Machined pistons, very close gap between piston crowns and Prus head, she is bloody tight.
Gave up on the idea of hand cranking, gave up on the idea of starter cranking, tow started it in 10 feet, wow, that was easy, just need to find that happy spot between high and low now.
My new engine would not start on the starter it was so tight. Towing it was the only way to start it. We towed it every night for a week, and drove laps in the neighborhood to break it in. Each lap was probably close to 2 miles, and we would do 4 laps an evening, 20 minutes to a half hour. I would estimate we have around 50 to 60 miles on it, and it is now starting on the starter. My buddy's T was tight to hand crank, but started on the starter before the battery went dead the first time. With about 500 miles on it now, it will hand crank pretty good. Good luck, and patience.
I tightened up the bearings and bored the cylinders with new pistons and rings - still no problems to hand crank start it fresh with a 0.100" milled Prus head and a high tension magneto but no impulse coupling.
The reason - Timesaver lapping compound gave perfect fit for the bearings and easier cranking
If all bearing and piston clearances are proper, and ring end gaps are correct then it won't be too tight.
If it's so tight that it needs to be pulled to start, then it was assembled too tight. It shouldn't be that tight.
Too tight to crank and/or too tight to turn over with the starter means something is wrong that needs to be fixed.
Gotta agree with Ken and Adam. When an engine is put together, it should be a little tight, but not excessively so. If you can't crank it over by hand, then something is wrong and it needs to be taken down and fixed.
I figure that it can burn up the bearings, hurt the crank journals, and possibly overheat.
So the bottom line is that a little tight is perfect. So tight that you can't crank it by hand is too much.
As the engine is assembled it should be turned 360 with each component attached. Each piston should fit snugly in the cylinder with a light tap with a composition hammer to slide it through the ring compressor and in to the cylinder. If more than a light tap it is too tight. Firstly each ring should be fitted in to each cylinder by pushing it down with an inverted piston. Piston and rings should all slide down freely. All carbon should be removed from the ring groves. With all the pistons fitted freely, when each connecting rod is connected and torqued the engine should be turned 360. With all four pistons and connecting rods assembled the engine should turn over freely by hand on the bench and should hand crank start without any issues. One misaligned rod cap or one with insufficient clearance will cause binding. To say an engine is stiff/tight because it is new/rebuilt is a mith, it should turn freely.
I expect that he is talking about too tight to crank over fast enough to start as opposed to can't get it to turn by hand. There is an initial "oil lock" that makes it hard to crank but once you break that it should be easier. I usually pull start my rebuilds the first time but can hand crank after that. I have no starters so I don't have much choice but if you prime the cylinders first and then hand crank if the car is set up right it should start on less than half a revolution.
wow, l thank you all for your comments, sorry l hadn't got back to you sooner, its running fine, new rebuild, hand turned very nicely with the head off, new Prus head ( 8:1) machined piston heads to suit, it kinda gets a bit hard to crank then, but pulled a little, got it fired up and found ------ the clutch band was just a little to tight, plus a new big 12V battery, fires up beautifully now.
Only got about 10miles on it so far today, she got a bit hot. as is to be expected on a new engine rebuild.
Tomorrow, we will venture out and about, have a new 12 V tractor generator attached that sounds a little rattley, so l will blank that off and drive it in.
Frank, another great bearing job, thank you sir.