Setting cylinder 1 to top dead center

[Mark2023]

Hey guys!

I have my head off and am contemplating cleaning the carbon deposits off the pistons. Mostly doing this because I have heard it helps with smog and reduces cylinder temperature. Not quite sure If any of that is true, but I’m already there so I might as well. That being said if I clean the carbon off I need to rotate the engine to get the lose carbon out of the piston rings. This means I will have to re set the cylinder 1 to TDC… any words of wisdom?

Is setting cylinder 1 to TDS something I can just do by putting my finger on the piston and feeling when it is at its highest or do I need a dial bore gauge? I don’t really like using the alignment tabs on the bell housing too much. How do you guys recommend I ensure that cylinder 1 is at its highest point?

Thanks and happy new year!

[danmartinic]

I rotated the head-less engine & I recall simply rotating it back using the marks on the flywheel (ie. bottom of bellhousing to agree with top). EDIT: not sure why you don't like using those markings but they are pretty simple and effective (I find the bottom one the best)

Come to think of it, I don't even remember lining anything up after that.. though it's possible I had to ensure camshaft was correct before putting its housing back on.

I certainly did not fret about finding TDC some special way

[Tom]

I'd only mess with it if there's an actual build up, because that can increase knock via hot spots. Maybe post a picture for opinions on whether it's worth the risk of getting gunk in your rings. When I did my old motor, I used solvents to break down the carbon rubbing with towels. Took forever, but no chunks or debris that way.

As for finding TDC, I second Dan's advice. Use the flywheel and bellhousing marks! If you just use your finger or eyes to see where the piston is at its highest, there's a good chance you'll be a few degrees off. The piston can be at the high point for several degrees of crank rotation, so engine builders will use a degree wheel and piston stop to find TDC (by rotating the motor in both directions until it hits the stop, and then splitting the difference). No sense in going to all that trouble just hoping to get true TDC, when the factory has already done the work for you with the marks. Besides, when the engine is back together, you'll need the marks to get the timing belt aligned. Bottom line, you pretty much need to get comfy with the factory marks to do this kind of work on the motor. Go with the flow on this one.

[gruhsy]

Final Wipe Solvent works well for removing carbon without scrubbing.
I posted on RL lots.
Any auto parts or body shop suppliers sell it.

[Thom]

Hold a vacuum cleaner in the other hand if you are worried about dropping some carbon between the pistons and the cylinder walls whilst you scratch the piston crowns.

[danmartinic]

Hold a vacuum cleaner in the other hand if you are worried about dropping some carbon between the pistons and the cylinder walls whilst you scratch the piston crowns.

Yes I remember now doing exactly this

[Tom]

As is my way, I once 3D printed a little nozzle for the end of the shop-vac hose, so I could put a little vacuum hose on the end and pin-point the suction. You need to vent the hose somewhere or it basically deadheads the vacuum, but it's great for stuff like this. You could do the same with duct tape of the like. If memory serves, I first did that to suck oil and solvent out of the head stud wells.

As for solvent, its dangerous, politically incorrect, carcinogenic, etc., but good old gasoline works pretty well too on carbon.

[danmartinic]

I'm pretty sure I used plain old WD40 to great effect. Or maybe brake cleaner. That Final Wipe Solvent has such a bad smell, it actually makes you feel like you're gonna "bring up" lol

Lots of ventilation needed!

[chris white]

two points:
I use grease smeared into the gap between piston and wall. Keeps debris out and can be cleaned up with any solvent (3M parts cleaner in the black can is really good stuff!)
Don't over think TDC. You are not 'degreeing in' a new cam. the level of accuracy is based on the belt tooth spacing and that's pretty big. If you are off by one tooth it will be very obvious looking at the flywheel / cam markings (just make sure you have tension on the right side of the belt!)

[dr bob]

Unless there's a serious carbon layer on the piston, waste no time unless you are taking glamour shots. That layer gets, um, replaced and/or reinforced after a short bit of run time. If you absolutely but work on it, try something like Permatex spray gasket remover. ATF also does an amazing job if you have the time to let things soak with the bores upright. My vote goes to "don't risk it" especially if you think sharp tools are OK -- they aren't.