Expert: Dan Liddy - 8/1/2011

Question
I am an amateur racing driver, driving a Mini Cooper 1275 cc, just for pleasure. I have been building my own engine for quite a while now but this is the first time that I am experiencing a problem. The starter motor would not crank the engine as fast as it should after the re-build. It feels heavy to turn by hand either. Starting it temporarily with a 2 x 12 volt battery helps but the engine doesn't seem to rev freely. What could be the problem, although I suspect a 'tight' spot could somewhere around the camshaft. If so, should I dismantle the engine again.

Answer
If you must use a wrench or spanner to turn the engine, it would probably be wise to take a good look inside.  Check the rod and main bearings for markings indicating a 'too-tight' circumstance.
It is also possible that the camshaft timing is off enough that valves are interfering with piston travel. That would cause an immediate catastrophic failure upon starting, and would have to be corrected.

I believe I sent you an earlier answer recommending a couple of companies that provide reduction-gear starters for your motor, but since you suspect a tight spot, it would be better to check first. I'm certain though, that you will ultimately need one of the racing starters.  Remember that you are asking a stock starter to crank a seriously modified racing engine and there is a lot more resistance in the cylinders due to the increased compression. Take the plugs out and try to crank it again, if it's still stiff you have a problem , if it frees up dramatically, it's just the increased compression and you'll need the starter to fix it.

It's really difficult for me to diagnose internal engine troubles without virtually being there myself and looking into it. It may be that you should take it to a mechanic you know and trust and ask his opinion .

Good luck

Dan Liddy
Sarasota, Florida, USA