Tall Block Conversions
Posted: Wed Aug 23, 2017 3:27 pm
I have a stripped tall block TC motor sitting in my office and keep thinking I should build it up and put it to use.
Interesting history in that it was built new by Vegantune for Caterham in 1979 (as a dry sumped unit) just before Caterham turned to conventional crossflow (1700) engines for their cars. I bought the engine off the chap who ordered the car from new but sadly it was written off a few years ago. It's a new (at the time) Lotus TC head, ie not the Vegantune belt drive version.
Interestingly it's on std crossflow bores but with pocketed pistons a la lotus but obviously not the 83.5mm lotus bores. I've had the block and pistons measuerd by a good machinist and he declares them to be good so I'm not intending to rebore (but will fit new rings). You can still see some trace of the honing marks, the engine has done just over 50k miles (genuine).
Anyway, everything else being equal if I build the short engine back up and use the same head and cams from my current Plus 2 (the head is nicely ported, the tall block head is completely standard), ie using the 711M bottom end, will the resulting engine be signifcantly better that my current unit?
There's no reason for me to do this other than I am pulling the Lotus engine shortly to fix a load of oil leaks and fit a close ratio 3 rail box. I'm thinking the increased torque might be useful to pull the tall first gear.
Yhe dyno curve for my current engine is attached - already produces good torque but what sort of improvement might I expect with the longer stroke 711M block?
Jon
Interesting history in that it was built new by Vegantune for Caterham in 1979 (as a dry sumped unit) just before Caterham turned to conventional crossflow (1700) engines for their cars. I bought the engine off the chap who ordered the car from new but sadly it was written off a few years ago. It's a new (at the time) Lotus TC head, ie not the Vegantune belt drive version.
Interestingly it's on std crossflow bores but with pocketed pistons a la lotus but obviously not the 83.5mm lotus bores. I've had the block and pistons measuerd by a good machinist and he declares them to be good so I'm not intending to rebore (but will fit new rings). You can still see some trace of the honing marks, the engine has done just over 50k miles (genuine).
Anyway, everything else being equal if I build the short engine back up and use the same head and cams from my current Plus 2 (the head is nicely ported, the tall block head is completely standard), ie using the 711M bottom end, will the resulting engine be signifcantly better that my current unit?
There's no reason for me to do this other than I am pulling the Lotus engine shortly to fix a load of oil leaks and fit a close ratio 3 rail box. I'm thinking the increased torque might be useful to pull the tall first gear.
Yhe dyno curve for my current engine is attached - already produces good torque but what sort of improvement might I expect with the longer stroke 711M block?
Jon