14point7 Spartan 2 install, Holley 4150 tuning, & exhaustcapades

Bustedknuckle

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Jun 5, 2020
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Kingman AZ
I confirmed the power valve size. 5.5 should be correct, but I think as insurance I may pick up another 5.5 PV when I pick up the sensor bung from the parts store.

Edit: The more I think about it I think I'll pick up a 4.5. I think I should err to the lower side with this, and since it was somewhere in the 10-11 inch range for vacuum, I'm going to go with 10 which would require a 4.5 power valve. Since they don't carry a 4.5 PV, I guess I'm at a standstill with actually going farther with the carb once I get the gauge installed. So this escapade will continue for at least a few days.....

IMG_20200422_114551__01.jpg
I like going a bit smaller, just a tad lean at full tilt, on the power valve; Tune the accelerator cam and squirter size to cover a hole in the fuel curve, if there is one. Then tune the secondaries
 
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LILCBRA

I wish I didn't have all of these balls in the air
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Dec 6, 2005
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My personal choice was to go a tad rich, especially under load. As I understood the effects of AF ratios before and over the course of going through this, lean conditions can lead to detonation which in turn can lead to engine damage. Then I found this video on the YouTube which helped to reinforce everything. It sounds like it's a common misconception that the AF ratio being a little lean produces the maximum amount of horsepower, but these guys dynoed an engine and produced the curves to prove that that is false and also explain the reasoning behind it. It logically made sense to me and reinforced what I had felt for a long time.

View: https://youtu.be/JzbLrn-2jyw
 
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extra_stout

Advanced Member
Aug 27, 2018
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I didn't know about that myth... but interesting to know that such BS goes around. With carb instead EFI it is a little more complicated because the amount of fuel is controlled by the volume flow. But the mass flow changes with temperature even if the volume flow is the same. This means if the car is tuned in warm weather near lambda 1. It can happen that if its cold outside you get lean condition. For partial load and idle that is not a problem IMO. But for WOT you should always be a little bit rich.
And exhaust popping can also come from lean condition...
 
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LILCBRA

I wish I didn't have all of these balls in the air
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I've had it out a couple times, but nothing of interest to post about. It's running great now though! A/F stays in the low 12s to mid 13s most of the time. There was a couple times where it popped into the high 14s/low 15s upon acceleration, but only for a split second and dropped back into the 12s/13s. I attribute that to shifting. It would be awesome if I could record the gauge for longer than a couple minutes to show instead of explaining it through text. :shrug:
 
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2Blue2

will be trying this sex one when I can find it
Mar 5, 2019
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Need to go track and get some new times
 
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LILCBRA

I wish I didn't have all of these balls in the air
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So I happened to run into this video last night and thought it might be relevant to share either in this thread or in my dyno thread. I'm excited to see what kind of difference having my carburetor set up more properly vs what it was when I had it dynoed the first time.

View: https://youtu.be/HXX4zcPr9IE
 
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LILCBRA

I wish I didn't have all of these balls in the air
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Another quick update: When I ordered the 50 cc accelerator pump I also ordered jet extensions and baffle tubes for the bowls. I finally got around to installing the extensions this past weekend and readjusted the float. I had the car started for a little while and what I noticed on the gauge is it was still reading in the 13-15 range. While I had the carb off I ended up replacing the secondary squirter with the only one I had laying around that was bigger - I believe it went from a 25 to a 32, but since I'm not at home to confirm that's just a guess for now. The weather is starting to get a little nicer here so I'm wanting to take the car out, but the last time I drove it it ended up leaving me stranded on the side of the road a couple different times. I tried to coordinate with a buddy of mine to be on standby in case it does it again, but he wasn't available last weekend. Maybe I'll be able to take it out this weekend at some point. As far as why the car was dying and leaving me stranded, I believe I found a partially bare power wire for the MSD that was above the brake booster. I'm pretty sure I've got the problem remedied, but I'd still feel more comfortable having someone on standby when I take it out again. :shrug:
 
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429MII

Mustang Master
Mar 10, 2019
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I like going a bit smaller, just a tad lean at full tilt, on the power valve; Tune the accelerator cam and squirter size to cover a hole in the fuel curve, if there is one. Then tune the secondaries
Anything in the 224-230 @.050 range for a cam and I use a couple sizes up on the jets ( a little more on the secondary) a 2.5 power valve and the lightest vac adv. spring. Seems to work great.
 
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