Ed and group,

This assembly problem is vexing. We really need to avoid these types of foul up! When I built race cars and motorcycles the assembler (usually me) would try to learn what kind of force it should require to turn over a newly built engine. That is, how much friction to expect when turning over a brand spanking new engine for the first time. Cosworth even has a torque table that suggests you use a dial torque wrench for that first rev or two. If you see higher than suspected torque do not turn the engine over or even through the tight spot! Learning these forces saved one of my best customers a completely mangled engine! (Anecdote warning!)

 Guy M. my customer informed me that he would do the basic assembly of the "long block" including putting on the head so all I would have to do was time the cams. (Engine was a Kawasaki 900 with considerable modification to run in an SCCA C sports racer.) Guy was an EXCELLENT mechanic in his own right so I thought, "great that part is easy but tedious so I won't have to do it." I installed the cams correctly, and did the all important first revolution by hand. At TDC there was a very small change in friction, that would have been easy to miss if I had not been super familiar with that engine. Guy wanted to just run it, but I wouldn't do it because that is where the engine has nearly no piston movement for about 20 degrees. I made him pull the head and was super glad I did. Guy had installed all four pistons reversed on the piston pin. The large valve cut out was on the exhaust valve side rather than the intake as was normal. The "tick" was the intake valve rubbing on the side of the piston cutout! If we had started the engine it would have run for a few seconds until the intake valves bent! We corrected the problem, and thankfully the intakes were not even bent. Believe me we checked. The result was a few hours lost rather than a destroyed engine.

 We need to develop a data base here. So if you do a new build up, or any build up for that matter, do us all a favor and put a dial torque wrench on there and record your max turn over torque. Oh yea, do that with the plugs out of course. On a rotary with plugs out you should get a pretty even torque with no compression so if you get any spikes in there you may want to pull it apart again before you do some serious damage. Mistakes can happen even to very competent mechanics so it would be a great help to everybody and might even save you some cash. Just a good idea. My $0.02.

Bill Jepson

 

In a message dated 1/29/2008 7:32:20 AM Pacific Standard Time, eanderson@carolina.rr.com writes: