The 4L Thor rods are longer then the 3.9 gems,, they did this to stop piston slap,,, can you run a complete gems piston/rod assembly in a thor block? overall length and diameter is the same,,
anyone?
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The 4L Thor rods are longer then the 3.9 gems,, they did this to stop piston slap,,, can you run a complete gems piston/rod assembly in a thor block? overall length and diameter is the same,,
anyone?
The rod/stroke ratio affects several engine dynamics, including piston speed and acceleration, piston dwell at top dead center and bottom dead center, piston side loads, cylinder loading and bearing loads. These elements play roles in engine efficiency, combustion and wear.Quote:
Originally Posted by Pedro_The_Swift
Generally, a lower rod/stroke ratio means a higher rod angle (in relation to the crank and the gudgeon pin), which creates greater potential for accelerated wear to cylinder walls, pistons, rings and rod bearings. A low enough ratio, due to a more severe rod angle, can literally punch a piston right into the cylinder wall, out the block. You've no doubt seen images of rods being sent outside...
High rod/stroke length ratio engines, on the other hand, don't have the same friction concerns, but compromise in other areas. Air doesn't fill the intake with the same velocity (i.e. slower), but there is also less demand for the ports to flow as well since there is more time to fill and scavenge the cylinder. This creates periods of stagnant airflow at low revs and overall weaker torque figures.
In the case of the 4.6 the displacement increase offsets these issues to an extent, but it does not negate them entirely.
Without a significantly redesigned induction system and multivalve cylinder heads, altering the rod/stroke ratio isn't going to net you any huge performance benefit. There are many things to consider beyond just the 'will they fit'. cylinder pressures, dwell time, camshaft static timing and ignition advance all have a significant influence on the efficiency when changing the ratio.
Because of the stroke increase of the 4.6, the engineers opted for a 'safer' longer ratio to reduce the overall rod angle at the extremes of crank rotation. It also allows more clearance between the base of the liners and the rod.
There are always things to consider that are not entirely obvious, such as the piston acceleration and dwell time at TDC.
I've seen plenty of rover v8's stroked out to 5.2, but there is a fair bit of work involved in clearancing as well as high rpm stability.
Gentlemen, engine in, all appearances are good. No noises no leaks. 300kms done so far ,only got to 250 last Time before exhaust noises started and knocking started at 500kms. Took out to rebuild at 1000ks...the countdown is on. 🤞🤞🤞🤞🤞[emoji482][emoji482]