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472 Timing jumping, car bogs some of the time

Started by WTL, February 05, 2017, 06:17:11 PM

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WTL

So I have been driving my 69 Fleetwood, with 135k miles an awful lot lately.  Probably 15k in the last 2 years. 

Just the other day, I had a bogging issue for the first time.  I rebuilt the carb myself in december, and it drove well for a bit afterwards, so I am really thinking this time its not fuel.  Acceleration pump and all seems to be working.  No vacuum leaks that I have found. 

Bought a timing light, plugged the vacuum advance, and set it at 5* yesterday.  This stopped the bogging, so I did some superbowl errands today, and then it started bogging again for a sec...checked timing again, and its off.   Seems way advanced at the moment, but I've seen it retard too...the distributor is tightened down so I dont think its moving.  So basically, it seems I have timing that wont stay the same...

My guess?  Timing chain.  What do yall think?  Its a cheap HEI unit, so I was also considering maybe that the vacuum advance is switching on and off randomnly, but not sure if thats likely...the timing really seems to just decide to be different an awful lot. 

TJ Hopland

How do the weights and stuff look?   The HEI's seemed a little more prone to having the weights rust and stick than other designs.   Sticking weights could cause the symptom you are describing. 

Timing chain is also possible.  When the plastic goes they tend to sort of ride up on what is left of the teeth so sometimes it may ride up other times not.     Quick check would be to rock the crank back and fourth while looking at the rotor.   If its really bad there will be quite a lag when you change directions.    One hassle is the 472's didn't come with a bolt in the crank so you have to find another way to turn the engine.   Strap wrench?  Pop the inspection cover and do it by the ring gear?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

WTL

So how much force would it take on the crank to see? 

Obviously, if there is a way I could rule out a sloppy timing chain without dropping the pan, or diving in there, thatd be sweet. 

TJ Hopland

It kinda depends on how worn the engine is.  A really worn engine sometimes you can rock them a bit by yanking on belts and or gripping pulleys.  Most of the time especially on a big engine you will need some sort of tool with at least a 1 foot handle to get you leverage.   A fresh 472-500 can take a lot of force even with the spark plugs out, its a big engine with a lot of surface area in bearings and rings.   At least for this test you are just trying to rock back and fourth so you don't really care where it is or have to take it past a compression stroke.

Most engines have a bolt in the front of the crank so a socket and breaker bar is how most people would usually do it.    There is a threaded hole in the Cad cranks but its not a real easy to find thread plus you need the right washer.   I don't remember the size, its not that rare as engines go but is not something you would find in a hardware store.   Its not the same as a Chev so parts stores are no help. 

You can usually see enough of the chain and cam sprocket to get an idea of its condition by pulling the distributor and looking down the hole.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

WTL

Halftime show is good for something!

OK, so I went back outside...first, I didnt mention that I replaced the cap and rotor yesterday as well. 

The weights dont appear to be sticking.  Havent been able to check the crank for wiggle yet, but I tried the inductive clip on various other plug wires, and it seems like there are some that are intermittantly missing a spark.  Its a harbor freight timing light, but I think the light is telling the truth...plot is thickening. 

35-709

48 years old and 135,000 miles on an engine series well known (infamous?) to have timing gear problems with plastic coated teeth.  Even if the problem turns out to be HEI or vacuum advance related, that gear and chain are long overdue for replacement.  IMO. 
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

Bobby B

Check all of the above, test every plug wire, coil, every terminal on the cap for continuity, and every plug, which has nothing to do with wandering timing, but I've gotten bad plugs right out of the box. Was the problem happening before you changed the cap/rotor? Put the old cap/rotor back on and try it again. HEI Coils are not that reliable either. You have to trust offshore parts today which can be a crapshoot. Yes, it could be your timing chain, but you might have something trivial going on with your ignition that you're overlooking. Good Luck!
          Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

Jeff Rosansky CLC #28373

I think it's a 9/16 fine threaded bolt in the center of the crank pulley. There may be a plug in there and/or the threads could be capped up. I lubed my bolt but it stuck in there anyway. Spark plug socket fit the head of the bolt perfectly. Breaker bar will allow you to rock it back and 4th.
Even tho you looked at the weights, be sure they are I all the way each time you check the timing. I can't remember if there is a way to tie them off but if so then try that to be sure it is the same each time. Also be sure your vac advance isn't sticking. Even if disconnected it may be sticking from the last time you drove it.
Bearings in the distributor shaft could cause a problem however we are hooking for something that just happened. Worn bearings would sneak up on you over time.
I don't know much about hei units so no help from me on that. Check to be sure the engine is still grounded well.
Good luck
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

TJ Hopland

Lots of ideas:

If something is going wacky in your vacuum advance a common failure with some age in the HEI was the wires coming out of the pickup coil crack because they move with the vacuum.   They crack internally so they look fine.  The symptom is it will usually idle fine but when you hit the gas it wants to die.   Sometimes you can feather the gas and get some speed up but it doesn't last.    Its easy to test,  disconnect the vacuum and test drive.   This will usually flatten the performance but should not cause bogging.   You can also probe the wires with an ohm meter and operate the vacuum with a hand pump and watch the ohm reading.  It should be steady. 

Where you do have the timing light probe clamped?   Try it as close to the spark plug as you can get and as far away from the other wires.    Some probes are very sensitive and will pick up or get confused near other wires or the coil itself.   This cold explain the floating timing if its picking up the wrong cylinders.   If #1 is close to other wires try #4,  its usually a little more open and will still align the timing marks.   For me the big advantage to using #4 is its 1 less wire near the fan and belts.   Lost a few timing lights to Cadillac motors that way.

Did you assemble the contact correctly in the new cap?    Contact in first then washer then coil.   

How is the coil ground?  The ground to the cap is the middle of the 3 terminals.   Sometimes its a bar other times its a wire.    On some of the coils the side where that bar goes isn't a very good connection point, the older ones had a brass like rivet there that would for sure conduct to the top where the wire from the coil went.    On some I have came up with another piece of wire to make sure the ground connection is good.   

For a test you could try running a new temporary power feed to the coil and disconnecting the existing one.   Note that the key probably won't shut it off that way.    Reason for this is the car would have originally had a resistor or resistor wire feeding the coil.   Checking voltage at the coil at idle IS NOT a valid test to see if the resistor is still there.   The resistor itself does not really seem to hurt the HEI much but the connections to the resistor could be having issues at this age.   Its a long shot but not that hard to test and eliminate.  ALso would not explain the change in the timing.   

Last thing which would not cause the timing to float around either is did you change the float in the carb?   I have seen it a lot lately where the arms of the float hit that plastic plug that holds the pivot down in that area before the needle seats.   A little work with a file or dremel in the plastic will take care of that.   

StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

chrisntam

Quote from: WTL on February 05, 2017, 08:30:11 PM
Halftime show is good for something!


Actually, the halftime show was pretty good. 

If you looked closely, the lights in the crowd were in the shape of a '70 convertible.

Not really, but I thought I saw the shape of something.

;)
1970 Deville Convertible 
Dallas, Texas

SIPLOWGUY

I had that happen to me on a 78 Chevy. It was the mechanical advance weights. Make sure they move freely.
SIPLOWGUY

cadman56

The bolt is a 9/16 fine thread.  The first thing I would check is for play in the timing chain since you have an aged engine with those miles on it.
Getting that chain cover plate back in place w/o lowering the oil pan will be a bear.  Been there done that.
Good luck,  Larry
1956 Cadillac Coupe deVille (sold)
1956 Cadillac Convertible (sold)
1956 Cadillac Eldorado Seville (sold)
1967 Cadillac Eldorado (sold)
1968 Cadillac Convertible (Sold)
1991 Cadillac Fleetwood Brougham dElegance
Larry Blanchard CLC #5820

WTL

Did a little extra research on the hole on the crank, and apparently they stuck a cork in there from the factory to protect the threads...and its still in there!

So that pretty much means that either somebody rather conscientiously put the cork back in there after a previous timing chain replacement, or far more likely, its never had the crank off.  Pretty amazing.  I was thinking it had to have been done before. 

The HEI is supplied via a relay, using the resistance wire.  The carbon button is under the washer, as I think is correct.  There could be something going on with the wires, they are routed close to each other, especially the passenger side wires...but when I placed the inductive clamp on #1, it wasn't too close to any other. 

One mechanical advance weight is out barely, barely, a little more than the other so that they arent quite symmetric...but I think that is just poor tolerances...springs have a good bit of springiness.  Vacuum advance seems smooth...havent tried driving with it plain disconnected, but it does change the rpms if you unplug the vacuum line while running. 

I changed the cap and rotor precisely because I was having a bogging issue.  The carbon button was previously pretty burnt. 

If it was the carb float, that would suck.  I already took the carb apart twice in december, cause the first time I did it apparently the hanger fell off the float...but I have a timing problem, and if it is jumping such a matter of degrees, pretty sure it is the reason for a bogging problem.  It just sounds like timing when it happens. 




Scot Minesinger

This happened to me too after I rebuilt the carb on my 1970, turned out that the shafts on carb were worn and needed to be re-bushed.  I missed this during carb re-build.  Also the worn shaft made the car idle too high much of the time, so you had to reach down and pull up on accelerator - no return spring would do it. 

Also as others posted replace that timing chain!  It is long overdue.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

That cork is interesting indeed.  You would not think they would have held up and stayed in place this long.  I think most of the engines I have dealt with still had them.     I replace them with a bolt just to make sure things stay together and for a handy place to turn them over from.

Do the CLC judges check for that?   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

WTL

Just wanted to pop in and thank you guys for the help so far.

I've decided that regardless, the time has come to take the timing chain off...also gives me a good opportunity to do the waterpump too (waterpump looks original, even though its clearly been off as theres some rtv speared around)...

Its just so easy with an engine this old, anytime something bad happens, to think "oh boy, there went the timing chain" or worse, "oh boy, is it a head gasket now?"...I've pushed the old girl harder than should be possible for a car her age, its time to fix some problems and take them off the list of things to worry about.. 

Who knows, I coulda got water in the gas and be chasing rabbits.  But this needs to be done. 


Gene Beaird

If you can get the car to run, putting a timing light on the timing mark while the engine idles and watching it will give you a good indication of how bad the timing gear is.  If the mark bounces back and forth while the engine idles, you can bet you need to replace the gears and chain.

Be careful on the lower(?) water pump bolts when putting things back together.  Those bolts go into a pair of nuts that are tack welded to the back of the timing cover, and are prone to getting stripped if you really crank down on them.  Follow the book for the torque specifications, especially with these two bolts!
Gene Beaird,
1968 Calais
1979 Seville
Pearland, Texas
CLC Member No. 29873

Jeff Rosansky CLC #28373

Exactly--
The torque values in the book for the little bolts are in INCH pounds.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

TJ Hopland

I don't think the factory was using RTV at that time so its likely been replaced at some point. 

From the factory there were no nuts on the back for those small bolts, all they had to grab on was the thin cover itself.    The highly recommended fix if you have the cover off is to weld a couple nuts on there which then should greatly reduce the chances of a problem. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

35-709

Grind the surface smooth first so the nuts sit on there nice and flat.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2