Fast burn 385 carb.
Thread Starter
Cruising
Joined: Sep 2007
Posts: 14
Likes: 0
From: North Jersey NJ
Fast burn 385 carb.
I just installed the Fast burn 385 turn-key GM crate engine in my 77 vett. The engine came with a Holley 750 I was told that the 750 carb w/ vacuum secondaries and automatic choke is to Big and I should use a 600 cfm ???? I use this car ever day. My question is when I'm at a light or just steping on the pedal it has a dead sport for just s sec. . I checked the vacuum at the carb. and it was 15 and the power val. in the carb. now it a 6.5 so I waas told that was good. I had three shops look at it and two worked on it and they tryed to sell me a smaller cfm carb. Can anyone help??
Instructor
Joined: Jun 2007
Posts: 209
Likes: 0
From: Unlisted
I have the same toy. At idle vac is 27 at 1000 rpm. Auto trany, in drive foot on brake my rpm drops to 850 rpm vac to 18. There is a lag when I hammer it but the smoken tires makes up.
Check that the mixture vs vac for max vac, then lean 1/16 turn mine likes to run rich, then check timing. I dont know where you pulled your vac for lights and heat from. Mine from intake port infront of dizzy. Not useing the port infront of carb. Be sure you dont have a vac leak. Plug these and check with in gear to see if leaken. Vac will drop. I had a leak in the front reseviore tank . Something hit it hard years ago and rusted thru.
Just the way mine works best.
To small I was thinken of putten the 750 back on when I got mine it came with a 750.
Check that the mixture vs vac for max vac, then lean 1/16 turn mine likes to run rich, then check timing. I dont know where you pulled your vac for lights and heat from. Mine from intake port infront of dizzy. Not useing the port infront of carb. Be sure you dont have a vac leak. Plug these and check with in gear to see if leaken. Vac will drop. I had a leak in the front reseviore tank . Something hit it hard years ago and rusted thru.
Just the way mine works best.
To small I was thinken of putten the 750 back on when I got mine it came with a 750.
Last edited by mdbelanger; Sep 23, 2007 at 06:32 AM. Reason: oops 770 back on.
Melting Slicks
Joined: Feb 2002
Posts: 2,625
Likes: 0
From: Cut n Shoot TX
Can't answer your question. but i am shopping for a new crate motor. What is this fast burn 385?? Does that mean 385 hp? Can you give me some details on the motor? How much would that engine set me back?? 
Safety Car
Joined: Apr 2001
Posts: 3,581
Likes: 28
From: Spring, Texas
http://www.crateenginedepot.com/stor...FRcbWAodsWVXcw
Instructor
Joined: Jun 2007
Posts: 209
Likes: 0
From: Unlisted
Safety Car
Joined: Nov 2004
Posts: 4,359
Likes: 57
From: Mundelein Illinois
I have same motor with 750 Holley, vacuum sec and auto choke. Had same problem. Look at excel pump, sometimes you need to bend the lower lever a little so it rests on the plunger, you don't want any space in there. It needs to kick in quicker. You do not need a smaller carb.
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