Jump to content

Finding TDC on a flat head engine


WPVT
 Share

Recommended Posts

My 1929 White 6 cylinder truck manual advises setting the timing using a mark that's on the flywheel. The inspection cover on the top of the bell housing requires a bit of work to access. The one below I'm reluctant to open, as it's a wet clutch system.

Would a compression gauge give me an accurate enough reading to find TDC ? It's a flathead, so I don't think I can access the piston from above. My old Dodge had a small hole for that purpose, but I don't see one on the White. 

Any ideas ?

Link to comment
Share on other sites

Not sure of your head design but you could potentially use an inspection camera down one of the plug holes?

 

cadillac suggest a screw driver at an angle in one of their books but I’ve never really figured out how to do it remotely accurately 

Link to comment
Share on other sites

You might consider this.   Remove the top cover and bring the engine to TDC.  Then make a pointer and attach it to the front of the engine over the front pulley and take a hacksaw blade and cut a mark on the pulley.  You would be right on the money and easy to time in the future.  Life is Good

  • Thanks 1
Link to comment
Share on other sites

1 hour ago, WPVT said:

Would a compression gauge give me an accurate enough reading to find TDC ?

No.

 

1 hour ago, WPVT said:

It's a flathead, so I don't think I can access the piston from above.

 

Does your manual have any pictures of the underside of the head? If there is a machined surface over the piston at the far side of the cylinder, like on these head Pontiac heads:

 

8351a9ca-481d-4a47-91a3-01911998b67a-jpe

 

Then there is a way. It might even still work if you don't have the machined area. The piston area is at the bottom of the heads in this picture.

 

Fashion a pointer for the front pulley or balancer. Make it so it can't get bent easily or move. Disconnect the battery and take all the spark plugs out. Feed a giant plastic zip tie in through the spark plug hole, which is presumably over the valves. This should be a really big one with a huge head, and a tail way too long to fall in. Feed it in sideways so the head of the zip tie touches the cylinder wall on the far side of the piston. Slowly crank the engine with a wrench until it stops, carefully managing the zip tie so you know it's head is on the far side of the cylinder stuck between the top of the piston and that machined surface. Make a temporary mark on the front pulley or balancer. Now use the wrench to crank the engine the other direction until it stops again with the zip tie caught the same way. Make another temporary mark. Make a third mark between the first two marks. This third mark is top dead center. Myself I would use a paint pen (junkyard marker) rather than cutting on the pulley if possible.

 

 

 

  • Like 4
  • Thanks 1
Link to comment
Share on other sites

  • 3 months later...

On a flathead I would use the connector and hose from a compression gauge to find a spot near TDC. But I would remove the gauge and valve from the hose, and connect only the hose to the spark plug hole of the number one cylinder. With the spark plugs removed, and with the use of a remote starter button, bump the starter with your thumb over the end of the hose. You can feel when the compression stroke rolls into the power stroke and, after a few repetitions of doing this you can determine approximately where the compression stroke ends and the power stroke begins. Somewhere in the middle of this change is TDC. Or, even more simple…..if you can access the number one cylinder spark plug hole with your finger, just use your finger instead of the hose. 

Link to comment
Share on other sites

I saw MG guru John Twist fill an engine cylinder with oil with piston down,screw in a plug adapter with a 3 foot clear hose on it and turn the motor over slowly by hand and watched the oil go up the hose till it peaked!
 TDC! Then made marks on the pulley and what ever for the future. Hard part was sucking out the left over oil when done....not too bad a job..just a pain.

Funny!

  • Like 1
Link to comment
Share on other sites

On a side valve L-head flathead engine: When any piston is at TDC on compression/power stroke, if the valve lash is set properly, both intake and exhaust tappets for said cylinder can be wiggled up and down. How much up and down wiggle? The valve set clearance amount.  This phenomenon does not occur when at TDC of exhaust/intake stroke. 
 

How do we access the tappets to confirm? Remove the valve covers. Grab the tappet with your hand and wiggle it up and down. 

  • Like 1
Link to comment
Share on other sites

  • 3 weeks later...

     Fliverking's suggestion and plan is the best ever.  Getting rid of the excess oil can be done by cranking it over with the plug out and a rag over the hole to confine the mess.

     Short of that.....Make a degree wheel, look up the specs. to see when the exhaust valve closes and set the degree wheel to that.

     

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...