LO3BIRD

Recently my old 1850 holley carb flooded in the back (the vac secondary circuits). Motor ran real bad and rich at idle (much smoother at speed), of course. As I was driving it to my Dad's garage, it suddenly lost a lot of power and became really rough (I was accelerating from a very rough idle). Now it seems that the motor is under strain to propel the car as I drive (lot of gas needed).

I replaced the carb with a new 750cfm unit, flooding obviously gone. However, motor is very rough, still resistant to reving, and will not time as normal.

Compression test was normal on all cylinders and no ticking sounds. All plugs and wires were checked. Cap/Rotor/distrib are like new. Fuel gauge is new and solid at 7psi.

Engine vacuum is solid at 15, no leaks.

Motor runs really rough at around 1200rpm (can't run lower, hitting the A/C stalls at this speed) with timing at 16 degrees or so BTDC (narrrow band of adjustment). As soon as I turn the distributor to make my normal 12 degrees or so initial (vacuum advance disabled) the motor stalls out.

While running at fast idle 1200+ and high timing, the exhaust is backfiring.

Sounds to me like I got a cheap double roller chain (and the Cloyes true roller is sitting in the plastic in the garage, figures), it stretched (over 7 months, hard racing), and jumped a tooth during the rough running (really rough running).

What do you guys think before I tear her down??

Air_Adam

Timing chains don't just jump teeth. It may be very badly streched, but they wont jump a tooth.

Maybe you should do a compression test. If it was running as rich as you say, it may have washed down the cylinder walls and killed the ring seal.

LO3BIRD

They do jump teeth, I've seen it before (typically the nylon gears, once cracked, but I've seen it on unbroken steel gears too & chain stretched). They also break. In my case, this is unlikely since it is a double roller 7 months of age; and the chain obviously isn't broke as the engine runs, but way off on it's timing. When I say rough running, I mean the car was violently shaking from side to side as I watched gas dump from back boosters...

Now with the flooding fixed (new carb), the engine is rough (not like before though) and is clearly off timing (which was never touched) from the exhaust (mostly) backfiring and resistant to rev...

It will not run at 12 degrees initial (my norm) at any thottle position... it must be well over that (16-20) to idle at all 1200+ RPM.

Quote:

Maybe you should do a compression test. If it was running as rich as you say, it may have washed down the cylinder walls and killed the ring seal.

I did state the compression test was perfect on all 8. Also the total time running rich was about 10 minutes. Prior to that, plugs showed the engine tuning was right on.

I stated this "event" happened all of a sudden, during those 10 minutes of running/driving rich/flooding as I was accelerating back to my garage, then I noticed a real sudden loss of power (lots of loss) and even rougher running (had to gas it at the red lights now)...

ede

timing chains jump a tooth just like you can get a distributor installed a tooth off

LO3BIRD

Another non-believer... (none of you guys had to work on an engine that jumped it's steel or belt driven chain a tooth or more off??? I find this impossible to believe as many as I've had to repair; SBC's being rare with steel gears, esp double's)

(not really sure what you mean here, any monkey can install a distrib 1 tooth off; I said I was DRIVING (good too) when my car broke, not swapping parts)

BTW, I've installed enough distribs to know when they are a tooth off. And my car DOES run like it's a tooth off. I'd fix that in a jiffy if I thought that was it... but as per my orig post, the motor was running FINE (awesome would best describe it) before the flooding, in other words, distrib not 1 tooth off...

I keep trying to say the same thing, it real simple. I drove REAL fast, then the car "broke" and began backfiring. I fixed the carb flooding; car remains broke. NOTHING else was touched....

Guys, I sincerely do appreciate the help, but unless someone popped my hood and pulled the distrib during the 10 minutes of carb flooding, the distrubtor gear is where it was left when the car was faster than most high end sports cars.

Best I can tell (15 years SBC fanatic), prob is definately timing... BELIEVE me, I'd LOVE it to be EXTERNAL. Someone enlighten me and tell me how it's possible. Vacuum and timing marks (under the light) are dead steady. Vac advance works fine as well.

five7kid

iTrader: (14)

30+ years working on SBC's, never seen a timing chain "jump" a tooth. Including the cheap, quiet, factory nylon gears.

Post your compression results, dry and wet, by cylinder.

JesasaurusRex

iTrader: (3)

Just check it bro, i never heard of it neither but I cant tell you for certain that it cant do that because i dont entirely know. Its an easy check tho just pull the water pump, unbolt ur timing cover and i dont even need to tell you how to do it im sure you know. Just check 2 be sure.

bluroc

Last summer mine did jump, granted it was the factory nylon cam gear that self destructed and actually caused the chain to hit the cover making me think I had spun a bearing. Anything is possible, especially if the car was running as rough as you say. Line up the timing mark on the balancer with the mark on your cover (at 0 degrees) and then see what cylinder your rotor is lined up with. If that checks out, I would do a compression check because if you had ALOT of gas going into it, you could have cooked your rings on one or more cylinders. Any blowby out the valve covers?

MonteCarSlow

It's too bad you disturbed the initial timing. I believe checking what it was set at would have proven to you that it jumped a tooth.

EdB

LO3BIRD

Wow, I only got 15 years SBC's, but I've seen more than a few nylons do it.

I've read it possible on other internet forums. But it's tough for me to believe even a cheap double gear did it, but it's what the motor feels like when I rev it (I bought a $300 Chevelle with the same problem, owner didn't know what happened, it was just a tooth off, and exhaust backfiring bigtime with no power).

Anyway, I've only had time so far to dry test the cylinders (I'll wet em when I change out the plugs).

1) 145
2) 150
3) 147
4) 140
5) 149
6) 140
7) 142
8) 149

I don't see a 10% variance, so I don't see a problem here, although granted this doesn't tell everything. #'s also closely match when the motor was built 7 months ago (even #'s 4&6).

Thinking of head (blown) gaskets; I can't think of a connection with a flooded carb at the same time.

BTW, even in it's crippled condition, the engine can rev (and fast) to 4000rpm without any valvetrain noises, she just shakes pretty good without much of a chance of an idle (it's way too weak, even at 1200+ with the exhaust backfiring real good). Fluids look good, temps are normal.

Reminds me when I first built the motor and had 2 wires wrongly placed, but it did drive to the gas station. Now it barely moves in the driveway and I've triple checked the wires and fire order.

Turning the distrib by hand with the timing light everything looks normal, but the motor stalls when you drop down to 12 degrees BTDC, or tap the A/C, or shift to Drive, etc.

I realize removing timing cover isn't that bad, it's just I've got a really bad back and with a possible Hurricane coming I'm trying to make time for this and try to head in the right direction. I'll be sure to snap digi-pics for you guys when I get in there.

Thanks for the input so far; what a bummer, just installed the dual e-fans and new modified water pump. Seems I have another bugger of a problem...

LO3BIRD

I turned the crank with a wrench for TDC (0deg), rotor points right at wire #1 on the money. Compression results are listed above (dry so far). No blowby....

When it was running rough, tach was real low (<500) and it looked like grey smoke from the tailpipes (assumed it was the flooding, hope the rings aren't damaged). Now with the new carb and flooding removed the exhaust is clear but smells of unburned fuel...similar to retarded timing (sounds diff too, like a boat motor, etc).

LO3BIRD

Well I made the mistake of driving the car to where the replacement Holley needle valve was, 5 mins away. Next time I'll keep the needles stocked in the car.

Actually the day before this happened I did set the initial timing to 12 BTDC. And I distinctly remember the position of the distributor body (pretty easy with the Accel super coil).

To get 12 BTDC initial now (right before it stalls out), it seems the distrib body is rotated more CW (to advance timing, and motor speeds up the more advance I give). Doesn't this indicate a cam/crank relation change? If it does, than the 12 BTDC that the strobe light shows now is not 12 degrees at all since the cam drives the rotor (well it is 12deg technically spark-wise, but still messed up timing wise if the cam shifted)...

The motor also sounds "retarded", like that of a boat motor sound....

ede

not worked on SBCs near as long as five7 but in the few months i've wrenched one i've never seen a chain/gear jump a tooth. have seen one or two nylon toothed gears self destruct

five7kid

iTrader: (14)

LO3BIRD

Thanks but most are saying this. True or not, nobody has any alternate suggestions?

Fuel and ignition check out thoroughly...

Compression pretty much checks.

Valvetrain is left... I've had the valvecovers off, no broken springs; while running rockers move normally. Engine rev's quietly and quickly to 4000rpm (much lower than normal).

Well, soon as I have the chance (today/tomorrow), I'll pull the (maybe fans), pump, pulley, balancer, & front cover. If I'm right, I'll snap pics for you guys. If not, I'll use the opportunity to put on the Cloyes double true roller chain I have laying around; of course, if I'm wrong why bother, it still won't run.

I've run motors with terribly leaking carbs, no balancer (outer hub spun off at 100+MPH on 1/4 strip) and within minutes my motor is worse than all this. If it's not timing related, the rotating assembly must be shot, I find that hard to believe from a flooding carb.

Ironic, this marks 2nd time two different Holley's flooded exactly 1 day after filling this car with "Premium" from the same gas station (yellow looking gas thru my filter). The first time the whole 5.9L motor filled with gas including the intake (electric pump).

The guy who sold me this car unexplainably lost his LO3 motor (fuel injected). After GM, yes GM, tore the motor apart to the pistons, they still couldn't see why it wouldn't run. I grabbed the car motorless for $700. Possessed? :hail:

Air_Adam

Is your choke maybe stuck closed? Whats the timing set to?

My old Qjet used to run kinda like that when the choke was closed.

84 Z-28 350

do you have a cat?, my first car's preivous owner used ledded AVGAS in it and that coupeled with it running allitle rich caused it to clog up with allot of the same simptoms your having, try taking off the reed valves that go the AIR pump on your exauast manifolds/headders so the exauast has somewhere to go other than the pipe, if it smothes up you know what the problem is. BTW I've seen the cheep nylon timing chains skip a tooth, but the one tooth uasally only lasts a few miniuts and than the rest go. just my $0.02

LO3BIRD

Brand new Holley 3310 750cfm vacuum secondaries, choke open (I always run a tad rich so I don't need the choke, I force it to stay open).

Init timing is 12deg BTDC. Car likes it.

LO3BIRD

Exhaust is like my sig, full race....

Yeah the nylon usually disintegrates pretty fast (real fast at highway speed). Metal gears I figure won't break nearly as easy, esp doubles like mine, pretty much impossible. Excessive chain stretch (possible, it was cheap taiwan set) is the only way this thing would hop a tooth, and even that's "stretching" things, but I gotta start somewhere... car is too much fun to drive.

Will keep you guys posted...

littlebagz

Regardless if the chain jumped a tooth or the distributor was installed off a tooth, a timing light will tell you what the exact timing is.

A timing light references the crank position the the spark initiation. This relationship will always be what the light indicates.

In the case above he states that he still has 12 degrees BTDC timing, Im assuming he is checking this with a light. Timing is not an issue. It would be cam / crank relation ship that is the problem.

There are two ways to confirm:

a . Pull water pump, crank pulley, balancer, and timing cover and confirm the timing marks for teh crank and cam.

b. Pull a valve cover and teh front pully and use a degree wheel and dial indicator to confirm the valve timing in relation to the crank.

Both require some labor and the second option requires some specific tools.

Streetiron85

I've only skimmed over this post, so if I missed something, my apologies.
But... Firstly, I'd have to say that jumping a tooth is highly unlikely to begin with.
Secondly, the problem originated when there was a fuel system malfunction, which makes it even less likely that the timing chain would be off. As the timing chain is something that would be the last thing to be effected by a fuel system related problem. With that in mind, IMO it would be a waste to remove your timing cover only to find out that everything in there is just the way it should be.
The next thing I'd do after a timing/ plug wire check would be a vaccum test.
My guess is that fuel flooding down the intake may have effected the gasket seal between the intake and the head.

After all possible tests are performed and if the problem still isn't located, and you still feel a need to chech the timing chain. Take a dial indicator and a degree wheel and use that to find out if the .050 opening or closing points are at the specified location in relation to TDC according to your cam spec card.
If your cam card is lost, the Crane site has those specs online.

I'd rather buy a dial indicator than R&R a timing cover.

LO3BIRD

Thanks for the help guys...

I agree. Plus reving to 3000 rpm's and dropping into drive just to get about 8 inches in the driveway is pretty weak motor no matter how you look at it (I had to move the car away from a tree for the Hurricane; my neighbors call police if they see you 'push' a vehicle, but re-starting 20 times is okay with them)

Was without power for over 3 days (Hurricane), but now I have the crank bolt already loose, so just the timing cover and water pump and I'll reveal with pics what happened (or didn't happen).

I'd be surprised if the marks don't line up, but it sure runs like they don't; and at this point, it's easier for me to pull the cover, I have extra gaskets.

BTW, ironically my sister's '89 Buick just jumped it's chain (I'm fixing it now, FWD, nylon teeth, PITA). It was still running (barely, real rich too, ECM couldn't cope and didn't fire a code either; dimples did not line up) when she brought it to me, almost identically to how my Camaro is doing... she's lucky, no valve damage; my Dad's '86 Buick I had to change the heads when the nylon gears broke at 80k, bottom end still was good.

five7kid

iTrader: (14)

Assuming that's a Buick V6 of the 3800 variety, they use a chain tensioner. Much more likely to jump and still keep going than the non-tensioner SBC design. I had such a '77 V6, nylon gear, made a rattling noise for a long time but kept on running - until the chain broke. It never jumped a tooth in the process.

(Family's '91 3800 had the cam sensor magnet fall out - the plastic holder fell apart. Replaced the timing set while I was at it. When you do this job on your sister's car, replace the sensor magnet while you're at it.)

LO3BIRD

Thanks for the advice (yeah it's 3800 they always mess the chain, will do sensor magnet while in there).

Tuff working on all these cars (they always break together don't they?) since my Dad's garage still has no power/phone service and the weather is still nasty from that Hurricane.

Really missing my Camaro; I love my Blazer (238K miles/2.8L/700R4) but you just can't ratchet-shift it at 5800RPM (not yet anyway)

Plus it's tough just getting ice/water/gas down here now...

pete0013

It is not probable like so many state, but very possible, had it happen to me 2 weeks ago, car running great, parked at work left for lunch and boom like I was driving a tractor, spent hours cussing and tuning, swapping parts thinking it could be this or that. Finally I took every thing apart marked my original #1 and found top dead center, low and behold it was one off, moved each wire one back and we had life again!! So as far as how impossible it is, just because it hasnt happened to you or you never heard of it does not mean it doesnt happen! ( will be replacing chain soon)