Tuning a Holley 4150...?

[longbed67]

So tuning a Holley 4150... does anyone have some good suggestions for tuning resources such as books that gives a basic reference as what to adjust during different portions of the rpm band/throttle position for either rich or lean? Here is a video of what I am going to be attempting to tune, as right now it is way to rich!

http://www.youtube.com/watch?v=z3MvI...ature=youtu.be

[mongoose]

um.. no offense.. send it off to csu or something.. holley can be a pain to tune at the best of times if you don't know exactly what you're doing.. a blow though carb is a whole different beast.. burn that thing up quick.

[Marv D]

Ya gotta agree with that!!!! A blowthru is a total differnt animal than your typical backyard tune on a 4150. Id suggest you lurk around the turbo boards. It totally blows (punn intended) but the turbo mustang board seems to have more of the experienced turbo guys around.

Be cautious.

[GASoline71]

You do have a blowthrough carb on there right? I didn't check your build thread... but just checkin'.

Gary

[longbed67]

Yes I modified the carb for a blow through setup... I know how to set the idle circuts, I guess I should be more specific with my questioning at what rpm/throttle position do the main jets and secondary jets work in. And I will be running an innovate wideband as soon as I finish wiring it with data logging as I tune, but I still live by plug reading.

[grumpy_old_fart]

Generally, (and i mean generally in naturally aspirated situations) a 4150 carb will start using the main jets and bleeds about 1500 rpm, or right about the time your throttle blade clears the idle circuit.

an easy way to test the theory is to get the truck to idle... then, unhook turbo piping, adjust the carb to where the idle circuit is no longer in use... you would have to remove the carb, screw the idle screw in until the throttle blade is above the transfer slot, put it back on and attempt to start it to get an RPM reading. probably not the most fun.

once you get the rpm reading, you have a baseline.

[longbed67]

lol its funny that I did that right before I tuned the idle circuits last night and got just over 1400 on the tach, I wasnt sure what that meant as far as what circuit/jets it was running on but I knew it told me when the idle circuit stopped. I'm not sure why I would have to remove the carb... the idle mixture screw is on both sides of the front bowl, and by screwing them all the way in you should be shutting them off correct?

[grumpy_old_fart]

the reason i would have removed it is to visually determine throttle blade location to ensure that the transition slot was completely uncovered.

yes, at this point you should be able to turn the idle air/fuel screws all the way in, but it may not give you exactly the info youre looking for, as the transition slot and idle air/fuel will still flow some fuel.

[Hertzdaddy]

Originally Posted by longbed67

Yes I modified the carb for a blow through setup... I know how to set the idle circuts, I guess I should be more specific with my questioning at what rpm/throttle position do the main jets and secondary jets work in. And I will be running an innovate wideband as soon as I finish wiring it with data logging as I tune, but I still live by plug reading.

IMO, plug reading is good up to a point but the clean fuel we have today doesn't leave much to read once the tune gets close. An A/F meter is a good tool for the last 10th of the process, especially with data logging.

[Marv D]

Originally Posted by longbed67

Yes I modified the carb for a blow through setup... I know how to set the idle circuts, I guess I should be more specific with my questioning at what rpm/throttle position do the main jets and secondary jets work in. And I will be running an innovate wideband as soon as I finish wiring it with data logging as I tune, but I still live by plug reading.

I'd highly suggest you take a look at this thread.
http://67-72chevytrucks.com/vboard/s...d.php?t=578261

I run Innovate LC1's and have had much headache and gnashing of teeth, and 3 returned units trying to get 4 that works (and it appears this last weekend another is now screwing up and flat-lining a 7.5:1 a/f)

I guess what I'm saying there is I'm not bad-mounthing Innovate trying to justify my purchase of some other brand of AF meter. I really like the guys there at Innovate but.... I have 4 Innovate WB o2 reading LC1's and 2 spare bosch sensors for them.

I think I'd trade the whole mess for 'one' Fast or AEM that works!

[longbed67]

Thanks guys for the info on the innovate! I might just have to sell it and go with the FAST or AEM before I even finish installing the innovate. BUT an update on the carb tuning...

I took both bowls off changed the jets took out the needle/seats and put it all back together because and well I was immediately able to adjust the fuel bowls to the correct level without a problem and have 3.5 threads up into the nut. I however still cannot drive it more than 6 miles because as soon as the engine warms up to full temp the engine is choked out because it is running rich, as soon as it cools down I can start it right back up... The carb started with 66 jets in the primarys and 73 in the rear, and I could only go 2 miles before choking out. I now have 64's in the primarys and 71's in the secondarys and still WAY to rich. So I have to order another jet kit, because the one I have only goes from 64-99 jet sizes.

I found out CSU wants $450 to set up my carb, and C&S wants $600 sooo with my broke a$$ budjet for the next 3 months until I finish my board licensing I will be trying to dial this one in.

[mongoose]

what exactly did you do to the carb? it should run fine with those jets... deffo burn it down with boost...

[longbed67]

took out the choke horn and girdle and sealed up the hole, and switched the floats to solid floats, other than that it is the way it came new from holley. This motor is 254 cu in of displacement. so it starts and idles fine and the plugs have a great burn color at idle, but in any throttle the plugs are black as coal and full of soot.