acerulz

Hello, here's the setup I have...350 flat top pistons with vortec heads and a mild cam comparable to an rv cam. Holley 4150 650 cfm and throttle body spacer with a cyclone intake. Everything about the engine is set to spec along with fuel pressure but it's a dog coming outta the hole. Light cruise it's perfect I drilled the jets out a bit at the end of our summer season and that made a huge difference. So I want to do it right and put the proper jets into it. What I want to know is what size of jets should I be running roughly. I would like to only have to order a couple different jet sizes instead of shilling out 140 bucks for a huge jet set that won't be used ever again. Is there anything else I should look for as well? I'm not exactly a carb guru but am teaching myself along the way. Thanks for any input and insight on this.

sofakingdom

iTrader: (1)

First things first.

Lose the spacer and see what happens.

Roughly, you should be running the size THE ENGINE wants, as seen through THAT PARTICULAR CARB. Since every list # of carb has different venturis, different air bleeds, different restrictions and orifices in different places, etc. etc. etc., it is NOT POSSIBLE to tell or even GUESS what jets will give YOUR ENGINE the amount of fuel that IT wants, via THAT carb.

Then go here https://www.thirdgen.org/forums/carb...ey-tuning.html and follow the process. Start at the beginning, not somewhere in the middle even if you think you don't need to do the initial steps. Follow each step IN ORDER, skipping none, IN ORDER, starting at the beginning, IN ORDER, following through until the end, IN ORDER, skipping nothing.

Might want to get the ignition timing optimized FIRST though, before messing with the carb. You need about 16 degrees of initial timing, about 36 degrees of "total" with the centrifugal curve starting just off idle (1200 RPM or so) and "all in" by around 2800 RPM, which NO stock dist will give; they're usually set up for ALOT more advance than that, meaning, if you set the "total" right, you will be around 10 degrees shy at initial. I'd recommend calling Performance Distributors and getting them to set up a DUI for you. Then on top of that, you'll want about 12 - 15 degrees of vac advance, starting to drop out at around 15 inches and fully dropped out by about 12.

acerulz

thanks for the link and the advice! Lots to do but sounds like its definitely worth it!

camarito

I'm using 68 jet on primaries for a 14:1 afr and 76 on secondary for a 12.5: wot.
Unless you have forced induction jet size will not change much.
this is your carb specs i believe: Primary main jets 70, Secondary main jets 70, Power valve 6.5, Primary Nozzle 28, Secondary Nozzle 29
If it's a dog off the line i would step up to a 35 Nozzle on the primary side and tune up the timing advance

acerulz

haha close. primary 67. secondary 73. power valve 65 primary nozzle 28 secondary nozzle 29. runs a lil rich at idle, sh*ts its pants when you stomp on it from takeoff or cruise. mild throttle runs perfect. guna play with the timing and carb, but gotta wait for the friggin snow to take a hike.