I think one of the major problems is that when you try to loosen it in 1st gear is that there is so much movement on mounts etc and engine twisting before it actually puts force on the bolt it is limited by this in the force applied.
I always put the car in 5th gear, and do from above, with rad pipes etc out of way(if convenient) you can get more swing, use extension just to make easier, I use this on my 4 foot ratchet a 3 foot extension, but so I have about 5 1/2 feet in total.
tabetha