Small Block & Big Block Chevy Specific - 540 blower motor tuning help
05-10-2007, 09:06 AM
i am working on tuning a 540 blower motor for a guy. it has a 871 blower with 2 950 hp blower carbs. it has dart alum heads a fairly small roller hyd cam 242 254 at .050 and 580 lift its a nitrous series cam from comp but no nitrous on car . the local engine builder in our town set it up. it is in a tubbed 70 chevelle. the problem is it is runnig very rich. i would think one 950 would be plenty for that combo and that was not a good choice of cam for that engine. any help on tuning this engine would be helpful. i have never worked on a blower motor. my first guess is to put bigger air bleed in the top of carbs. thank you
05-10-2007, 03:28 PM
what kind of carbs are they?
05-10-2007, 04:05 PM
05-10-2007, 06:04 PM
Try replacing the power valves in them both, also make sure the floas are not stuck. I had a holly 625 on my Impala and now have a holly 750 and the floats are bad for hanging up also if the engine has backfired through the carbs it could have blown the power valves.
05-11-2007, 06:25 PM
When is it running rich? At idle? all the time? Can you turn the idle screws in and make the engine stall? If you can do that chances are the power valves arent blown. have you verified its running rich with a wideband or gas analyzer? Depending on when and where its rich will depend on what needs to be done to lean it out. Air bleeds are a very small adjustment. If its not close at all, changing air bleeds wont do a damn thing. They are only for last minute adjustments for very small changes.
05-11-2007, 06:29 PM
If you really need help, shoot me a PM or email. We do blower motors all the time. Got a shop full of big block chevys. The motor in my avatar is a 502/8-71 with dart heads, roller, Accel DFI gen 6. Refined, improved and tuned by us.
05-11-2007, 06:36 PM
Hi Super Pimp.
I had this exact combination on top of a 468 big block. The picture in my Avatar was on the way to a 8.29 pass with this combo while spraying. The 950 HP blower carbs are great for this combination. You didn't say that you were having problems with anything other than it running rich, so why don't you start down jetting it until it cleans up. If it's doing it at idle, check your power valves to see if they are blown. The last thing you would need to touch would be the air bleeds. You may want to confirm they are the right ones though.
05-13-2007, 08:18 AM
ok thanks for the info
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