Where do the dots go for TDC

[crazeetxn]

So I'm putting my 350 back together with some refreshed heads. I have the timing cover off as I painted and cleaned up while it was out.

I obviously need to find TDC before I put my distributor back in...there is a lot of info on here about the magic dots, but nothing (that I saw) that said definative, this is what you want/have to do. Just talk about it's on compression or exhaust.

So, dot on crank and cam gear both point at 12, means TDC for #1. Is that when I want to stab the distributor back in, or do I need the crank dot at 12 and the cam dot at 6? I think I had them pointed at each other last time I did this, but that was a few beers ago

Thanks for any help ya'll have...

[77ChevySharkBite]

Yes both are supposed to be at 12 that's TDC for #1. Reason I know is I just finished putting mine back together yesterday.

[geezer#99]

Originally Posted by crazeetxn

So, dot on crank and cam gear both point at 12, means TDC for #1.

That is correct but you install the timing chain and gears with the cam dot at 6 and the crank dot at 12 for accuracy. Quite easy to be out a couple teeth if you try to eyeball it the other way. It was designed that way.
Then crank it one turn so you're on #1 tdc.

[crazeetxn]

Cool. Gonna take a straight edge and get the dots closer at 12 each. Hopefully it'll fire enough for me to get a timing on it. I do remember last time I did it, backfired through the carb, adjusted the timing and bit and it ran like it was made to.

Thanks for the help fellas!

[geezer#99]

After you set it at 12 and 12 crank it round to 6 and 12 and see how accurate you are!

[LONGHAIR]

It's far easier to set it a 6 and 12, then just drop the distributor at the number 6 terminal instead of number 1.

[crazeetxn]

So it'll be pointing at #6 vs #1? Or it'll be on the right stroke and still point at #1?

Sorry if these seem like rookie questions, but I'm just trying to make sure I have this right with it still on the stand

[geezer#99]

When the dots are at 6 on the cam gear and 12 on the crank gear you're on #6 tdc.
You can install the distributor with the rotor pointing at #6 or you can rotate the crank one revolution and install the distributor with the rotor pointing at #1.
Your choice!

[Desert1957]

Cylinder 1 at TDC

[Jake Wade]

Originally Posted by geezer#99

When the dots are at 6 on the cam gear and 12 on the crank gear you're on #6 tdc.
You can install the distributor with the rotor pointing at #6 or you can rotate the crank one revolution and install the distributor with the rotor pointing at #1.
Your choice!

This is correct.

[Jake Wade]

Originally Posted by Desert1957

Attachment 1176705

Cylinder 1 at TDC

Correction, this is at #6 TDC

[Katrina/10]

Originally Posted by Jake Wade

Correction, this is at #6 TDC

Could it be #1 at TDC, but exhaust stroke instead of compression?

[bnoon]

Originally Posted by Katrina/10

Could it be #1 at TDC, but exhaust stroke instead of compression?

Correct. #6 and #1 are both TDC at the same time. The cam timing will determine where you drop the distributor.

[Desert1957]

Originally Posted by Jake Wade

Correction, this is at #6 TDC

Never seen a thread so all over the place, bring number one to TDC, align the cam and crank gear as I posted above, drop in the distributor with the rotor pointing to one.

What is the problem??????

Desert

PS: the OP got way over is own head over analyzing the process anyway, C'MON MAN....

[geezer#99]

Originally Posted by Desert1957

Never seen a thread so all over the place, bring number one to TDC, align the cam and crank gear as I posted above, drop in the distributor with the rotor pointing to one.

What is the problem??????

Desert

PS: the OP got way over is own head over analyzing the process anyway, C'MON MAN....

Problem is you'll be firing 180* off on #6.

[Keith Seymore]

Agree.

I think the confusion is coming from simply stating "TDC #1".

There needs to be a distinction between TDC #1 firing vs not firing.

K

[king-918]

It doesn't matter if both are at 12 o'clock or cam is at six. Remember TDC is at the end of compression and recheck for that after complete assembly to insure that even though things get moved around you will be spot on

[geezer#99]

Originally Posted by king-918

It doesn't matter if both are at 12 o'clock or cam is at six. Remember TDC is at the end of compression and recheck for that after complete assembly to insure that even though things get moved around you will be spot on

It does matter!
So you can put the distributor in correctly with the rotor pointing at #1 so it starts.

[bnoon]

The problem with both dots at 12, you can be a tooth off and think you're correct if you're not looking at the engine straight on. This can be a problem if you're timing the engine in the engine bay and not on an engine stand. It's much easier to see that you're tooth to tooth at the 6/12 position, then rotate to the 12/12 position or vice versa to double check. Dropping the dizzy is easy at either position, you just have to know if you need it to point to 6 (at the 6/12 position) or number 1 (the 12/12 position). Mistakes can be made, we're just giving ways to double check, which is good, because we're dealing with a not-so-confident engine builder here.

[crazeetxn]

Originally Posted by Desert1957

PS: the OP got way over is own head over analyzing the process anyway, C'MON MAN....

Dang it Desert, you weren't supposed to tell anyone

I started just searching threads, and that led to something else, then I found myself creating my own

Good thing is, I still have the intake and timing cover off, so that'll come in handy when I'm putting the rockers back on...

[Tx Firefighter]

Originally Posted by Desert1957

Never seen a thread so all over the place, bring number one to TDC, align the cam and crank gear as I posted above, drop in the distributor with the rotor pointing to one.

What is the problem??????

Desert

PS: the OP got way over is own head over analyzing the process anyway, C'MON MAN....

Your engine won't start. With cam at 6 and crank at 12, you better drop distributor pointing at number six if you want it to run. Otherwise, turn crank one revolution until both crank and cam dots are at 12, now drop in pointing at number one.

[faribran]

this is an interesting post.. i have been doing this for years.... lets keep this simple....
did the original poster even change or remove the timing gears/chain? looks like one could just get #1 cyl at tdc.. and jabb in the distributor..... should be good to go..

[Tx Firefighter]

Originally Posted by faribran

this is an interesting post.. i have been doing this for years.... lets keep this simple....
did the original poster even change or remove the timing gears/chain? looks like one could just get #1 cyl at tdc.. and jabb in the distributor..... should be good to go..

Remember, there are two TDC to account for. One where the ignition should spark, the other with the valve open. You must make sure you're at the right TDC to drop in the distributor. Just having the harmonic balancer mark lined up is making a 50/50 guess that you have it right. You must have the balancer mark lined up AND compression to assure you have it right.

[faribran]

yes, the valves must be closed, hence compression stroke..

[78maliburat]

Post #9 pic is correct your motor is timed.you just have to time the dist ...........................forget all that #6 at tdc crap