SBC, Holley floods, fixed, seems timing chain wrong - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-01-2004, 09:30 AM
360Camaro's Avatar
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SBC, Holley floods, fixed, seems timing chain wrong

My 1850 holley carb flooded in the back (the vac secondary circuits, bad needle valve). 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 (lots of loss) 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 3310 unit (no cost, local speed shop is good to me, built my motor/trans from him), flooding obviously gone. However, motor is still quite rough & resistant to rev's, and will not time as normal.

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

Plugs showed engine was tuned perfect before carb flood (car runs 12's, nearly 390hp, 5700rpm reving high/flat torque motor)

Engine vacuum is solid at 15, no leaks, sprayed intake, etc.

Timing mark is dead steady.

HEI vac advance works properly.

Motor runs really rough at around 1200rpm (can't run lower, hitting the A/C stalls motor 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.

At 1200+ RPM and high timing (16-20 BTDC) she runs shaky & the exhaust is now backfiring real bad.

Sounds to me like the timing chain is off a tooth (can't be distrib, it wasn't touched). Problem is that it is a double roller (a really cheap one tho, not the Cloyes, which I do have unused) and the car ran great for 7 months with it (hard racing tho). Is it at all possible that the chain stretched enough (in 7 months), that during the 10 minutes of REALLY rough running that the chain jumped a tooth?

She flooded, suddenly lost way more power driving to the shop, fixed flooding, now won't time/run as normal. Nothing was touched/swapped. I want to look at the chain markings now (even in my disbelief). What do you guys think before I tear her down??

Thanks

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Old 09-01-2004, 09:56 AM
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If your are 100% sure you've gone over every part of the fuel and ingnition system I only see the valve train is left. You should look for timing marks, signs of burning, worn cam lobes, collapsed hyd. lifters or broken springs. Cam timing would have to jump more than 1 tooth to run that badly. Camparing actual compression numbers with previous numbers can clue you into what's happend.
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Old 09-01-2004, 10:16 AM
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Quote:
Originally posted by johnsongrass1
If your are 100% sure you've gone over every part of the fuel and ingnition system I only see the valve train is left. You should look for timing marks, signs of burning, worn cam lobes, collapsed hyd. lifters or broken springs. Cam timing would have to jump more than 1 tooth to run that badly. Camparing actual compression numbers with previous numbers can clue you into what's happend.
My previous compression #'s are identical. So I was kinda relieved, hoping for no physical damage to the motor.

As for jumping 1 tooth or more, I don't know. But tooth jumping is still possible even on a double chain right if the chain is stretched enough?

This event did happen all of a sudden, as I was driving the flooding car to the garage, it lost a great deal of power and motor seemed to be straining (almost like a spun bearing). But my gut says it sounds/smells/looks like ignition is off.

It just seems like if the carb never flooded, and the engine never ran violently, that this wouldn't have happened; as strange as that sounds.

I've worked on SBC's that were only 1 cam tooth off and they ran pretty bad and backfired through exhaust like what I have here (couldn't compensate at the distrib much at all).

BTW, the engine can/will rev to nearly 4000rpm in this condition without any valvetrain noise. Am I sorta on track in my thinking of the timing chain? It's just that I have a really bad back and this is a fully dressed 92 camaro...

Last edited by 360Camaro; 09-01-2004 at 10:42 AM.
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