If you were going to rebuild a diamante motor, I suppose you could always put the Montero pistons instead of the Diamante ones.
Yes, but you might like the Montero cams better if you used the Montero pistons. The dynamic CR would be reduced with the dished pistons and Diamante cams..... The only way to tell would be to try it. The benefit to upper rpms and the lack of worry about fuel grade might overcome any loss of low end torque.
I'm guessing that's what is changing the CR ratio, but it still may be an interference motor due to the change in valve timing.
It would not be an interference motor with the Montero pistons and Diamante cams. Valve lift is the same for both cams and valve diameters are identical, so there would be no interference. The Diamante SOHC heads are the same as the Montero SOHC heads with the exception of the cams.
The static CR is 10:1 for the Diamante pistons with Diamante cams and 8.9:1 for the Montero pistons with the Montero cams. The dynamic CR is where it gets interesting:
Dynamic CR Choices 1) 6.99:1 = Montero pistons and Diamante cams
2) 7.39:1 = Montero pistons and Montero cams
3) 7.83:1 = Diamante pistons and Diamante cams
4) 8.28:1 = Diamante pistons and Montero cams
One thing's for certain..... the #4 choice would come off the line in a hurry..... #3 would probably win the race.
When I worked in the machine shop, we used a general rule of 4hp per compression point change (if nothing else was changed). That was a rough number we've seen on dyno pulls. Some gained more but most were in that 4 HP range.
Exactly - there's not as much to gain as most folks think - primarily you get a crisper throttle, but I suppose if you're building an engine for maximum HP, the CR gain is an incremental benefit. I think the amount of gain is actually a percentage and depends on engine size.... here's a calculator that shows a 3.0L to gain 5HP (3%) from 8.9:1 to 10.0:1:
CR/HP Calculator That does not consider the change to Diamante cams... which probably adds a few more HP, but moves the power band higher.
Frank
