68 TI distributor install question - again -

jims427400 · 05-06-07, 10:12 PM

Well when I pulled the distributor from the old intake, I did'nt mark the location of the rotor under the cap. But when I pulled it, I did'nt touch it, so the rotation should be close to where it should be when I reinsert it. "RITE" ??

My question is if I have'nt cranked the engine at all can I just drop it rite back in or do I have to bring #1 cylinder to top of comp. stroke, and then point #1 wire at #1 cylinder.

I promise this will never happen again....
Anybody w/ TI dist. experience-please help..

BarryK · 05-06-07, 11:19 PM

if you didn't turn the motor over than than you should be able to drop the distributor in and have the rotor point where you had previously marked it...... but since you didn't mark it than you have no clue where proper orientation is.
Also, you may not have deliberately turned the rotor or shaft when you pulled the dizzy out but it can easily move and rotoate on it's own.

You are much better to turn over the motor to bring #1 cylinder to TDC on the compression stroke and than install the dizzy with the rotor pointing to the #1 cylinder wire. This way you can be sure it's very close to right than fine tune after starting with your timing light.

Of course, this is with a points unit but I don't see where the differences between a points unit or a TI unit would make a difference with a correct installation procedure.

6880 Mike · 05-07-07, 07:49 AM

Bring #1 to TDC in the compression stroke, lower the distributor into the block, and align the stake marks on the manifold and distributor body. That will get you close enough to fire her up and set the timing.

minifridge1138 · 05-07-07, 05:45 PM

If you have no idea where the rotor was pointing (you have a 1 in 8 chance of getting it correct on a guess) then you will need to turn it over by hand until you get #1 at top dead center.

Ensuring that it is the compression stroke is more difficult.
Here is some useful information:
When #1 is at top dead center for compression, #6 is at top dead center to fire.
So if you get #1 to top dead center when it is NOT the compression stroke, then you need to point the rotor to #6. Basically, spin the rotor 180 degrees and you'll be fine.
I made the same mistake when i rebuilt my motor. I just rotated it by hand until the timing mark was at 0 degrees and then pointed the distributor at #1. I knew that if I was wrong, then I was off by 180.

Also, you can rest well knowing that the stock motor is NOT an interference motor (if you've put in high-rise cam it could be).
Interference Motor = piston will crash into valves when timing is off.
Non Interference = piston will not hit valves no matter how far timing is off.

So even if you are WAY, WAY, WAY off, you should not damage anything.

Good luck.

jims427400 · 05-07-07, 09:15 PM

Just want to clarrify a couple of things..
-TDC on #1 cyl... does that mean I'll beable to feel top of piston w/ my finger through the plug hole when its on top of comp. stroke ??
-If and when the #1 is TDC,, will the timing mark then be at 0 ??

Sorry for the need for clarification but I need to make sure I understand everyones input, and dont want to screw something up I cant fix or replace.

Mike, I have'nt forgotten the stake marks..

Barry, I'm still trying to figure out if TI distributors are set differently than a point type system

minifridge1138 · 05-07-07, 09:23 PM

Quote:

Originally Posted by jims427400

Just want to clarrify a couple of things..
-TDC on #1 cyl... does that mean I'll beable to feel top of piston w/ my finger through the plug hole when its on top of comp. stroke ??
-If and when the #1 is TDC,, will the timing mark then be at 0 ??

Sorry for the need for clarification but I need to make sure I understand everyones input, and dont want to screw something up I cant fix or replace.

Mike, I have'nt forgotten the stake marks..

Barry, I'm still trying to figure out if TI distributors are set differently than a point type system

will you be able to feel top of piston with your finger? I don't know if your finger will be long enough. I'm not sure the distance between the plug and the top of the cylinder. Just make sure you don't drop anything in there (i.e. if you stuck in a screw driver to feel for cylinder)

Yes, when the timing mark is at 0 cylinder #1 will be at top dead center (assuming the harmonic balancer hasn't slipped and moved the timing mark).

I know you're afraid, I was too. But don't worry. It is not nearly as scary as it seems.

bossvette · 05-07-07, 10:01 PM

bump it over with the starter with your finger covering the spark plug hole you will feel the compresson stroke when the mark is at "0" you will be at TDC assuming the balancer is correct and has not slipped.

petes74ttop · 05-07-07, 10:02 PM

Hi minifridge, when the crankshaft makes one revolution the camshaft only goes half way around, so if you line up the at "0" you can be on the compression stroke or you can be on the exhaust stroke. If you install the distributor as instructed before and you car won't start then line up the pointer at "0", then pull the distributor one more time, give the crank one more revolution, then put the distributor in again.
Hope this helps, PG

6880 Mike · 05-08-07, 08:27 AM

Quote:

Originally Posted by petes74ttop

Hi minifridge, when the crankshaft makes one revolution the camshaft only goes half way around, so if you line up the at "0" you can be on the compression stroke or you can be on the exhaust stroke. If you install the distributor as instructed before and you car won't start then line up the pointer at "0", then pull the distributor one more time, give the crank one more revolution, then put the distributor in again.
Hope this helps, PG

Correct. If you miss TDC on the compression stroke, not really a big deal. Timing will be out 180 degrees and #6 will be ready to fire. The distributor doesn't have to come all the way out. Just raise it enough to turn the rotor 180 degrees and set her back down.

LVMYVT76 · 05-08-07, 10:52 AM

If you have the valve covers off, you can check and see if the valves are closed on #1, then it is on compression stroke: exhaust valve open, exhaust stroke.

JohnZ · 05-08-07, 03:30 PM

Quote:

Originally Posted by minifridge1138

Also, you can rest well knowing that the stock motor is NOT an interference motor (if you've put in high-rise cam it could be).
Interference Motor = piston will crash into valves when timing is off.
Non Interference = piston will not hit valves no matter how far timing is off.

So even if you are WAY, WAY, WAY off, you should not damage anything.

Good luck.

Nope, that's only true for VALVE timing, not IGNITION timing; the only thing that changes VALVE timing is to screw up installation of the timing chain.

minifridge1138 · 05-08-07, 05:12 PM

Johnz: You're right. When I removed my distributor it was at the same time i replaced the timing chain. I had a senior moment when i typed that.

LVMYVT76: correct. with the valve cover off, you can see which is open.

6880Mike: yes, if you set the timing for #1 during the exhaust stroke instead of the compression stroke then you are off by exactly 180 degrees.

pets74ttop: I got lucky and had it put it on the compression stroke, not exhaust stroke. I had a 50/50 shot of getting it right, and it was the only bit of luck I had on the whole project.

Joining corvette action center's forum has bee the best thing I ever did (aside from buying the corvette in the first place).