502 running lean
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502 running lean
I have a 502zz,the motor runs lean on number 4 and 6 cylinders.The carb is a holley 850 vac sec.It is jetted with #90 pri & #94sec.All cylinders but #4&6 are running rich.I did not find any vacuum leak.Can anyone steer me in the right direction. Thank You Lorne.
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Re: 502 running lean
Originally Posted by RumRunner
Has this always run this way, or is this something that has just started?
6 cylinders were scuffed from running lean.
#5
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Re: 502 running lean
I can't help but pin it on the intake gasket area.
If 1,4 were lean I'd say your primaries (on the right side) are too lean and it was showing up WOT. It 6,7 were lean, I'd say your secondaries (on the right side) are too lean and it was showing up WOT. But 4,6 too lean? And 1,7 look fine?
I say intake gasket seal. Just cause it doesn't exhibit evidence of a leak up above, doesn't mean it isn't leaking into the lifter valley from below.
If 1,4 were lean I'd say your primaries (on the right side) are too lean and it was showing up WOT. It 6,7 were lean, I'd say your secondaries (on the right side) are too lean and it was showing up WOT. But 4,6 too lean? And 1,7 look fine?
I say intake gasket seal. Just cause it doesn't exhibit evidence of a leak up above, doesn't mean it isn't leaking into the lifter valley from below.
#7
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Re: 502 running lean
I had the same problem with a marine 850 vac. secondary. Tried various jets and cross jetting, spacers of both types and never did get it right. 6 and partially 4 were always lean. In order to get them to show any color I ended up at 92 and 96 but then the other cylinders were fuel washing. Next step was to go with a 800 and Dart single plane. Got better with cross jetting but not perfect.
Final fix was to put a blower on with Nickerson prepped carb. Perfect color all around at all rpm ranges. You might consider calling Nickerson and see what he says.
Good luck but be carefull about fuel washing, when I was runing jets in those size ranges it would water your eyes if following close.
Final fix was to put a blower on with Nickerson prepped carb. Perfect color all around at all rpm ranges. You might consider calling Nickerson and see what he says.
Good luck but be carefull about fuel washing, when I was runing jets in those size ranges it would water your eyes if following close.
#8
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Re: 502 running lean
The 850 may be too large, causing poor distrabution at your cruise speed. Try installing a 4-hole carburetor spacer between the carb and intake. This will increase the air velocity, and may help with your situation.
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Re: 502 running lean
Originally Posted by Panther
Are you running power valves? That sounds like a lot of jet if you are running PV's.
#10
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Re: 502 running lean
Originally Posted by formulaz583
Are you saying that the spacer will richen the motor up?
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