What causes cylinders to get a taper as you move down the bore, i.e. the diameter decreases? This is in my Model A.
Rings pushing on the bore wall and a lot of miles!
So, it's time for a bore job to oversize with new rings and pistons.
Mike it's the ring tension causing wear. It is also egg-shaped too in a used bore. The compression and the explosion of the charge is what causes the rings to expand and scrape the walls. As the piston travels down the bore the power causing the rings to expand becomes less causing the less wear at the bottom of the cylinder. The rotation of the piston rod plus the lateral spinning force is what does the side wear plus the piston (when the wear gets excessive) rocking at the wrist pin. Cylinders actually wear bell shaped and oval. That is why we always use to 6-way mike each cylinder bore when determining cylinder condition. Also look for scuffing and scrapes in the wall. (broken rings, trash sucked into the cylinder or even hard carbon scrapes). Also check the pistons for galling from lack of oil. Also check for skirt shrinkage at the bottom of the pistons. The longer and engine is ran with dirty oil, continuous hard revolutions, poor cooling will cause these problems sooner. In our race engines it can happen in a matter of minutes or seconds. In a restoration or old car it takes much longer for this to happen. But if you are the NEW owner of said car then it depends upon what type of maintenance and common sense that the owner used with the engine.
Hope this answers your question.
How much taper is there?
This helps me a lot.....thanks! I know now that I need to go through the engine thoroughly since i plan to keep the car and drive it often. Probably needs a new radiator too.......not a fan of old radiators.
wear, the rings wear more near the top--never thought of why, I suppose it has to do with oil and the pressures of combustion. This is what leaves a ridge at the top of cylinder bores. The T doesn't get a ridge because the rings actually travel to the top of the bore (wide rings!).
Craig....not sure....can find out tomorrow. But from what Joseph said I think I need to go all the way.
And that's where all that black goo on the magnets comes from.
Mike,I have a cousin who is looking for a Model A fordor. Do you know of any for sale?
Hmm, Josephs' very clear post wasn't there when I started my post--one of the disadvantages of dial up!
Jack, unless it sold this week, there is a RHD 30 model A in Adamsville Tn. Guy wants 3500.00. Says 95% of parts are there with doubles of a lot. Good project if some one wants a RHD. KGB
Mine will be as soon as I finish up the engine. It has a very solid body. Actually a nice A.
Is Sue still speaking to you after the Facebook post of her birthday
I told her I was entirely to young to be married to a 70 year old woman.
Thank you for the cylinder wall wear explanation. I never really understood why they don't just wear in a cylindrical shape. Your explanation cleared the fog!
The term TAPER is somewhat misleading because the cylinder is not tapered it is more oval at the top and more square at the bottom of the cylinder. The "taper" is a determined line taken from the bottom of the cylinder to the outward most wear area of the cylinder and that straight line is the "taper". It is the difference between the bottom of the cylinder and the most warn portion.
Oh wow Jack, you know just what to say!
The larger Continental aircraft engines, O-520, O-550 are bored with a taper so that when at operating temperature the bore will be straight.
They are air cooled and there is a bit of expansion toward the head end.
Even little 'ol 65 horse Continentals are ground with a choke like you describe.