fordy Posted May 17, 2003 Share Posted May 17, 2003 Is that at the wheels, or flywheel Im not being sarcastic, ive got a xflow too and id be interested to know your engine spec - i got mine setup the otherday and they only managed 100BHP at the wheels (about 120 at the fly) - that was with piper 285 cam, 1300GT pistons, vulcan maxiflow 1a head, 45 webers, lucas rally dizzy (no vac advance) - i was expecting more like 115 at the wheels from it. Quote Link to comment Share on other sites More sharing options...
furtive Posted May 17, 2003 Author Share Posted May 17, 2003 I'm guessing it must be 106bhp at the flywheel then as my engine is bog standard (as far as I know) apart from the twin weber 40's. Quote Link to comment Share on other sites More sharing options...
JonnyBoy Posted May 17, 2003 Share Posted May 17, 2003 My car now runs lovely and smoothly, and is pushing out 106bhp Quick.....edit your post to say at least 109 before wrox see's he's actually got more horses than someone! Quote Link to comment Share on other sites More sharing options...
neilwillis Posted May 17, 2003 Share Posted May 17, 2003 Moi, sarcastic? No, honestly, whatever the output, your car is tuned. To be honest, the numbers don't really mean a lot. If it runs sweetly, is tractable, and makes you smile, what else could you ask for? Quote Link to comment Share on other sites More sharing options...
samcooke Posted May 17, 2003 Share Posted May 17, 2003 Doesn't sound right, fordy. What rpm did they bottle it at? I had to tell my RR to take it beyond 6k as they wouldn't do it without my say so. Power was still climbing at 6800. FWIW mines a 711m 1600 block with 1300 pistons, piper 285, steel rocker gear with double springs, lumenition / magnecor, roger king built but only twin 40DCOEs. Managed 110bhp. Quote Link to comment Share on other sites More sharing options...
Blatman Posted May 17, 2003 Share Posted May 17, 2003 I wouldn't rev them to more than about 6500 with the 1300GT pistons. The caution shown by Sams rolling road fella was well advised, IMO. The 1300GT pitons are a well known weak spot in tuned crossflows....... Quote Link to comment Share on other sites More sharing options...
fordy Posted May 19, 2003 Share Posted May 19, 2003 Peak power seemed to be at around 5700 rpm, graph shows they took it to about 6100 rpm, but i wasnt climbing at that point. the pistons i have arnt acutal 1300 GT pistons - just 1300 GT spec, but i believe they are Hepolites - they have an AE number stamped on them and the reciept shows them as being around £100 for the four Quote Link to comment Share on other sites More sharing options...
Blatman Posted May 19, 2003 Share Posted May 19, 2003 Sounds like they're cast pistons, as opposed to forged. Forged pistons are *much* better........ I bought forged pistons in 1996 for my Atmo Cossie, and they were £150 each...... Quote Link to comment Share on other sites More sharing options...
fordy Posted May 19, 2003 Share Posted May 19, 2003 Are cast pistons weak??? - are they still better than 1300GT pistons, or are they exactly the same??? cheers Chris Quote Link to comment Share on other sites More sharing options...
studbuckle Posted May 19, 2003 Share Posted May 19, 2003 Been following this thread... 120BHP at wheels at 6000 rpm. On the road it runs up to 6500 rpm now. engine spec slightly unknown but what looks like a Vulcan Stage 2 head. Piper 285 Cam and of course Twin 40's When I had the head off though the pistons didn't look like standard and have a lovely black finish to them that doesn't look like carbon deposit. Any ideas what spec they are? Quote Link to comment Share on other sites More sharing options...
Blatman Posted May 19, 2003 Share Posted May 19, 2003 IIRC, they're exactly the same. Casting is a cheap way of producing pistons, so manufacturers use that method to keep costs down...... The "1300GT piston in a 1.7 x-flow" issue, is a well known weakness, especially when engines are routinely revved to above 6000rpm. I have heard of pistons breaking up at as little as 15000 miles. I'm not wanting to p*** on anyones chips, but it is something you should be aware of......... Have a read of this, especially the last posting from ashaughnessy, and in particularly, read this, especially the 8th post from Roger King. What RK doesn't know about crossflows isn't worth knowing.....seriously..... Quote Link to comment Share on other sites More sharing options...
Blatman Posted May 19, 2003 Share Posted May 19, 2003 The black finish will clean off with a rag and some brake cleaner........... I don't think there is any way to tell piston spec from a photo......... Quote Link to comment Share on other sites More sharing options...
studbuckle Posted May 19, 2003 Share Posted May 19, 2003 The black finish will clean off with a rag and some brake cleaner........... I don't think there is any way to tell piston spec from a photo......... coat on...... Quote Link to comment Share on other sites More sharing options...
fordy Posted May 20, 2003 Share Posted May 20, 2003 Studbuckle, seems you have the same spec as me, exept ive got twin 45's, not 40's, but im only getting 100 at the wheels - the 45's have got 36mm chokes - could this be loosing me this 20 bhp?? Quote Link to comment Share on other sites More sharing options...
studbuckle Posted May 20, 2003 Share Posted May 20, 2003 I suppose it's possible, To be honest I dont know how much difference that'll make. My stock engine on 40's was producing 90+ so either the RR figure is down or something is amiss Quote Link to comment Share on other sites More sharing options...
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