zz4IROC

Okay. 1988 iroc. 350 zz4 with 11.5:1 compression, custom cam, .550 lift, roller hydraulic, that is having problems with the fuel system. I have changed the pickup in the tank to a factory carb pick up out of 82 camaro. Using factory tpi fuel line(3/8) into -6 an line which runs under the radiator into a mechanical street performer rpm edelbrock mechanical fuel pump. Then going to a proform mechanical secondary 750cfm carb. The original fuel filter is in place( under rear of car) and i have installed another fuel filter between pump and carb. Fuel pressure shows 5psi. Cars pulls hard on the street in all gears. At the track, i ran a 13.5 at 97. I could feel the car sputtering and starving for fuel all through 3rd and 4th gear. I raised the floats...saw improvement..and i wound up raising the floats to the point that the bowls are full. I ended up with a 12.970 at 107 with the car still noticably sputtering through fourth gear.

I have been told the motor should be 450hp. Am i sucking the bowls dry due to the fuel pump not being able to keep up? Vapor lock? too small of fuel line? With floats adjusted so bowls are filled, i ran my best time but still felt the car nosing over in 4th gear. All help appreciated. Thanks. Joe.

Ozz1967

iTrader: (4)

It could be the needle and seat in the carb are too small, not allowing enough fuel into the bowl from the line to keep the car fed. I ran into that problem when I swapped from my Factory 305 to a 350, had to have the carb rebuilt to handle 2x the HP/torque. The builder said the larger needle and seat would keep it full of fuel and it has so far. Been really happy with it.

89redliningRS

I would say just throw an electric pump on there. I'm running a walbro 110 lph pump, with no issues. You would probably have to see if it's putting out 5psi when your on the throttle that long.

zz4IROC

ok so i switched to a carter pump rated at 120 gph. The car feels the same. So please can i get some help before i spend money somewhere i dont have to. Heres my options considering my fuel pump should be sufficient.

*Sump tank and run -8 line to pump. Leave -6 from mech. pump to carb.
*hook -8 line to stock pick up and run -8 from pump to carb if needed.
I have heard that hooking up -8 line to stock pick up is pointless. Any truth? Thanks.

pancherj

Unless there is a blocked fuel filter, I can't see the pump and lines you have being an issue. I had a stock $20 mechanical pump on a 406 that ran 12.0's with no starvation. Put a fuel pressure gage on there that you can watch from inside the car (doesn't have to be a permanently mounted one). This will tell you.

If the fuel pressure checks out okay under full throttle, it is time to start looking at the carb. Maybe it is just running too lean? Maybe it is the needle and seat? Confirm the fuel pressure at WOT before you dig into the carb.

Apeiron

The size of the line isn't a problem, you should have no issues on 3/8" tubing.

Pumps don't like sucking through filters so much, have you tried taking the factory filter out?

zz4IROC

yea i tried taking the factory filter out and the fact that by raising the bowls from the bottom of the sight glass to the point where the bowls were filled i went from running 13.5 @97 to 12.970 @ 107 and still cutting out

five7kid

iTrader: (14)

Time for a wideband O2 system. You're guessing and shot-gunning now.

onebad82z

iTrader: (7)

This bothers me a little. That is a lot of added length. Maybe at that load.. WFO in 3rd and 4th it is enough to slow down the siphon of fuel to the pump and causing these issues. You have to have added 4-5 feet at least. By raising the float level to fill the bowl it added enough reserve to allow the car to pull longer before it started to lean out. My best guess.

Aside from that I have ran 119 through the 1/4 on a 100 shot with zero fuel supply issues with almost the same fuel system. '82 carbed car only difference I can see is I run a Holley blue electric pump but that ain't where your problem lies. I think your pump is more than adequate.

Have you tried to shorten the fuel feed line up? Reroute it over the top of the trans and up the pass. side frame rail to the pump like a factory carb car OR I have seen people run it down off the TPI line across the crossmember under the engine to the pump. Myself I like the factory routing with a mechanical pump. Electric pump like I run I have the feed line routed like a TPI car and run from the regulator across the front of the motor to the carb connect.

Reroute the fuel line and shorten it up. I would do that before anything else. Cut a splice in it right next to the trans and use rubber 3/8" for a test. Do not use it permanently. Make the splice, reroute up over the trans, along PS frame rail and turn down to pump. Make a pass and she how she does.

zz4IROC

Well since im not selling the car anytime soon, I think i will just sump the tank. Thanks for all your input guys and i do think that the length is an issue. Im just tired of ****ing around with this fuel system and ready to move on to the next mod. I figure if i make a bulletproof fuel system now ill never have to look back. And onebad82z, that car is bad ***. Where do you run that thing?

onebad82z

iTrader: (7)

Not a terrible idea depending on the direction you are going with the car. I do think the length and routing of the current setup is what is causing your current issues.

Thanks! I run it at Island in NJ most of the time, otherwise Englishtown also in NJ and that pic in my avatar is from a local airport that held some 1/8 mile racing this summer.

cuisinartvette

Check your fuel pressure under a load meaning run a safe line from the pressure side to a gauge maybe tape it to the windshield so you can monitor it. If all is well there Id check to make sure you arent getting valve float. It happens long before you can hear it btw the car will just lay down. Bitch to chase down trust me done the same as you.Fooling with pumps, carbs, cams intake etc and the whole time the springs werent set up right and were floating, Eventually a few broke. No damage thank God

Whiteaw57

iTrader: (1)

x2 what crusinartvette said. My old boss at RCR used to tell me 9 out of 10 carburetor problems arent actually carb problems. Id have a spring pressure checked and see where youre at

zz4IROC

Turned out to be heat. Nothing a carb plate and fuel line wrap couldn't fix.