47-55.1 Finding TDC

[TX3100Guy]

My 53 pickup has a 1969 261 cubic inch engine. I currently have the spark plugs out, the valve cover off, and I've removed the Vertex magneto to get it serviced. While I noted the position of the rotor on the cap prior to removing the magneto, I suspect in servicing it the company will have rotated and spun the magneto out of that position.

While I know I can simply advance the gear so that the rotor is in the same position, I've read that it would be better if I got the engine to TDC (cylinder #1) and then when I reinserted the magneto, I could ensure that it was set at the #1 firing position. However, I'm not certain I know how to ensure that I've rotated the engine manually to TDC. Any guidance or tips would be appreciated.

[mr48chev]

I've taught a few hundred kids how to crank and engine over and bring it up on compression with your finger in the number 1 plug hole to get it up on tdc but that isn't the only way.

It will be easier if you get under the truck and turn the flywheel so that you can clean up and maybe put a bright mark next to the ball that marks TDC on the flywheel so it is a tad easier to see.

Figure out which rocker is the intake rocker on number 1 cylinder.

Crank the engine over by hand until the rocker opens and then closes the intake valve.
When the valve is pretty well closed watch for the timing mark in the hole in the bellhousing and center it on the pointer.

That will be exact TDC for you to properly line up your distributor.

[TX3100Guy]

Originally Posted by mr48chev

It will be easier if you get under the truck and turn the flywheel so that you can clean up and maybe put a bright mark next to the ball that marks TDC on the flywheel so it is a tad easier to see.

Figure out which rocker is the intake rocker on number 1 cylinder.

Crank the engine over by hand until the rocker opens and then closes the intake valve.
When the valve is pretty well closed watch for the timing mark in the hole in the bellhousing and center it on the pointer.

That will be exact TDC for you to properly line up your distributor.

Many thanks. I have the truck on a four post lift, so I won't have to crawl under it to see the flywheel. Should I take the dust cover off to see more of it?

[mr48chev]

Yes you need to take the dust cover off if you want to clean off the flywheel in the spot around the timing mark . You don't have to but if it is clean and possibly has a mark with something like a paint stick that they mark lumber and stuff with it is a whole lot easier to see looking though the hole in the front of the bellhousing. The cleaning it up and marking it is all about making it easier to see.

[_Ogre]

this ogre had to turn to mr google for Vertex magneto
never seen a magneto on any road vehicle since the model t
other than weak spark at cranking, is there an advantage?

[mr48chev]

Originally Posted by _Ogre

this ogre had to turn to mr google for Vertex magneto
never seen a magneto on any road vehicle since the model t
other than weak spark at cranking, is there an advantage?

Worth 500 Bubba points at car shows but unless you are all out racing there is no real advantage over modern distributors that are available now.

Most race cars that run a mag don't have a battery or electrical system at all. Sprint car, fuel dragsters, funny cars. Land speed cars. If they have a battery it powers the computer setup that tells what was going on with the car during the run/race.

[TX3100Guy]

Originally Posted by _Ogre

this ogre had to turn to mr google for Vertex magneto
never seen a magneto on any road vehicle since the model t
other than weak spark at cranking, is there an advantage?

That is a great question and one I had to ask when I acquired the truck (it was in it when I purchased it).

The fact is, there are no know autos sold today with a magneto and likely an electronic ignition system beats a magneto today. But this truck is a piece of hotrodding history with the Vertex magneto, McCulloch supercharger, and Hillibrand quick change rear end. The former owner and the truck spent a fair amount on time on the Bonneville salt flats prior to its current and final restoration. At this point, I'm trying to retain those unique elements of the truck while updating and refreshing other areas of the truck.

[TX3100Guy]

For your education and viewing pleasure on magnetos.


https://www.youtube.com/watch?v=4t7C2AYHvuM

[_Ogre]

Interesting. Platinum points that last forever?
Where were you all thru my youth???

[TX3100Guy]

I found these marks on the engine side of the flywheel. Is this the TDC mark and to what do I line it up with?

[mr48chev]

The ball, and that bugger can be a tad hard to see when you are looking for it through the hole in the bellhousing.

[TX3100Guy]

By George, I think I've got it.......

[mr48chev]

Right on point.

[_Ogre]

Since your motor is a 4 stroke that is TDC
But it can be TDC on compression stroke, which is good
Or TDC on exhaust stroke, aka 180° out

[VWNate1]

The triangle is the TDC mark, some times it's a chevron .

The ball bearing pressed into the flywheel is the timing mark to be used at or blow 700 RPM .

It's 10 DBTDC IIRC .

My GM factory training was long ago but I still remember the basics .

Remembering the firing order is simple too, you just think about women :

15 is too young .

36 is too old .

24 is *just right* .

If your magneto still runs points the dwell is 16 degrees .

[mr48chev]

Originally Posted by _Ogre

Since your motor is a 4 stroke that is TDC
But it can be TDC on compression stroke, which is good
Or TDC on exhaust stroke, aka 180° out

See post 2= Watch the intake rocker and it will be open on the intake stroke and closed on the compression stroke and when it reaches TDC the mark lines up.

[VWNate1]

By the same token you can use # 6 cylinder to time it....

Many older Chevies have passenger car valve covers with the oil cap in the center, only trucks used the front oil filler....

[mr48chev]

Originally Posted by VWNate1

By the same token you can use # 6 cylinder to time it....

Many older Chevies have passenger car valve covers with the oil cap in the center, only trucks used the front oil filler....

I've done that on a straight six that had an old York air compressor hanging on the engine making it rather hard to get my finger in to the plug hole let alone remove and replace the plug. I think it was on my 59 ElCamino. You have to remember to have the rotor point the #6 spot on the cap rather than 1. Not needed 99.9 % of the time though.