A
Anonymous
Guest
How much porting is recomended on a crossflow head? I think I remember hearing that porting a crossflow head was not needed do to the near perfect design.
The port size on 1980 to 1993 Alloy Head and Alloy Head II engines is small but perfectly formed. Each ports Square area is very small, only 1.3 sq in for both 200 and 250 cube cross flows. Ford Australia reduced it to
a) allow the evenly spaced ports to fit the tight compact Cortina body.
b) to improve brake specific fuel consumption. Smaller ports pay big dividends by reducing the wetted area where fuel can condense. The smaller ports cause more suface interuption, and re-intreduce atomised fuel into the air stream. (Every new Ford engine from the 1969 Lee Morse era had enormous ports, which were great at 6 grand, but useless at other speeds. The Alloy Head engines marked a departure from this principal. Keneth Duckworth commented that Ford would do better casting an arrow on the intake ports saying 'this way'!)
The Honda cast alloy head has little wall thickness to go beyond the 1.3" port diameter. Advanced states of tune in Australia have some ultra sophisticated external welding done to create an oval section port with more port area for performance.
Interestingly, the 1976 to early 1980 cast iron heads have worse shape, but very much bigger ports, over 1.6" in diameter, about the same size as the 1971-1974 2V Heads. Square area is about 2.2sq in for a 250 cube engine.
A bench mark for a big six cylinder engine is the 215-245-265 Chrylser Hemi I6. It had 2.7 sq in of port area.
Summary is that there is quite a lot to be gained by savage porting the intake section. Dick Johnston, an old Turbo and Carb Cross-flow developer, found the primary icrease was in the intkae port size and manifold size, not the shape.
The fact that 200 cube US engines run very well with a 250 2V head shows that the port size of 1.6" diameter would also work well on a 250 X-flow.
Peak flow for a really well moded Alloy head at 500 thou lift (28" H20 flow pressure) is 240 cfm from what Aussie7Mains said a while back.
a) allow the evenly spaced ports to fit the tight compact Cortina body.
b) to improve brake specific fuel consumption. Smaller ports pay big dividends by reducing the wetted area where fuel can condense. The smaller ports cause more suface interuption, and re-intreduce atomised fuel into the air stream. (Every new Ford engine from the 1969 Lee Morse era had enormous ports, which were great at 6 grand, but useless at other speeds. The Alloy Head engines marked a departure from this principal. Keneth Duckworth commented that Ford would do better casting an arrow on the intake ports saying 'this way'!)
The Honda cast alloy head has little wall thickness to go beyond the 1.3" port diameter. Advanced states of tune in Australia have some ultra sophisticated external welding done to create an oval section port with more port area for performance.
Interestingly, the 1976 to early 1980 cast iron heads have worse shape, but very much bigger ports, over 1.6" in diameter, about the same size as the 1971-1974 2V Heads. Square area is about 2.2sq in for a 250 cube engine.
A bench mark for a big six cylinder engine is the 215-245-265 Chrylser Hemi I6. It had 2.7 sq in of port area.
Summary is that there is quite a lot to be gained by savage porting the intake section. Dick Johnston, an old Turbo and Carb Cross-flow developer, found the primary icrease was in the intkae port size and manifold size, not the shape.
The fact that 200 cube US engines run very well with a 250 2V head shows that the port size of 1.6" diameter would also work well on a 250 X-flow.
Peak flow for a really well moded Alloy head at 500 thou lift (28" H20 flow pressure) is 240 cfm from what Aussie7Mains said a while back.
A
Anonymous
Guest
out of couriosity what is the volumetric efficiency of the 2v head stock and ported?
and the combustion chamber volumes?
and valve sizes stock and reccomended for macho torque.
I find that the falcon 6 performance handbook ask for this.
and the combustion chamber volumes?
and valve sizes stock and reccomended for macho torque.
I find that the falcon 6 performance handbook ask for this.
Anote to all.
Early iron 40 mm and 35 mm intake X-flows are best cammed and alloy head ones converted to stud mounted rockers to allow high lift cam instillation. All the latter 1985 valves are bigger, and work very well in the earlier x-flows. The later ones run the traditional High Swirl Combustion shrouded valves. The use of just bigger valves, just bigger cams will eliminate the need for porting up to about 250 hp. Past that, you may need to get flow bench work.
The Aussie 2v has poor exhast flow, stock US valve sizes, but bigger guides. Who cares though.. it flows so much better in stock form that VE is raised to over 85% with just a head, exhast and better carb!. I think KaStang got 105 rwhp with just the head on a 8:1 compression, where stock 200's have trouble giving more than 67. Taken together, it's a bolt on 45 hp flywheel over any stock US 1-BBL 200 of any year.
When really modified, it may have some issues with the exhast and valve guide sizes. According to Jimbo 65, all pre 1974 log heads and the Aussie 2V have a small stock exhast valve, and when enlarged to post 1978 US 200/250sizes, it gets mighty close to breaking into the water gallery when an unleaded exhast valve insert is fitted. Since exhast flow must be 70% of intake to flow best power, the exhasts are the Achilies Heal of this head.
There is no need to up the 42 mm intake ports, they are H-U-G-E. Gas flowed with the exhast ports welded up to increase the exit size, you could possibly balance the intake flow only with some savage work. The stock 500 thou lift figures are 170 cfm at 28"H20. Modern Motor placed the stock 400 thou lift figure of the alloy head x-flow as 145 cfm at 25 "Hg. That should be about 192 cfm at 500 thou in 28"Hg figures.
The 200 x-flow gave 114 flywheel hp in its emissionised form with just the stock 1-bbl carb, and the Xflow EFI and 170 hp gross 2V had the same net horsepower 149 hp rating and 16.9 sec quarter mile time in a 3100 pound car. The x-flow only gives more power than a 2V when the cam, carb and compression are the same. It has smaller intake ports, nice big valves and they are a much better balanced head.
Torque with any Xflow head is bigger than the 2V becasue it can maintain drivability at low valve lifts. There is little shrouding with the canted valve head, quite a lot with the 2V and log heads. Plug placement is better on the x-flow, and the chambers are 53 cc from the factory, while the 2V and logs sit around 58 cc.
The best idea is to search the aussie forum for Aussie7Mains posts. Mark ZE had a little info on x-flow heads. Its possible to go to 240 cfm at 28 " H20 with these heads, enough for 300 hp plus. To do so, you need to look at welding the long side raduis, and cutting and reworking the 33 mm port to 42mm's.
Early iron 40 mm and 35 mm intake X-flows are best cammed and alloy head ones converted to stud mounted rockers to allow high lift cam instillation. All the latter 1985 valves are bigger, and work very well in the earlier x-flows. The later ones run the traditional High Swirl Combustion shrouded valves. The use of just bigger valves, just bigger cams will eliminate the need for porting up to about 250 hp. Past that, you may need to get flow bench work.
The Aussie 2v has poor exhast flow, stock US valve sizes, but bigger guides. Who cares though.. it flows so much better in stock form that VE is raised to over 85% with just a head, exhast and better carb!. I think KaStang got 105 rwhp with just the head on a 8:1 compression, where stock 200's have trouble giving more than 67. Taken together, it's a bolt on 45 hp flywheel over any stock US 1-BBL 200 of any year.
When really modified, it may have some issues with the exhast and valve guide sizes. According to Jimbo 65, all pre 1974 log heads and the Aussie 2V have a small stock exhast valve, and when enlarged to post 1978 US 200/250sizes, it gets mighty close to breaking into the water gallery when an unleaded exhast valve insert is fitted. Since exhast flow must be 70% of intake to flow best power, the exhasts are the Achilies Heal of this head.
There is no need to up the 42 mm intake ports, they are H-U-G-E. Gas flowed with the exhast ports welded up to increase the exit size, you could possibly balance the intake flow only with some savage work. The stock 500 thou lift figures are 170 cfm at 28"H20. Modern Motor placed the stock 400 thou lift figure of the alloy head x-flow as 145 cfm at 25 "Hg. That should be about 192 cfm at 500 thou in 28"Hg figures.
The 200 x-flow gave 114 flywheel hp in its emissionised form with just the stock 1-bbl carb, and the Xflow EFI and 170 hp gross 2V had the same net horsepower 149 hp rating and 16.9 sec quarter mile time in a 3100 pound car. The x-flow only gives more power than a 2V when the cam, carb and compression are the same. It has smaller intake ports, nice big valves and they are a much better balanced head.
Torque with any Xflow head is bigger than the 2V becasue it can maintain drivability at low valve lifts. There is little shrouding with the canted valve head, quite a lot with the 2V and log heads. Plug placement is better on the x-flow, and the chambers are 53 cc from the factory, while the 2V and logs sit around 58 cc.
The best idea is to search the aussie forum for Aussie7Mains posts. Mark ZE had a little info on x-flow heads. Its possible to go to 240 cfm at 28 " H20 with these heads, enough for 300 hp plus. To do so, you need to look at welding the long side raduis, and cutting and reworking the 33 mm port to 42mm's.
