I have a 70SS with a pretty fresh 454 making (of course) 500 h.p. (505 h.p. actually and 521 lb.ft.tq) It is 350 TH auto, with a 331 posi.
I have a Holley 850 carb (vacuum secs.) The jets are #79 primaries and #84 secondaries. It runs a little rich at idle probably, even with mixture set correctly; secondaries are maybe a little disappointing (maybe just the nature of auto trans and vacuum secs). Do I just go out and buy the whole kit of jets, most of which I'll never use? Can anyone with similar car set-up maybe give me a kind of benchline as to their jetting, and even accel. pump? Thanks for the help!!

tim

Post the list number from the front of the choke horn, we'll see what model it is and look up the correct jets and stuff. That sounds like the vac sec carb that Chevy sold on some of the crate engines. I've heard some other complaints about them but I'ver tuned one myself.

What I would do is get it back to factory jets and power valves and then try changing the jets up and down a little, followed by installing a quick-change sec diaphragm cover for trying some different springs.

Tom

in my opinion, just buy the jet-kit. i did (like you not wanting to) but it turned out to be a great investment. i can fine tune when ever i want. and when a friend needs to tune his holley, i just let him use it...

My 950HP came with 78's square and 6.5 power valves,I'm guessing you're a little fat on the backside.

Yeah, I should have noted that it is the 80531 carb that came on the 502 crate engine. Not sure what the orig. jets were, but I'd guess that I'm probably a little rich all around too. I guess I'll bite the bullet and get the kit! Hey Rapid Robert, you mean that the #84's are too much, ("fat on the backside") or both are too much? Thanks for the replies guys! Hey Robert, I've heard nothing but good about the 950 HP! I've considered it. What are your engine specs? Is it a good fit for my 454, or is your mill a step or two above mine?
Thanks for taking the time out to answer!

tim

I like the 950HP,,,great throttle response,beat my old 750DP all to heck. I'm guessing were in the same HP and torque numbers or real close. Mines .030 over,Lunati solid .540/.558,Edelbrock RPM intake,1.75 headers(dynomax),049 heads with 2.19/1.88 Stainless steel valves,no port work,mallory unilite dist. with blaster 2 coil,nothing fancy,10.5-1 compression. According to the e.t. charts,its around 425hp to the back wheels,which would put it right at 500 at the flywheel. The fronts are probably too much,moreso than the back.Look up the model# or I would try 76-80's,,,whatever comes from Holley,you shouldnt have to vary 2 sizes one way or the other,,,or its the wrong carburetor.