TDC may not change, but you still need to check it. No way to tell if the timing mark on the balancer and that on the tab are in the correct spot, so it needs to be checked to ensure you're getting off on the right foot.
You wont find it bumping the engine with the starter, as it will move too fast. Pull all the plugs so it's easier to turn, and then crank it by hand with a breaker bar. Once the mark is checked, then if you had a degree wheel you could check to make sure the tab was in the right location and that it will line up at 6 degrees. If the tab isn't in the right location you will have to make a new tab, or build a extension off the existing tab to ensure you can mark it at 6 degrees. Normally that less than an inch from TDC, so if you find TDC, the tab should be mounted in such a way that it's within that range to TDC.
I had a friend who couldn't get his engine timed and when I checked it the timing cover was off a completely different SBC and the tab was sitting aropund 20 some degrees away. He'd never have gotten it timed by trying to use that cover and tab.

 

have everything off so my son can help me locate tdc tommorow. i also checked the carb and the mixture screws was 1 turn out so i set to 1.5 turns out.

 

^ Yep, you never know what someone may have done in the past. If his timing tab to harmonic damper relationship is off, that new found TDC line as I described in the previous post would be used as the new "notch" mark on the damper.

 

I knew I was forgetting a step in there, thanks 69. It has been a long time since I had to play with an old school engine.

Chevy SB has a few different timing marks and harmonic balancers you have to make sure you get the correct set matched up. Some time the engine through the water pump, some are on the driver's side and I think if I remember right some of the late emissions engines had marks on the pass side too. Anyway make sure the marks you have and your HB are of the same type.

Yes the engine didnt want to idle with the timing set at 6 or so degrees with lean mixture settings. Lean mix takes longer to burn so you needed more timing to keep it running. Now you have a bigger cam so you need more fuel to be added to the more air you are stuffing in the engine. I would run the screws out 2 turns and then lean them out after that once everything is getting set right. a rich engine will run easier than a lean engine will. Good luck you are almost there.

Massey

 

does it matter if i use exhaust tdc to find the highest point of the piston (tdc)? the reason is that the threads in my crank are not the best so i cant turn it over with a breaker bar, i have to screw a piece of flat steel onto the bolts were the crank pulley attaches to and lay on my back under the car and turn by hand. pain in the butt!!

 

TDC is TDC. Both intake and exhaust valves are closed, so they are in equal positions. You need to find TDC based on the proceedure that Camaro 69 described using the piston on #1 cyl. Don't try to find it by measuring rocker arm or valve movement. It can be done, but it's not as accurate, unless you've got a dial indicator and can get it very exact off the valves.

 

yes i was going to find it that way. if the mark is within 5 degrees of were i thought it was, should i pull the dizzy and reset it? or is it close enough to leave the dizzy there? i set the dizzy at what i thought was 12 btdc.

 

You don't have to pull the dist. unless it's so far off that it wont turn enough. Just loosen it and make the adjustment with the engine running and a timing light. I don't know of any way to set a dist. with the engine not running and pulling it would mean dropping it in one tooth off, which would require turning the oil pump shaft to drop it.
I'm getting confused now.

 

I was confused a long time ago!!!!!!

 

PM answered.