do i need a choke?

[jerome]

what should i do? i have a HP series holley 4150 750cfm mechanical secondaries carb that i bought brand new. my motor is almost fully assembled now and i need to figure out if the carb is right for my purposes.

it is for a 82 S10, street driven almost 100% of time, even in winter. this is in WA state, lows of around 25 in the winter.

the motor is a sbc 383:
AFR 195's
air gap intake
10.5:1 compression
forged pistons
mallory ignition

from what i have heard, in the winter, the car will start just fine, but it will run rough and i will have to keep my foot in the gas to keep it alive. but i've also heard with the newer multispark ignitions will ignite the leaner mixture just fine on cold mornings and it wont be a problem?

should i trade this carb in for a 750 dp w/choke? and if i do, what kind of power loss am i looking at?

Thanks,
Jerome

[sporter]

I run an electric choke without the choke flap. This gives you the fast idle you need at cold start but otherwise acts like a chokeless carb. I live in Florida but I've driven the car in the 20's once or twice with no issues.

[Hidro]

from what i have heard, in the winter, the car will start just fine, but it will run rough and i will have to keep my foot in the gas to keep it alive. but i've also heard with the newer multispark ignitions will ignite the leaner mixture just fine on cold mornings and it wont be a problem?

should i trade this carb in for a 750 dp w/choke? and if i do, what kind of power loss am i looking at?

Thanks,
Jerome

Your problem is going to be a iced up carb.(you described it exactly)Happens everytime around here in winter.Choke or no choke, no difference.Not having a heat crossover on the intake or heads is your main problem.Anything below 40 degrees outside you will see this.

good luck.

[Shaker455]

As Hidro mentioned icing up will be what you'll have to address and this happens to any style carb.... choke flap will not be the problem.

If you had an exhaust crosssover passage in the intake but not in the heads you could plum the passage in the intake for coolant "but" you using the air gap which has no crossover.

You may want to swap to a standard RPM intake in the winter and tape off the front portion of your airfilter so it's not getting direct cold air and plum some hot air ducts from your headers like a factory heatriser setup.....with some time a well designed winter set up will ensure comtinued performance.

[HILROD]

Any Holley that I use for any cold weather driving has an automatic choke kit installed. Just pump the pedal once and crank her up. Even put them on my buddies roots blown car. A Holley with a manual choke without being careful at every startup can cause flooding, hard starts or worse. I would either remove the choke, wire it open, or install an auto setup. Way less hassle, for the average driver.

[jerome]

well the afr website says that the heads have a heat riser. what can i do with that? i have no idea, i thought heat riser was for egr, but i also read something about some carbs having a provision for hot exhaust to be run through them.

hilrod by automatic choke, do you mean electric choke like holley sells or something else. i remember on our old jeep, we used to step on the gas all the way down to open the choke. that seemed like some sort of thermostat operated valve. where can i get such a kit?

this carb i have has no provision for a choke even. theres no choke "tower" or anything. will i be able to install the electric choke kit that holley has, just to dump more fuel in?

I dont have the intake installed yet, and i could exchange it for a manifold that does have an exhaust crossover, but i thought generally only stock applications had these. none of the aftermarket performance intakes have them?

thanks,
Jerome

[Shaker455]

What AFR heads are they...I'll look them up and if they do have a riser get the standard RPM intake that has the passage.

If your HP is jetted correctly you will not need a choke.

Some Holleys I build I will include an electric choke deal but just use the fast idle cam set up so you don't have to nurse the throttle for the fist min.

[jerome]

i have afr #1036
http://www.airflowresearch.com/195sbc_sh.php
they have the heat riser

how does the fast idle cam work? i start the engine, it idles higher than usual, and then when i step on the gas it will back down to normal idle?

i cant seem to find the part number for the performer rpm that has an exhaust crossover.

Jerome

[Shaker455]

I looked at the link and the head in the pic has no passage but I'm going to assume the pic is not the actual part as I used a set of they're BBC 305cc as cast and the pic was not the acutal part either.

So look at your heads for me please and tell if there's a hole where the passage should be?

And yes the fast idle came will work off the electric choke spring in housing and you can set the hi idle speed via an adjusting screw and the choke spring can be adjusted for the duration it's engaged.

As you know HP series carbs do not have all the bosses on the side of the casting to mount the electric choke set up but that can be modified.

Summit PN for RPM intake EDL-7101

[Shaker455]

Summit PN for RPM intake EDL-7101

[HILROD]

I was talking about the electric kit Holley sells. If you don't even have a choke tower, you can't add a choke to it at all.

[jerome]

fast idle cam:


fast idle cam plate:


is that what i need? and how/where do i attach it on here:


i'm not home right now, so this is someone else's picture of the same heads in the 65cc version which should be the same.

i'm not sure where i should be looking, but i think the little hole in the middle on the intake side is what you're talking about?

also, the summit website:
http://store.summitracing.com/partde...1&autoview=sku
says "No exhaust crossover"...

here's the pic:

is the vertical ridge in the middle of the intake the exhaust crossover?

Jerome

[HILROD]

You don't need the crossover at all with the electric chokes. It only helps warm up and extreme cold, keeping the carb from icing up. You can't add a choke to the carb you have without at least changing the main body.

[jerome]

is there a valve available to close the crossover once engine is warmed up so that it doesnt rob any power?

also, still looking for an answer to how to use the fast idle cam.

Thanks,
Jerome

[Shaker455]

jerome,
I was at my machine shop this weekend and they were assembling a SBC with the AFR 1034's and they also had the exhaust crossover passage....very small like the pic and I'm sure it can't do much so don't worry about it.... it will help a little in the winter.

HILROD,
He's going to need additional heat from that crossover to help warm the carb in the winter regardless of the choke.

Also your right about the elec choke not being able to bolt right up to the HP mainbody in stock form but as I mentioned eariler the mainbody can be modified to accecpt the elec choke so the fast idle cam set up can be run off of it.....I've done this mod per customers request.

[jerome]

Found the valve that goes on the passenger header collector. 3" valve from hedman

does anyone know how that works? obviously it blocks off exhaust so it all goes up into the intake and out the drivers, but when does it know when to open up?

Shaker, how hard is the modification to get the fast idle cam on the HP body? drill and tap holes or something? and is it possible just to use the plate to mount the fast idle cam instead of the electric choke? that looks like what it is meant for (manual choke equipped non-HP 4150's).


Thanks for your help,
Jerome

[Shaker455]

Jerome,
The manual and elec use the same mounting points, I'm a machinist so I'm able to make posts to add you HP mainbody to support the elec choke hardware.

[jerome]

i've been looking at pics of the HP carbs and it doesnt look like theres bosses where the choke would be. so i understand you could make posts, but how do you attach it to the main body?

I took machine shop at school here last semester and have the basic skills with mill and lathe to make the posts, i'm just not sure on how to attach them, is it by welding, or are you attaching them to other points on the carb?

[pitts64]

You don't need a choke. I've been running without one for years. Its also a good idea to have the heat risers blocked.
I use an electric AC solenoid to bump up the rpm when cold.

[jerome]

yeah, ive basically decided to go without the choke. i will use the heat riser though, I dont think there will be much, if any power loss if i use the valve to control when the crossover is open. the only thing i have to figure out is how to get a fast idle. the most elegant solution is the choke fast idle cam. next i think would be a hand operated throttle knob on the dash. i'm gonna look into using the solenoid to do it as well.

Jerome