Davehb Posted December 30, 2020 Report Share Posted December 30, 2020 Hi All, i have a monsoon GX4 fitted to a fast fuel 1000 TBI on a 10lt big block chev. Fitted with a MSD 6AL. up to 2000rpm it tunes well, ie, if the a/f is 14:1 and i move the fuel table from 20 to 30 the A/F moves to 13:1. the problem i am having is at 2000rpm there appears an invisible line that the engine wont rev past. some times the A/F goes to 16:1 so i add 30 points of fuel and it will show 13:1 and rev further then i let it back to idle, bring the revs up again to 2000 and it will show 11:1. once the engine gets passed 3000rpm all appears well. the A/f is measured 150mm from the collector with the dyno O2 screwed directly into the pipe. all fuel enrichments are turned off the ign is not controlled by the GX4 and a timing light verifies the the advance and no misses on the balancer. i have tried to find out the cam specs but to no avail,i am suspicious of a vacuum leak but dont know what manifold pressure this engine should have and it is a major job to pull the manifold in frame to check the gaskets. when the engine had a 950cfm carbie it would come off the cam at around 2000 rpm and smooth out nicely. any ideas would be apreciated. Dave Quote Link to comment Share on other sites More sharing options...
koracing Posted January 7, 2021 Report Share Posted January 7, 2021 Please attach your tune file and a datalog showing what's happening. Quote Link to comment Share on other sites More sharing options...
Davehb Posted January 10, 2021 Author Report Share Posted January 10, 2021 looks like it is all good now. there was a miss on number 8, right in the roughest part of the cam. the leads were 3000km old and the plugs 1 tank of fuel, i replaced them and the miss has gone. Dave Quote Link to comment Share on other sites More sharing options...
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