together. I now have a dead line to make! Thanks to "hotroddwayne" for the advise! This forum rocks! Without it I would have surely wasted a lot of time pulling the pan off the change a rod bearing that didn't need to be changed...

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[Psychoholic]

That is damned good info. Everyone should cough up some reputation points for him (it's the little scales on the left).

[northgahearse]

ahhh the timing gear

[Custom Coffin Works]

ahhh the timing gear

WAIT!! THAT WHAT A TIMING GEAR LOOKS LIKE?!? OH MAN I THINK I PULLED THE WRONG THING... THIS IS WHAT I PULLED OFF....
Oh Man....what did I do...

[northgahearse]

oh shit thats the waterpump how the hell you going to flush now?

[hotroddwayne]

Hey, GLAD I could help ya dude! When you described how poorly it was running, the knock, loss of power, and advancing the timing cleared it up some I just KNEW what had happened. At this point I need to recommend you change the cam & lifters too. Since the timing chain was whipped you know it hasn't been apart in a long time... maybe never. Chances are the lobes are worn on the camshaft & the lifters are dished out @ the contact points with the cam. To change them you'll have to pull the distributor & intake to get the lifters out & the cam. A Crane "economiser" cam & lifter kit will perk that old girl right up with added performance too!
Since you're working against a deadline though, keep the cam & lifter upgrade at the top of your list for later when you park the coach to do some upgrades. You did a good job describing all the newfound "issues" with the engine performance & sounds! That makes helping you out much easier. Good luck with the repairs! And for GOD'S SAKE make sure you get the cam, crank, and distributor ALL in time (lined up) before you put it all back together. YES the NHAA forums are excellent, I learn new things on here all the time too thanks to everyone involved here.
Thank you to those who are giving me the reputation points... i've been involved with NHAA for almost 3 years & try to post with help to any problems ya all post, and until today my rep points were at a big fat ZERO so thanx, I appreciate it! -hotrod Dwayne

[Custom Coffin Works]

Well, it's back together with a new chain and gear. It was surprisingly easy to change out. I had to come up with a make shift Harmonic Balancer mount installer but that was simple too. By the way if anyone wants to know what size bolt goes into the crank in front, it's a fine thread 9/16. I still have a bit of a knock but it comes and goes. I assume it is a cap and the heating of the engine closes the gap. I need to change the oil this weekend and try to get some of those plastic gear teeth out of the pan. If any one does this type of service on theirs make sure you put a rag in the bottom under the crank so when your socket falls off your ratchet it doesn't drop into the pan.

Thanks again all who helped!
Custom Coffin Works.com

[northgahearse]

might want to look at the valve seals as well
you might find the chunks in the oil pan with the gear teeth......

[Custom Coffin Works]

might want to look at the valve seals as well
you might find the chunks in the oil pan with the gear teeth......

The umbrella seals? Those are under the springs correct? It doesn't smoke at all. It does go through a quart a month though. That reminds me of a joke about blowing a seal...well never mind.

[northgahearse]

The umbrella seals? Those are under the springs correct?

yep them under the springs things

with age they fall apart you can get them for about 25. for a set