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MuscleCarpenter 12-29-2012 03:09 PM

Carb issues w/BB Chevy w/BDS blower
Hi. hope someone is willing to help. I'm having trouble with the idle on my ride. It's a '69 El Camino with a 468 and it has a BDS 8-series blower with two Holly DP's.

I live in Ft. Lauderdale and am trying to get the car ready to cruise again. It's too hot to ride in the summer down here without A/C, so the car sits for long periods (I frequently start and run around the block, but probably not often enough).

I've read and heard that the ethanol in gas has really screwed with a lot of "old school" rides so i switched to an alcohol free fuel called "Rec-90". I was using 93 octane, with Stabil while car was stored. I also learned that ethanol attracts water in the tanks of stored vehicles. I mix VP C13 race fuel to fatten up the mix about 1 to 4.

Before I made the switch to the "Rec-90" the idle was a little rough/uneven and on the low side (not too bad, still very drivable). I often had this problem after getting the car out of storage, but it always cleared up with some driving and fresh fuel. Normally the curb idle is about 900-950 and about 800 when in gear. right where it should be.

After the switch and a few spins around the neighborhood (with a few mild hole-shots to clear out the gunk), the car stalled out when I came to a stop to turn around. It easily restarted, backfired, and started again no problem. Shortly after, the idle speed climbed to around 1500 and won't come back down. Other than the fast idle the car seems to run great.

Does anyone know what the issue might be? I'm a carpenter by trade and my mechanic is out of town for the holidays. I would like to be able to drive it while I have some time off myself. I would appreciate some advice/help, if someone is willing to offer it.

Thanks in Advance,

NOlowrider 12-29-2012 04:06 PM

Are you able to get the idle down by adjusting the curb idle screw? I always back the idle screw completely out on the rear carb and adjust the curb idle by the front carb, assuming you have a 1-1 linkage. Are you able to check the float level while it is running? Also check your fuel pressure. I run 5.5 psi

MuscleCarpenter 12-29-2012 05:02 PM

I haven't tried anything yet. was wondering what would/could cause it to fall out of adjustment so quickly. Was perfectly dialed in. Blown power valve perhaps? Didn't want to start messing around until I had an idea where to start

MuscleCarpenter 12-29-2012 05:12 PM

Thanks for getting back to me. I know rec-90 is low octane. The car typically runs fine on 93 alone, I add the race fuel to fatten it up and to be safe to prevent detonation (and smells better too). It's a low comp. motor (8.5-1), very street-able, doesn't make a lot of boost (between 8-10 lbs. at WOT. Never runs hot, only 185 degrees in stop-n-go traffic. Bad, stale gas makes a car run crappy, and I would agree with what you say normally, but the car is running great other than the fast idle. If its too lean would that make it idle fast?

MuscleCarpenter 12-29-2012 05:16 PM

Ethanol is bad for fuel lines, gaskets, etc. in motors not designed for that right? I know its done a job on my old mower and small gas powered generator (fuel leaks)

NOlowrider 12-30-2012 11:04 AM

I would check the easy stuff first before I dive into the carbs for a rebuild. Take a can of carb cleaner and spray around the base of the carbs, around the carb fittings. It the idle changes then you found a leak. Make sure the linkage is not binding. Make sure the floats are not sticking alowing the fuel to bypass the needle and seat. Holley's don't need alot of fuel pressure (5.5 psi should do it). It is possible that just the temp change alone it the culprit. The air density changes from summer to winter and minor adjustments are required. Dry rotted and cracked vacuum line?

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