Here is an instalment on how the Australians make there siamese port Chev-cast offs and the 12 port later versions do lots of hp.
Just a quick note. The amount of specific power an engine has is equal to a factor. For me, I've found just taking the cubic capacity, and multiplying it by the rpm at which it occurs, then divide it by one of these factors below, you'll get an acurate way of assessing how much net HP your ride will produce. Try it on any engine you see power figures on, and see if I'm right!
Case 1: Holden Six, 202 cubic inch (1971 to 1980) . Head 9 port, engine is a miniture 230/250 with same bore spacing as FordS 144-250 I6's
Test one: Guy comes into Speed shop with an Eccon Rail with a 202 engine which won't past the 10.99 cut off for entry into the class. It has tube headers, triple SU 1.75" carbs, a worked head, 11.2:1 compression and HEI ignition. Dyno triggers 210 hp net at 4750 rpm, and torque peaks at the same 4750 rpm as 190 lb-ft. This shouldn't happen if the cam is sorted. Normally peak torque is at about a third this speed ( 3600 rpm). So the 308 degree high lift screemer cam is removed and replaced with a Waggot E3, a cam known for good results.
Test Two: the new cam is set at 22 thou lash, and the carbs get some ram tubes placed on them to smoothen the entry of air into the carbs. Dyno reads 222 hp at about 5700rpm, and now produces 205 lb-ft from over 5000rpm to 195 lb-ft at 3000 rpm. Something is not right with the exhast tunning. The torque peek should still be at a lower rpm.
Test Three: Six dyno runs are done with lesser valve clerances until 10 thou lash gives 236 hp at 5250 rpm. Over 219 lb-ft at 5000 rpm. Still looks to be an issue with the exhast system.
Test Four: Some bright spark grabs a set of old cast iron twin branch headers, used on the touring car special XU1 GTR. These on there own, with some tubing pipes running from them, loose 9 hphave shortened tubular pipes running off them for the dyno test. From 3000 to 4000 rpm, there is now an extra 20 lb-ft extra, but maximum power is only 227 hp at 5250 rpm.
Test Five: The dyno operator tries an old motor cycle trick...painting the tubes in acrylic paint, runs the engine at hi rpm, and cuts the tube where the paint stops burning off. Suddenly, during the last run, a mighty 254 hp @ 5250 rpm appears. At 2500 rpm, there is another 42 lb-ft there! The torque peek is now much lower at about 3800 rpm.
Now, do the sums. 202 cubic inches, times 5250 rpm, divided by some factor, gives 252 hp. What is it? 4208. At the start, it was only 4570. This makes the engine tunned to almost a "full-house, gas flowed, carb'd 300 degree + cammed motor". All this form a day on the dyno!
Case 2: A later model 202, called a 12 port 3.3liter, runs a very good cylinder head, but a milder 280 degree cam.The headers are special Genie tube items. For the first dyno run, a 500 cfm #2300, 4412 Holley 2-bbl carb on an alloy intake manifold is fitted up to a cars engine bay. A control trans, tire and diff is used. The rear wheel horspower figures have been read off the chart, and turned into net flywheel figures by multiplying by 33% for the drive train and tires losses.
Then a 1985 GM Tuned Port Injection manifold is placed on, with an EFI rail and a Haltech F9A fuel only electronic control module is calibrated on the rolling road. The figures between Test One and Test Two are listed below:-
5250 rpm......Test One 201 hp......Test Two 221 hp
5000 rpm......Test One 203 hp......Test Two 216 hp
4750 rpm......Test One 195 hp......Test Two 213 hp
4500 rpm......Test One 188 hp......Test Two 209 hp
4250 rpm......Test One 177 hp......Test Two 200 hp
4000 rpm......Test One 177 hp......Test Two 193 hp
3750 rpm......Test One 157 hp......Test Two 168 hp
3500 rpm......Test One 123 hp......Test Two 144 hp
3250 rpm......Test One 109 hp......Test Two 120 hp
Maximum torque for Test One is 232 lb-ft at 4000 rpm, and 254 lb-ft at 4000 rpm for Test Two
In a vehicle weighing around 2950 pounds with a driver, there is a 14.2 second quarter with Test Twos EFI combination. The EFI system brings an extra 10% torque and power right through the rev range.
Calculations find that the 202 *RPM over delivered power is 4975 for Test One, and 4798 for Test Two. These figures indicate the engine maps as a "worked to an expert semi-race spec" machine.
Conclusion: If the Aussies are doing this with an inferior headed vehicle which has similar cubes and smaller vlaves than some of the US 200 cube Ford I6's, why aren't we doing it too?
Just a quick note. The amount of specific power an engine has is equal to a factor. For me, I've found just taking the cubic capacity, and multiplying it by the rpm at which it occurs, then divide it by one of these factors below, you'll get an acurate way of assessing how much net HP your ride will produce. Try it on any engine you see power figures on, and see if I'm right!
Case 1: Holden Six, 202 cubic inch (1971 to 1980) . Head 9 port, engine is a miniture 230/250 with same bore spacing as FordS 144-250 I6's
Test one: Guy comes into Speed shop with an Eccon Rail with a 202 engine which won't past the 10.99 cut off for entry into the class. It has tube headers, triple SU 1.75" carbs, a worked head, 11.2:1 compression and HEI ignition. Dyno triggers 210 hp net at 4750 rpm, and torque peaks at the same 4750 rpm as 190 lb-ft. This shouldn't happen if the cam is sorted. Normally peak torque is at about a third this speed ( 3600 rpm). So the 308 degree high lift screemer cam is removed and replaced with a Waggot E3, a cam known for good results.
Test Two: the new cam is set at 22 thou lash, and the carbs get some ram tubes placed on them to smoothen the entry of air into the carbs. Dyno reads 222 hp at about 5700rpm, and now produces 205 lb-ft from over 5000rpm to 195 lb-ft at 3000 rpm. Something is not right with the exhast tunning. The torque peek should still be at a lower rpm.
Test Three: Six dyno runs are done with lesser valve clerances until 10 thou lash gives 236 hp at 5250 rpm. Over 219 lb-ft at 5000 rpm. Still looks to be an issue with the exhast system.
Test Four: Some bright spark grabs a set of old cast iron twin branch headers, used on the touring car special XU1 GTR. These on there own, with some tubing pipes running from them, loose 9 hphave shortened tubular pipes running off them for the dyno test. From 3000 to 4000 rpm, there is now an extra 20 lb-ft extra, but maximum power is only 227 hp at 5250 rpm.
Test Five: The dyno operator tries an old motor cycle trick...painting the tubes in acrylic paint, runs the engine at hi rpm, and cuts the tube where the paint stops burning off. Suddenly, during the last run, a mighty 254 hp @ 5250 rpm appears. At 2500 rpm, there is another 42 lb-ft there! The torque peek is now much lower at about 3800 rpm.
Now, do the sums. 202 cubic inches, times 5250 rpm, divided by some factor, gives 252 hp. What is it? 4208. At the start, it was only 4570. This makes the engine tunned to almost a "full-house, gas flowed, carb'd 300 degree + cammed motor". All this form a day on the dyno!
Case 2: A later model 202, called a 12 port 3.3liter, runs a very good cylinder head, but a milder 280 degree cam.The headers are special Genie tube items. For the first dyno run, a 500 cfm #2300, 4412 Holley 2-bbl carb on an alloy intake manifold is fitted up to a cars engine bay. A control trans, tire and diff is used. The rear wheel horspower figures have been read off the chart, and turned into net flywheel figures by multiplying by 33% for the drive train and tires losses.
Then a 1985 GM Tuned Port Injection manifold is placed on, with an EFI rail and a Haltech F9A fuel only electronic control module is calibrated on the rolling road. The figures between Test One and Test Two are listed below:-
5250 rpm......Test One 201 hp......Test Two 221 hp
5000 rpm......Test One 203 hp......Test Two 216 hp
4750 rpm......Test One 195 hp......Test Two 213 hp
4500 rpm......Test One 188 hp......Test Two 209 hp
4250 rpm......Test One 177 hp......Test Two 200 hp
4000 rpm......Test One 177 hp......Test Two 193 hp
3750 rpm......Test One 157 hp......Test Two 168 hp
3500 rpm......Test One 123 hp......Test Two 144 hp
3250 rpm......Test One 109 hp......Test Two 120 hp
Maximum torque for Test One is 232 lb-ft at 4000 rpm, and 254 lb-ft at 4000 rpm for Test Two
In a vehicle weighing around 2950 pounds with a driver, there is a 14.2 second quarter with Test Twos EFI combination. The EFI system brings an extra 10% torque and power right through the rev range.
Calculations find that the 202 *RPM over delivered power is 4975 for Test One, and 4798 for Test Two. These figures indicate the engine maps as a "worked to an expert semi-race spec" machine.
Conclusion: If the Aussies are doing this with an inferior headed vehicle which has similar cubes and smaller vlaves than some of the US 200 cube Ford I6's, why aren't we doing it too?
