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Post by mike53 on Aug 21, 2018 10:08:00 GMT
Possibly getting a bit premature here as the 400N isn't even running satisfactorily yet, but has anyone had any success squeezing a few more hp out of their SD? I'm not talking about anything crazy, but the engine has a reputation for being bombproof so seems a good candidate for some tweaking... Perhaps push the compression a little, flow the head, possibly even a cam? Has anyone ever come across such things as high comp pistons or hot cams for these engines? I recall seeing an SD based race bike on this forum somewhere, wonder what had been done to it engine-wise... Purely hypothetical questions, but there is a spare engine sitting at home which could become a bit of a project  |
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Post by grahamb on Aug 21, 2018 11:47:19 GMT
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Post by buster on Aug 21, 2018 12:23:10 GMT
Possibly getting a bit premature here as the 400N isn't even running satisfactorily yet, but has anyone had any success squeezing a few more hp out of their SD? I'm not talking about anything crazy, but the engine has a reputation for being bombproof so seems a good candidate for some tweaking... Perhaps push the compression a little, flow the head, possibly even a cam? Has anyone ever come across such things as high comp pistons or hot cams for these engines? I recall seeing an SD based race bike on this forum somewhere, wonder what had been done to it engine-wise... Purely hypothetical questions, but there is a spare engine sitting at home which could become a bit of a project personally I’d forget high compression (pump fuel just isnt upto it, never really has been) porting and flowing the head is a good thing to do to any petrol engine (its just not practical in mass production) but its a skilled job best left to an expert (6 ports shouldnt break the bank) you could also ask an engine tuner to optimise the squish that generally sharpens the throttle response a bit. also remember thats its pointless spending money on these jobs then sticking a £150 aftermarket pipe on it, to get the best out of your porting and squish it needs a proper exhaust, most likely have to be custom made it needs to have a smooth consitent flow (no narrowing of the pipe on the bends!) and if the expense of that little lot hasnt put you off then I wish you good luck |
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Post by mike53 on Aug 21, 2018 14:18:20 GMT
I'm neither really for nor against the idea, just wondered if it had been done before and to what avail really! I spend quite a lot of time working on TVRs so i'm reasonably familiar with (moderately) highly tuned engines and their various pitfalls!
Re. compression, completely agree buster, only just checked the specs and see that the SD is already at over 9:1, which is probably already somewhere near the limit for pump fuel. I know of a petrol engined land rover running a 9:1 head which pinks pretty severely unless run on ultimate/nitro/premium fuel of your choice.
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Post by buster on Aug 22, 2018 0:18:10 GMT
I'm neither really for nor against the idea, just wondered if it had been done before and to what avail really! I spend quite a lot of time working on TVRs so i'm reasonably familiar with (moderately) highly tuned engines and their various pitfalls! Re. compression, completely agree buster, only just checked the specs and see that the SD is already at over 9:1, which is probably already somewhere near the limit for pump fuel. I know of a petrol engined land rover running a 9:1 head which pinks pretty severely unless run on ultimate/nitro/premium fuel of your choice. yep, used to be able to lay my hands on toluene (firm I worked for nothing sinister) but sadly not anymore |
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