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Discussion Starter #1
I have a 1150 HP Dominator that I got for little $. I'm running it on a tube chassis 68 Camaro, 565 BBC. I'm pretty much within .006 in the 60' range but 330 is off .010-.015 depending how long I stay on the 2step. If I'm crossed over by a good bit and get on the 2step early, It slows. Getting on it at the second amber it is faster. I'm guessing here that it has something to do with the 3rd stage. I have called Holley Tech and their expert Help of 20 year olds and they don't have a clue! :rolleyes:
Anyway, I tried plugging the intermediate tubes as that's one solution I read but it was really lean off idle. I didn't however richen up the main circuits. I have no time for T&T as out track you only get 2 TTs before eliminations. I replaced a 1050 old style dom with the same issues. My 4150 works great but not nearly enough. Any help would be welcome.
 

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Thanks guys. All very good ideas. I have built 4150's for 30 years and know them well enough to tune without issue for the most part. I have researched the web many times trying to understand the workings of the intermediate circuit and when it actually functions. What I have discovered is that it basically works at all times except idle.
So with that said, I have off idle 8 fuel sources that signal is based on air density. I have considered sending it to one of the big builders to modify it but being a Mechanical Engineer and the need to understand things I was hoping to figure out or get advise from someone who actually had did it.
With all that said, I have read the article on the mod on Motorsports village about new metering blocks and the drilling and tapping required. The only diff I can find between mine and new ones are the intermediate circuit in the blocks. They are actually identical besides these ports.
So, My goal is to get it down to running on 2 circuits and do away with the intermediate (iffy circuit) as I strictly Bracket race. Thanks again for the recommendations and any information that y'all run across would be greatly appreciated!
 

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how big is the actual third circut fuel jet? not the discharge but the actual feed jet. in the pro stock world that is a pretty big deal. when the vp goes above .550 or so you better get rid of some of that fuel. i know that we had been down as small as .017 for the 3rd circut fuel jet when the air got real bad like that. also lowering floats and uping the fuel pressure were changes that got made, not big changes but that thing if you didnt work on that stuff it would actually go out there and miss at like 1.9 into run, O2's would not show it correctly but the egts would every time
 

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Those threads are kind of confusing. But it has be interested.

What effect does moving the idle jets from the top of the blocks to the bottom have?

Also what effect does drilling those jets larger have.
 

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Idle jet location info at the link below.

http://racingfuelsystems.myfunforum.org/viewtopic.php?f=25&t=18

Drilling what jets larger? If you mean the idle jets, it will supply more fuel to the transition circuit, low throttle opening, and will require the mixture screws to be turned in more.


how big is the actual third circuit fuel jet? not the discharge but the actual feed jet. in the pro stock world that is a pretty big deal. when the vp goes above .550 or so you better get rid of some of that fuel. i know that we had been down as small as .017 for the 3rd circuit fuel jet when the air got real bad like that. also lowering floats and uping the fuel pressure were changes that got made, not big changes but that thing if you didn't work on that stuff it would actually go out there and miss at like 1.9 into run, O2's would not show it correctly but the egts would every time
Most of the 3 circuit stuff I see uses around a .040 intermediate jet, usually very, very rich at part throttle. Which is why I prefer to change them over to a 2 circuit in most cases, the fuel is atomized more completely if it all comes from the booster. The right booster helps as well.
 

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Actually it came from Holley open! Threaded ports with nothing between them and the 3rd circuit tubes. I tried plugging them with #8 allen plugs. I did not however raise the main jetting. It came with front and rear PV's and .092 jets square. I removed the PV's and left the stock .092's. It didn't lean out at all! I thought that was strange. It ran strong and very smooth through out the rpm range. Plug read was decent but I'm almost sure that's a product of the fuel pouring in due to the 3rd circuit. I also opened up the intermediate air bleeds from .060 (stock) to .070. Seemed to be a little smother and settle the car a little but it also wants to slow down when the air gets better on a given day. With that said I still have a two tenths difference from winter to summer which is about normal on race gas. (Aviation LL100). The problem is on a race night and DA improving with the late day, It may run identical passes 3 times and then start dropping .010 a round...
 
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