quick question on rpm limits
Discussion
my engine is a 1275 metro engine with an MG head, Maniflow LCB, Kent 286 camshaft and a 1.75" SU with the usual K&N & needle upgrade..question is, while being followed yesterday by a 350z I held the revs a little longer than I usually do, to about 5900 and it just seemed to pull a lot harder than if I changed at my normal 5500. I drive ten tenths everywhere in my mini and the original dials told me the red line was at 5600 so does having this cam mean that I can rev higher? and if so, why? the engine has not been balanced/lightened/prepped in any way..puzzled 
Yes
Coz the engine "breathes" better.
For relaibility keep it to 6000...if u don't care then 6500-7000...just don't expect it to last long with similar performance....or at all !!!
Original red lines go out the window once into modified engines.
Balancing just helps smoothness and reliability.
Coz the engine "breathes" better.
For relaibility keep it to 6000...if u don't care then 6500-7000...just don't expect it to last long with similar performance....or at all !!!
Original red lines go out the window once into modified engines.
Balancing just helps smoothness and reliability.
Chuggaboom said:
Yes
Coz the engine "breathes" better.
For relaibility keep it to 6000...if u don't care then 6500-7000...just don't expect it to last long with similar performance....or at all !!!
Original red lines go out the window once into modified engines.
Balancing just helps smoothness and reliability.
edit: I understand the concept of valve/cam timing re breathing & top end power but it's this issue about over revving that has me tied in knots
so if an engine breathes better the components can take more strain? I don't understand!!! shirley the components have a recommended stress tolerance level that is finite and red lines increased only if components are upgraded?
>> Edited by minimax on Wednesday 8th December 11:18
Andrew Noakes said:
I know it has an MG head, but an MG head isn't going to have whizzo valve springs, just the usual Leyland rubbish. Unless it's been modded.
standard valve springs in mine i'm afraid..I think i'll be keeping it to a max of 6000 just in case the fiery gods of hell rain pestilence upon my bank balance and cause me to lobby cooperman to build me a new engine!
minimax said:
I know it has an MG head, but an MG head isn't going to have whizzo valve springs, just the usual Leyland rubbish. Unless it's been modded.
standard valve springs in mine i'm afraid..I think i'll be keeping it to a max of 6000 just in case the fiery gods of hell rain pestilence upon my bank balance and cause me to lobby cooperman to build me a new engine!
I've ran mine (standard MG Metro with LCB and K&N) up to 6250 rpm, for 20 minutes (in 4th gear!) with no problems at all. I only stopped there as that was the point at which drag dictated not more acceleration was to be had
minimax, yes that cam will allow ur engine to rev higher through more duration nd lift, it sounds like ur mota is overcammed if its a street car, yes it will rev but might not last , it might hav been better with mg cam in,good enough for a se7en racer ! as to you drivin at 10 10ths u forgot t say sideways aswell, i remember u frm croft. IMHO keep it under 6 unless u like oily hands.
haynes said:
My 286 engine with a half decent modded head would go to 7000rpm quite happily, now completely rebuilt with a race head and 296 cam, 8000 is about the limit. You can tell when an engine is happy to rev or not.
you can always tell when an engine is not happy revving - unfortunatley normally just after its blown up!!
just out of interest what is the rest of the spec of your engine, it must be fairly good if its taking 8000 rpm fairly often??
guru_1071 said:
you can always tell when an engine is not happy revving - unfortunatley normally just after its blown up!!
just out of interest what is the rest of the spec of your engine, it must be fairly good if its taking 8000 rpm fairly often??
My engine was built by Neil Slark down in Amesbury, Wilts. It was built as a hillclimber, wedged crank, ultralight flywheel, sccr box and drops, 3.7fd, race valves and springs, massive ports. I'm using twin SUs and drive it on the road, although not every day. Previously I used a 286cam with standard box, verto flywheel, 3.1fd and it had some grunt but was never blisteringly quick, 0-60 in 9 seconds. This engine is much more exciting.
ive been planning to bung a mates webber on just to try it out, just havent got round to it. The SUs are heavily modified, cut down spindles, sharp edges taken off the internals and a maniflow steel manifold which made 9hp gain over a cast one, on Neil's rollers. With the 3.7fd it gives just under 120mph at 8000rpm on 10s, which makes you laugh outloud, though the noise is deafening and you think somethings about to explode (hmmm, does this contradict my previous comment).
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