Guest sball Posted July 9, 2002 Share Posted July 9, 2002 Just installed a motor I built, L26 bored to 85mm with flat top pistons and 1,3/4" SU carbs with all the right set up and every component new or referbished it should run well ! It does except under load the pinging is quite bad, so I need to replace fuel with 98octane fuel from the current 89 octane in the tank. The problem that has got me baffled is after about 2 km of driving it dies like there is no spark or running on 1 cylinder, as the revs drop it gains it's composure and goes again it idles well and is ok if left idling for a while then as I build speed it dies. Ive checked and replaced the condensor on the ditributor and put new wires through the low tension circuit, but it's exactly the same, in fact it does it in exactly the same spot on the road every time no matter what I play with under the bonnet. Could it be the Low Octane fuel ? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 9, 2002 Share Posted July 9, 2002 sounds like you have some kind of a problem , I bet my old tech. teacher could help you beter then nayone on this bored. If it's ok with you'll I'll give youhis e-mail address and you can forward all your questions to him. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted July 9, 2002 Share Posted July 9, 2002 Don't overlook a fuel problem. A weak fuel pump or sticky/restricted/poorly adjusted float level could be the culprit. Especially if the engine runs properly once the load is off it. Also which SU's are you running? In the states the 260's switched to a redesigned SU that had flat tops. These smog carbs were notorious for vapor locking when they got hot. Quote Link to comment Share on other sites More sharing options...
johnc Posted July 9, 2002 Share Posted July 9, 2002 Sounds like a fuel problem. As Jim said check for vapor lock, float level, fuel filters, fuel pump, etc. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 9, 2002 Share Posted July 9, 2002 I would make sure my timing was set right first. Then check your fuel supply and also the distributor cap and rotor. A cracked cap can cause problems as well. Also, make sure your harmonic balancer bolt it tight. Seems like I recall I had a misfire problem related to the balancer being loose. 1 3/4 SU's tend to denote the good kind, and I hope that is the case. Make sure they are adjusted properly, and that the pistons go up evenely when you rev the engine. Quote Link to comment Share on other sites More sharing options...
Guest sball Posted July 10, 2002 Share Posted July 10, 2002 Thanks for the feed back, it turns out the 240z SU carbs had another SU's floats fitted and when I pulled them down for plating, and reassembled I put the two different length main jets in the wrong float cover, so one was rich and one was dry. Appart from going off the manual for the float level adjustment is there a fool proof way of getting the exactly right float level, because if the float chamber is not originaly off these carbs the fuel level is just a guess that works, and not neccessarily the best setting. Quote Link to comment Share on other sites More sharing options...
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