SSC

355cu, shifting @6400rpm needs around 616.32 CFM worth of carb.
I finnaly got to open the bad boy up tonight on a well lit street "eating a ***** of course " Well anyway when I looked back I noticed there was a fair amount of black smoke about where The seconadries popped open "Holley 600cfm vac sec" The primaries are clean but the secondaries are rich. I dont see how this could be possible this engine made well over 400hp on a "real" engine dyno
and I would think the wieand excellerator thats on it now would do a better mixing job than the action+ and still this carb is only 600cfm it should be a bit lean wide open compared to the 750 it was dynoed with.
What do you think?
SSC

Apeiron

The mixture depends on the tuning, not on how big the carb is.

ChillPhatCat

I second that, you shouldn't be seeing a problem because of carb size... 600 seems a little skimpy for 400 Hp... You're probably not losing much power though and saving money on gas at the same time.

fast_broker

iTrader: (1)

Sounds like it's rich (if true black exhaust smoke) and deserves a 30-60 minute visit to a chassis dyno shop to help you diag and fix the problem. If it was running that rich at the engine dyno before, though, they surely would have seen it. Maybe a needle vale is dirty?

I think the carb is big enough, but if you NEED 10-15more hp, get a bigger carb... On the converse, if the carb was sheitty ich and made 400h, I guess it is big enough.

SSC

The carb that the engine was dynoed with was set 4% lean in primaries and secondaries to cope with the altitude. I dont know why the 600 is rich, I was thinking it could probably use a bit more but I guess I'll drop down a few sizes and see what it does.
Thanks!
SSC

82camaro

Running too small of a carb at high rpm will can cause it to go rich. Too much velocity through the small throttle bores will be restricted, causing a vacuum. Which then sucks more fuel in. The cfm calculator is just an estimate.


------------------
350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

F-BIRD'88

Your exhaust system has probabily got carbon
in it from cruising around/idling.
Then when you tromp on it, your blowing that stuff out. 600 vac sec holleys are usually too lean in the secondaries out of the box.
Try 66 primary, 76 sec or a #21 metering plate.