TDC marks

[DaddysTruck]

I'm pretty sure I set it at TDC correctly, but I noticed there are two lines. Any idea what the other one is for, and where exactly do I set it for 10 degrees when I'm done?

 

[Angie]

Do you have more lines on the other side of the crank?

 

[DaddysTruck]

I don't believe so, unless they're covered in the oily gunk.

 

[RonD]

They are covered by oily gunk

Clean off gunk on both sides of TDC line, scotchbrite pads or SOS.
You can often put some "white out" on the pulley wait a few minutes and then sand it off, it will highlight the marks.
Or any light color paint can be wiped on to pulley it will go into depressions, old marks.

Or you can add your own marks.
Measure the diameter of the pulley/balancer.
Say it is 8 inches
To get the distance around the outside of the pulley, circumference, you use 3.14(pi) X diameter

so 3.14 x 8 = 25.12 inches around the outside

There are 360 degrees in a circle
Divide 25.12 by 36 = .697 inches for each 10 degrees, .687 is 11/16th of an inch

So make a mark 11/16ths on either side of TDC, for 10deg BTDC and 10deg ATDC , then another mark at 1 3/8ths inch for 20deg BTDC
11/16th + 11/16th = 22/16th = 1 3/8s inch


So diameter X 3.14
Divide that by 36 to get 10deg measurement

 

[kimcrwbr1]

The pointer is bent so you will not be accurate once you get it marked at 10 degrees. You will be alot closer bending the pointer to where it is straight 90 degrees to the damper on the flat side. You want to tighten that bolt also for the heater hose tube before it hits the road.

 

[DaddysTruck]

Oily gunk it was. I guess I chose the wrong mark for TDC since the numbers are bigger going towards that line. It looks like the numbers go 12 20 25 33.

As far as the loose bolt, I'm in the middle of a complete tear down, so it won't be hitting any roads anytime soon.

Btw I notice it's some of the same guys usually answering my noob questions around here. I just want to say I appreciate all your help a lot. Thanks.

 

[RonD]

We just have NO LIFE, so hang out on forums all day, lol.

And thanks for the thanks

The numbers are all Before TDC since that's when you want spark to start igniting air/fuel mix, you want it to fully ignite the cylinder at 5-10deg After TDC to give best leverage on the crank, and it takes a few milliseconds for full ignition to occur.
And of course the faster the crank is turning(RPMs) the earlier(more advanced) the spark must be started, so you get into the 30deg BTDC

12deg BTDC was spec with SPOUT connector removed for TFI systems and engine RPMs under 800.

TFI distributor, like most, has a centrifugal advance, this advances the spark solely based on RPMs, it starts working above 1,000rpms.

You also need an advance change based on engine load and fuel mix, richer air:fuel mix burns faster than regular air:fuel mix.
Vacuum advance was used for that on earlier distributors
TFI uses computer to do this since it knows the air:fuel mix and engine load based on RPM and throttle position.
That's what the SPOUT wire is for, SPark OUT from computer, it changes spark timing in TFI module, so must be disconnected to set base spark timing same as you would disconnect vacuum advance when setting base spark timing.

 

[kimcrwbr1]

It has been my experience 10 DBTDC works best for the 2.8. The large groove with TC on it is TDC make a yellow mark on the mark just before 12 that is 10 degrees and is spec for the 2.8. I have tried every possible combination between jets, ignition timing and idle air mix. First confirm TDC with a piston stop tool and adjust the pointer for TDC. Set base timing at exactly 10 degrees before TDC. Put in smaller jets than factory mine runs best with #42 jets. Then adjust the idle air jets for the highest vacuum pressure possible or engine rpms normally 3 1/2 to four turns out. I basically just disabled the choke just turn the thermostat spring to hold it open full time. The vacuum guage was the best tool i found for troubleshooting you want to see at least 17 inches vacuum at idle speed if not your timing is bad or you have a vacuum leak. If your getting black smoke out of the exhaust at high speed pulling a hill put in smaller main jets. If your not going to pull the heads be sure and change the valve guide seals. If original they are bad. Just use air pressure to hold the valves up and pull the springs. Stick a long screwdriver in the spark plug hole and turn the crank until the piston is all the way up. With a compression test hose apply 35psi in the cylinder to hold the valves up one of those palm spring compressors worked good for me just be careful you dont drop the keepers down one of the oil drain holes in the head. I have the tune up parts on hand but have not had to do anything for three years now except change the PCV and fuel filter.

 

[AndyB.]

Ten degrees before top dead center is the factory spec, with the spout disconnected. Each has mark on the crank pulley is 2 degrees (12, 14, 16, 18, 20), so 10 degrees is the minor hash mark before 12.

A piston stop to identify tdc sounds like a good idea, but the plugs go into the head from the side, so it's not a good solution in this case. The real way to identify TDC with these is with the head off and a dial indicator--not sure I'd do that if you're not pulling the head anyway.

 

[DaddysTruck]

I don't plan to remove the heads unless I have to. Really don't need the extra trouble and cost of getting everything resurfaced.