Custom 454 won’t idle.

[Cookscustoms]

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Hello Chevy lovers. Let me start by saying over the past 20 years I’ve typically been restoring 1978 and 1979 Ford broncos so I have built many many 351M or 400 motors for these trucks without an issue. This customer came to me with a 98 two-door short bed with a V6 and a quarter million miles on it, that was totally dead. He stated he wanted a truck that would whoop his brothers 2010 challenger RT. I told him I don’t think a truck will do it but he still asked me to build 454 because he likes old school. He also provided me with a turbo 400 transmission(which I had rebuilt). I found a donor 454 out of a 1999 three-quarter ton suburban so That way it was a roller motor. I then took it to my machine shop where they bored it .30 over, decked the heads, did a three angle valve job, and put on beehive springs to go along with the cam That I had chose for this truck. I got rid of the fuel injection system on it and put on a weiand dual plane intake and a 750 Edelbrock carburetor. Now that the truck is all together, it will start and stay running, as long as you’re constantly pumping the gas. Even if you try to hold the throttle pedal steady at let’s say 3000 RPM it will still slowly idle down until it dies if you are not pumping it. What am I overlooking here? I’ve never had this issue with a Ford However, I have never attempted to build , a high horsepower monster big block. And from what I have learned over the last 30 years of working on vehicles is that you cannot kill a Chevy with an old-school motor. Also, I bypassed the fuel pump in the tank for a seven psi pump on the frame. Any and all advice would be great. I’ve checked for vacuum leaks and have found none even spraying starting fluid around the bottom of the carb or along the sides of the intake where they meet the heads. I have also tried using another 750 carburetor that I already have sitting here in the shop, as well as a 650 and they all yield the same results of no idling. Thanks again .

 

[b454rat]

Do you have a fuel pressure regulator? I think they only want 4-5 pounds. It's been long time since I had a carb'd motor, and wasn't good at all tuning them. Are the plugs wet?

 

[95burban]

What’s your fuel pressure on a gauge?What’s your fuel system consist of? If it’s small mr gasket pump it’s junk .

I would put a in tank pump back in it and use the factory feed and return lines with a quality return style regulator and gauge, then use something other than an edelbrock if it was mine.

 

[Road Trip]

What is the base timing, and what distributor are you using? I'm assuming
some variation of the HEI with centrifugal advance weights for RPM and a vacuum
advance for load sensing?

EDIT: Do you have a vacuum gauge connected, and if so, what kind of readings
are you seeing?

(Thought process -- assuming a known-good carb delivering a decent A/F mixture,
really late timing will make that big block act like that.) And the cam seems a bit
lumpy but quite reasonable given the displacement.

 

[Hipster]

E-brocks are notorious for flooding above 5psi. Agree cam looks big on paper, what you trying to set idle at? Agree timing might br way retarded. What's initial set at?

 

[Cookscustoms]

Thank you all for such fast responses. First I will respond to b454rat-I do not have a fuel pressure regulator. The factory pump was 45 psi. I know from past experience all the small blocks I have dealt with I use the Edelbrock 3 to 5 psi electric pumps and they were great. This is an a edelBrock 5 to 7 psi pump and the carburetor is much larger than the typical 550 or 600 that I put on to the Ford motors so I figured the PSI would be about correct based on what I have also read online for this size motor and this size carburetor. Please see picture of plugs. Pulled

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four different ones out they all look identical.

 

[Cookscustoms]

What’s your fuel pressure on a gauge?What’s your fuel system consist of? If it’s small mr gasket pump it’s junk .

I would put a in tank pump back in it and use the factory feed and return lines with a quality return style regulator and gauge, then use something other than an edelbrock if it was mine.

Fuel pressure on the gauge is about 5.5 to 5.9. It is a Edelbrock electric pump and I haven’t had issues with them and I’ve been putting them on the bronco restorations for about 15 years now.

 

[95burban]

so it dead heads, the pump has some sort of a bypass in it. Have you swapped pumps?

 

[Cookscustoms]

What is the base timing, and what distributor are you using? I'm assuming
some variation of the HEI with centrifugal advance weights for RPM and a vacuum
advance for load sensing?

EDIT: Do you have a vacuum gauge connected, and if so, what kind of readings
are you seeing?

(Thought process -- assuming a known-good carb delivering a decent A/F mixture,
really late timing will make that big block act like that.) And the cam seems a bit
lumpy but quite reasonable given the displacement.

Haven’t been able to set base timing because I can’t get it to idle under 3000 RPM. Distributor is a Accell HEI unit with vacuum advance. I can throw a vacuum gauge on it but the reading will be at a high rpm.

 

[Cookscustoms]

E-brocks are notorious for flooding above 5psi. Agree cam looks big on paper, what you trying to set idle at? Agree timing might br way retarded. What's initial set at?

Ideally the idle at 700 or so would be great. If I turn the distributor, either way clockwise or counter clockwise more than a half inch then the truck will not start at all. When I do have it running by constantly pumping the gas, I have been able to put it into drive and go around the block, but if you try to give it gas more than just light pumps while driving it backfires through the carburetor instead of picking up speed.