Originally Posted by Garage19
Using the specs for the cvh 1600 i could find off the net I have worked out the rod ratios for both engines
CVH 1.65
zetec 1.58
As you can see the ratios are not all that different!
From this we can see that the cvh may have slightly lower piston / bore side loading, but bore wear has neve been an issue on a zetec so no advantage there.
Rod length can effect cylinder filling at different rpms and there for ignition advance figures and camshaft choice and will also effect torque characteristics, but the difference between the cvh and zetec rod ratios will simply not have that much of an effect.
As for bore wall thickness... if zetecs are not cracking bores at 400 bhp i cannot see it being that much of an issue. Bore flex and cracking is not simply effected by bore thickness. I think you will find block design and structual rigidity is has a lot to do wih it!
I got 1.66 for the 1600 CVH and 1.55 for the 2000 Zetec.
CVH
Stroke - 79.52mm
Rod - 131.9mm
Zetec
Stroke - 88mm
Rod - 136.2mm
I agree that the cylinder dwell will not have that much of a detrimental effect at TDC but it can still have a difference. The Zetec is drastically helped with the reduced dwell time at BDC in a turbo application.
What are your views on adverse acceleration/deceleration (and thus increased loading/stresses) on the pistons/rods at TDC and BDC?
The block thickness was inspected by Karl Norris while he was at Jaguar. He disected a CVH and Zetec block to compare them. I don't have the exact figures but I remember at the time the CVH was around 1 point something mm on average thicker than the Zetec.
Bearing in mind, the Zetec is a CVH with a few modifications and a 16v head, the Zetec should technically be better although if I was to build one, I personally would like to ditch the crank and rods for something more like the CVH rod ratio, or maybe even higher.
P.S I was only naming 1 aspect where the CVH is technically superior to the Zetec.
