ORIGINAL: combatpilot

Ok maybee i dont know it all but what i do know that as a holder of a FAA Airframe and Power Plant licence (for twice as long as you been converting engines) is how to find true TDC. I must find true tdc or people may die! are you gona fly on an aircraft where the mechanics eyeballs the dead spot (which from what your describing is what you do) in the slop of whatyou determines to be tdc or are you gona fly on the plane that the mechanic had a sure method to determine true tdc.

So ok lets see why your method is inacurate. first we must see how much movement you can detect with your eyeball. how much can you detect? .001 .0001 .01?????? is your eyball calibrated. do you realize that 1 degree movement close to tdc in the wheel can be assmall as .001" again can you see that???? how do i know this? cause i checked my degree wheel against a dial indicator set up on the piston. Oh by the way on a ryobi engine you will see if you use a dial indicator that there is actually only a 4 degree dead spot. meaning that the time theneedle stops to the point to where theneedle moves again is only 4 degrees. I think this will be the same on most any engine of this size as the strokes are all so similar. Your saying10-12degreedead spot by eyeballing it. can you see the inacracy here??? so knowing this with confirmed by dial indicator and compared to your callibrated eyeball data I can tell you your eye is off by 6-8 degrees.

I dont care how smart or how good you think you are you are in no way gona know just where the dead spot starts or stops without the aid of a measuring device! it is absolutly imposible for you to eyeball this accuratly. most dial indiactor measure to one thousands of an inch and i can garuntee you you cannot see that much movement and know how much it was accuratly.

Ok so now to prove that i dont know eveything i always use a dial indiacator method. why? because that is the FAA approved way. that was the only method i know and i will not again describe it here as it has been described by me on a few threads already. however it was brought to my attention by avi8tor77 that if you use a piston stop. this can be something as simple as a spark plug with the guts smashed out and a rod jb welded or epoxied in so the piston will have a POSITVE stop. positive means that every time the piston comes to the stop it will be at the same degrees on the wheel every time. ok so roll engine one way till it is up agains the stop. roll the engine the other way till it is up agains the stop. place tdc or zero in the very middle of the two and you will have true tdc. this is a garunteed method as the piston stop isABSOLUTE and far more accruate than your calibrated eyeball. i cannot use this method for an aircraft as this is not an FAA approved method and besides that it is terrible to rotate an engine backwards to its normal rotation. not so much for the engine as the accesories like alternator brushes that are worn to one direction!!! so i will continue with the dial indicator for aircraft and I will now use a piston stop for my rc engines.

So the fact that you have been converting engines and selling them for 8 years DOESNOTimpress me. In fact it scares me that you have been shipping engines out for eight years not knowing where the timming was set at and claiming that you did. really makes me wonder about the quality of your conversions????? dont think im gona buy one anytime soon. its ok though i went to the parts store the other day and the stupid parts guy didnt know what a matched set of belts meant so your not alone in the ignorant catagory.

again i just dont understand why this is so freaking hard to understand. this subject has been discussed to death and the methods for finding true tdc have been posted many many times and yet there is always someone (saying someone and refraining from what i really want to say) that will post (well i just eyeball tdc and take the middle of that)