I am old enough to remember when Ford introduced the crossflow motor in the Cortinas with much fanfare. There was much made of the better efficiency (which was true), but it wasnt until years later I realised that the cross flow had little to do with it. Better gas flow, certainly, but the idea of of the gases helping efficiency by coming in from one side and going out the other was marketing hype. The inlet and exhaust cycles are two separate events, and the gas doesnt care which side of the head it exits from. The valves were inline along the engine, so theoretically could have exited either side room permitting. In the grand scheme of things it doesnt matter, I was just reflecting how even a skeptic can be sucked in by advertising hype. I had a Peugeot that had a pushrod head design that was remarkably similar to the much vaunted hemi found in Chryslers with the valves across the engine like pretty much all OHC engines today.
There seems to be more scope for different valve orientation in pushrod motors.
I recall Rover's overhead inlet and side exhaust that surprisingly had sound engineering principles in the context of the time it was produced.
What other Quirks of engine design were out there?
bjmh,
Sep 14, 6:35am
You forgot to mention the "Bowl in Pistons " ha ha . i'm amazed at the likes of Mondeo . that have a full girdle to hold the crank and a windage tray.Any thing that was remotely 4 bolt mains was the bomb in the old days. Now every small engine is built like its containing a grenade.
budgel,
Sep 14, 6:46am
Yep, as a young fella I remember looking at the layout of a Lotus Cortina twincam engine and being impressed by it. These days, Nana's shopping basket often has a fairly trouble free twincam engine in it.
tony9,
Sep 14, 6:54am
It was a bit more than just hype. Not having the inlet manifold and carburettor on the hot side above the exhaust would have lowered intake temperature and improved efficiency. And of course there is more room for bigger ports.
elect70,
Sep 14, 8:13am
Well it certainly improved the perfomance .Thses things arent done for no reason hours on a test bench testing optimum flow rates etc
franc123,
Sep 14, 11:20am
There was loads of advantages to cross flow engines. they're not switching back to non cross flow again ever. One of the biggest was heat soak, having all that heat below the carb was never desirable. These days plastic intake manifolds are the fashion so again they should be kept away from the exhaust manifold for obvious reasons, ditto any sensors associated with the engine management system shouldnt be subject to high levels of heat.
toyboy3,
Sep 14, 11:42am
The inlet manifold needs heat for the engine to function correctly As the carburettor Is an atomiser of the fuel the manifold turns the fuel into gas so the engine can burn the fuel , that’s why the cross flow engine has water flowing around the manifold to heat it . The non crossflow uses exhaust gas to heat the inlet manifold
stornello,
Sep 14, 5:40pm
Yes, a carburettor needs heat to vapourise the fuel, it is atomised in the carb. The exhaust was a convenient way to get that heat into the manifold. Crossflow engines had coolant hoses to the carb, and so did fuel injection throttle bodies. Crossflow allows more room for better porting - no siamesed ports.
franc123,
Sep 14, 5:47pm
Water heated manifolds or PTC heaters under the carb are far better ways to assist atomization than exhaust heat. No argument.
stornello,
Sep 14, 6:09pm
Before the crossflow there was no need to think of other methods. even V8's used exhaust gas to heat the inlet manifold.
budgel,
Sep 14, 7:11pm
No argument with the heat dispersion, but that's not got a lot to do with the flow across the head, which never really happened.
framtech,
Sep 15, 3:23pm
Funny, talk about the ford crossflow, back in the day we built a crossflow for a mk2 escort for the shellsport series, what we did to get around the rules was to do a radicle job on the crossflow, we had a plate cut to sandwich between the head and the block to create a chamber, shaped it for the burn and fitted flat top pistons, the car won the series the following year from memory , A non crossflow bored 1500 all steel thick wall block fitted with a downport head(modified) can make 180 hp @ 9000 rpm using 40 weber side drafts. Valve max size inlet 42mm with 8mm lift. The Dodge hemi motor is a classic that is still kicking arse using old technology fitted to Rams, challengers 5.7l, 6.4l, 6.2l and the supercharged hellcat and demon Big valves = more swept volume , ya can't beat good head design, the rest is just beefing up to use the power.
Re heated inlets, The heating of inlets is a road car issue in the winter. Most race engines before injection used side suckers with no heating, the colder the inlet the more power they made, carb icing was only an issue in very cold weather (frosts), and production cars used to have a air cleaner with a bi pass off the exhaust that was opened and closed by a simple valve, but the key to more power was to cool the inlet manifold near the head.
sr2,
Sep 15, 5:58pm
No offence intended mate but at the risk of calling it misinformation you’re spouting off a bunch of contractional facts.
A carburettors job is to turn a liquid into very small droplets, it’s simply a process called atomization. Vaporising is when a liquid is ‘boiled off” to produce a vapor, the last thing you want in an intake system! (Anyone experienced vapour-lock?).
In the ideal world the colder the inlet charge - the better the volumetric efficiency. Heating an inlet manifold becomes an acceptable compromise for cold starting, meeting emission standards or when running a single carb with unequal length runners, (eg. A single carb 6 cyl where the heat assists with keeping the particles in suspension).
Once again no offence intended but get the science right and the rest comes easy.
sr2,
Sep 15, 6:07pm
You're on to it mate.
bill-robinson,
Sep 17, 3:04am
even the flathead V8 is cross flow.way earlier then that modern ohv 4 you mention. and the 1917 chev V8 was cross flow way before the ford.
mannix51,
Sep 18, 2:41pm
Was it the 2 liter cortina that advertised the radically new "bowl in piston" engine?
strobo,
Sep 18, 4:37pm
Some older buggers likie myself may remember the briggs? inlet gaskets we used to retro fit to the likes of toyota landcruisers 6cyl petrol engines ( the old chevy 6 engine to improve atomnization of fuel to take place nearer the combustion chambers further away from the carb and closer to the inlet chamber ports of the cyl head to give better low down power and better fuel efficiency. The gasket had similar steel mesh such like used in a kitchen spud strainer or colander .They were made /designed in ozzie and either a Biggs or briggs? a brand not sure now,i did a quick google search and didn't find it but . The fuel from the carb would hit the mesh and spray out ,well ya get the idea .they were popular then and disappeared around early or late 80's I spose when fuel injection become more popular.
No.it was the Kent crossflow that introduced that a few years earlier. The 2 litre OHC Pinto engine used flat top pistons.
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