This is a piece of information from an August 1990 Australian Street Machine article on high performance sixes. It's from Bill Santuccione, a Ford Australia development engineer who worked on the Aussie 250 and Cleveland V8 engines during the 60's and 70's. It is worth a read to determine ways of making a six cylinder Aussie Cross flow Falcon engine produce big power.
"The 250 six is a good engine to modify in a mild sense - if you make the torque work for you. On an around - town street car, a strong 250 can be a lot quicker in the first 50 to 100 yards away from the lights than even a V8.
Bill says the biggest problem with the 250 is its design. "Almost across the board, I believe the 250 suffers because of its stroke/rod length ratio. Rod length verses stroke is a crucial factor when it comes to determining the optimum 'revability' or torque output of engines. The Falcon six has a bloody terriable ratio copared to the ideal formula.
"Back in the old days at the engine laboratory in Geelong, we did a lot of development work on cams for the 250. You know, aiming for driveability, torque - getting the best of all worlds if you like. And I remember then playing with compression ratios and valve sizes and all the things you do in research and development. It didn't matter what comp ratio. valve sizes or cams we evaluated., all wen were able to do was move the horsepower peak up or down in terms of horsepower out put but not in rpm.
"Mormally when you start to 'cam' an engine up, the horsepower goes up and the power peak moves up accordingly. On the Falcon six, due to what I believe was that rod lentgh ratio, it didn't matter what you did. It remained at around the 4800 rpm mark'. Bill reckons the Ford six can rev to around 7500 - which is prettydamned good for a stock Falcon six. It's just there's no point in doing it. Peak grunt happened 2700 rpm ago...
"What I'd be suggesting to anyone going for more horsepower is to be conscious of that characteristic and aim to fill the torque curve as much as possible, " Bill says. "Your horsepower will increase proportionally but not much further than that rpm point." Bill says that the 250 is agood street package. But for racing, he thinks you'd have to consider increasing the rod length. Okay.Fine. And you wonder why there aren't many killer 250's around! As it happens, Bill is curently planning a kit designed specifically to get around this problem...
Lets assume you want to get good power out of a 250. First port of call is, of course, the cam. "I'd think of someone like Crow Cams," Bill says. "They 've got a coputer so you can feed that kind of stroke/rod length data into it and come up with the best result."
The same torque characteristics come into play when you're talking about carb choices. " The fact that you're only revving to the 5000 rpm mark means big carburation isn't that critical. But the tripple Webers are probably the best package to go with because they lend themselves to 'pulse - tuning' (Timing the pulse to coincide with the next intake filling charge). That complements the fat torque curve situation." Bill says he's also done a lot of promising development on four barrel Holleys by altering the tune length of the intake runners.
Headwise, Bill reckons you just have to go for the better breathing crossflow head."In terms of making maximum torque and horsepower, it just breathes that much better - the port shapes and angles are very, very good. But with the Series II alloy head, I think, the combustion chamber shape was different to the earlier one. They changed to an almost kidney shaped chamber and I remeber they appeared to be a bit prone to pinging. That's a particularly critical thing if you start building a higher compression engine."
Bill says that apart from the torque curve and the possibly suspect later model alloy head - plus the fact that the water pump location tends to cause number one cylinder to run cooler than the rest - the 4.1 litre (sic)engine is a pretty srong engine. "I've never found any weaknesses in the bottom end, the bearings or any thing else." That means if you'd like to build one up, normal rules apply."We almost always up - rate the oil pump output - that's always good insurance. And the standard conrod bolts tend to be a bit on the plsticine side. Even if you're not reving the engine too high I'd still go to a set of high performance bolts."
"The 250 six is a good engine to modify in a mild sense - if you make the torque work for you. On an around - town street car, a strong 250 can be a lot quicker in the first 50 to 100 yards away from the lights than even a V8.
Bill says the biggest problem with the 250 is its design. "Almost across the board, I believe the 250 suffers because of its stroke/rod length ratio. Rod length verses stroke is a crucial factor when it comes to determining the optimum 'revability' or torque output of engines. The Falcon six has a bloody terriable ratio copared to the ideal formula.
"Back in the old days at the engine laboratory in Geelong, we did a lot of development work on cams for the 250. You know, aiming for driveability, torque - getting the best of all worlds if you like. And I remember then playing with compression ratios and valve sizes and all the things you do in research and development. It didn't matter what comp ratio. valve sizes or cams we evaluated., all wen were able to do was move the horsepower peak up or down in terms of horsepower out put but not in rpm.
"Mormally when you start to 'cam' an engine up, the horsepower goes up and the power peak moves up accordingly. On the Falcon six, due to what I believe was that rod lentgh ratio, it didn't matter what you did. It remained at around the 4800 rpm mark'. Bill reckons the Ford six can rev to around 7500 - which is prettydamned good for a stock Falcon six. It's just there's no point in doing it. Peak grunt happened 2700 rpm ago...
"What I'd be suggesting to anyone going for more horsepower is to be conscious of that characteristic and aim to fill the torque curve as much as possible, " Bill says. "Your horsepower will increase proportionally but not much further than that rpm point." Bill says that the 250 is agood street package. But for racing, he thinks you'd have to consider increasing the rod length. Okay.Fine. And you wonder why there aren't many killer 250's around! As it happens, Bill is curently planning a kit designed specifically to get around this problem...
Lets assume you want to get good power out of a 250. First port of call is, of course, the cam. "I'd think of someone like Crow Cams," Bill says. "They 've got a coputer so you can feed that kind of stroke/rod length data into it and come up with the best result."
The same torque characteristics come into play when you're talking about carb choices. " The fact that you're only revving to the 5000 rpm mark means big carburation isn't that critical. But the tripple Webers are probably the best package to go with because they lend themselves to 'pulse - tuning' (Timing the pulse to coincide with the next intake filling charge). That complements the fat torque curve situation." Bill says he's also done a lot of promising development on four barrel Holleys by altering the tune length of the intake runners.
Headwise, Bill reckons you just have to go for the better breathing crossflow head."In terms of making maximum torque and horsepower, it just breathes that much better - the port shapes and angles are very, very good. But with the Series II alloy head, I think, the combustion chamber shape was different to the earlier one. They changed to an almost kidney shaped chamber and I remeber they appeared to be a bit prone to pinging. That's a particularly critical thing if you start building a higher compression engine."
Bill says that apart from the torque curve and the possibly suspect later model alloy head - plus the fact that the water pump location tends to cause number one cylinder to run cooler than the rest - the 4.1 litre (sic)engine is a pretty srong engine. "I've never found any weaknesses in the bottom end, the bearings or any thing else." That means if you'd like to build one up, normal rules apply."We almost always up - rate the oil pump output - that's always good insurance. And the standard conrod bolts tend to be a bit on the plsticine side. Even if you're not reving the engine too high I'd still go to a set of high performance bolts."
$300 for a crank???
