Re: Where do the dots go for TDC
 

Bingo, thank you Maliburat

Re: Where do the dots go for TDC
 

Post #9 shows the dots together, which means number 6 should be firing. If you put the dizzy at #1 firing with the shown cam timing, your engine will not run because the cam just finished closing for the exhaust stroke and starting opening for the intake stroke. Firing the plugs 8* before TDC on the exhaust stroke does not make an engine run. The timing dots together at te 6/12 position vs. the 12/12 position is nothing more than a double check on yourself. Treat it as such. Whether you want to stab the dizzy in at #1 TDC or #6 TDC, or any other TDC is up to you, but it HAS to be between the compression and power stroke by referencing the cam.

Re: Where do the dots go for TDC
 

Whatever ,,,,,,,,,, you confused the ones that have never put a motor together line up marks and youre engine is timed correctly... The only issue you have now is timing youre dist and that being said if dots are lined up its either on compression and will fire up and run or pop its 180 out pull cap if its 180 out rotor will be facing opposite of 1 spot restab and youre done....want me to school ya on degreeing a cam now or i can walk you through timing a detroit or cat

Re: Where do the dots go for TDC
 

one other thought... keep in mind the slotted gear drive on the oil pump is easily adjusted with a long screw driver. this way the distributor can be clocked to sit in the ideal position.

Re: Where do the dots go for TDC
 

A PHILLIPS OR FLAT BLADE ......................LOL :mm:

Re: Where do the dots go for TDC
 

No it is not. That is 180º out. It will not run if you drop the distributor at #1 with the dots together. No one knows "why" GM did this?, but that's just the way it is....

Forget the screwdriver thing too... Just drop the distributor where you need it to be, and if it doesn't line-up with the oil pump drive, you just "bump" the starter....it will drop right in.

Re: Where do the dots go for TDC
 

Ive been building motors for 35 + years that is how you time the motor

Re: Where do the dots go for TDC
 

Oh with youre piston at tdc youre camshaft determines the compression both valves closed compression stroke..youre turn

Re: Where do the dots go for TDC
 

The cam gear is huge the crank gear is small line dots up install chain and rotate motor they wont line up till another turn thats why you have a key way and a dowel to install gears ..... Thats were youre getting the 12 and 6 stuff

Re: Where do the dots go for TDC
 

Do you get what we are saying in that cam at 6 o clock, crank at 12 o clock, you're not ready to drop the distributor in for number one firing ?

You either drop distributor in with rotor pointing at number six or you turn the crank a turn until the cam is pointing at 12, then drop distributor in pointing at number one.

But, if you drop distributor in pointing at number one when your timing set is showing 12 on the crank and 6 on the cam, you're 100 percent guaranteed to have a non running engine.

Personally, I don't do the try it to see if it runs then turn the rotor 180 degrees if it doesn't thing. I put it together the first time where it's guaranteed to start.

Re: Where do the dots go for TDC
 

so do i ...but some dont understand tdc dot aligned balancer line 0 on tab motor at tdc both valves closed it starts

Re: Where do the dots go for TDC
 

That is correct. Every time.

I think there's something getting lost in the discussion here though.

That picture of crank at 12 and cam at 6, is TDC, but it's the TDC valve open. You turn the crankshaft one complete turn until the crank dot is again pointing up at 12 o clock. Except now, the cam dot will also be pointing at 12 o clock. Now you're at TDC, compression both valves closed.

The crank sprocket is exactly half the size of the cam sprocket. Every complete turn of the crank only turns the cam half a turn.

To time the engine internally, ie crank to cam relationship, you can do either 12/12 method or 12/6 method. Both are right. Do one and turn the engine a complete turn and you'll have the other. It's only when you want to drop distributor into place that you need to either verify 12/12 positioning or check for compression at the number one hole, or line up balancer and watch both valves closed.

It's just so easy to line up crank and cam at 12/6 orientation and either drop distributor pointing at number 6 wire or turn the engine a complete turn and drop distributor pointing at number 1 wire. That way you don't have to watch valves, stick your thumb in plug hole for compression, or even have the harmonic balancer installed onto the engine yet.

Re: Where do the dots go for TDC
 

you got it haha................ I just look thru the hole to see tdc .big block ftw i know were im at.......

Re: Where do the dots go for TDC
 

That's pretty much what I was trying to Say. There is a good chance he will move engine timing as he's reinstalling everything. And I doesn't matter to the dizzy wich is #1 cylinder. Put it together then check for compression TDC

Re: Where do the dots go for TDC
 

Longhair, we are just trying to help the guy...no need for your negativity

Re: Where do the dots go for TDC
 

Not sure how the 6/12 to time the cam to crank and rotate to 12/12 to time the dizzy at #1 is confusing anyone, but glad we all got on the same page.

Now, let's discuss not only degreeing a cam as 78maliburat suggested, but advance and/or retard the cam vs. advance/retard the distributor. That would be a never ending thread relative to timing straight up discussion we just had here LOL!

Re: Where do the dots go for TDC
 

Haha...................... my cam is 8 degrees advanced and my dist is locked out now what....... and its a tall deck 427 that all the experts say wont run....:mel: so heres 3 things to debate / discuss 1 cam installation 2 dist locked out 3 tall deck motors

Re: Where do the dots go for TDC
 

Nah, tall decks run just fine, they just carry a bit of unneeded weight at stock cubes. Throw a stroker crank at it and then we'd be talking!!!

For the distributor locked out: There comes a time when you're running so much air and fuel in a carbed motor that moving electrical timing just becomes a tuning nightmare and causes more headaches than it's worth. Just like in golf: Aim high, let it fly!

As for the cam: It's all related to the initial cam design as to whether it's got any advance/retard built in (what the centerline is), and what the intent of the motor is (RPM range). Advanced cam on a big motor = stump puller.

Re: Where do the dots go for TDC
 

Most confusing thread I have ever seen posted on the internet.

Re: Where do the dots go for TDC
 

I'm being called negative for trying to straighten out mis-information?
I thought that was the point?

Re: Where do the dots go for TDC
 

Fixed!

http://1.bp.blogspot.com/-oiAo9s9mt3...r-equation.png