Carb too small ?
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From: Corsicana, Tx
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Once the fuel pressure/volume issue is determined.....it may be time to start playing with PVCR's. You can add a good bit of fuel by opening them up. That way you maintain clean street cruising with little juets and get the fuel you need at WOT.
JIM
JIM
Pro
Joined: Jan 2004
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From: Darwin, Australia NT
Originally Posted by MotorHead
I am using the stock fuel line from the tank.
Anyone out there with expert knowledge on fuel lines?
Race Director
Joined: Oct 2000
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From: central FL, near the beach.
Originally Posted by Matt Gruber
.
also remove and discard both brass inlet fuel filters.
also remove and discard both brass inlet fuel filters.
u have failed to respond to. So i now have the answer to the Question:
ARE YOU A GOOD MECHANIC?
Thread Starter
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I don't think Holley 750DP #4779 come with inlet filters, if I recall from a few years ago when I was putting the fuel lines on, one of the first things I checked for. 
Thread Starter
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Interestingly enough someone else on the LM-1 forum is having the same problem :
QUOTE>Hi guys.
Was finally tinkering w/the LM-1 today, and made some observations. At idle, the AFR is at 12-12.8. Cruising light about 12-13. Heavy throttle 14-15. I'm too rich at idle and too lean under load right? I need to reverse this setup. If I put bigger jets I think I will worsen the low speed situation. Also, how does one lean out the idle mixture (screws?)
Carb is a 870 vac sec on a 454HO.
Thanks
Vince
69 CHEVELLE SS
454HO
(8:75:1, rec-port, 211/230 .510/540 roller)
800 DP/GM rec. port highrise
1.75,2.5" Flowmstr/MSD HEI/6AL
M20/C-FORCE DF/3.31<QUOTE
Now the idle and cruise I am not too worried about as you can lean the idle mixture screws , drill small holes in the throttle blades, put a small wire ( 0.005" ) idle-feed restrictor holes or re-jet the primary smaller.
It is the WOT that I am worried about, you would think that giving it a shot of gas the A/F would get richer not leaner.
QUOTE>Hi guys.
Was finally tinkering w/the LM-1 today, and made some observations. At idle, the AFR is at 12-12.8. Cruising light about 12-13. Heavy throttle 14-15. I'm too rich at idle and too lean under load right? I need to reverse this setup. If I put bigger jets I think I will worsen the low speed situation. Also, how does one lean out the idle mixture (screws?)
Carb is a 870 vac sec on a 454HO.
Thanks
Vince
69 CHEVELLE SS
454HO
(8:75:1, rec-port, 211/230 .510/540 roller)
800 DP/GM rec. port highrise
1.75,2.5" Flowmstr/MSD HEI/6AL
M20/C-FORCE DF/3.31<QUOTE
Now the idle and cruise I am not too worried about as you can lean the idle mixture screws , drill small holes in the throttle blades, put a small wire ( 0.005" ) idle-feed restrictor holes or re-jet the primary smaller.
It is the WOT that I am worried about, you would think that giving it a shot of gas the A/F would get richer not leaner.
Drifting
Joined: Jul 2003
Posts: 1,253
Likes: 1
From: East China MI
No expertise here, but I just read an article on this topic that seems to fit. I will look for it when I get home.
The heart of the text was that while testing WOT low fuel conditions, it was found that (in condition simular to yours) low fuel in the bowls was the cause. However, what the authors found was that the solution was not to increase the line pressure as they found the needle valve was the real problem. Increasing pressure caused tubulence in the bowl at low levels, causing feed problems. The size of the needle valve is the restricting factor. They cured the problem by lowering the fuel pressure and installing a larger needle valve (available through Holley). This gave them less velocity but more volume into the bowl: which cured their starvation problem.
To me this makes sense as, in hydronics, we don't increase volume with pressure. We do it with line size. Yes, pressure increase will give you some volume through increased velocity, but your not feeding an injector, your just filling a bowl and your goal is a steady volume.
Something to think about.
The heart of the text was that while testing WOT low fuel conditions, it was found that (in condition simular to yours) low fuel in the bowls was the cause. However, what the authors found was that the solution was not to increase the line pressure as they found the needle valve was the real problem. Increasing pressure caused tubulence in the bowl at low levels, causing feed problems. The size of the needle valve is the restricting factor. They cured the problem by lowering the fuel pressure and installing a larger needle valve (available through Holley). This gave them less velocity but more volume into the bowl: which cured their starvation problem.
To me this makes sense as, in hydronics, we don't increase volume with pressure. We do it with line size. Yes, pressure increase will give you some volume through increased velocity, but your not feeding an injector, your just filling a bowl and your goal is a steady volume.
Something to think about.
