michael_cini
Well-known member
i am trying to figure out which cam to get with my rebuilt 250-2v head. just curious, what is the lobe center on the stock 200/250 engine?
lobe center
- Thread starter michael_cini
- Start date
michael_cini
Well-known member
thanks for that guys. i am surprised, i thought the lobe center would be like 110-112.
Having done some more research, the common late sixtees cam specs were normally 21,51/57,15, with intake duration 252, 36 degrees of overlap (ie average of 51-21, and 57-15) and thus a lobe centre of
((21+51+180)/2)-21 = 105
((57+15+180)/2)-15 = 111
Lobe centre is therefore an average of 105 and 111, or 108 degrees LCA.
This was a common cam since the first Stirrat designed Windsor 221 V8 in October 1961.
The later engines have gone to wider lobe centres for emissions, and have tended to use high intensity roller rockers ratios of over 1.73, roller cams with fast ramps, and concnetrated on allowing the engine to rev more. This allows low end torque to flourish.
The reason was that all early Fords had very tall gearing (3 speed on the tree gearboxes were common), and often automatic. The later 200's and 250's had a large increase in cam duartion since the 1960-1965 era, and with an automatic, it was very easy to get a 'hole' in the torque delivery just off idle, especially since the stock stall speed was often about 1600 rpm, or 2.8:1 stall ratio. When the lobe centre is widened to 112, 114, or 116, that hole disapears. Typically, 106 to 108 lobe centres were very common for early 60's Fords, but the high performance versions often went to a wider lobe centre to avoid poor compatbility with auto transmissions. So 113 degree centres were found on quite a few engines which could have benefited form a narrower lobe centre. Ford did this on the 1600 and 2000 cc performance versions of the Pinto engines on purpose. So cars like Cortina GT's got tube headers, high lift cams, high compression, huge ports, but very mild cams. Same with the Clevelands, a very undercammed 256 degree engine in the stock versions, but there were a vast array of ballistic hydralic and solid lifter cams with wide centres with lifts above 490 thou and durations from 280 to 310 degrees. Ford made these work because in spit of huge ports becasue they used very wide 110 degree lobe centres to tame raggard, savage low end characteristics. Hi stall FMX's with 2350 rpm converters were common options, and manual cars had stump puller dif ratios and very heavily dampened vacum secondary carbs which allowed just enough driveability on the street, but full throttle upchanges at 6200 rpm.
In comparison, our Ford I6's have very short rod ratios, small intake ports, and don't need wide lobe centres. All 144-250 I6's are very latent engines, missing the spark you'd find in other engines because durability forced Ford to avoid any long duration, wide lobe centre cams. Cams after the ill fated Cleveland dead end of the 70's have been high intensity, low duration, high lift ratios (last 200 had 1.6:1 rockers apparently), and dual pattern to control gas bleed off for emissions.
The future for us is more towards the wide lobe centres, because were now trying to focus on power and good economy with significantly more duration than Ford intended. Better heads like the post 1978 items, and especially the Classic Inlines and 2V heads require wide lobe cams to make them streetable, especially if the rockers are changed to ratios greater than 1.5:1
((21+51+180)/2)-21 = 105
((57+15+180)/2)-15 = 111
Lobe centre is therefore an average of 105 and 111, or 108 degrees LCA.
This was a common cam since the first Stirrat designed Windsor 221 V8 in October 1961.
The later engines have gone to wider lobe centres for emissions, and have tended to use high intensity roller rockers ratios of over 1.73, roller cams with fast ramps, and concnetrated on allowing the engine to rev more. This allows low end torque to flourish.
The reason was that all early Fords had very tall gearing (3 speed on the tree gearboxes were common), and often automatic. The later 200's and 250's had a large increase in cam duartion since the 1960-1965 era, and with an automatic, it was very easy to get a 'hole' in the torque delivery just off idle, especially since the stock stall speed was often about 1600 rpm, or 2.8:1 stall ratio. When the lobe centre is widened to 112, 114, or 116, that hole disapears. Typically, 106 to 108 lobe centres were very common for early 60's Fords, but the high performance versions often went to a wider lobe centre to avoid poor compatbility with auto transmissions. So 113 degree centres were found on quite a few engines which could have benefited form a narrower lobe centre. Ford did this on the 1600 and 2000 cc performance versions of the Pinto engines on purpose. So cars like Cortina GT's got tube headers, high lift cams, high compression, huge ports, but very mild cams. Same with the Clevelands, a very undercammed 256 degree engine in the stock versions, but there were a vast array of ballistic hydralic and solid lifter cams with wide centres with lifts above 490 thou and durations from 280 to 310 degrees. Ford made these work because in spit of huge ports becasue they used very wide 110 degree lobe centres to tame raggard, savage low end characteristics. Hi stall FMX's with 2350 rpm converters were common options, and manual cars had stump puller dif ratios and very heavily dampened vacum secondary carbs which allowed just enough driveability on the street, but full throttle upchanges at 6200 rpm.
In comparison, our Ford I6's have very short rod ratios, small intake ports, and don't need wide lobe centres. All 144-250 I6's are very latent engines, missing the spark you'd find in other engines because durability forced Ford to avoid any long duration, wide lobe centre cams. Cams after the ill fated Cleveland dead end of the 70's have been high intensity, low duration, high lift ratios (last 200 had 1.6:1 rockers apparently), and dual pattern to control gas bleed off for emissions.
The future for us is more towards the wide lobe centres, because were now trying to focus on power and good economy with significantly more duration than Ford intended. Better heads like the post 1978 items, and especially the Classic Inlines and 2V heads require wide lobe cams to make them streetable, especially if the rockers are changed to ratios greater than 1.5:1
