Horizontal Posted April 8, 2005 Share Posted April 8, 2005 Just got new "baby" a Silverstone. 146 bhp, 1760cc, Kent 244 cam, high lift rockers, that's about it over and above "supersprint". i.e still got std bottom end and cast pistons 😳. Question is what is a safe max rpm and sustained rpm. The Kent cam site gives power band of 3,000 - 8,000 rpm. I know forged pistons is recommended. But CC say cast are OK to 150 bhp. Anyway I've no money left!!! thanks Link to comment Share on other sites More sharing options...
mikes Posted April 8, 2005 Share Posted April 8, 2005 I have what is probably a similar performance engine, same cam, but when the engine was rebuilt it included polished, balanced, tuftrided crank competition bearings etc, and forged pistons. Anyway, the power drops off after something like 6200 rpm (haven't go the latest rolling road results with me at the moment) so there is no real advantage going much over that. I think the rev limiter is set to 7200 and the shift light to 6500. With the extra weight of the cast pistons thundering up and down I would err on the lower side - unless you want an excuse to rebuild it again next year!! Mike Link to comment Share on other sites More sharing options...
Joe 90 Posted April 8, 2005 Share Posted April 8, 2005 I would suggest 6500 max if you are feeling conservative, and up to 6800 if you are feeling brave. SEP field working, not spotted in 103,300 miles. Some photos on webshots, updated 25 Jan Link to comment Share on other sites More sharing options...
rgrigsby Posted April 8, 2005 Share Posted April 8, 2005 Hmm I'd agree with Oliver you wouldn't want to go much past 6500 with standard pistons. I had forged on a 155ish spec 244 cam Xflow and the limiter was set at 7200, peak power was around 6500 I think. Rob G www.SpeedySeven.com Edited by - rgrigsby on 8 Apr 2005 14:32:15 Link to comment Share on other sites More sharing options...
Tyrone Posted April 8, 2005 Share Posted April 8, 2005 I Have a similar spec engine albeit with a Piper cam. First blat out in 7 company, I bent two exhaust valves over-revving the engine to somewhere in excess of 7500!! Fortunately, I didn't damage the pistons. I bought a rev limiter immediately after repair, it's set at 6000, shift light comes on at 5500 for every day use. I dial it up to 6500 for trackdays and special blats. Link to comment Share on other sites More sharing options...
Coose Posted April 8, 2005 Share Posted April 8, 2005 Would that be for when chasing Pertolheed and oioi, Tyrone? We will mend it We will fix it... Link to comment Share on other sites More sharing options...
Horizontal Posted April 8, 2005 Author Share Posted April 8, 2005 Thanks for the advice, seems like 6500 max for me then, it does sound good though at anything over 3000, so lots of scope for playing 😬 😬 Really couldn't cope with additional expense this month at least!! Hoping to go to the Lincs meeting later in the month to collect more info. Cheers again. Link to comment Share on other sites More sharing options...
Richard K Posted April 8, 2005 Share Posted April 8, 2005 Horizontal - Is this the Silerstone that was recently for sale at CC South. If it is i'm v.envious. Such a good looking car !! When I saw it the engine was described as a 'Red Top' does this mean anything ! or is it just CC's way of identifying it has a few more tweeks on the inside. If you do consider going on the track you might want to think about a GRP nose as the Ali one will be very costly to replace / repair. I know you will enjoy the car Have fun Richard (Old 1700 x/f with Vulcan 145bhp) and flares 😬 Link to comment Share on other sites More sharing options...
Horizontal Posted April 9, 2005 Author Share Posted April 9, 2005 Richard K, Yes, the same one, I fell for it when they had it for sale last year and couldn't resist it this time around. The engine is as described above plus twin 45's instead of 40's. It spits a lot until it clears it's throat, what a lovely noise 😬 😬 Still pinching myself every morning, to check I'm not dreaming. Is that sad? Or just plain excitement? Link to comment Share on other sites More sharing options...
Matthew Willoughby Posted April 9, 2005 Share Posted April 9, 2005 Yes it is sad...............in a good way I miss that feeling since selling mine ☹️ Link to comment Share on other sites More sharing options...
Bewls Posted April 9, 2005 Share Posted April 9, 2005 I'm getting a 155bhp xflow with forged internals, I have been told that 7000rpm is fine, but it has no rev limiter. Should I fit one and how easy is it and how expensive? Thanks Joe Link to comment Share on other sites More sharing options...
Leadership Team Midas Posted April 9, 2005 Leadership Team Share Posted April 9, 2005 I have a similar spec engine to you, built by SPR, and with standard pistons . I asked a similar question to Roger King and he recommended that I stick to a max of 6000 rpms max if I wanted the engine to last very long - anything over 6000 and your chances of failure increase dramatically (apparently) Link to comment Share on other sites More sharing options...
xflow7 Posted April 9, 2005 Share Posted April 9, 2005 There seems to be a somewhat higher spec iron crank available now that is supposedly stronger than the OE 711M crank (though not as good as forged), but at far less than the cost of a forged crank. I don't know much about it (like how many more revs it would be safe to), but found out about it here. Dave Link to comment Share on other sites More sharing options...
Irrelevant Posted April 10, 2005 Share Posted April 10, 2005 joseph: I'd fit a limiter if I were you. I don't think going slightly over 7000 will be a problem but there are occasions where a limiter can save an engine, for example, if you don't engage a gear properly whilst accelerating hard. In this situation you can have full throttle with no gear connected so, especially if your rotating bits are seriously lightened, you can get MASSIVE revs in a second or so. A limiter will reduce the risk in this situation. Cost is from about £60 new I think for a simple Omex one and fitting is just a few wires - i.e. coil +, coil -, and an earth IIRC. xflow7: My Crossflow had a standard crank & rods (although it was all lightened, balanced, stress relieved, etc. etc. - basically everything the FF crank doesn't need) and it was rated at 7500rpm by the builder, 7200rpm if I wanted longer between strip downs. Dunno if it would be cheaper modifying a std crank (like mine was) or buying a FF one for coping with highish revs. That link you reference quotes ally heads at $650 - that's not a lot of £££s for a lot less weight - high up weight too, and miles cheaper to get modified than iron. Getting there.... Link to comment Share on other sites More sharing options...
xflow7 Posted April 10, 2005 Share Posted April 10, 2005 Yeah, I've seen the ali heads listed on there. Very tempting to add one to the upgraditis treatment regime. 😬 And with our dollar in the toilet, probably doubly attractive to you folks over there. Dave Bean has all kinds of xflow and Lotus goodies available, and seem to be a pretty helpful bunch from the few times I've been in touch with them. Link to comment Share on other sites More sharing options...
Nigel Riches Posted April 12, 2005 Share Posted April 12, 2005 That $650 cylinder head price was for September 2002!!!!!, didn't find a more up to date price. 1982. 5 speed, clamshells. B.R.G / Ali. The True Colours. Link to comment Share on other sites More sharing options...
Bewls Posted June 4, 2005 Share Posted June 4, 2005 Ok, BTTT, my 7 definatly has forged pistons but i'm not sure about the crank and rods. The previous owner said 7000rpm was perfectly ok, I don't think I have gone over 6500rpm, definatly not over 7000rpm, is 7000rpm safe presuming the worst case scenario of standard bottom end? The spec is: 155bhp 1700 xflow, dry sumped, kent 244 cam, twin 40DCOEs Thanks, Joe. Link to comment Share on other sites More sharing options...
RossCarmichael Posted June 5, 2005 Share Posted June 5, 2005 No one has suggested an answer for the second part of the question - max sustained rpm. I have a 1700 xflow 4-spd and when leaving Dunsfold a couple of weeks ago was completely unable to keep up with Fast Lady and another Sevener as at about 85mph I'm doing about 5000rpm. If my ears and arms can cope with it, is it OK to stay at that rpm, or should I be looking to keep it more in the 4000 range? Cheers, Ross Link to comment Share on other sites More sharing options...
Burt1969 Posted June 5, 2005 Share Posted June 5, 2005 My 1600 goes higher mph than that down the motorway, can't say what RPM is though as my eyes are normally watering 😬 Our Kitty! Link to comment Share on other sites More sharing options...
rgrigsby Posted June 5, 2005 Share Posted June 5, 2005 Hmm that's a trickier one to answer, with my xflow on a few european trips I did spend long periods of time (ie 15-20mins) above 5-6K on the Italian motorways without any problems but that was with forged pistons. I think as long as the oil temp/pressure are ok and the water temp is alright there is no reason you shouldn't do this. Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
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