08-03-2025, 10:03 PM
Thanks everyone for the helpful input.
Low 20s horse power sounds exactly the kind of thing that I think I'm looking for Alan, so that's good to know. And yes I'm well aware I will sacrifice reliability to get there. I've a collection of broken engine parts in the shed to remind me of the past 15 years of modified engines!
I had presumed that the double valve springs would be a 'common sense' mod, having read about the single valve springs not being happy above 4,000rpm? but I had not considered that being side valve it would put load on the crank case. So thank you, and I will take that advice to stick to the standard single spring set-up.
In terms of making sure the engine hangs together, are the oil system modifications (mentioned in guides like this one from the 750mc https://www.750mc.co.uk/ugc-1/1/52/0/the..._garre.pdf) of boring the oil pump bigger and modifying the cam bushes to reduce oil loss worth while in an engine of this level of tuning? Or would that be overkill?
Makes sense about balancing, Howard. The flywheel and clutch assembly is a heavy old thing, I'm sure there would be a gain to taking some weight out of it... it's a slippery slope isn't it! I tend to try and find time in the evenings when I'd otherwise just be sat on the sofa. I try to get out to the shed 2/3 times a week after the kids are asleep and all the chores are finished!
I think I am leaning towards 'doing it properly', having the bores taken out to +40 and fitting some new slipper pistons. As someone mentioned on another forum, if I were to just chuck it back together as it is and it turns out I love driving the car then having to pull the engine in a few months time to do it right when it keeps oiling plugs would be very frustrating, and if I didn't bond with the car then selling it with a properly rebuilt engine will be easier. My wallet won't enjoy this plan though!
Low 20s horse power sounds exactly the kind of thing that I think I'm looking for Alan, so that's good to know. And yes I'm well aware I will sacrifice reliability to get there. I've a collection of broken engine parts in the shed to remind me of the past 15 years of modified engines!
I had presumed that the double valve springs would be a 'common sense' mod, having read about the single valve springs not being happy above 4,000rpm? but I had not considered that being side valve it would put load on the crank case. So thank you, and I will take that advice to stick to the standard single spring set-up.
In terms of making sure the engine hangs together, are the oil system modifications (mentioned in guides like this one from the 750mc https://www.750mc.co.uk/ugc-1/1/52/0/the..._garre.pdf) of boring the oil pump bigger and modifying the cam bushes to reduce oil loss worth while in an engine of this level of tuning? Or would that be overkill?
Makes sense about balancing, Howard. The flywheel and clutch assembly is a heavy old thing, I'm sure there would be a gain to taking some weight out of it... it's a slippery slope isn't it! I tend to try and find time in the evenings when I'd otherwise just be sat on the sofa. I try to get out to the shed 2/3 times a week after the kids are asleep and all the chores are finished!
I think I am leaning towards 'doing it properly', having the bores taken out to +40 and fitting some new slipper pistons. As someone mentioned on another forum, if I were to just chuck it back together as it is and it turns out I love driving the car then having to pull the engine in a few months time to do it right when it keeps oiling plugs would be very frustrating, and if I didn't bond with the car then selling it with a properly rebuilt engine will be easier. My wallet won't enjoy this plan though!