In my growing effort to see how far we can carry the 4.0L sohc, I have found the first problem in the link. Up till now I have continuously pushed the 4.0L to a level I feel, at this moment, hasn't been pushed before. With my engine nearing 100k I am starting to see my first signs of age. The top end! After a dyno session the other day with a boost setting of 12psi we ended up (with problems) max hp 358 & max torque of 448lb.ft torque , from 2400-4600rpm the torque never dropped below 400 lb.ft. We shut down at 4900rpm due to valve float, if we could finished the pull the truck would've easily made 450-460hp. After evaluating the dyno sheet it was obvious that the valve springs (at the higher boost setting) werent controlling the valves they were only there for the ride. Thus ending my fun.. This confirms lately while tuning for higher boost why the truck hasn't felt to get any faster. It seems as if it were accelerating with the brakes on. This is the only drawback to street tuning. You cannot see what is happening with the vehcle. This is why I always tune on the street then follow up on the dyno. Just to see where the engine likes to make power and if it is over timed. (too much timing).
I am currently working on a ported set of heads and stiffer springs for the 4.0L sohc guys which I hope, won't necessitate a modified head. The set-up will hopefully be able to be run with the stock heads unlike others in the current market. I am only in the infancy so I hope this can be achieved. I will probably, 1st install the cams and then move to ported heads. Dynoing both times to see what, if any differences are to be had from the port work. Initially I am going to install a set of springs and get #'s from bone stock heads then install the cams and move onto ported heads. My pre-mature evaluation is that the stock heads flow so well just porting them without adding cams will be a waste, hence my reasoning for not testing with stock cams+ported heads. A little hint, I am working on getting this truck into the mid to low 7's in the 1/8th by the end of the year... Did someone say dual power adders? :scratch: We will see how it goes. Unfortunately business has slowed to a point that I cannot give a time guarantee, but it will happen. Thanks for all and I will keep you informed.-j
I am currently working on a ported set of heads and stiffer springs for the 4.0L sohc guys which I hope, won't necessitate a modified head. The set-up will hopefully be able to be run with the stock heads unlike others in the current market. I am only in the infancy so I hope this can be achieved. I will probably, 1st install the cams and then move to ported heads. Dynoing both times to see what, if any differences are to be had from the port work. Initially I am going to install a set of springs and get #'s from bone stock heads then install the cams and move onto ported heads. My pre-mature evaluation is that the stock heads flow so well just porting them without adding cams will be a waste, hence my reasoning for not testing with stock cams+ported heads. A little hint, I am working on getting this truck into the mid to low 7's in the 1/8th by the end of the year... Did someone say dual power adders? :scratch: We will see how it goes. Unfortunately business has slowed to a point that I cannot give a time guarantee, but it will happen. Thanks for all and I will keep you informed.-j
