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Re: [GMCnet] EFI vs Carb [message #368543 is a reply to message #326033] Sun, 23 January 2022 18:12 Go to previous messageGo to previous message
Bullitthead is currently offline  Bullitthead   United States
Messages: 1411
Registered: November 2013
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GMC came with Weber Edelbrock carb when I got it...noticed the hatch was crushing the air cleaner but still made it home from Danville OK. Drove it around town twice before swapping out the 600CFM Weber for the Quadrajet I had on my Bronco II V6. Runs nice, smooth, and have to be slow taking off in the rain going right. Even with the 3.07 F.D. And doesn't crush the air cleaner (which also came from the Bronco II).
Anyway, I went and bought a '69 Firebird and drove it up from Florida back in 2019. Came with a Holley 750 and corresponding Edelbrock intake. Terrible gas mileage, terrible fumes, reasonable power, didn't start right up when cold, and didn't run worth a fart until it was warm. Hood also trying to crush air cleaner. I knew I was going to change that carb before I bought that car but it ran good the day I got it.
After it's introduction to cold, damp Virginia, driveability became worse every ride and finally decided to put the Quad on there, like from the factory, but this meant changing the manifold since I could not use an adapter, just like on the GMC (because of extra height).
Gotta bench full of Quads, so bought and swapped manifold using crossover block plates (have not done this on GMC yet)and proceeded to play musical carbs using stock on hand and had one that really agreed with the engine. It came off my boat, and had no PCV or power brake vacuum ports. Started right up, ran like crazed cocroach in full escape mode. Decided to get a rebuilt Quad from EBAY, bad move, assembled from mismatched parts (airhorn not right for main body)and no returns. Found correct parts in collection and assembled working carb. Put on car and would not run right, figured I didn't get the rebuild right, but couldn't see what was wrong. Got another rebuilt quad, this time from JEGS. Really pretty, matched parts, replated butterflys, polished exterior, same $300. as the one from EBAY.Started right up, ran 8 seconds and quit. then repeat, holding/pumping throttle until it was warm but still would not run right. CLUE: only pulling 7 inches of vacuum at idle, NO vacuum leaks, smoked it to be sure. Finally took a functioning carb off other Firebird and tried that, could not adjust it to run even though smooth as glass on other engine (these are both 350s).
Well, rowing across the fuel induction river I was now halfway to the price of fuel injection, so do I keep plugging/sinking with these carbs or row back and get a different kind of boat? I chose the new boat and ordered the F.A.S.T. system since it was advertised as fitting the Quad manifold I had installed. I have decided that the P.O. put too big of a cam in there and the injection removes the variable fuel delivery at low RPM due to the low vacuum.
It's wonderful, starts right up, lopes a little until I load it going up the hill, and then I have to be careful to not tear up the gravel driveway. System comes with its own external H.P. pump that I am feeding off the stock mechanical pump. They want the pump lower than the tank and that isn't happening until the front of the car. Might be a little power drop-off at full throttle right now, but it's still real quick the 100mph, good enough to get me arrested so I'm just liking it right now. It was expensive, but at least I can now drive my antique car without a half-hour prep. And hardly any fumes from unburned fuel, actually cleaner than the GMC.
Now I see the price has gone up $400. !!! I just got it back in December for $1467...ridiculous,price gouging, but here is a link:

https://smile.amazon.com/gp/product/B016V2BB3U/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

Terry Kelpien ASE Master Technician 73 Glacier 260 Smithfield, Va.

[Updated on: Sun, 23 January 2022 18:15]

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