What jet and pv size on a 4150HP on SB?

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mshred

mshred

The Green Manalishi
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hey guys,

I have a 4150hp (750hp holley) carb on my mild 340. I dont have the jet specs on hand at the moment (not sure where they are) but i believe i have a 71 primary jet and 82 secondary jet with a 5.5pv on it. Ive been driving the car quite a bit lately and ive noticed a few things

first off, whenever i floor it, smoke is coming out from the exhaust. I know this could either be a sign of a rich condition or burning oil, but im hoping its the former since just playing with the jets will help me (which is why id like to see what jet sizes you guys are running)

secondly, my car drinks gas like its going out of style! and im not exagerating here! yes my carb is a double pumper, yes i do like to get on the gas here and there, but damn, i can actually watch that gauge drop down! its quite scary actually lol...i knew it was gonna suck gas, but i didnt think it was going to be this bad, which is why im wondering, maybe the power valve is the wrong size and dumping too much fuel? maybe its running way too rich? (I am getting burning eye syndrome after lots of driving, but thats also because i have dumps)

anyways, any opinions on this stuff or suggestions would great! as always, im open to hear what you guys have to say

thanks!
Matthew
 
Thats the same size primaryy and secondary jet and power valve on my holley 800 dp, on top of a 408 stroker, so yeah, you might be running a bit fat. What color is the smoke comming out of the pipes, blue/black, or white? hook a vacum gauge to the carb base plate, and find out what pv you need, kinda dependent on the cam in the motor.
 
EL5DEMON340 said:
is that an annular booster carb?
Click to expand...

i believe it is a downleg booster style, but to be honest im not 100% sure how to check that...I dont think it is annular booster since i would have had to pay more for that i think, but it doesnt hurt to double check

stroker_valiant said:
Thats the same size primaryy and secondary jet and power valve on my holley 800 dp, on top of a 408 stroker, so yeah, you might be running a bit fat. What color is the smoke comming out of the pipes, blue/black, or white? hook a vacum gauge to the carb base plate, and find out what pv you need, kinda dependent on the cam in the motor.
Click to expand...

so maybe i am running a bit fat then. My 340 is very mild comp 230 dur at .50 cam 480 lift single pattern, air gap, 1-5/8 headers to 3 inch xpipe exhaust, .30 over with stock heads, deep pan with tray, 3.91 gears

as far as the power valve goes, when hooked up to the vacuum gauge it looks like the pv i have is the appropriate size, but im just wondering since i felt that i have a rich condition and it seems like its overly sucking gas, so i thought it might be a possibility and wanted to see what you guys are running
 
the 71 on the primary side seems ok. check what vacuum you are pulling with the car in gear, you want a PV that is 1.5 to 2" lower
 
EL5DEMON340 said:
the 71 on the primary side seems ok. check what vacuum you are pulling with the car in gear, you want a PV that is 1.5 to 2" lower
Click to expand...

what about on the secondary side. also, the car is a stickshift...will that make a difference for checking vacuum in gear?
 
mshred said:
hey guys,

I have a 4150hp (750hp holley)

secondly, my car drinks gas like its going out of style! and im not exagerating here! yes my carb is a double pumper, yes i do like to get on the gas here and there, but damn, i can actually watch that gauge drop down! its quite scary actually lol...i knew it was gonna suck gas, but i didnt think it was going to be this bad, which is why im wondering, maybe the power valve is the wrong size and dumping too much fuel? maybe its running way too rich? (I am getting burning eye syndrome after lots of driving, but thats also because i have dumps)
Click to expand...


Ha ha ha, yep! That's all about right, I have been whatching gas tank gauges drop for a long time now....they do this you know...on something with some power, OH hell ya they'll do it right in front of your eye and stay down there.
Your build below is about just right for this "Drinking like a whino fresh outta overweekend lock up into a free whine tasting store with no one around but him"
Don't worry though, it's normal. Just wait till you build something with a boat load of power. Then you'll really feel it.

mshred said:
i believe it is a downleg booster style, but to be honest im not 100% sure how to check that...I dont think it is annular booster since i would have had to pay more for that i think, but it doesnt hurt to double check



so maybe i am running a bit fat then. My 340 is very mild comp 230 dur at .50 cam 480 lift single pattern, air gap, 1-5/8 headers to 3 inch xpipe exhaust, .30 over with stock heads, deep pan with tray, 3.91 gears

as far as the power valve goes, when hooked up to the vacuum gauge it looks like the pv i have is the appropriate size, but im just wondering since i felt that i have a rich condition and it seems like its overly sucking gas, so i thought it might be a possibility and wanted to see what you guys are running
Click to expand...

Like it said above. A vacuum gauge is very helpful with tuning. You shouldn't have the burning eyes syndrome. That is running rich. When you achieve the highest vacuum reading on the gauge, 1/2 of the reading plus 1 or 2 is wheat the PV will be.

Remember twisting the distributor is all part of the tune as well. This will all take some time. Enjooy some track runs while doing this.

Rob
 
rumblefish360 said:
Ha ha ha, yep! That's all about right, I have been whatching gas tank gauges drop for a long time now....they do this you know...on something with some power, OH hell ya they'll do it right in front of your eye and stay down there.
Your build below is about just right for this "Drinking like a whino fresh outta overweekend lock up into a free whine tasting store with no one around but him"
Don't worry though, it's normal. Just wait till you build something with a boat load of power. Then you'll really feel it.


Like it said above. A vacuum gauge is very helpful with tuning. You shouldn't have the burning eyes syndrome. That is running rich. When you achieve the highest vacuum reading on the gauge, 1/2 of the reading plus 1 or 2 is wheat the PV will be.

Remember twisting the distributor is all part of the tune as well. This will all take some time. Enjooy some track runs while doing this.

Rob
Click to expand...

Hey rumble, my dad says the same thing...he told me i have a double pumper and if i drive like an idiot i should expect it...its a good thing im working full time to pay for all the gas now lol...as far as the vacuum guage and burning eyes syndrome, i agree it shouldnt be happening, which is why i know its running fat. As far as timing goes, before my timing tape flew off (gotta get a new one) my initial was set at 15, but other guys were saying i need closer to 19 or 20...could this be a cause for this? if i add more initial, will i need to increase the octane rating of the gas im using, even if i keep the same total?
 
ramcharger said:
Check the vacuum with the car at idle in gear with your foot on the brake if you have an auto trans. Note the reading, divide it by two and that will be your correct PV size.

http://www.holley.com/data/TechService/Technical/power_valves.pdf

Holley has a wealth of tuning info on their website:

http://www.holley.com/TechService/Library.asp
Click to expand...

Hey ramcharger, i have a manual transmission, and that info you provided from the holley site (thanks btw!) says to check it at idle for a standard transmission, which is how i did it before
 
I'll just leave it at, "You'll need to play around with it" rather than tell you what I think since everyone has an opion of what intail should be.

I followed the MP books advice and it works fine for me.

If I'm racing at the track, that's a different story. And so is the octane available.

My old street racer cars were basic bombers built on a poor mans budget. I used to run them without a vacuum advance with as much intial as possible. Things got really interesting when I was given a MSD start retard box and ran a locked out lean burn distributor.

If the total timing stays the same, then I do not think you'll need to change octane. But to much intail could require more octane to prevent the pining. IF it pings with to much intail, then I say you went to far.
 
mshred said:
Hey ramcharger, i have a manual transmission, and that info you provided from the holley site (thanks btw!) says to check it at idle for a standard transmission, which is how i did it before
Click to expand...

You should be OK in the PV department then but you can always drop it down one size and see how it runs. If you get a puff of black smoke on take off, you can go with a smaller squirter and it never hurts to experiment with jet sizes. The lighter the car, the higher the gear (numerically) and the higher the stall, the less squirter you need. Pick up a set the blue reusable float bowl gaskets and a Holley jet kit and move down two sizes at a time. You'll know when it's too lean plus keep on eye on your plugs. How do the plugs look now?

You can mess with the air bleeds too but I don't really recommend it without having a quality air/fuel meter at your disposal.
 
rumblefish360 said:
Ha ha ha, yep! That's all about right, I have been whatching gas tank gauges drop for a long time now....they do this you know...on something with some power, OH hell ya they'll do it right in front of your eye and stay down there.
Your build below is about just right for this "Drinking like a whino fresh outta overweekend lock up into a free whine tasting store with no one around but him"
Don't worry though, it's normal. Just wait till you build something with a boat load of power. Then you'll really feel it.



Like it said above. A vacuum gauge is very helpful with tuning. You shouldn't have the burning eyes syndrome. That is running rich. When you achieve the highest vacuum reading on the gauge, 1/2 of the reading plus 1 or 2 is wheat the PV will be.

Remember twisting the distributor is all part of the tune as well. This will all take some time. Enjooy some track runs while doing this.

Rob
Click to expand...

I,m hoping for 7 mpg. lol
 
hey guys,

for some reason i wasnt getting notified about this thread...anyways....

i have now moved to a brand new carb, a holley 750 street hp #0-82751...i got the carb on today, adjusted the idle slightly, and its running great at idle. However, when i go to stab the throttle slightly im getting a pop, which is making me think it may be a lean condition...i have no idea what jets or pv are in this carb (ive tried looking at the instruction sheet and googling it to no avail) but im thinking i might have to go up? i havent gotten a vacuum gauge to it yet since i cant figure out where my dad has put it and hes not around.

That being said, Holley mentions that you dont really need to do much fiddling with the carb, but every car likes something different obviously...what jetting do you guys very roughly recommend on a mild 340? just looking for some too big and too small numbers here
 
I've read that you want an 8 size split between the primaries and secondaries since the PV adds about an 8 size jet of fuel when it kicks in. So on my 340 I have 68's on the primaries, and 76's on the secondaries and upped the squirter to a 35. Still tinkering with it using a wideband O2 and vac gauge, but it's really close I think. Runs much better than it did when I started. O2 sensor is handy. I have a 6 PV in and run about 15" of vac at idle in gear.
 
rednesss said:
I've read that you want an 8 size split between the primaries and secondaries since the PV adds about an 8 size jet of fuel when it kicks in. So on my 340 I have 68's on the primaries, and 76's on the secondaries and upped the squirter to a 35. Still tinkering with it using a wideband O2 and vac gauge, but it's really close I think. Runs much better than it did when I started. O2 sensor is handy. I have a 6 PV in and run about 15" of vac at idle in gear.
Click to expand...

this is good info that i was looking for

im not sure what jets came in this new carb that i have (i think the primary is a 68) since its not the instructions or anywhere on the net....i upped both squirters to a 35 and the hesitation is pretty much gone now. However, i still sometimes (only sometimes) get a lean pop when i step on it or tip in. Right now timing is 15 initial, 36 total, and im pulling 10 inches of vacuum at idle...i believe the carb currently has a 6.5pv, so i assume i will have to change that

now the only problem i have is even when the car is warm, it for some reason doesnt want to idle, especially if i throw it into neutral and coast to a light...sometimes it does, othertimes it doesnt, even when warm
 
With 10" of vacuum, I have read that you want a PV that is 1.5-2.0" less than that. So somewhere around an 8.5 or 8.0 PV. I'm running about 18 initial with about 34 total timing at 3200.
 
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