Thursday Tech Tip: Timing is Everything With ATI and SBC Engines
We’ve all been there, struggling to find the correct timing marks on our SBC engines. Things got complicated after 1968 when GM decided to move the timing tabs in 1969, but we were all able to deal with the 2 degree and 10 degree off the key-way timing until 1980 when the timing tags changed again to 30 degrees off the key-way.
To complicate matters, GM has introduced different harmonic dampers into the mix. A 6 3/4″ X 1 3/16″ for Chevy 350, a 6 3/4″ X 1 11/16″ for the 267 and 305 SBCs and a larger 8″ x 1 ½” for the later SBC 350. The 400 SBC was a beast of it’s own with internal or external balancing.
Mixing and matching SBC components has become so commonplace that often a home garage engine builder with end up with the wrong timing cover (and timing pointer) with the wrong harmonic damper (with timing marks) which ends up making the engine’s timing a difficult task to achieve.
So what is a person suppose to do?
Make your own timing system!
Thankfully there are companies like ATI Performance Products that understand the numerous combinations of OE and aftermarket timing components that can be rightly and wrongly bolted onto the front of a small block Chevy engine. A quick call to their tech line (877-298-5039) can get you going in the right direction to solving the timing dilemma. You will likely be asked by the technician on the other end of the phone line at ATI, what type of crankshaft you have in your engine and some other basic information. From the information you supply, the technician can tell you which damper you might want to consider purchasing.
ATI offers harmonic dampers in the following sizes and configurations for your SBC:
- 6.325″ Standard ATI Damper with steel shell
- 7.074″ Standard ATI Damper with steel shell
- 6.325″ Standard ATI Damper with aluminum shell in 2 ring or 3 ring construction
- 7.074″ Standard ATI Damper with aluminum shell in 2 ring or 3 ring construction
Other options are available for serpentine and supercharged applications.
Adjustable timing pointers for ATI dampers are available and are machined from aluminum billet. Providing a 4 degree range of adjustment, these pointers can help achieve accurate timing and optimum performance.
Once the ATI Performance parts arrive at your door, you can install the components and begin the task of setting your own timing marks. The procedure is fairly simple, requiring a small amount of patience and following the step-by-step procedure:
- Start by removing all the sparkplugs (making sure to label the spark plug wires for easy installation) so the engine can be turned over by hand.
- Fashion a temporary timing pointer, or bolt in the ATI timing pointer for a temporary reference point.
- Turn the engine over so that cylinder #1 is near bottom dead center (BDC)
- Install a piston stop in the spark plug hole of the #1 cylinder
- Rotate the engine over by hand until the piston touches the piston stop
- Make a temporary mark on your harmonic damper where the temporary timing pointer is locating a reference point
- Rotate the engine by hand in the opposite direction until the piston touches the piston stop again
- Make a second temporary mark on your balancer where the temporary timing pointer is pointing
- Remove the piston stop
- The mid point between the two temporary marks is your true top dead center (TDC)
- Measure precisely, within a 16th of an inch or closer, the center point between the two marks and make a third temporary mark on your balancer
- Rotate the engine over to align the 3rd mark with the temporary pointer. Your engine is now at true TDC
- Install the permanent timing pointer and adjust it so that the pointer is indicating 0 degrees or TDC
- Re-install the spark plugs and wires and set static timing before attempting to start the engine.
The procedure is fairly simple but will help save some time if you have any doubts on where the accurate timing marks are for your small block Chevy. Should you encounter any problems, we suggest calling the tech line at ATI Performance Products or another trusted professional for extra help and guidance.
Optimal engine performance, much like a great comedy routine, is all about timing. Nobody remembers the bad comic or the worst timed engine at the show.