[Yellow68SS]

I have a holley 850 with a proform main body and of course am always trying to tune it a bit more. The 850's didn't come with the little holes drilled in the butterflys so of course way too much of the transfer slot was exposed.

So i drilled a little hole in each of the butterflys and it helped, but i think it would help more with bigger hole but i don't want to get all wild with the drill. Right now the secondaries are set just right as far as the transfer slot but the primaries are too far open to keep from idoling rich.

What is the size of holes that come in like the HP's blades and what is as big as i should go. I will work up to this size in little steps.

Thanks

[BlackoutSteve]

The Holley books recomend a 1/8" hole in each of the primary's throttle blades.
If you have a "4 corner idle curcuit" in your carb, you shouldn't need any holes. The new HP Holleys have a 4 corner idle and would surprise me if the have holes. (My 1000cfm HP doesn't have holes.)
However, more recent Holleys with 2 corner/primary idle did have these 1/8" holes as standard from the factory if memory serves.

Before drilling any holes, make sureall of your air bleeds, vents and emulsion tubes within the metering block/s are nice and clean. These could cause poor idle quality if dirty and you may not require drilling holes in the first place.

[cody]

My HP950 holley has four corner idle and holes in each butterfly

[Yellow68SS]

i tried everything before i drilled the blades, that was a while back. but it only makes 5.5 in of vacum on a good day at 1100 and will die below 950rpm. The main reson i'm trying to get the idol just right is because so much of the cruise mixture comes from the idol mixture. Which i can't get to lean out. when i get close with jetting down it is about 6-8 jets too lean at WOT.

not to mention the plugs are usually black, unless at the track doing passes. and it takes about a pass or so to clear it out.

it helped when i enlarged them jsut a bit, but they are still smaller then the HP i've seen on display.

Thanks

[cody]

I'm no carb expert but I think we have somewhat similar motors, you have a little more compression/cam though, My HP950 will let my motor idle pretty far down, I can get it down to 800 if I wanted, at about 900 I have 6 1/2" of vacuum. Like I said My carb has holes on all four butterflies, sounds like you need the same from your description. Also at idle the jets shouldn't affect it at all. How much of your transfer slots are showing? Also not sure how drilling the blades will work because the HP's have the tunalbe air bleeds. BTW how do you like that cam?

[Yellow68SS]

I do have the adjustable air bleeds, the proform body made that happen. I know the jets dont affect the idol but it all seems related some what. The jets affect WOT and a bit of cruise. The idol mixture also gets part of the cruise.

from what i can figure, it idols at a low vacum and gets the amount of fuel it needs. Then when i start to cruise, vacum goes up and it pulls to much fuel from the idol mixture, runs rich. The secondaries are set so that the transfer slot is square. Primaries are about, twice as long as wide. (Bad)

It used to be able to idol at 800, no problem. Just really rich. Fouled plugs when cold. now that its leaning out it has to be higher, seems odd to me.

Don't know if elevation effects anything, i'm at 6000ft and DA gets to 10,000. But when i was at a lower elevation i did not have these problems, at least as bad that was at 2500 ft.

Cody,
I like the cam, wish i had a roller but just couldn't afford it. I have always had a bit of trouble getting it to pull past 7000 rpm like it should. Like to see how yours runs once you get it finished a bit more. Ours are pretty similar.

Thanks

[SIDEWAYS]

Did you try to crack the rear blades open a little more? I would definitely do that before drilling the blades.

[BlackoutSteve]

Correction.
Cody, you prompted me to check my carb and my HP 1000 does have the holes. I never thought it did but hey.. it does!
I never noticed (or remembered!)

[cody]

Do you have a four corner idle? the air bleeds in the rear of the proform main bodys are setup for a rear powervalve and idle mixture screws, so if you are using a box stock main body and no rear mixture screws that could be a problem also, I would go bakc to square one, get the correct air bleeds in the rear, and then put the stock jetting back in it(whatever a holley 850 comes with) and then re-set the transfer slots, and see what you have. If you do have a four corner idle, I would definetly drill all of the blades to the correct size.

[Yellow68SS]

i do have four corner idol. I am afraid that if i crack open the rear anymore it will expose too much of that transfer slot as well.

I havent changed the air bleeds that came in the body, don't know where i could get some, or really what i would be doing! lol i read about how they change the time the circuits change from say idol to main.

The box stock jetting is 80/80 with front and rear power valve. The main body came with 76/84 jets and said to ditch the rear power valve. This is just about the jetting it needs at the track,78/86 usually. But when im driveing around it needs like 72 or 71 in the fronts with 80's in back. Thats my problem. i just want it to always run well with the same configuration for the most part, street and strip.

Thanks for the help guys.

[cody]

You got something weird going on, you need to start from scratch. You need to call Proform and verify what bleeds you need for your setup, I would put the 80's back in and run a rear powervalve, and drill all the blades. Going back to square one always helps. My 950Hp Is box stock jetting, 5.5" powervalves, idle mixture screws are 3/4 turn out, 31 squirters, stock bleeds, barely any transfer slot showing and it idles just a little fat, and runs perfect

[SIDEWAYS]

Kyle,

Just curious, what kind of initial timing are runing, and any vac advance hooked up and where is it connected to?

With that size of cam, you'll need a whole bunch of timing for sure.

Keith

[cody]

just out of curiosity do you know your cranking compressioN?

[Yellow68SS]

i am running my timing locked out at 38*. no vac advance. The cranking compression is 175-180 throughout. Its lower than optimal but just like the rest of the motor its set up for nitrous. i want run a 150 shot on 91 octane no detonation yet. Haven't ran but a couple of passes though on the bottle.

The ADV duration is 304/316. Thats not in my sig, maybe you guys needed it.

Thanks guys

[Bobs 72]

I used to run 78/80's in my 950HP w 4.5 powervalves. Mine was real fat at idle, had to baby sit for 2-3 minutes before it would idle on its own, then added the Mallory Hyfire ignition box, now its hit the throttle,hit the key and it starts and idles. I'm running the Comp xr286r and it will idle at <800 in gear if I want to idle it down that far.