Thread: Need help with ignition timing

Tweet

The degree markings on my Chevy 350 Small Block engine are all scratched off.
I can't tell where the timing is on a new motor i bought.
It wouldn't start when i put it in the car so i found top dead center and that still didn't work. I flipped the distributer around 180 degrees and the car runs now but will not accelerate. I believe my motor is 180 degrees off but i have no markings to figure out where to go.

How do i time this motor COMPLETELY from scratch?
This is my first motor swap and I'm really stuck so i appreciate any help anyone can give me. Thanks!

I posted this a while back when this question came up, and it fits here, too. If you don't have a timing pointer on the block, or if you don't trust that it's right you can find exact TDC in six easy steps:

1) Make an indicator from some clear plastic tubing, a jar of light oil (cooking oil, olive oil, whatever) and an old spark plug.
2) Break up an old spark plug and attach a length of clear plastic tubing to it (make it airtight). A hot glue gun can help here, or you can use silicone if you're patient.
3) Remove all the spark plugs.
4) Stick your thumb OVER the #1 cylinder spark plug hole. Rotate the engine until you feel pressure on your thumb. That's the compression stroke, and TDC is at the top of this stroke.
5) Screw the spark plug with plastic tubing attached into #1 cylinder, and insert the other end of the tube into a the jar of light oil. Continue rotating the engine. Bubbles will appear until the piston reaches the top of its travel. When it starts down on the next stroke the bubbles will stop and oil will begin traveling up the tube. Stop at a convenient point and mark the tube. At the same time mark the crank pulley and the engine body at a convenient spot.
6) Rotate the engine backwards and watch the oil recede into the jar. Continue rotating. As the piston continues past tdc and downward it will again suck oil into the tube. Rotate the engine till the oil again reaches the mark you made in Step 5. STOP! Mark the crankshaft pulley where it lines up with the mark you made previously on the engine. You should now have two marks on the crankshaft pulley. The midpoint of these two marks lined up with the mark on the engine is TDC.

Thanks rspears I'm gonna give that a try. I'm a little busy today but ill try on tuesday and post back after. Thanks again

The "old" way of doing it was to remove all the spark plugs (to make it easier to turn engine over.)
Then turn motor over while holding a finger/thumb over the #1 plug hole so you can feel the compressed air pushing out of the cylinder.
When the air stops, use a long thin screwdriver or a piece of wire (etc.) and use it to touch the top of the piston.
Turn / Rock the crankshaft forward and back until the piston no longer rises /falls. That's TDC.

You can use timing tape to replace the missing markings. Measure the diameter and call Summit for the right part number.


HTHs..

Yeah Mike, the problem with the "old way" is that it is very hard to "feel" the actual TDC with a wire or screw driver because of the angle of insertion through the plug hole, and anytime you use a rigid tool there is risk of getting it bound up and scratching up the piston surface or worse. I'd be surprised if I could get +5 degrees either side of actual TDC using that approach, but that may just be me. The beauty of the oil/tubing method is that a person can repeat the process, going smaller bites away from the center, until the marks on the damper are like 1/4" apart. Also, though it's not stated in the original process, using a smaller tube is better, like aquarium air tubing that's 1/4" OD with about 3/32" ID. The smaller ID improves the accuracy of the volume displacement.

No debate here Roger. Whatever works for you. Just offering another avenue that has worked for many of us in the past.

Originally Posted by 34_40

No debate here Roger. Whatever works for you. Just offering another avenue that has worked for many of us in the past.

Same here, whatever works for the individual. I can't claim originating the plug/tubing method, but I really like it for the potential accuracy. It's about the best I've seen short of pulling the heads and using a dial indicator.

And you gotta know that I'd have pulled that damper off and replaced with new already!! LOL..

Originally Posted by 34_40

And you gotta know that I'd have pulled that damper off and replaced with new already!! LOL..

I think the damper on my SBF new build has three different sets of marks on it, depending on where your pointer is mounted. If my engine guy had not marked the correct zero with a red paint dot I would have been clueless which one was the right one to use for true zero TDC. Anytime you have an engine someone else has messed with the timing reference can be a challenge.

You have the damper I needed.. LOL.. I swapped to a right hand water pump, so the timing marks were covered. No problem... make a new pointer on the other side and mark new zero.. Toss the damper into the rotary table \ bridgeport at the friends shop, and set in a new set of marks every 2 degrees..