Finally done chasing lean tip in problem!
Finally done chasing lean tip in problem! I have been chasing a lean tip in problem with my Pro-Systems 780 since I put it on the car. I have tried just about everything. I even sent it back to Pro-Systems and had them completely gone through it and send it back. Still, it would go dead lean just over idle.
Well, today I really went after it. I started swapping everything from my Holley 750HP. I tried the metering plate, high speed and low speed bleeds and nothing worked. Then, I tried the one thing that should not have made a difference. I swapped on an old 750 base plate off the shelf and whamo! Lean tip in problem gone. I have no idea what is wrong with the Pro-Systems base plate. It looks fine to me. Obviously I am missing something. So, I will call Brad on Monday and tell him what I found. I am relieved to have found the culprit, but puzzled as to what the problem is with this base plate.
Well, today I really went after it. I started swapping everything from my Holley 750HP. I tried the metering plate, high speed and low speed bleeds and nothing worked. Then, I tried the one thing that should not have made a difference. I swapped on an old 750 base plate off the shelf and whamo! Lean tip in problem gone. I have no idea what is wrong with the Pro-Systems base plate. It looks fine to me. Obviously I am missing something. So, I will call Brad on Monday and tell him what I found. I am relieved to have found the culprit, but puzzled as to what the problem is with this base plate.
I changed out my Holley baseplate because of a sticking throttle condition and saw a similar change in the carb performance.
I moved up to a quick fuel baseplate and I know they use much better throttle shaft seals. Or maybe the machining was just more precise.
I moved up to a quick fuel baseplate and I know they use much better throttle shaft seals. Or maybe the machining was just more precise.
Congrats on getting it figured out! I admire your patience and diagnosis technique. I'll be real curious to hear what Prosystems has to say about this since they use their own baseplates. Was your lean tip in condition only apparent on the wideband or could you notice it otherwise?
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I know which is which. I know the <750 from the 850> from the others. I have been at this for 25 years. In fact. I used the same throttle body gasket that came with the Pro-Systems carb.
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Verdad Gallardo Congrats on getting it figured out! I admire your patience and diagnosis technique. I'll be real curious to hear what Prosystems has to say about this since they use their own baseplates. Was your lean tip in condition only apparent on the wideband or could you notice it otherwise?
TECH Regular
iTrader: (5)
Joined: Jan 2008
Posts: 452
Likes: 2
From: Sparta, Mo. in southwest Missouri
I have been chasing a lean tip in problem with my Pro-Systems 780 since I put it on the car. I have tried just about everything. I even sent it back to Pro-Systems and had them completely gone through it and send it back. Still, it would go dead lean just over idle.
Well, today I really went after it. I started swapping everything from my Holley 750HP. I tried the metering plate, high speed and low speed bleeds and nothing worked. Then, I tried the one thing that should not have made a difference. I swapped on an old 750 base plate off the shelf and whamo! Lean tip in problem gone. I have no idea what is wrong with the Pro-Systems base plate. It looks fine to me. Obviously I am missing something. So, I will call Brad on Monday and tell him what I found. I am relieved to have found the culprit, but puzzled as to what the problem is with this base plate.
Well, today I really went after it. I started swapping everything from my Holley 750HP. I tried the metering plate, high speed and low speed bleeds and nothing worked. Then, I tried the one thing that should not have made a difference. I swapped on an old 750 base plate off the shelf and whamo! Lean tip in problem gone. I have no idea what is wrong with the Pro-Systems base plate. It looks fine to me. Obviously I am missing something. So, I will call Brad on Monday and tell him what I found. I am relieved to have found the culprit, but puzzled as to what the problem is with this base plate.
Ron
Hey, "tigger". Good job finding the fix. A couple of the tuners on the Innovate web site were having the same problem a few months ago and solved it the same way that you did, by swapping to a Holley base plate. If I remember right, they finally decided it was the thickness of the aftermarket plate and the length of the transfer slots that caused the problem.
Ron
Ron
Well, I am thinking that my 4.8 just doesn't get a great signal down low possibly for the existing air bleeds on the 750 vac sec. They are not adjustable though so I think finding a 650 would get me set. Only does it at slight roll I to throttle down low when taking off.
Well, I am thinking that my 4.8 just doesn't get a great signal down low possibly for the existing air bleeds on the 750 vac sec. They are not adjustable though so I think finding a 650 would get me set. Only does it at slight roll I to throttle down low when taking off.
TECH Regular
iTrader: (5)
Joined: Jan 2008
Posts: 452
Likes: 2
From: Sparta, Mo. in southwest Missouri
Ron
Launching!
Joined: Aug 2010
Posts: 242
Likes: 0
I have seen the throttle cable adapters that bolt under the carb create a bad stumble off idle. The plate acts like a shear plate and pulls the fuel out of suspension then it just runs down the side of the intake.
On The Tree
Joined: Jul 2008
Posts: 128
Likes: 2
From: Stockett, Montana
I have a 5.3 with a carburetor, and my 750 Quick Fuel did the same thing. I tried everything, squirters, air bleeds, transfer slots, etc. Finally gave up on it, and put my buddy's AED 850 on the thing. It didn't work at first either, but was better. It finally started backfiring through the carb on the hit, then I knew what was wrong. I put on bigger squirters, and the biggest pump cams I could find, and it worked great. Took it to the track and had a 1.78 60 ft. in my Nova. Carbed LS engines are tricky to tune, but once you get them right, the work awesome.
Good luck finding your problem Tigger!!
Good luck finding your problem Tigger!!
I wanted to update this thread because I have learned more since facing this issue. Putting the old baseplate on the newer carburetor was not really a true fix for what was wrong with my carburetor. The reason it helped is because the old baseplate was a two corner idle baseplate. They have idle transfer channels and different secondary idle ports. So, while it made the problem go away, it was not really a real fix per se.
The real fix was to drill the idle feed fuel restriction orifices in the metering blocks out .002". In this carb that meant going from a .035" idle fuel restrictor to a .037" idle fuel restrictor.
My particular combination just needed more fuel at low speed cruise and tip in. I hope what I learned helps somebody in the future.
The real fix was to drill the idle feed fuel restriction orifices in the metering blocks out .002". In this carb that meant going from a .035" idle fuel restrictor to a .037" idle fuel restrictor.
My particular combination just needed more fuel at low speed cruise and tip in. I hope what I learned helps somebody in the future.
53, 750tip, aed, backfiring, baseplate, carb, carbureted, carburetor, in, lean, pop, pro, prosystems, stumble, systems, tip
