Holley Jet Sizes - Street Driven Small Block

I have a 650 Holley, the 650 was a low mileage carb that was run on a drag car, it has the nozzle type squirters and had larger jets in it. It is on a 10.5 to 1 Small Block Chevy (350 cubic inch) with a 302 duration 480 lift hydraulic cam (Fireball 2) pretty ported #186 casting number heads, 2.02's, 1.60's., ported single plane intake.

The motor runs good, just got it running, I had pulled it from a car I owned years ago that I built - car had gone 12.50s at 108, nice street car when I built it 20 years ago. I had built the motor..sold the car, the person abused the car, sat for years, bought it back, got it running, stripped car, now have motor in new car.

Now that I have it in another car and at idle it seems to load up when sitting, seems to be running rich. I took carb apart and it is a 4777-2 that calls for 67 jets in front, 76 in rear. It had 70s in front and 79s in the rear, so am thinking it may be a bit overjetted for my application? The needle and sets both seem clear (I took apart, inspected, cleaned, no debris), floats are set right...but am thinking of jetting it down to say 66 in front and 74s in the rear, just looking to make it fun and driveable, not heavy dragway use.

I run an aftermarket ignition, I have not put a light on it yet, but am betting it is around 10-12 inital right now, probably like 36 total, but havent messed with timing yet, car runs great, no popping, revs up clean, very responsive.

I appreciate any input on jet sizes you guys can offer, has been awhile since I am this deep in a carb, pulling jets etc, a lot of times recently have run out of the box carbs with minimal tuning.

Regards, Tim

 

66 @74 sounds close but you need the correct power valve..

 

I would set the timing first. Second the jets dont supply idle fuel, set your idle screws for that. I would use the 67/76 that it calls for and go form there.

 

I read up on the holley site and although I do not have a vacuum reading yet, moving to say a 45 power valve vz the 65 it came with may also help reduce the load up at idle, even though the cam is not "radical" it is fairly lumpy, fair amount if duration..so maybe that is a factor....

I also have a brand new 45 valve, so maybe try that at the same time. Thanks for the info, keep it coming!

 

Nix the power valve and that will lean the engine about two steps, if the engine backfires the power valves usually DIE, so....just block them...the mains will handle all the fuel the engine needs and run vacuum secondary to prevent stumbling on secondary opening,...

 

removing the power valve will change about 10 steps,Time it first and check vacuum,if it is to low, advance base timing and limit total.Always time first before changing jets

 

I bet you always have a few "unneeded" extry parts on your rebuilds

 

I know I can step up ten jet sizes and nix the power valve, but I am going to leave the power valve for now...start with jets as the carb is apart, then I will time it....also going to make sure the accelerator pumps clearance is correct etc, just make sure it is back to a stock set up and go from there, thanks for the input!

 

Also on a holley if you turn it over there is a tiny little screw that adjusts the opening of the secondary butterflys at idle. Check and make sure that they are not propped open to far, it will draw fuel at idle from the secondaries if they are proppeed open to far and make it an eye burner. You should just barley be able to see light though the throttle bore when they are set correctly.

Oh and donot nix the power valve ubnless you are building a full on race car, you need it for tip over, a full on race car does not need it because it launches above idle. Take your time and get the proper power valve set up.

 

Porknbeaner, any pics you can post of this screw for the secondaries? I will take a look at it later....yeah just going to be a mild street car

 

I have to snap some pics of some carbs I have for sale I'll get you one then. Let me look and see if I have a pic of one that is usable in the mean time.

Nope don'y have a good pic. Give me a bit and I'll get you something.

OK here are some pics that may help, nearly all holleys have a way to adjust the initial opening of the secondaries and it will normally be on one end or the other of the rear throttle shaft, more often than not on the opposite side from the throttle linkage. It will almost always be done though a hole in the bottom of the carb as well.

What happens is when these butterflies are open too far the vacum draws fuel from the booster, if you are idleing you don't need that extra fuel and you get an eye burner.

Hope this helps a bit.

 

thanks....I know years ago my dad drilled the butterflies on my brothers 67 Camaro due to a similar situation, it worked great that car ran the balls and with a healthy cam...but I really dont want to go that route, just want to do adjustments...the car ran great as mentioned, just loading up a bit at idle.

 

I would put it all back to stock specs, and see how it does. I have a couple 4777 carbs on my blower motor...they actually work really well in stock trim. They are designed for performance engines.

 

Any ballpark, pictures of how to preset the floats during assembly to get them in the general range of how they should look

thanks!

 

The top of the float should be in line with the bottom of the holes for the screws that attach the float bowls.

 

I make the sweat line lever with the top of the bowl then I drop it a bit. Better to start out low then pull the site plug and adjust it. If it is high it is impossible to get it adjusted.

Let me see if I have a bowl off a carb that I can snap a pic for you.

OK I'm back I am going to have to trow a float bowl together unless someone else has a pic. it will probablty be this afternoon before that happens.

 

thanks guys!

 

To get you in the ballpark, turn the bowl upside down and make the top of the float parallel to the float bowl. You should be able to use a yellow octagon shaped #2 pencil like a feeler gauge in between the float and bowl while still upside down.

You really need to get a vacuum reading in gear before just changing power valves too.

 

That works on side pivot floats, but I'm pretty sure the 4777 is center pivot.

 

Thats what swade is talking about. I second that.

 

With a center pivot bowl, the float is parallel to the top of the bowl no matter where it's set.
I'm assuming you're talking side to side.

 

Like this Larry. It does not stay parallel as it PIVOTS.

 

So the seam in the float is not parallel to the top of the bowl if the float is dropped or raised?
You'll notice that the top of the float is even with the bottom of the holes for the through bolts in the picture.

Here's the set up for side hung bowls. This is what I think about when I hear setting them even with the top of the bowl.

http://www.fordmuscle.com/2007/04/adjusting-holley-floats/

 

You wearing a blindfold?

 

Nope, just old and blind I guess. Or maybe I've got on dark shades. Yea, I know it doesn't stay parallel front to rear in the bowl, but when you look at the float you see it side to side.

Anyway there's enough info for the OP to dry set his float so that's what counts.