472 engine vibration

[Scot Minesinger]

The shop manual discusses vibration and the ways to deal with it at the beginning in the general section.  Had vibration problems on a 1975 Caddy and I read the manual and narrowed it down to the fan clutch being bad.  This was done by removing the fan belt and then seeing if the vibration whent away and it did.  I suggest going back to the basics and narrowing it down.  There are not too many causes of vibration in the engine, misfire, balance, bad engine mount, etc.

Good luck,

Scot

[The Tassie Devil(le)]

Ok did a compression test. Here's what I got...
#1 150psi dry/150psi wet
#3 150psi dry/160psi wet
#5 155psi dry/160psi wet
#7 150psi dry/150psi wet

#2 150psi dry/165psi wet
#4 135psi dry/150psi wet
#6 145psi dry/165psi wet
#8 145psi dry/155psi wet

Not sure if it matters but ran the car out of gas last saturday and it hasn't been started since. Should it have run before the compression test? Or is it better cold?

The increase in the cylinders 2, 4 and 6 indicate the Rings are sealing better with the oil in the cylinders.

These are the ones with the greatest improvement.   The others show the rings are reasonable, but the Valve Seats might be not as sealing as the rest.

Bruce.

PS.   How much oil did you squirt down the cylinders for the Wet Check?

[RobW]

Bruce
I used one of those little oil squirter cans with the pump lever and did about 2-3 full squirts.
I too thought that any increase wet meant rings and/or pistons. But then yesterday I'm looking on the net for interpretations of compression tests and see a few that say an increase in wet readings indicates a valve problem. I realize there's a ton of mis-information out there but now I don't know what to believe.
The other thing I can't understand is if I have bad rings or valve seals why isn't there any oil on those plugs? How can they all be the same worn clean brownish color?
As for the manual, I did see that section. It's a bit curious that they even have that section. Sounds like they had problems early on.
Anyway, before I can go any further I have to get the exhaust back on. Bought the complete set from classic exhaust. Having a little problem lining up the crossover pipe and I'll need to chase the threads on the manifold studs. After I get the exhaust back on, I'll remove a belt at a time and see if that changes anything.
If I can't clean up the studs, I'm thinking of removing the manifolds and letting a machine shop install new ones. But that just opens another can of worms. At that point, why not pull the heads and send them out too? Not sure what it would cost to do the heads.  But maybe do the heads, intake manifold, and timing chain. So at 90,000 + miles (assuming original miles) why not do cam, lifters, pistons/rings, bearings, etc? Or maybe its cheaper, faster, easier, to buy a reman engine for $2000?

[The Tassie Devil(le)]

G'day Rob,

The Wet Check doesn't have much bearing on the Valve Seat condition, as the lubricant is only sealing the compression rings, and won't get up as high as the Valves.   Put in too much oil, and you will fill the Compression Gauge with it, and the other cylinders with their Plugs out will blow it out the Plug Holes, and all over the engine bay.

The reason your plugs are looking good could be a result of the Oil Control Rings around the Piston being in good condition, and not allowing excess oil up into the realms of the Compression Rings.

Bad Oil Control Rings, which are actually scrapers and an in-between spreader, will allow the oil to escape up the cylinder wall, and the compression rings on the Piston's downward movement will allow the oil to escape into the combustion side of the Piston/cylinder, and therefore will get burnt off on the next firing stroke.

Compression rings are at their tightest (to the cylinder wall) condition on the compression and firing stroke, as the pressure is applied to the top and back of each ring, and the bottom of the ring, sitting on the piston land stops the excess compression from feeding back into the engine internals (Sump) which is called "Blow-by".

Bruce.

[RobW]

OK so bad rings? Or not bad enough to be the problem or worry about yet? Does that mean I haven't found the "miss" or vibration  yet?

["Cadillac Kid" Greg Surfas 15364]

Rob,
We are still "pointing" to the #4 cylinder valves.
Greg

[RobW]

Greg
Do you think #4 valve got bent if chain went bad? Shouldn't more than one valve hit?

["Cadillac Kid" Greg Surfas 15364]

Rob,
It doesn't necessarily have to do with the timing chain.  I have had a single valve go bad, either cracked or seat not sealing twice and I was never able to determine why, but after replacing the single valve (actually I did bot valves of that cylinder) I had a flawlessly running engine for many many miles.
Greg

[RobW]

so maybe the plastic bits i found when I removed the valve covers were valve seals? I did find them on both sides though

[RobW]

Looks like I need new studs on the exhuast manifolds. They are 3/8-24 threads but are worn. Tried thread chasers and even a die but neither helped.
So guess I need to pull the manifolds. Can't wait to see the next can of worms! I'm thinking I might as well do the heads while while the exhuast is off. Any ideas what a machine should charge for the heads?

[TJ Hopland]

The Cad heads I have had worked on typically have not needed that much work so it should not be that bad.  Most guys that are doing a little performance upgrade have the guides cut down to make room for more cam and the more typical positive seals vs. the original umbrella type.  Since the OE seals come in the gaskets kits many guys have them laying around.  If you are tanking the heads off you are going to need enough gaskets to likely make it worth just getting the complete gasket set vs. buying them individually so you will get a set also.   The one part that does not come in the fel pro set is the intake / valley pan gasket.  That has to be ordered separately.     

I have been buying parts from here:
http://www.500cid.com/Store%20Home.htm
The are actually out there developing parts for these engines to keep them going.
They also have hardware kits that I think are well worth the money, its nice to just have new bolts vs spend the time to clean and keep track of all the old stuff.   

["Cadillac Kid" Greg Surfas 15364]

Rob,
We talked about the #4 cylinder being the culprit, so my suggestion is to pull the heads (after pulling the intake and the exhaust manifolds), taking them to a GOOD machine shop and see what they say.  With the heads off you can visually inspect the interiors of the cylinders for gouges, grooves, excessive wear, etc.
You will also be able to easily check the cam chain through the oil return opening in the front of the lifter "valley" under the intake manifold next to the distributor.  If you are able to "lift" the chain on the cam gear (you can do this gently using a screw driver or even your finger) then the chain and/or the gears are worn and need replacement.
Regarding the exhaust manifold "studs", there should be 3/8 inch bolts holding the manifold to the head.  If it is the bolts that are worn out they can be easily replaced. TJ mentioned MTS, and they can provide a replacement Stainless steel bolt set (they make the kits for just about everything in the engine if you need them).
If it is the threads in the cylinder head that are bad then the machine shop can fix those for you.
Typically I have paid about $650. for shop work on a pair of heads (stock) including valves and springs.
Were with you Rob.
Greg Surfas

[RobW]

Been a slow day so started tearing into the engine. Was thinking about just pulling the exhaust manifolds to change the studs. Tried loosening the bolts holding them to the heads. the last one one the right was missing its head. Tried very carefully working the adjacent one back and forth but it snapped the head off too. So with two bolts stuck I can't lift the manifold off w/o removing the head. So guess I'm doing the heads. Start pulling everything else off the front and top off the engine and now that I can get a better look at the cam gear I can see it wasn't changed. Half of it still has the nylon while the other half doesn't.
So now I'm looking at the chain and doing the heads. Machine SHOP says about $220 for the pair if they just need to be cleaned up, magnafluxed, and new seals. If they they need guides and seats maybe closer to $400. OK not too bad. So for around $6-700 I'd have the heads done new timing set and gaskets water pump(might as well while I'm there) anti-freeze, oil, etc. But my rear main seal is a little leaky too. Machine shop suggested pulling the lifters and checking the cam. I'm thinking about maybe just pulling the engine and getting it rebuilt. Plan on keeping the car forever anyway so might as well go for the almost $2000 for the rebuild. Then might as well do the trans for another $4-500. And then... and then...

["Cadillac Kid" Greg Surfas 15364]

Rob,
Don't forget to take a good look at the #4 cylinder's valves to see if that in fact was the cause of the vibration, or you need to look further.  If you do rebuild the engine a good use of some bucks is always to have it fully balanced.
Greg Surfas

[RobW]

Now if I could only find 17 people to help take the hood off............

[TJ Hopland]

I would pull the engine.    You will get a much higher quality repair that way.  Working bent over the hood wears on even the best mechanic.  Trying to get the oil pan on and off and sealed again while its in the car is also a lot of work.  Doing all that in a stand is simple.

[RobW]

Well its almost ready to come out. Still need to drain the oil, unbolt the trans and motor mounts and remove the hood. Its probably easier to leave the tranny in the car, right? Or maybe take the tranny out by itself from below?

[TJ Hopland]

It depends on your setup.  To pull it out from underneath you need quite a bit of room, more than you usually get off of jack stands.  To pull it from above with the engine you need some room from underneath and you need lots of clearance above for the boom of your hoist.    If you remove the engine first you need to support the front of the trans somehow so take that into account if you have to move the car around or change the height of it.