TDC is at beginning or end of CS? (1 Viewer)

[drtyfun]

I've recently put back together my 1989 3fe after getting it back from the machine shop. Now I'm attempting to find TDC to then set the dizzy. I made a little port stem and balloon to stick in to plug port for cylinder #1. I hand crank the crankshaft bolt, and It works perfectly, very obvious when compression begins and or tapers off.
however I am unclear if I should stop turning the crankshaft when I fist detect compression or at the end of that stroke or somewhere in the middle?

Any help is greatly appreciated.

 

[Output Shaft]

TDC compression is when piston #1 is at its peak upward travel in the cylinder bore during the compression stroke, just before it starts heading back down.

You stop turning the crank when the TDC mark on the drive plate lines up with the pointer.

If you overrun it, don't back up, go around another two times.

 

[drtyfun]

Thank you for the response , just curious, what happens if one does turn crank backwards.

 

[Dynosoar]

You really wont mess anything up turning it back wards just a little bit. This happens naturally when you park it in gear and the truck rolls back a drop.

Dyno

 

[Output Shaft]

On an old worn engine (theoretically) there is a bit of play in the rotating parts; crank, bearings, timing gear. When the crank is slowly turned clockwise all the parts in the engine are loaded up. When the engine is then turned backwards a tad, if there is any play in the timing gears, the crankshaft will turn, but the timing gears will require a little more rotation before they engage going the other way. This will effect how the camshaft turns (late), and ultimately the valve lift.

Or so the theory goes....

 

[FJ60Seth]

When you know your on the compression stroke, put a long zip tie in the spark plug hole. You can watch go up and peak.

 

[Output Shaft]

I made a little port stem

Any pictures? Details?

 

[drtyfun]

So I like the zip tie technique. Gonna try that. My balloon works but I can see where the zip tie could be more accurate.
I got the dizzy set, but I'm sure I either am a little off on my TDC or my dizzy is slightly off. It starts, but doesn't stay idling, some backfire and a fairly high rpm until it dies out.

 

[drtyfun]

Ya ill take a few pics and post em.

 

[drtyfun]

So basically I took an old brass airchuck fitting and a balloon, put some Teflon tape over the male threads of the airchuck threaded the Chuck into cylinder #1 and turned the crankshaft.
The threading diameter on the airchuck is slightly less than that of the spark plug, so the use of the Teflon tape not only helps with this size discrepancy but also provides an ok air seal.

 

[doug720]

Another option is to knock the porcelain out of an old spark plug. I made a TDC device from a dial indicator and an old spark plug.

 

[drtyfun]

Little to no success today. I'm having difficulty identifying if I'm on compression stroke. I have the valve cover on and would like to keep it that way, so seeing the valves isn't doable.
I think I had it better yesterday than today. At least it fired and started yesterday.
Wife's looking concerned.

 

[FJ60Seth]

Wad up some wet paper towel and stuff into the plug hole. Compression stroke will blow it out way before TDC.

 

[Tools R Us]

Your motor doesn't have a timing mark? Turn the motor in the normal direction, stick your finger in the #1 plug hole, when you feel pressure, start watching for the timing mark. Set it on the mark, adjust the dizzy, put the plug, etc, back on, start the motor and set the timing with the light.

 

[Output Shaft]

Take off the oil cap and feel the rockers on #1 with your finger. If the piston is at the top of the stroke as verified by a zip tie in the spark plug hole, and the timing mark on the drive plate lines up with the pointer...AND both rockers are loose for #1, you're at TDC compression.

 

[Spike Strip]

Just put your thump over the spark plug hole. If it's pushing air out, you're on the Compression Stroke. At that point, the timing marks on the flywheel should be visible. Line up the pointer with the notch (not the BB) and you're at TDC.

I've gotta ask - you're checking the cylinder at the front of the engine, closest to the radiator (#1) ?

 

[drtyfun]

Yes, I am checking at the front of the engine. Getting it close, it fires but won't stay running.
I am not clear if the two rocker arms for cylinder#1 are side by side, or is it one rocker arm for cylinder#1 then skip one then the third rocker arm is the second rocker for cylinder #1 ?

 

[doug720]

Side by side

 

[roadstr6]

EI IE EI IE EI IE where E=Exhaust and I=Intake

 

[drtyfun]

It's hot outside so I am taking a quick break to update on findings and try to avoid some heat stroke!
It seems that at no point does the second rockerarm for cylinder #1(2nd back from front or the I valve ) ever get loose. At one point it loosens enough to sorta lightly force to one side but it wants to stick there. I wouldn't guess that it is supposed to do that. However obviously I'm no expert on this issue