Matt Reader
6/7/22 8:18 a.m.

I've been running a Holley double pumper on American V8's for a million years and they're great, I'm not putting anything electronic on my car in the foreseeable future (except a wide band AF gauge is planned right away). Does anybody have any set up tips that will make it a bit better for road racing/AX? stuff like float height, fuel pressure, pump cams, needle and seat specs, what about power valves?? i run a good elec pump set at 6.5 psi at idle - don't know what it drops to (if at all) at full speed.

I've always just ran it like the factory set it, but have recently had a couple hiccups (needle/seat stuck open in a corner, power valve had hole in diaphragm, running really rich all the time to name a couple) - so i thought I'd post it to the collective.


6/7/22 9:49 a.m.

The AFR gauge is a good idea but I found that in order to use it, you need someone along to read it  and make notes while you repeat a given  throttle maneuver.   Steady state, full throttle and off throttle, ect. 


I find myself wanting to have Throttle position, MAP, RPM and AFR on a data log so that I can make sense of carb tuning. Kinda how I ended up buying a Fitech. Too bad the Fitech is pretty much junk.

The one thing I did get to like on the Fitech was the ability to monitor and log fuel data against engine operation. 


APEowner GRM+ Memberand SuperDork
6/7/22 10:10 a.m.

I try and do all my tuning on the dyno so I can spend time optimizing part throttle metering under different loads.  My Formula Ford has a TPS and O2 sensor connected to the data acquisition system during test days so I can monitor those conditions but tuning is time consuming as compared to dyno tuning.  It's also not a 4150 but the carb tuning philosophy still applies.

As far as modifications are concerned I use screw in jet extenders

Image 1 - 4 Pack Holley Carburetor Main Jet Extensions Screw In Style Brass 4150 4500 Carb

vent extenders and road racing floats with more trapezoidal ends.

The rest is just tuning accross the operating range.

Matt Reader
6/7/22 6:57 p.m.

This is fantastic- thank you!!

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