LA small block timing is suddenly way off

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Tonight I removed valve covers, removed distributor cap, removed spark plugs. Turned engine over slowly by hand and confirmed that harmonic balancer 0° mark perfectly aligns with TDC of compression stroke on cyl 1 (i.e, both cyl1 valves closed, thumb on spark plug hole to feel compression building, a wooden dowel on top of piston until crankshaft is just barely past the point where piston stops moving).

THIS IS NOT HOW YOU CHECK TDC. REPEAT REPEAT REPEAT YOUR TRANSMISSION YOU WERE GARBLED IN TRANSMISSION REPEAT REPEAT MAYDAY MAYDAY DI DI DIT DAH DAH DAH DI DI DIT................................

Reat the earlier posts GET OR MAKE a PISTON STOP

A PISTON stop is the only practical accurate method to check timing marks and TDC
 
. At this point the distributor rotor points about 30° past the cyl 1 post on the distributor cap, with the distributor set where i previously had it. This means my previous ear tuning (fast smooth idle) must have been 30° advance timing,.

No Wrong. A distributor rotates at HALF crank speed. This means the relationship of the rotor is not the same as crank degrees. That would be more like SIXTY at the crank.

AGAIN you are GUESSING. STOP guessing. JUST STOP

GET A PISTON STOP Do this RIGHT

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This means my previous ear tuning (fast smooth idle) must have been 30° advance timing, but the engine did seemingly run well and i never detected any knock or ping. Aha, but i then found that the harmonic damper has at least 3 other strike marks around the perimeter. .

Amazing. DO IT RIGHT

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So other than the fact that i have been using about 30° advanced timing at idle which is probably not good, i no longer think i have a timing problem causing the bad missing. I can turn the distributor in the retard direction to properly set timing, and i did try this a couple days ago but it was making the miss even worse (daughter in car feathering the throttle and keeping the rpm's up to keep the engine limping along). But i still have not found the real problem, so maybe i had a backfire that did something to one of my edelbrock 1404 carbs. The name of this thread is now wrong, but before i started thinking i had a timing problem i did remove all 4 fuel/air idle screws and shoot a blast of compressed air in each hole to remove any debris from the idle circuit, this tip came from an edelbrock youtube video i saw earlier from an edelbrock guy. I also pulled out all 4 metering rods and wiped them off but they were clean.

See you are just going in 40 different directions.

GET the timing marks CORRECT

THEN figure out what the cam timing SHOULD be and estimate whether it IS correct. This is easy to do, as the intake event occurs somewhat near TDC, so even if you do not have a degree wheel, you can measure around the dampener and compute inches / per degrees to work this out.

AFTER you have proved to yourself that TDC is right, that cam timing is as correct as you can "see" it, then attack your distributor

YOU NEED A timing light which works with MSD

YOU NEED to figure out what the mechanical advance is, how much it advances, and whether it's stuck, rusted, or has other problems.

If you cannot do any other thing after you get the timing marks checked (did I mention with a piston stop)

Time the thing at high RPM at about 35* with no vacuum, then see "where you are."

PISTON STOP

Remove the no 1 plug. Wrench the engine or bump it so the piston is "down a ways." Unhook the battery ground

Install the piston stop. You may need to play with the length. Wrench the engine around carefully until the piston stops against the device.

CAREFULLY and accurately make a temporary mark onto the balancer next to the TDC on the timing tab. You are NOT trying to stop the piston at TDC, but rather down in the bore somewhat.

Now wrench the engine around CCW until it again stops on the device. Make a SECOND mark next to the TDC timing tab onto the balancer.

NOW you have 2 temp marks "some distance" apart. True TDC will be 1/2 way in between, and if the original is correct, that is where it will be.

THEN measure around your damper, circumference, carefully and accurately, figure degrees per inch around, and mark off the correct distance for something say, 60 degrees, 50 degrees, or 40 degrees. having done so, CHECK your work carefully. You MUST MUST use a tape for this first measurement.

Then take a pair of dividers and divide this distance into halves, quarters, etc. to get down to 10's of degrees, etc.

NOW you can see what advance is "doing."

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I am betting the timing chain has skipped a cog. The rebuild could have reused the original nylon gears and a new chain. As most of us know the nylon gears tend to loose chunks. I have been there, and managed to get the car running enough by twisting the distributor (ran like a bag of crap) to limp it home.

Please don't "test" exhaust, or anything else for that matter by revving the crap of an engine in park or neutral. It is just plain not good for anything and would absolutely lead to a timing chain skipping.

As was stated previously, with the distributor cap off, turn the crank back and forth and watch the rotor. There should be no, or very little lag in the rotor following your turning the crank.

My two cents worth.
 
Here is a quick check for cam timing.
-Crank at #1TDC: thats proven TDC,.. as piston stop used.Drivers side valve cover off.Plugs out. If on compression stroke, rotate 1 full revolution.Now while observing the rockerarm motion at #1 cylinder,reverse rotate the crank to about 10*advanced, then forward rotate about to about 10*retarded. Repeat several times. If cam is anywhere near correct you will be able to observe the valves going through split-overlap, the time when both valves are slightly open, the one closing and the other opening. A sloppy chain or a large cam may require slightly more degrees of rocking. The point is,split overlap with a good chain should occur at or near the TDC mark( probably within 5*).Are you starting to understand how important the TRUE TDC mark is? A jumped chain is easy to spot this way.
-If your chain has jumped, replace it with a double roller set. And I have used the Mopar tensioner to good effect so recommend it as well. Those chains go a long long time.
-and after replacing a chain, the dist. will have to be retimed.
 
To d55; I can totally understand that. I once bought a 71 Demon with a jumped chain. With retiming, just to get it to idle(barely) the throttle had to be wide open. Obviously, I couldnt drive it home.
 
OK I will build and use a piston stop to prove TDC and follow the other advice above. Although I had read somewhere that rotating your engine backwards is really hard on crankshaft bearings. Apparently that is not a widely held opinion since no one here mentioned it. Yes I do have two Edelbrock 1404 4-bbl carbs and an Indy ModMan intake maniflold. It was set up this way by the previous owner.

Based on a comment above I realize that the distributor rotates once for every 2 engine revolutions so my last night's static visual estimate of timing advance was off by 2x. A 360° circle divided into 8 sections has 45° per section. The rotor was pointing well past cyl1 distributor cap tower (about 3/4 of the way to the following tower) so last night I estimated I previously had 30° advanced timing, but that estimate would actually be 15° advanced timing relative to the crankshaft, which is a more reasonable value. Anyway I will use a piston stop and do this all again. And based on comments that I need a timing light compatible with MSD ignition, maybe that is true since I believe the MSD shoots a double spark and I don't know the relative timing of those 2 spark events, I assume my old timing light will fire on the first spark event.
 
MSD shoots up to 6 sparks at low RPM and gets down to one fat one above abput 3000. If your timing light sees 6, just use the first one. Edels dont have power valves, a backfire wont do damage 99% of time. Pulling the timing cover may be well within your future, even to check on your chain make-up. Replace the nylon if you got it. timing chains are inexpensive. while you are down there, buy a Mopar tensioner, best thing you can do short of a gear/cogged belt drive for timing consistancy. 30 crank/15 DISTRIBUTOR timing off is bad but it wont disable the car. you should be able to adjust it out by turning the dizzy. 15 CAM timing is bad. that is your chain.
 
MSD shoots up to 6 sparks at low RPM and gets down to one fat one above abput 3000. .

This is exactly why I suggested timing at high RPM for about 35 degrees. This will give you a "all advance" starting point that since you have MSD, should be an easy "work around" quickly, regardless of timing light problems
 
Although I had read somewhere that rotating your engine backwards is really hard on crankshaft bearings. Apparently that is not a widely held opinion since no one here mentioned it. .

Utter and complete nonsense. I guess you've never heard of a reverse rotation marine engine?
 
Not trying to argue, I'm the novice here, but even a reverse rotation engine would have a normal rotation direction, and manually rotating in the non-normal direction would be a reverse from the intended direction. Maybe it's more of a concern with an overhead cam engine, apparently not for our LA engines. A long time ago I was also warned to never turn a clock or watch backwards, some of this may be a wive's tale.
 
Not trying to argue, I'm the novice here, but even a reverse rotation engine would have a normal rotation direction,

Reverse rotation engines use the very same main and rod bearings that normal engines use.

About the only (very minor) thing rotating one backwards causes, is if you are trying to resolve a timing issue, LOL, you need to rotate it BACK far enough, that you can then rotate forward again far enough to take the slack out of the timing chain.
 
you're doing it by hand, you can't hurt the motor in any way doing this.
 
-A circle has 360*. If you divide the circle into 8 equal parts, each part would be 45*. So if the rotor was 30* past the no 1 tower, then the ignition system might be firing into the next tower past the true #1 at full advance or it wouldnt run at all. .

Cam is at 1/2 crank speed,, so 30* at the crank is only 15* at the rotor,, hence, - rotor is still 30* from the next tower.. ( 60* at the crank )

hope it helps
 
I have an inline fuel filter -> mechanical fuel pump -> inline Edelbrock fuel filter -> inline fuel pressure gauge -> line then splits and feeds dual Edelbrock 1404 carbs. No fuel pressure regulator. I have a steady 5psi of fuel pressure on the gauge at idle and at least up to around 2,000 rpms. 5psi used to work OK, but maybe 5psi is generally too high? I probably should install an inline fuel pressure regulator but have not researched what a good psi setting would be. Since I have a steady 5psi of fuel pressure I believe my fuel filters are not clogged. I also peered inside the fuel inlet of the carbs and down inside the carbs, pulled out metering rods, I don't see any gummed up carb parts yet. Have not pulled the tops of the carbs of yet to check floats.

I'm also thinking maybe I should buy a new MSD 6AL ignition box in case mine went bad. This bad missing problem was somewhat intermittent for the last few drives before it became permanent. I could try the ignition isolation test (pull one spark plug wire at a time) but right now there is so much missing going on I don't think I could tell anything. As you can tell I'm still trying to narrow down the real problem.
 
Cam is at 1/2 crank speed,, so 30* at the crank is only 15* at the rotor,, hence, - rotor is still 30* from the next tower..

Yeah you are right. I won't comment further about what my actual timing is or was until I do the piston stop test and use a timing light, probably measuring total timing advance above 3000 rpms (if I can make that happen under current conditions). But anyway I tried retarding timing yesterday with the engine running and it only made the problem worse so right now I am suspecting carburetion or maybe a failing MSD 6AL ignition box. There is a good hot rod engine shop about 4 miles from home, if I get desperate I may have to get it towed over there for professional help, at least I could tell them what I have learned up to that point.

Yesterday I also did a visual inspection of pushrods and shaft-mounted adjustable rocker arms. Everything looks right, and looks just as I left it this spring when I had to pull the intake manifold and replaced all 16 hydraulic flat tappet lifters since one of them would not pump up and I had valve noise. Back then I also set the lifter preload/valve lash according to what the Comp Cams guys told me to use since all of those parts are Comp Cams.
 
I'm still thinking a pushrod thru a rocker,, or bent pushrod.. Did you ever check and inspect all your rockers to make sure they all rock an even-ish amount or at all..

lol .. you were reading my mind, and typing faster.. cheers

hope it helps
 
It seems to me that you might want to focus, and start with the basics and work your way through. Del has you on the right path, just stick with it.

Bouncing around like a fly on an outhouse door is only going to frustrate you.
 
I'm also thinking maybe I should buy a new MSD 6AL ignition box in case mine went bad. This bad missing problem was somewhat intermittent for the last few drives before it became permanent. I could try the ignition isolation test (pull one spark plug wire at a time) but right now there is so much missing going on I don't think I could tell anything. As you can tell I'm still trying to narrow down the real problem.

Excellent point BadSport, sometimes it's hard to stay focused all the way through a problem, but it sure makes finding the problem easier and usually faster.

If I remember correctly MSD has a test sequence than can be run on the boxes, but I don't know if it would show n intermittant or partial problem as it might be a "works or doesn't" test only.
Also, there does seem to be an awful lot of MSD failures going around lately.
Must be the China boxes are getting spread around more or something.
 
Did not read the whole thread.
If it is in a 67 cuda, and you have a 360 motor, wonder if somebody did not switch the timing chain cover to the early style?
Thus you could never get the marks to align.
 
Did not read the whole thread.
If it is in a 67 cuda, and you have a 360 motor, wonder if somebody did not switch the timing chain cover to the early style?
Thus you could never get the marks to align.

And this is part of why, we use a piston stop...........................
 
Ditch that MSD for testing. Id grab a points and wire it up. I know an ignition box isnt going to throw you off 30 degrees but F'n with an MSD with a standard timing light is not easy. Jumped chain will also cause valve timing issues. Just pull the cover. Ita about 30 minutes of work and peace of mind. 5psi is fine for an edelbrock.
 
Ditch that MSD for testing. Id grab a points and wire it up. I know an ignition box isnt going to throw you off 30 degrees but F'n with an MSD with a standard timing light is not easy. Jumped chain will also cause valve timing issues. Just pull the cover. Ita about 30 minutes of work and peace of mind. 5psi is fine for an edelbrock.

This is the truth!
 
Thanks for the help, guys. I found the problem to be a leaking float in one of my Edelbrock carbs. Sorry for the wild goose chase on thinking my timing was retarded, I guess it was me that was mentally challenged. Found a float kit nearby and had it running shortly after. With timing light I set timing to 10° advanced at idle, which was about 30° advanced at 3,000 rpms. I could easily tweak this if needed.

Before finding the carb problem I followed the earlier recommendations. Piston stop tool, confirmed the reference mark on harmonic balancer is correct for cyl 1 TDC. Checked timing chain slack to be about 6° crankshaft rotation by observing distributor rotor and turning motor by hand. Verified cam phasing by watching rocker arms for cyl 1 at TDC exhaust stroke. Tested my MSD ignition box ability to spark, per MSD test instructions.
 
I'll bet...........!!!!!!!!!!!!........... You learned a lot!!!!!!!!!!

Tuck this away. "Some of us" on this board HAD no www. We learned the hard way, and sometimes, we learned "wrong" for "awhile."

I learned how to deal with piston stops, distributors, cam and igntiion timing in the early 70's----I was in my mid 20's..........

Somewhere around 1972............

That's a V code 70 RR you can see part of

http://www.forabodiesonly.com/mopar/attachment.php?attachmentid=1714576996&stc=1&d=1356805732
 
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