v8zed Posted November 6, 2001 Share Posted November 6, 2001 Hey Guys, I am having a problem seting the timing on a 355ci. Cam is 256 dg at .50 .485 lift on intake and .513 on exhaust. 30 thousanths clearance on both . It is a cam from a 69 Z28 with a 302 .Carb is Holly 750 single shooter on a Victor Jr. Compression is approx 10.5 to 1 . Significant lag and sometimes small hicup when punching loud peddle from low rpm. Runs like stink from 3000 to 6800 . Idles at 1000 and no lower. Any ideas will be appreciated . Thanks, Dennis Quote Link to comment Share on other sites More sharing options...
pparaska Posted November 6, 2001 Share Posted November 6, 2001 Those old Chevy hi-po cams are pretty peaky. And I remember hearing from the 69 Z/28 crowd that that cam is VERY peaky and was not alot of fun to drive around town with in that car. I bet it sounds nice though, and really screams up top! Anyway, it sounds like you might be lean on tip in and might need to look at the accelerator pump shot, nozzles, diaphram, etc. You may need more jet than that carb came with as well. The power valve might not be right for that cam also. As for timing, that could be a factor. Try 12 deg BTDC with the Vac advance unhooked. You might want some lighter than stock springs and/or heavier weights in the distributor too. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 7, 2001 Share Posted November 7, 2001 A 50 cc accel pump is a must for getting through the off idle stumbles with a cam of this duration. Don't be afraid to start the car and reset the timing to 20+ degrees and run the hard stab of the pedal test until you eliminate the bog. If 20+ degree initial timing works, you porbably will have to restrict the total centrifugal advance. Hook up a vacuum gauge and verify what kind of numbers your engine produces at various timing settings. Obviously higher numbers are best for off idle response. I run 18 degrees initial on a 234 @ .050 cam and found that only considerable accel pump DURATION could make the transition time to main/power valve jet fuel delivery. The flexibility of the Holley to achieve both volume and duration in accel pump volumes is a strong point in these carbs. Fouled plugs will act the same way, as well as marginal ignition voltage production off idle. You will need a markedly improved ignition to light this motor's fire from the basement on up. Quote Link to comment Share on other sites More sharing options...
v8zed Posted November 10, 2001 Author Share Posted November 10, 2001 Hey Guys, Thanks for the info. I upped the timing to 16 deg and it helped a lot . I will now work with the power valve as I know my vacuum is a little lower than stock even with the 114 lda .Great to have this forum. Yhanks Again, Dennis Quote Link to comment Share on other sites More sharing options...
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