Hello everyone...Have a question. Have a sbc 327 in my C3. Just bought the car last year, drove horribly. Checked the distributor to find it 1 tooth off when i brought the #1 cylinder to its compression stroke and the timing mark at TDC. It helped a lot. Now for the winter project i started, I wanted to check the timing chain because i had no clue about the engine. The block is from a 1968 and the heads are from an LT1 350 motor 75cc chambers. The cam i know nothing about, but the previous owned told me there was about 20k on the engine, but he also told me that the engine was a 350 until i ran the numbers. OK, now for my question. I put the engine on TDC with the compression stroke up on #1 and the rotor facing the #1 terminal on the distributor cap. i removed the timinmg cover to find a new double roller steel gear and chain. The chain is tight and not loose, like new. But now the confusing part. the crank gear alignment dot is at 12 o clock, where it should be, but the cam gear is also at the 12 o clock position. Is this normal? I thought it was to be at the 6 Oclock position? Are the dots supposed to be at 12 and 6 or not? The engine ran OK after i reinstalled the distributor last year. If i put the cam gear at 6 Oclock, will the engine run? I dont think so. Im at a loss, so any help please ....Thanks......Ron

 

Pull off your driver side valve cover. then crank the motor over watching the valve events for the number one cylinder. When you see the #1 intake valve open then close glance down at your damper timing mark and the cover indicator. You should probably be 20-30-or 40 degrees Before top dead center. Just rotate the crank the additional few degrees. If you distributer is right it will be say 12 degrees past the number one cylinder. That is if you use 12 degrees of initial advance.

 

#1 TDC Firing Position is both gears at 12:00.

Usualy we assemble the gear/chain set with crank dot at 12:00 and cam gear dot at 6:00 but that would actualy be #6 TDC Firing Position.

Lots of threads about this if you want to look for them. A common misconception.

-Mark.

 

Thanks Mark, I don't think that I ever had the front timing cover off and tried to time my car. During istallation I just line the dots up.

 

My car is setup with the cam at 6 and crank at 12 with the number one at tdc.

 

The confusion is whether #1 in on compression or exhaust stroke when at TDC.

 

Exactly! If you look at the picture, it shows an engine that is on #6 TDC Firing Position AND #1 TDC Exhaust position. #1 and #6 are both at top dead center but #6 is the only one that is ready to fire.

-Mark.

Now, where is that horse emoticon?!?!

 

 

OK, so is my engine timing index marks correct at 12 Oclock for both gears or not? If i were to install a new cam now, do i set it at 12 and 12 or 12 and 6???

 

OK, my engine is torn down except for the heads and cam. I dont seem to get a direct answer to my question. Are the timing indexes wrong or right? 12 and 12? I have done many cam replacements before and every engine i tore down was always at the 12 and 6 position whenever i set the engine at TDC. Problem is that it has been many years since i last worked on a performance engine and i am not quite sure . If i were to install my new camshaft right now , do i install at 12 and 6 like i always have or do i replace it at the current setting of 12 and 12???

 

Can you explain this a little better to me? Dont understand your answer. Maybe i am a little thick here, but i have always installed cams at 12 and 6. If i were to install my new cam right now on my compression stroke for #1, do i replace it the same as it is now at 12 and 12 or do i install at 12 and 6??? Please read my other responses to the other members in the forum

 

Either one is correct for crank to cam timing. 12 and 12 ,number 1 is fireing. 6 cam and 12 crank, number 6 is fireing.

 

It doesn't matter if the crank is at 12 and the cam at either 6 or 12. In fact you could set the the crank at 6 and the cam at 3 or 9.
Most people will use the crank at 12 and the cam at 6 because it is at the position where the dots are easiest to see and align.

As for setting the distributor. To a certain degree, you can not be off tooth. The distributor is meant to turn. When someone speaks of the distributor being off a tooth it is because the vacuum can is hitting the intake or something behind it. It is unable to be turned adeqauetly to set the ignition timing.

 

You misunderstood the explanation about the distributor. I needed to remove and reinstall the distributor up by one tooth in the cam gear a year ago. The engine ran, but poorly. I checked the #1 cylinder to TDC on the compression stroke and the rotor in my cap was not pointing to the #1 wire terminal. Once i repositioned the distributor, the engine ran a lot smoother and accelerated better.

But as far as your explanation with the timing index marks, it makes sense now. Thanks for everyones help.....Ron