Racing Fuel Systems

This is my first post. I was told this was the best place to ask questions so here is my story. I have an 8.2 deck 347 with Trickflow Cleveland heads, 10.5 comp. on pump gas, Crower 15416 solid roller with an ancient Holman Moody 2x4 dual plane intake with 2 Holley 1850-4 600 vacuum secondary carbs. The linkage is 1:1. The problem I have is it runs rich. Idle is ok but 2k on up it is rich. It has about 8.5" of vacuum at idle. The carbs are stock except for the choke flaps are removed, I installed plates on the secondary side with replaceable jets, tied the secondaries together and installed 3.5" power valves. I ran them with the stock 64/66 jets and 6.5 power valves initially. I could not get the mixture screws to make any change. I found the carb pad on the intake did not cover the passages all the way on the base plates causing vacuum leaks. I fixed that and now it idles at 1,000 and the mixture screws function. I drove it several times and the plugs were black. I installed the 3.5" power valves and 62/60 jets. Better but still black. I installed a Daytona Sensors dual channel wideband. At idle it shows 18.0 to 1. I think this is due to the header setup I have either leaking at the slip joints or pulling air in the tail pipes.
You can see it here. https://www.youtube.com/watch?v=zb9bLhDpni4&t=33s
The o2's are in the back of the muffler between the pipes. They are stepped 13/4" to 1 7/8" to 2" into the muffler with dual 3" tail pipes. At 1,500 rpm it is 13.8 - 14.1. Once you get past 2,000 it goes rich at 12.4. It is this way up to at least 5,000. I did not get to drive it yet due to the weather so I have no idea what WOT is at. The question is, if it is the same way driving what do I need to do? It is a MAB issue?
This is the intake. Thanks for any help.

Nice

tuner's recipe for dual 1850's is excellent... link to thread below from old forum outlines it, post #3...

https://www.tapatalk.com/groups/racingf ... 850#p23669

Here's the missing image with numbers that tuner refers to in that thread when explaining the modifications:




I did a pair a couple years ago and they worked great. Here's how I calibrated them...

Thanks for posting this. I had seen this somewhere before but lost track of it. I guess I have some work to do.

What is considered a late model 1850?

What are you using for the 3/16 plug in the main well? Can I use a piece of aluminum rod? How thick does it need to be?

As a side note... forget about most "normal" driving and cruise as having anything to do at all with the main jets or the power valve rating...

Most "normal" driving and cruise has everything to do with the carburetors' off-idle/transition function, the PIFR's (primary idle feed restrictions) and PIAB's (primary idle air bleeds).

Also, everyone would seriously benefit from forgetting about anything they ever heard about considering idle manifold vacuum as to installing a certain number rating power valve/s into the carburetor/s according to that. Power valve/s open or shut at idle/off-idle means and affects nothing... the idle/off-idle circuit gets it's fuel limit based on the idle feed restrictions.

Thanks for the tips. I have some marine JB so I will probably go that route. I plan on taking them apart tonight so I will post some pictures of the metering blocks. I knew the power valve had nothing to do with cruise but just wasn't sure what mods to make and to what. I am anxious to see how it runs when I am done.

Wow, cool setup. what is that gizmo on the passenger side with the vacuum hoses? And that wire, orange with black stripe?