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#1
08-28-2007, 10:09 AM
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Falling off at launch...
..to follow up on other post, here is problem. At dead stop, in 1st car launches real good, up to about 5000, shift to 2nd, no problem, shift to 3rd, falls on it's face at about 4500, let off, hit it again, takes off. All this time was thinking I didn't have enough fuel, so I borrowed an electric pump and replumbed fuel lines. It did this with current Q-jet and I put a Holley 3310, same results. Now I find out from a friend that it may be to much pressure on Q-jet. Currently using a Holley 12-837 http://store.summitracing.com/partde...5&autoview=sku without a regulator. Gonna "rig" fuel pressure gauge up front to check pressure when car starts falling off. Thoughts? Kel
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'69 Pontiac 400 YA, .060 over, stock crank, 10.2:1 comp, CAT H-beam rods, HS 1.65 rockers, Crane cam 248/252 660 lift, Edelbrock 72cc heads ported 300 cfm, Performer RPM Intake, Ruggles 800 cfm Q-jet, Summit 140 gph electric fuel pump, 12 bolt 4.10 posi, 200-4R, Transgo HD shift kit, 2800 stall, aluminum radiator, 2" MadDog Headers, DMH 3" cutouts. 12.51 et @ 111 mph 
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#2
08-28-2007, 03:42 PM
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Hey Kel, this maybe stupid but when launching, how much gas do you have in the tank. Is it uncovering the pickup. Just a thought.
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1969 Firebird "400". 408 Pontiac, #62 heads, 274 XE cam, Eddy RPM intake, Quick Fuel Slayer 750, Carter Super Street fuel pump, Mallory Unilite, Turbo 400 with shift kit, Continental "Jim Hand Special" 3200 stall, 12 bolt 4.10 posi. 1 5/8 inch headers, 2.5 exhaust with Dynomax Ultraflos. |
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#3
08-28-2007, 10:12 PM
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james408 is correct my gto does the same thing if I have under half tank,if I run with half or more no problems at all .I think someone on here made a mod. for the pick up tube.
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#4
08-28-2007, 11:01 PM
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Tank problem usually shows up in lower gears where you are pulling the fuel away from the pickup. By the top end of third the gas should have settled back down, but this does sound like a fuel starvation problem. Tell us about the electric pump you tried and how it was plumbed in. Normally too much pressure screws up the idle with fuel spilling over into the venturies. Also, since you can get right back on it and it picks up would go against the too much pressure theory. If it was excess pressure, getting out of it would probably flood the engine and it would really sputter along when you got back in to it. So it still sounds like lack of sufficient fuel at the top end of third.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 Catalina Safari Wagon. |
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