Chevy 350 is this a common thing?

[marq]

I timed my engine last week with a timing light,after i had timed it to 10 degrees btdc the engine ran like shit so i timed it by ear until the engine ran smooth and gassed nice and smooth.After putting the timing light back on to check the degrees i found the mark on the harmonic balancer must be timing at about 28 degrees btdc,way off the scale.I can only assume that the timing chain case must be wrong for the engine or something is way out ,but the engine runs really well.....any ideas ?.......Marq

[Mr 42]

Are you sure you have the right timing pointer?
There is different types over the years.

The outer ring can move on the harmonic balancer, if ite old and murky.

[Baumi]

Maybe you have a "long waterpump"-style timing cover combined with a "short waterpump"- style dampner? A buddy of mine had the same trouble, his timing was about 30° off while the engine ran fine.

What you could do is remove the 1st cylinder´s spark plug and mount some kind of piston stop. Turn the engine over clockwise by hand carefully until the piston # 1 hits the stop.
Mark the balancer , for example, where the tag says "0". Then turn the engine back counterclockwise until the piston hits again. Mark again at the O sign.
The real TDC is exactly in the middle between the two marks.

Chris

[C9]

28 degrees sounds about right if the vacuum advance is connected and operating correctly.

When you shoot the timing for an initial timing figure, unhook the vac adv line and plug it.
Then shoot the timing and once the initial is set, spin the engine up and see if the centrifugal/mechanical advance is advancing properly.

After that, hook up the vac advance, advance the engine revs to about 1500 or so and 'wing' the throttle. (Winging defined as a short burst of throttle so as to bring the rpms up, but most importantly to drag the vecuum level down. Don't pick up too many revs doing this.)
When the vac level drops you should see the timing back off momentarily proving that the vac adv is operating correctly.

You may want to think of the vac adv as a vacuum retard.
Even though it's called vac advance, it's responsible for both functions.

Timing on a street engine is - and should be - affected by both rpm and load.

[Just Gary]

Yes. This happened to me, too. It was as Mr42 described. The harmonic balancer was kinda old and twisted around the machined hub. I tuned it by ear & seat-of-pants.

Since then, I got a chrome "proform" brand cover at a swapmeet. It has the timing marks printed on it and the screw holes keep it from twisting. A better solution would be to get a new harmonic balancer.

[fab32]

Is it possible that you have a "late model" balancer and an early model timing cover? On the later engines there was a timing probe socket behind the water pump and when the timing was set you had to look behind the water pump ot line up the timing mark. Just a thought, but there are a lot of SBC parts floating around and its easy to get things mixed up. Another possibility is that the inertia ring has slipped on the inner hub.

Frank

[Jimv]

Its very simple,the timing mark on alot f SBC;s is at the top(say 12 oclock) you have a timing ab thats at about2 oclock!!
put the timing mark on te damper at 12, then mark the zero on the side tab & you'll be styling.
JimV

[marq]

So basically what your saying is move the timing mark on the damper to 12 o'clock then mark the damper again at the zero point of the pointer scale on the timing case.................?.........marq