Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Monty Takes A Deep Breath

Despite what the internet says, I'm reliably informed the standard rods in a Duratec are not the weak point, it may appear that standard rods in a Duratec exceeding 235hp are failing, but I'm told a closer forensic examination of the engine internals will typically reveal it was actually the standard Ford hard silicon aluminium bearings that gave out first. As rod load increases the big end bearing can momentarily touch crank journal as the oil film strength is overcome, this despite the hydraulic wedge effect that should ensure the bearing is always kept separated from the journal by that film of oil.

Valve float can also be an issue at higher engine speeds, I'm managing this on Monty by using 180lb beehive springs, I've been running these for the last 3 years now and despite the Phase 2 cams falling over at 6,500rpm, I have buzzed Monty's Duratec above 7,500rpm many times. The 180lb valve springs definitely do their job brilliantly, back in the day we'd use double valve springs for high rpm engine builds, however, these days instead of running inner & outer springs a single beehive spring is preferred as it provides similar control with a lot less mass, friction, and heat.



Running beehive valve springs also means you have fewer components to fail when compared with a double valve springs, and its conical shape results in a smaller lighter retainer, anything you can do to remove mass from your valve train improves efficiency and solves a host of undesirables too. Valve float happens when inertia overcomes spring force, by reducing inertia, you’re effectively helping the spring win without needing to run absurdly high spring rates/seat pressures.

Beehive springs also naturally create a more progressive (non-linear) spring rate, the coils at the top (smaller diameter) are more flexible while the lower coils (larger diameter) are stiffer. As the spring compresses the softer upper coils compress first, then the stiffer lower coils engage which gives better control during initial valve opening/closing and strong resistance near full lift where float is most likely.

Traditional straight springs can, and often do, suffer from unwanted and uncontrolled harmonics. Basically, the spring oscillates at certain frequencies, which can cause valve bounce and loss of control even if spring pressure is sufficient. Beehive springs help here because each coil has a slightly different diameter, this produces different natural frequencies along the spring so resonance can’t build uniformly and the result being more stable behaviour across a wider RPM range.

Of course, the best way to mitigate risk is simply to avoid the risky behaviour in the first place, just because Monty's Duratec will have the capacity to rev out and keep making power all the way to 8,000rpm if I use individual throttle bodies, doesn’t mean that's what we're going to do. My persistence with the Fusion Fabrications long runner inlet is all about delivering on my design brief that centres around the core objective of creating a street friendly engine that makes good horsepower, but more importantly a really broad spread of torque from idle to an absolute maximum of 7,500rpm.

The Fusion Fabrications long runner inlet will actually limit power over 7,500rpm, this combined with some valve timing tweaks where we are advancing the inlet cam by 1 degree and retarding the exhaust cam also by 1 degree from Newman's base number, will all come together to effectively become their own rev limiter. Obviously, I will also be running my true ignition based 7,500rpm soft rev limiter strategy, and a hard rev limiter at 7,650rpm, but the long runner inlet manifold and the valve timing tweaks will certainly help here too.

So in summary, the plan is to limit the engine to 7,500rpm but then build it as if we are taking it to 8,000rpm! To this end, we are fitting Mahle Motorsport PTFE coated tri-metal big end bearings, ARP rod bolts, and moving my 180lb beehive valve springs across to the new ported big valve head. The idea is to mitigate risk by never going into the danger zone, but then completely removing all risk by building Monty's Duratec to be 8,000rpm ready

Here's the latest projected dyno graph that shows how we hope the small, but significant in influence valve/cam timing changes will increase torque towrads the end of on-street overtaking events at the expense of a few horsepower over 7,500rpm, an area we won't be visiting anyway



With the proposed 1 degree adjustments around Newman's base timing settings, peak torque actually arrives 1,000rpm higher up the rev range. Initially this looks like we've delivered the very opposite of what we are trying to achieve, especially as that peak torque number is 2 ft/lbs lower than the suggested base timing. Interestingly, despite making the changes, both timing settings actually deliver exactly the same torque from idle to 5,000rpm, so we've neither gained or lost any torque.

However, as the engine passes 5,000rpm and reaches 6,000rpm, by making our minor 1 degree adjustments we magically produce another 12lb/ft of torque in that zone. Of course, this isn't magic at all, what we've done is simply hold cylinder pressure inside the combustion chambers a little longer, and before we open the exhaust valves to let it out to atmosphere.

The real genius here is we'll actually sacrifice nothing for this meaningful gain; this is because any horsepower lost would exist above our self-imposed 7,500rpm rev limit, a place the engine will never visit. Despite our gain only existing in a 1,000rpm window between 5k & 6k, in a car that only weighs roughly 930kg you're definitely going to feel that additional 12lb/ft! It also now makes perfect sense to hold onto the gear a little longer before changing up, this ultimately translates to more punch during overtaking manoeuvres on the road.

This 'win win nothing lost' result makes the strategy of advancing the inlet cam by 1 degree and also retarding the exhaust cam by just 1 degree from Newman's recommended numbers an absolute no-brainer, especially given our objective is to create a street friendly engine that makes good horsepower, but more importantly a really broad spread of torque from idle to an absolute maximum of 7,500rpm.